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1Back to top Go down   [solved]k75 Strange starting problem Empty [solved]k75 Strange starting problem Sat Oct 30, 2021 7:37 pm

costellon

costellon
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Hi all,

I recently purchased a 1993 K75 non runner (non abs) with a sprag clutch problem. On investigation it turns out that the PO had refitted the male alternator flange without the bolt and damaged the sprag/ idler gear mechanism. I stripped off the bell housing and found the countershaft spring broken, teeth on the back of the countershaft ground off in one spot (all sitting neatly below the shaft) and the splines on the intermediate shaft completely destroyed. I replaced the offending items along with bearings and seals and rebuilt everything. Splines lubed etc ....

When I hooked everything up and pressed the starter button the motor just whirred - seemed like the sprag was not catching. Stripped everything off again right down to the sprag - all good, I checked and double checked and rebuilt everything again. I pressed the starter button ..... same result - whirrrrr - but no rotation of the engine !

Pulled off the crankshaft cover and starter motor and rotated the countershaft with my fingers ..... perfect ! Sprag engaging and engine turning. It could only have been that the starter was rotating in the wrong direction. Contacted a helpful and knowledgable friend who explained that once by chance he had rebuilt his starter motor with the centre housing the wrong way around (thanks Will) and his starter ran in the opposite direction.

I stripped the starter motor, flipped the centre housing, rebuilt it and refitted it to the bike. Took a deep breath and pushed the starter button - rotation !!!!! Woohoo !!!!

Fuel pump was whirring happily and I had a healthy spark - so I thought i'd address the other issues. Dropped the sump and desludged it, cleaned the primary oil strainer, changed oil filter, refitted sump, fresh oil in bevel drive, gearbox and motor, fresh coolant, changed fork oil, greased and adjusted steering head bearings, fitted 2nd hand rear shock, changed fuel filter in tank, stripped instrument cluster and replaced bad bulbs, fitted manual over ride switch to radiator fan (just like I always do), fitted fresh heavy guage wire from starter relay to starter motor, fitted new starter relay, gapped and fitted new spark plugs (7mm), charged the battery and put fresh fuel in the tank.

HERES WHERE MY PROBLEM CURRENTLY LIES .... Hit the starter button and the engine turned over nice and healthily but didn't fire. Pulled the plugs - getting loads of fuel, checked the spark - good healthy spark. Bypassed the clutch switch - still the same.
Took it out onto my street, put it in 3rd gear and gave it a push - fired up straight away. Drove back into my garden, stopped it and tried it on the button again - it did start but after cranking for far too long than is necessary or good for the starter motor and only with the throttle wide open.
I bump started it again (fired up straight away) and went for a 10 mile spin. Drove fine, smooth, good power, no farting etc ... Got back, stopped the engine again and tried to restart it on the battery - nothing. Checked again, on the button, healthy spark, wet plugs. Gave it a short push - fired straight up. I stripped off the HES cover in case the pickups might have been dirty - but no, nice and clean and timing plate in the correct position. I pulled and cleaned all of the electrical connectors from all the switchgear, checked all of the fuses, gave the relays a tap and even checked to see that the headlight goes out whan I press the starter - yep, no problem there with the load shed relay.

To recap: It'll start fine on a push - but takes far too long for it to "catch" on the starter - far too long and the throttle has to be wide open ....... any suggestions would be greatly appreciated ?????

N.B.
One thing I did notice when I was changing the fuel filter - with the fuel tank lid open and the starter button pressed (fuel pump whirring) there seems to be a substantial flow of fuel on the right hand side at the front part of the tank - never noticed that before on a K-  like a little waterfall of fuel falling from just in front of the filler cap back down into the tank. The fuel filter is the correct way around

Cheers



Last edited by costellon on Sun Oct 31, 2021 10:46 am; edited 1 time in total

    

2Back to top Go down   [solved]k75 Strange starting problem Empty Starting problem Sat Oct 30, 2021 8:35 pm

daveyson

daveyson
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Sounds like too much fuel. If you can get it to run with the fuel tank unplugged, that's another sign of too much fuel.

Could be a bad temperature sensor. 

While idling, with a screwdriver to the injectors you should hear a ticking as they turn on and off.



Last edited by daveyson on Sat Oct 30, 2021 8:41 pm; edited 1 time in total


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Point-Seven-five

Point-Seven-five
Life time member
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I think the fuel you are seeing in the tank is return from the fuel pressure regulator.  No big deal, it shows your fuel pump is working.

Have you checked and cleaned the grounds and battery terminals on the bike?  A bad ground may be causing the voltage to the engine control unit to drop to a point where proper operation is prevented.  When you push start the bike the starter isn't drawing large current from the battery so the voltage drop isn't there.

What is the voltage on the positive battery terminal when the starter is running?  Try to read it both on the terminal and then on the connector that is attached to it.  A dirty or corroded terminal may cause low voltage when the starter is running.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

Laitch

Laitch
Life time member
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@costellon wrote:One thing I did notice when I was changing the fuel filter - with the fuel tank lid open and the starter button pressed (fuel pump whirring) there seems to be a flow of fuel on the right hand side at the front part of the tank ..... like fuel being recirculated around the tank - never noticed that before on a K-  like a little waterfall of fuel falling from just in front of the filler cap back down into the tank. The fuel filter is the correct way around
The fuel return line dumps from the tank ceiling on late model Bricks like yours. It's mounted forward of the filler cap above the vapor chamber in the location you described. That's normal


__________________________________________________
1995 K75 81,000 miles
[solved]k75 Strange starting problem Usa-lo10
    

Arlina

Arlina
Moderator
Moderator
I'm with .75 , first thing came to my mind, voltagedrop.


__________________________________________________
[solved]k75 Strange starting problem Eu-log10  K1100RS/LT - R1200RT - R1100RS (RIP) - Cagiva SST 350 Ala Verde - K75LT project - K75 Schurgers - K75S
    

6Back to top Go down   [solved]k75 Strange starting problem Empty Thanks for the replies Sun Oct 31, 2021 12:06 pm

costellon

costellon
active member
active member
Thanks to all for the replies.

@ Daveyson:
It fires straight up with the tank disconnected - but doesnt run for long. I neglected to mention the VERY strong smell of fuel when cranking with the tank connected.
Injectors are ticking happily at idle.
I want to possibly eliminate all other possibilities before I go ripping the tupperware off to remove the coolant sensor for testing, however I did manage to disconnect it and crank the engine - same result.

@ Point seventy five:
Regarding earths and connections, I made up 2 new earth cables last week from heavy guage 16 square "weldflex" cable. One goes from the battery to the usual spot on the gearbox, the other goes up under the tank to the earth point on the frame, earths are good and clean as are the mating faces between the starter housing and the gearbox.
Voltages are as follows:
When not cranking, 12.4v at battery
When cranking: 11.2v at battery positive
When cranking: 10.9v at starter motor positive terminal

@ Laitch:
Thanks. It seems like its dumping a LOT of fuel .... its not just a fast drip, its a flow - funny how I never noticed this before on my other 3 post 92' K's

@ Arlina: Thanks

I'd imagine that if it was a voltage drop that it wouldnt start at all on the starter.
It WILL start - I just have to keep the throttle wide open and my finger on the button cranking it relentlessly for around 15 seconds until it eventually "Catches"- which I REALLY dont want to have to do. It does seem that its flooding/ overfuelling .... fuel regulator ?

Incidentally, the old plugs that came out of it were black

Thanks again

    

Laitch

Laitch
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@costellon wrote: like a little waterfall of fuel falling from just in front of the filler cap back down into the tank. 
@ Laitch:
Thanks. It seems like its dumping a LOT of fuel .... its not just a fast drip, its a flow - funny how I never noticed this before on my other 3 post 92' K's
Most of the waterfalls—even the little ones—I've visited are relaxing. Pull up a chair and have some tea; you'll feel refreshed afterward.  Smile  The fuel from the return line flows but at much less pressure than fuel from the delivery line. If it were incoming inside the fuel tank an unregulated rate, you'd be describing it as a torrent.

If relaxation is not in the program, it's simple enough to check the delivery and return fuel line pressure to confirm if the pump and fuel pressure regulator are working at specification, if the correct set of gauges and adaptors are available.

My moto's return line flows like a water feature in a tiny coy pond for miniature coy.


__________________________________________________
1995 K75 81,000 miles
[solved]k75 Strange starting problem Usa-lo10
    

Arlina

Arlina
Moderator
Moderator
Check this page how to check the pressure, down at the bottom of the page;

http://www.kforum-tech.com/electrical/EFI/bike-wont-start-EN.htm


__________________________________________________
[solved]k75 Strange starting problem Eu-log10  K1100RS/LT - R1200RT - R1100RS (RIP) - Cagiva SST 350 Ala Verde - K75LT project - K75 Schurgers - K75S
    

Laitch

Laitch
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@costellon wrote: When not cranking, 12.4v at battery
The battery is not in optimal condition at 12.4V. It should be ≥12.6V. Try charging it fully then try again.


__________________________________________________
1995 K75 81,000 miles
[solved]k75 Strange starting problem Usa-lo10
    

10Back to top Go down   [solved]k75 Strange starting problem Empty Update Thu Nov 11, 2021 1:35 pm

costellon

costellon
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Thanks again for the advice and imagery, hehe.

I have now fitted a replacement temperature sensor, fuel regulator (replaced all pipes and blanks) and TPS (reset also), manifolds in good condition, crank breather pipe good.

I have used a brand new PC680 battery to turn it over and am still having the same problem.

Removed starter motor and gave it a good clean.

It still starts first tip with the tank electrics unplugged, still starts after 15 seconds on the button but only with the throttle wide open (as before).

Starts from a bump within a few feet.

Plugs removed, cleaned and re-gapped, good healthy spark.

I have no gauges and fittings with which to check the fuel pressure but it is definitely overfuelling (fuel is dripping out of the header pipe union of the exhause system on continued cranking).

Any other suggestions ? Fuel pump ?

Thanks again and apologies for the late reply, been hectic at work.

    

MartinW

MartinW
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Check the wiring from the temperature sensor to the fuel injector control unit to pin 10. Check that the sensor has a good earth where it screws in. Any thread tape or sealant can effect the earthing and cause problems.
Regards Martin


__________________________________________________
K75s Hybrid
    

12Back to top Go down   [solved]k75 Strange starting problem Empty Strange starting problem Thu Nov 11, 2021 5:03 pm

redrockmania

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Further to Martin W's post 10: Make sure previous owner has not put a non-conducting washer under the sensor where is mates with the engine block. There needs to be a good metal to metal connection. This also applies to Coolant Temperature Sensors (CTS) working efficiently. In order to retain a good metal to metal contact over time I now smear the base of the sensor and the engine block where the sensor screws in with a copper-based ant- seize paste. I recall Charlie advising the he tins both sides of a copper or brass washer with solder to retain good conduction and resist future corrosion.

    

Laitch

Laitch
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@costellon wrote:Took it out onto my street, put it in 3rd gear and gave it a push - fired up straight away. Drove back into my garden, stopped it and tried it on the button again - it did start but after cranking for far too long than is necessary or good for the starter motor and only with the throttle wide open.
I bump started it again (fired up straight away) and went for a 10 mile spin. Drove fine, smooth, good power, no farting etc ... Got back, stopped the engine again and tried to restart it on the battery - nothing. Checked again, on the button, healthy spark, wet plugs. Gave it a short push - fired straight up.
This tale had a familiar ring to me. Based on groundbreaking work by daveyson with followup collaboration by robmack, the cause could be a defective fuel injection relay. Read this thread .



Last edited by Laitch on Fri Nov 12, 2021 7:06 pm; edited 1 time in total (Reason for editing : Return of the Lost Consonant.)


__________________________________________________
1995 K75 81,000 miles
[solved]k75 Strange starting problem Usa-lo10
    

14Back to top Go down   [solved]k75 Strange starting problem Empty Update Fri Nov 12, 2021 11:38 am

costellon

costellon
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Cheers Martin, continuity to pin 10 ok.

Cheers Redrock, I fitted the new sensor carefully and its earthing perfectly.

Cheers Laitch, i'll read that whilst feeding the miniature fish at the base of the waterfall - with tea in hand.

Update: Changed the FI relay with a known working unit and checked wires going into the block .... problem still exists.

I'm going to replace the fuel pump tomorrow with a known working unit

Thanks again.

    

15Back to top Go down   [solved]k75 Strange starting problem Empty Strange starting problem Fri Nov 12, 2021 8:10 pm

daveyson

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A couple of easy checks.

After your brick has been running (or even while it's idling) remove the vacuum hose from throttle body three, it goes to the fuel pressure regulator. If there are signs of fuel or moisture, the regulators diaphragm is leaking, causing over fueling. Check for signs of the fuel hoses leaking.

Does it start easier with the fuel return hose removed from the tank and directed into a bucket? 

Since the previous owner put so many things on wrong, maybe the fuel pressure regulator hoses are on the wrong way around.

Maybe check for Voltage drop while cranking also at the coils (pins 15) ICU (pin 10) and fuel injection computer (pin 9)


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

16Back to top Go down   [solved]k75 Strange starting problem Empty Update Sat Nov 13, 2021 5:44 pm

costellon

costellon
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@daveyson wrote:A couple of easy checks.

After your brick has been running (or even while it's idling) remove the vacuum hose from throttle body three, it goes to the fuel pressure regulator. If there are signs of fuel or moisture, the regulators diaphragm is leaking, causing over fueling. Check for signs of the fuel hoses leaking.

Does it start easier with the fuel return hose removed from the tank and directed into a bucket? 

Since the previous owner put so many things on wrong, maybe the fuel pressure regulator hoses are on the wrong way around.

Maybe check for Voltage drop while cranking also at the coils (pins 15) ICU (pin 10) and fuel injection computer (pin 9)

Thanks Daveyson. I fitted a known working fuel pump today - no change.

I pulled vacuum hose 3 (which I replaced a few days back with the proper flexi hose - it goes to the bottom of the fuel regulator) No real change in the way the bike ran and no moisture or fuel present, dry as a bone. BTW the replacement fuel regulator is an unknown entity that I took off an old set of K100 throttle bodies

I then pulled the return hose to the regulator off the injector rack, replaced it with a longer hose and directed it into a bucket ..... First tip of the button engine fired, idled for about 7 seconds and died. Tried it again, fired up straight away, idled for about 7 seconds and died. During this test I collected over a pint of fuel in the bucket.
Return hose from injector rack is new and goes to the horizontal fitting on the fuel regulator (no leaks). The return hose from the fuel regulator is also new and is connected to the vertical (top) outlet/ spigot and goes to the the tank (front most spigot) - no leaks.

Reconnected the return pipe from the injector rack to the regulator, hit the button - nothing, back to original problem - turns over but doesnt start as it should. Does this indicate that the fuel regulator is goosed ?

I am currently charging the battery in order to conduct the electrical tests.

Thanks again

    

17Back to top Go down   [solved]k75 Strange starting problem Empty Strange starting problem Sat Nov 13, 2021 7:04 pm

daveyson

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The fuel pressure regulator hoses are connected the right way. 

Since it starts with the return hose removed from the tank, I don't think you have a Voltage drop problem.

Edit: With a hose to the front barb, can you blow air into the tank, I think you can but does it feel restricted? Maybe repeat the test with the longer hose, your original one might be kinking, say at the bend, or something.

To reduce the amount of guesswork, it's time to put a pressure gauge on. I think there is a post where Martin made one. I'd test with the return hose removed from the tank, and again with it connected. I'm guessing the regulator will fail the test. 

It's hard to meld these two results which seem contradictory. It's as if the pressure is too low with the return hose removed, and too high with it connected.



Last edited by daveyson on Sat Nov 13, 2021 7:22 pm; edited 1 time in total


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

costellon

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@daveyson wrote:The fuel pressure regulator hoses are connected the right way. 

Since it starts with the return hose removed from the tank, I don't think you have a Voltage drop problem.

With a hose to the front barb, can you blow air into the tank, I think you can but does it feel restricted?
No problem blowing into the tank - the tank pressurises with filler cap closed and air flows back out, with filler cap open air doesnt pressurize.
Pipe clear, not restricted.

Edit: No kinks in the new pipe, no kinks in the old one either.  I'll check out Martin's Gauge - it does sound like the only route left really.

The fuel pressure regulator is Bosch # 0 280 160 200 and seems to be used in many classic cars. I've found spurious units for less than £50 .... could anyone recommend a sturdy alternative ?

Its great to have an excellent resource like this, much obliged to one and all.

Thanks again

    

Laitch

Laitch
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@costellon wrote:Does this indicate that the fuel regulator is goosed ?
Thanks again
No. By disconnecting the rack, fuel delivery was depressurized; consequently, injectors stuck in the open position from a wonky fuel injection relay were delivering less fuel. The spark plugs were able to fire until there was no fuel. It seems similar to the spookiness in the link I posted earlier. I'm surprised that daveyson doesn't acknowledge the similarity.
[solved]k75 Strange starting problem 652573
You're welcome, as always.


__________________________________________________
1995 K75 81,000 miles
[solved]k75 Strange starting problem Usa-lo10
    

20Back to top Go down   [solved]k75 Strange starting problem Empty Strange and getting stranger Sat Nov 13, 2021 8:55 pm

daveyson

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It might be kinking only when under pressure or something like that. I feel sure Martin has had this issue and knows more about it.

In my strange, strange case the injectors weren't making a ticking sound cause they were constantly open. In this case they are ticking. I'm now thinking the relay swap was a coincidence and maybe the fuel injection case was earthed, dunno if that makes sense, and I haven't been game to try it for fear of cooking the computer. The other cases of constantly open injectors I've read about since, have had different symptoms, so I'm still puzzled about it.

This case is baffling too, if there is no restriction in the return side, why are the results so different with the return hose removed? Maybe give the longer hose a try anyway.

If you use the long hose to bypass the regulator and direct the fuel back in through the fuel filler cap, the result might match one of the results you got.

Maybe it's simply fuel pressure too low.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Laitch

Laitch
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@daveyson wrote:In this case they are ticking.
Tinnitus could be involved here and misleading accurate diagnosis. Maybe it's time for an audiologist.


__________________________________________________
1995 K75 81,000 miles
[solved]k75 Strange starting problem Usa-lo10
    

MartinW

MartinW
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OEM external fuel hoses had the bends molded in. Non OEM hoses can kink over where they enter the tank especially when subjected to Qld temperatures in traffic in summer. My hoses were fine initially but collapsed on a hot day in traffic. To cure the problem I ended up fitting a Unicorn Unicoil.
Regards Martin.
[solved]k75 Strange starting problem Unicoi14


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K75s Hybrid
    

23Back to top Go down   [solved]k75 Strange starting problem Empty Strange problem Sun Nov 14, 2021 5:41 am

daveyson

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In the meantime, another simple check, I think not mentioned yet, check and clean the connectors to the fuses, and replace the fuses, especially fuse 6. 

With a failed start, I think the pump should continue for a second or two after the engine has stopped.

The four pin tank connector is often the problem.

Maybe more tests of the temperature sensor are needed.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

costellon

costellon
active member
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Thanks for the replies guys.

After my fuel pump swap test yesterday evening I put 2 new (differently sized) connections on the pump wires, they were tatty and fragile. Replaced the hoses to and from the fuel filter whist I was in there and nipped up all connections. Fuel pump fitted is a 43mm CNT 400-1044 - enough said

Laitch: FI relay good, 100%, Injectors ticking, 100%, Motronic case not earthed, 100%
Tinnitus & audiologist ... Hehe ... engine rooms have taken their toll through the years on me ears alright. I gave away my stethoscope after a backfire during a diagnosis on a vMax blew my safety glasses off and sent my hat 100 feet into the air. I can now breathe through my ears when not wearing my helmet.
Cheers

MartinW: I read about your unicorn last night when I was looking for your DIY fuel pressure gauge post (which I couldnt find unfortunately). The unicoil looks like a nice simple solution - nice share, must try and make one.
Found a good moulded return pipe in my box of bits, which i'll fit tomorrow, just pulling the air box off now.
Cheers

Daveyson: The fuel pump runs on after failed starting attempts - and it seems to run on a tad longer than any of the K's i've had before - but that could be the time slip displacement coming to the fore.
All fuse connectors cleaned, new fuses fitted 100%, Tank connectors checked and cleaned, 100%
Stripped out the airbox for access, gonna refit the original regulator and will run further checks on the temp sensor.
Im going to buy more hose and hunt down a fuel pressure gauge tomorrow - I think I know a guy
Cheers


Much obliged



Last edited by costellon on Tue Nov 16, 2021 12:32 pm; edited 1 time in total

    

Laitch

Laitch
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@costellon wrote:Motronic case not earthed, 100%
Much obliged
Your moto has an LE-Jetronic fuel injection control system, not a Motronic. Motronics are on the 16V models. I'm still processing the rest of that phrase but I think I'll turn my attention to fresh-baked cornbread instead. cheers


__________________________________________________
1995 K75 81,000 miles
[solved]k75 Strange starting problem Usa-lo10
    

MartinW

MartinW
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Piccies of my fuel pressure gauge. The gauge was salvaged off possibly a compressor 100 PSI is a good choice and the fittings were just cobbled up with bits and pieces.
Regards Martin.
[solved]k75 Strange starting problem Fpr_te13
[solved]k75 Strange starting problem Fpr_te14


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K75s Hybrid
    

27Back to top Go down   [solved]k75 Strange starting problem Empty Strange problem Mon Nov 15, 2021 12:53 am

daveyson

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Doh, if your confused by my replies after post 16, thats OK you should be cause I've misunderstood post 16. I thought you replaced the return hose from the regulator With a longer one so that you could direct it into a bucket, but you said you replaced it from the fuel rail. So I think it's normal that it would stall after 7 seconds cause there's not enough fuel pressure like that, with the fuel pressure regulator removed from the system. The fuel pressure regulator provides the resistance to increase the fuel pressure.

I'll try to read this thread more carefully later, to check that I haven't made more stuff ups like that.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

costellon

costellon
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active member
Cheers MartinW, no worries Daveyson.

Been hectic here and have not had time to do anything except swap back the original fuel regulator that I replaced with an unknown entity.
Still the same story, fires up first push of the button with the injector rack return directed into a bucket. I reconnected the rack to the regulator, extended and routed the long moulded kink free return pipe from the regulator to directly inside the tank - its returning fuel alright but the bike won't start as before.

Hopefully i'll find the time tomorrow to fab a pressure gauge.

Cheers

    

92KK 84WW Olaf

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Are you happy the temp sensor is for 2v engine and not the 4v engine? Physically they look the same......but they are not.

Is fuel pressure regulator correct for 2v engine? 4v runs higher fuel pressure.

Just a thought.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 40,490 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

MartinW

MartinW
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Are the spark plugs wet or dry after failure to start??
Regards Martin.


__________________________________________________
K75s Hybrid
    

costellon

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Thanks for the replies.

Olaf: I got the temp sensor off Sid in Motorworks UK - so I presume its the correct one. The fuel regulator is the correct unit also - i've got a replacement on the way from Holland.

MartinW: after the failed starting attempts the plugs are dripping wet. It starts with the tank unplugged AND with the fuel regulator bypassed.

Cheers

    

MartinW

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Have you taken readings of the new temperature sensor. I bought a cheap $10.00 Au digital temperature sensor off a local electronics store boiled up two cups of water Make a cup of tea with one stick the sensor in the other with a multimeter connected to it set on Ohms insert the thermometer and take and note the readings as the water cools. There is not much difference in the appearance of the 8v and 16v sensors.
Regards Martin.[solved]k75 Strange starting problem K100_t13
[solved]k75 Strange starting problem Pb170110


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92KK 84WW Olaf

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Olaf: I got the temp sensor off Sid in Motorworks UK - so I presume its the correct one.


Possibly.........possibly not.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 40,490 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

Point-Seven-five

Point-Seven-five
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Just read this thread twice and can't find any indication that you have removed the fuel injectors to check their operation.

The engine is flooding when you attempt to start with the starter and the fuel pump and regulator connected.  It will start when bumping or when the regulator is disconnected.  You claim that your damaged hearing can detect the injectors firing when the engine is cranking.

Observation #1: Bump starting does not start the fuel pump until engine rpm exceeds 700rpm.  This prevents fuel from flooding the engine until it is already firing on the residual fuel in the throttle bodies and the cylinders.  Using the starter runs the fuel pump while the starter is cranking the engine.  The fuel pump is then dumping large amounts of fuel into the cylinders while the engine hasn't yet started.

Observation #2: Starting without the fuel regulator reduces the pressure in the RAIL to near zero.  This prevents the overfueling by the injectors, but can't supply enough fuel to continue running beyond a few seconds before the low pressure starves the engine.

Observation #3: you have confirmed that the battery, all the electrical connections, and the starter are operating properly, eliminating electrical issues.  Unless you have multiple bad parts, the fuel pressure regulator and the temperature sensor are okay.  Further confirmation is that the engine is claimed to run well once you bump start it.  Essentially, you have confirmed that you have good spark and fuel delivery up to the fuel injectors.

Conclusion:  You have confirmed proper operation of everything required to START the engine with the exception of the fuel injectors.  You say you can hear them firing, but what you hear is probably the injectors being opened.  What you can't hear and haven't confirmed is that the injectors are CLOSING completely.   Partially open injectors will flood the engine on starting if the fuel pump is running and make the engine run rich.  Even a small opening gap when "closed" will allow engine intake vacuum to suck excessive fuel into the cylinders when cranking. 

My advice at this point is to pull the rail and injectors and see what they are doing when you momentarily press the start button to cycle the fuel pump without running the starter.  Do it outdoors and with a fire extinguisher close by because of the fire danger of spraying fuel mist.  I'm going to guess that as soon as the fuel pump runs, the injectors are going to start drooling and/or streaming fuel.  If that's the case, you need to have them cleaned.


__________________________________________________
Present:
1994 K75RT
1991 K100RS
1988 K100RS SE

Past:
1994 BMW K75S
1992 BMW K100RS
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

costellon

costellon
active member
active member
What a crazy week, finally got a chance to get out to the workshop.

I cobbled together an in line fuel pressure gauge (thanks MartinW) but could only test it with the engine not running. When cranking, the needle went up to almost 40psi (between tank and FI rack) but more often than not showed around 35psi. Same reading from fuel rail to fuel pressure regulator. The return pipe from the fuel pressure regulator to the tank read zero psi - though it is returning fuel to the tank - but obviously at very low pressure.

I pulled the injectors as point seventy five suggested, even spray pattern on all 3 injectors, no dribbling, no "open" injectors. Pulled them off the rack anyway and gave them a good cleaning - they are operating perfectly on the bench.

Put them back in, hooked everything up and the problem persists exactly as it was.

Martin & Olaf, I should be getting a thermometer tomorrow and intend on checking and testing the temp sensor for type and operation.

I've got a replacement fuel pressure regulator on the way from Thom Hellbrekkers in Holland along with a few other bits and bobs - might be here tomorrow - Tuesday at the latest.

Comments/ Thoughts ?

Thanks again

    

36Back to top Go down   [solved]k75 Strange starting problem Empty Strange Fri Nov 19, 2021 6:23 pm

daveyson

daveyson
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Bit of a long shot, what's the part number of the injectors, do they spray from one hole or four?

Was it a constant flow of fuel or on and off?


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

costellon

costellon
active member
active member
Injectors are Bosch 0280 150210 units, looks like one spray hole, 100% not leaking when fuel rail full and pressurised.

Cheers

    

38Back to top Go down   [solved]k75 Strange starting problem Empty Strange problem Fri Nov 19, 2021 7:03 pm

daveyson

daveyson
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You have the right injectors, and not leaking, goodo.

From memory it's hard to tell if the fuel spray is constant or pulsing, cause of the tiny times involved, but you should be able to pick it, but I know this is a desperate question since you hear them ticking. 

If you thought that's sounding desperate, listen up. How's this, when you turn the key to on, do you hear the pump turn on? You shouldn't, the pump should not come on until the start button is pressed, although it's hard to hear then since the engine is cranking. I'm 99 percent sure that's not your problem, but just checking.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

costellon

costellon
active member
active member
Thanks for the prompt post.

The injectors pulse when hooked up to the bike and the pump only kicks in when the button is pressed - as I mentioned in a previous post - the pump seems to run-on fractionally longer after I remove my finger from the button than any of my previous K's pumps did.

Question: Seeing as I have zero psi pressure coming from the return pipe on the fuel pressure regulator (although it is returning fuel to the tank but at a pressure that doesnt register on my pressure gauge) - does that not indicate a buggered regulator ? What PSI should the return pipe run at ? The pipe is not kinked or trapped.

Cheers

    

40Back to top Go down   [solved]k75 Strange starting problem Empty Strange problem Fri Nov 19, 2021 8:29 pm

daveyson

daveyson
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I think the regulator is good. I still need to read the thread again. I'm going um and ah at the moment.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Laitch

Laitch
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@costellon wrote:. . .does that not indicate a buggered regulator ? 
No. The only concern is the pressure at the injectors. If fuel was returning at pressure, relaxing at the waterfall with your tea would be difficult. As long as fuel is returning, and delivery pressure is at specification things are good. The starter won't provide pressure from the fuel pump as consistently as the running engine.

How many terminals does your fuel injection relay have?


__________________________________________________
1995 K75 81,000 miles
[solved]k75 Strange starting problem Usa-lo10
    

42Back to top Go down   [solved]k75 Strange starting problem Empty Strange starting problem Fri Nov 19, 2021 9:21 pm

daveyson

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Righto, so the fuel pressure isn't too high or too low, but just about right. 

So maybe another thing to look at is the Voltage drop suggestions again.


__________________________________________________
11/1985 bmw k100rt (late model)  Vin. 0090567
 ~120,000 km
    

Arlina

Arlina
Moderator
Moderator
@costellon wrote:Thanks for the prompt post.

The injectors pulse when hooked up to the bike and the pump only kicks in when the button is pressed - as I mentioned in a previous post - the pump seems to run-on fractionally longer after I remove my finger from the button than any of my previous K's pumps did.

Question: Seeing as I have zero psi pressure coming from the return pipe on the fuel pressure regulator (although it is returning fuel to the tank but at a pressure that doesnt register on my pressure gauge) - does that not indicate a buggered regulator ? What PSI should the return pipe run at ? The pipe is not kinked or trapped.

Cheers

That's good, pump should run short with the starterbutton.

The returnline suppose to have zero pressure, it's a return, nothing holds the fuel back Smile


__________________________________________________
[solved]k75 Strange starting problem Eu-log10  K1100RS/LT - R1200RT - R1100RS (RIP) - Cagiva SST 350 Ala Verde - K75LT project - K75 Schurgers - K75S
    

costellon

costellon
active member
active member
Greetings.

Martin & Olaf: - conducted a test on the temp sensor - using an analogue meat thermometer and a dodgy laser gun. I added my results as red dots over the image kindly provided by Martin. The curve correlates but the results are different .... Knackered ?
The only alphanumerics I can see on the sensor sensor are "Bosch 050 L 369. Yet again I tested continuity on, sensor to pin 10 on computer, sensor to pin E on temp relay, pin 9 on temp relay to fuse 6, fuse 6 to block connector on fuel tank etc ... I can't remember if my past K75 temp lights came on with the oil and battery lights when turning on the ignition - mine doesnt - but it tests fine by earthing pin A3 on the temp relay or by jumping Pin A2 to 31 on the temp relay.

Cheers

[solved]k75 Strange starting problem K100_t10

Daveyson: Hopefully i'll get time on Tuesday to check the voltage drop again.
Cheers

Laitch: My Fuel injection relay has five terminals, I exchanged with my mate for the unit from his running K100 - same oem relay - but same result for me unfortunately, tea, waterfall - even nano fish - but no vroom vroom.
Cheers

Arlina: The pump runs on after the starter button - but it seems to run on for just a little bit longer than my other past K pumps.

I have another temp sensor - i'll run another test hopefully on Tuesday.

Thanks again to all, much obliged

    

MartinW

MartinW
Life time member
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It's possible that depending on it's quality the meat thermometer could be slightly out. How does the temperature readings compare between the digital and the meat thermometer.
Regards Martin.


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K75s Hybrid
    

costellon

costellon
active member
active member
Ahm - I was right to read the resistance across the two connector pins ? Thats what I did. I used 3 different thermometers in total - one of which was very accurate under 50* - and used the mean above 50* - with crossreferences from the gun. At shed temperature - the sensor is reading 7780 @ 11*c


[solved]k75 Strange starting problem Press_10

Thanks again

    

MartinW

MartinW
Life time member
Life time member
The readings are supposed to be taken between one of the pins and earth. That is why it is important not to use thread tape or sealant to insure correct function.
Regards Martin.


__________________________________________________
K75s Hybrid
    

costellon

costellon
active member
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Duh! Well that was 4 hours of my life that i'll never get back - but now I know.
Edit: Currently reading 2500 @ 24*c - corresponds nicely with the graph of values.
cheers



Last edited by costellon on Sun Nov 21, 2021 8:12 pm; edited 1 time in total

    

MartinW

MartinW
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I have both in stock and they are identical to look at. The 8v one should have identical or near identical Ohms readings between either pin and earthing on the body. The 16v one no reading between the either pins and the body.
Regards Martin.


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K75s Hybrid
    

MartinW

MartinW
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Life time member
The reason I have a 16v one is I ordered one advertised as BMW K75 off Aliexpress. When tested it was incorrect and was for a 16v. I sent them an email and the kindly sent me another 16v one which I gave to a mate and kept one as a comparison.
Regards Martin.


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K75s Hybrid
    

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