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1Back to top Go down   Starting problems 86 k100 8v Empty Starting problems 86 k100 8v on Sun Dec 20, 2020 12:27 pm

bigminiandy

bigminiandy
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Hi all. I’ve been scratching my head over this so hoping somebody might be able to help.
Last time my K100 ran it started and ran perfectly but now doesn’t want to start, other than the fact it was hammering down with rain there was nothing unusual about its last ride.
The bike has spark on all four cylinders, there’s good compression on all cylinders and the injectors are working and spraying nicely. There’s plenty of fresh fuel in the tank and I’ve checked there’s no water in the fuel given how hard it was raining. The engine doesn’t want to run but makes some enormous bangs and has created some incredible flames!
As the bike was ticking over nicely when I arrived back from its last ride I can’t foresee any engine timing issues but I have already done the following: changed the fuel pump for a new one along with a new fuel filter, fuel hoses and fuel regulator. I’ve also replaced the water temperature sensor, changed the ecu under the seat and the air flow meter in the air box. The battery is in great condition and I have a spare which I’ve tried for the sake of it too.
After cranking over for a while I get fuel dripping from the joints in the exhaust - guess this is the cause of the big blue flames! If I unplug the fuel tank/pump the bike makes a small attempt to run but very quickly goes back to popping and banging but no running..... any ideas?

    

2Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sun Dec 20, 2020 2:24 pm

MartinW

MartinW
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It looks like you are over fueling, you need to check the temperature sensor connector at the sensor and at the computer. There is also another connector under the fuel tank which is often overlooked. There are posts on how to check this. It is also important not to use thread tape or sealant on the sensor threads, it seals with the washer on the sensor body. Using sealant or tape can stop the sensor from earthing.
Regards Martin. santa rendeer


__________________________________________________
K75s Hybrid
    

3Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sun Dec 20, 2020 3:06 pm

Point-Seven-five

Point-Seven-five
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There is a check valve in the return line fitting on the fuel tank. There is a chance that it is stuck closed and preventing the fuel bled off by the pressure regulator from flowing back to the tank. This will cause a very high pressure in the injector rail and too much fuel being injected.

A quick way to check it is to disconnect the return line from the tank and add a few feet to it so you can stick it in the filler opening. This will bypass the check valve. Then try starting the engine. If it starts and runs, the check valve is the problem. Fortunately, it can be removed and cleaned, or you can replace it fairly inexpensively(in the U.S. it's less than $10).


__________________________________________________
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
    

4Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sun Dec 20, 2020 3:58 pm

bigminiandy

bigminiandy
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Hi. I forgot to mention that I’ve already tried this but has the same result.

    

5Back to top Go down   Starting problems 86 k100 8v Empty No go on Sun Dec 20, 2020 4:03 pm

daveyson

daveyson
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The fuel should be pulsing, not constant. With a screw driver between an injector and your ear, you should hear a tick, tick, tick, while cranking.


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

6Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sun Dec 20, 2020 4:27 pm

Laitch

Laitch
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Have you tested the ignition control unit using the steps in the Portal's troubleshooting guide, or cleaned its plug's contacts, reinserted it firmly then tried restarting the engine?



Last edited by Laitch on Sun Dec 20, 2020 4:36 pm; edited 1 time in total


__________________________________________________
1995 K75 81,000 miles
Starting problems 86 k100 8v Usa-lo10
    

7Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sun Dec 20, 2020 4:31 pm

Point-Seven-five

Point-Seven-five
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Are the ignition coils bone dry?  I'm not sure, but your bike may have the early version coils that were replaced sometime around '86 or '87.  These early coils have been known to fail relatively often.  One of the failure modes is a weak spark that will work when the plug is out of the engine, but not under the pressure in the cylinder at the top of the compression stroke when it's needed to ignite the fuel.  Any moisture on the coil will make this loss of spark more likely to occur.

Another long shot is the spark plug wires.  Others have been known to mix up the wires for cylinders #3 & #4.  If you have factory wires, check the numbers on them and the cylinders they are connected to.

Ignition problems on the k100 usually result on the engine running on only two cylinders when it does run.  When you unplugged the tank and the engine ran, was it running on all four cylinders?  

When starting, you aren't opening the throttle, are you.  The fuel injection on these bikes can easily flood the engine if the throttle is opened before it's running.  If that is the case, unplugging the tank and cranking the engine to blow out the excess fuel can help the engine start.


__________________________________________________
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
    

8Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sun Dec 20, 2020 5:11 pm

bigminiandy

bigminiandy
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@daveyson wrote:The fuel should be pulsing, not constant. With a screw driver between an injector and your ear, you should hear a tick, tick, tick, while cranking.
The injectors are working as they should having tested them into a container

    

9Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sun Dec 20, 2020 5:12 pm

bigminiandy

bigminiandy
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@Laitch wrote:Have you tested the ignition control unit using the steps in the Portal's troubleshooting guide, or cleaned its plug's contacts, reinserted it firmly then tried restarting the engine?
is this the computer under the tank? If so I’ve tried a donor one and cleaned all the contacts which made no difference.

    

10Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sun Dec 20, 2020 5:18 pm

bigminiandy

bigminiandy
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@Point-Seven-five wrote:Are the ignition coils bone dry?  I'm not sure, but your bike may have the early version coils that were replaced sometime around '86 or '87.  These early coils have been known to fail relatively often.  One of the failure modes is a weak spark that will work when the plug is out of the engine, but not under the pressure in the cylinder at the top of the compression stroke when it's needed to ignite the fuel.  Any moisture on the coil will make this loss of spark more likely to occur.

Another long shot is the spark plug wires.  Others have been known to mix up the wires for cylinders #3 & #4.  If you have factory wires, check the numbers on them and the cylinders they are connected to.

Ignition problems on the k100 usually result on the engine running on only two cylinders when it does run.  When you unplugged the tank and the engine ran, was it running on all four cylinders?  

When starting, you aren't opening the throttle, are you.  The fuel injection on these bikes can easily flood the engine if the throttle is opened before it's running.  If that is the case, unplugging the tank and cranking the engine to blow out the excess fuel can help the engine start.

The coils I believe are sound. They other a very strong spark when testing the plugs against the block. When/if it starts when the tank is unplugged it runs on all four.
The leads are in the correct order.
No throttle is used when trying to start like you say I know it doesn’t like. Even with the throttle closed fuel starts dripping from the exhaust pretty quickly followed but some bog shotgun style bangs and blue 2ft flames. Goes to show it’s got a spark I guess

    

11Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sun Dec 20, 2020 5:19 pm

bigminiandy

bigminiandy
active member
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@Point-Seven-five wrote:Are the ignition coils bone dry?  I'm not sure, but your bike may have the early version coils that were replaced sometime around '86 or '87.  These early coils have been known to fail relatively often.  One of the failure modes is a weak spark that will work when the plug is out of the engine, but not under the pressure in the cylinder at the top of the compression stroke when it's needed to ignite the fuel.  Any moisture on the coil will make this loss of spark more likely to occur.

Another long shot is the spark plug wires.  Others have been known to mix up the wires for cylinders #3 & #4.  If you have factory wires, check the numbers on them and the cylinders they are connected to.

Ignition problems on the k100 usually result on the engine running on only two cylinders when it does run.  When you unplugged the tank and the engine ran, was it running on all four cylinders?  

When starting, you aren't opening the throttle, are you.  The fuel injection on these bikes can easily flood the engine if the throttle is opened before it's running.  If that is the case, unplugging the tank and cranking the engine to blow out the excess fuel can help the engine start.

The coils I believe are sound. They offer a very strong spark when testing the plugs against the block. When/if it starts when the tank is unplugged it runs on all four.
The leads are in the correct order.
No throttle is used when trying to start like you say I know it doesn’t like. Even with the throttle closed fuel starts dripping from the exhaust pretty quickly followed but some bog shotgun style bangs and blue 2ft flames. Goes to show it’s got a spark I guess

    

12Back to top Go down   Starting problems 86 k100 8v Empty No go on Sun Dec 20, 2020 5:27 pm

daveyson

daveyson
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Clean and dry your battery and brick.

I had an overfueling problem once, so it wouldn't start at idle speed, but it did start at revs because at revs it needs a high fuel flow.

If throttle isn't the cause of flooding, but helps with starting, that might show that flooding is the problem.



Last edited by daveyson on Mon Dec 21, 2020 2:45 pm; edited 1 time in total


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

13Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sun Dec 20, 2020 5:46 pm

Laitch

Laitch
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@bigminiandy wrote:. . . there’s good compression . . . There’s plenty of fresh fuel . . .  changed the fuel pump . . . a new fuel filter, fuel hoses and fuel regulator . . . replaced the water temperature sensor, changed the ecu . . . and the air flow meter. The battery is in great condition . . . The coils I believe are sound . . .The leads are in the correct order . . .  the computer . . . I’ve tried a donor one and cleaned all the contacts . . .The injectors are working as they should having tested them into a container . . .
We're approaching ancestral curse territory now. Have you done a thorough geneology?


__________________________________________________
1995 K75 81,000 miles
Starting problems 86 k100 8v Usa-lo10
    

14Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sun Dec 20, 2020 5:55 pm

Point-Seven-five

Point-Seven-five
Life time member
Life time member
A coil with failing insulation will spark when the plug is out, but can have problems with voltage leakage if it is wet and trying to fire into the high pressure in the cylinder. It's the one part of the equation that can sometimes look good when you test it, but not when you try to start the engine. A failure to ignite the fuel on the first couple compression strokes will soak the plug tip, and then it will be very hard to get a good spark.

You don't mention changing the spark plugs. How old are they? Make sure the gap hasn't opened up. Reset the gap to spec or even a little less. That will reduce the amount of voltage needed to spark.

You mention the heavy rain. I would try to do a thorough drying of the coils. Pull the wires off and hit the plugs and the terminals with a hair dryer. Clean any dirt on them as well. You want them spotlessy clean and dry.

If you have access to replacement coils, it might be worthwhile to try swapping them.




__________________________________________________
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
    

15Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sun Dec 20, 2020 6:18 pm

bigminiandy

bigminiandy
active member
active member
@Point-Seven-five wrote:A coil with failing insulation will spark when the plug is out, but can have problems with voltage leakage if it is wet and trying to fire into the high pressure in the cylinder. It's the one part of the equation that can sometimes look good when you test it, but not when you try to start the engine. A failure to ignite the fuel on the first couple compression strokes will soak the plug tip, and then it will be very hard to get a good spark.

You don't mention changing the spark plugs. How old are they? Make sure the gap hasn't opened up. Reset the gap to spec or even a little less. That will reduce the amount of voltage needed to spark.

You mention the heavy rain. I would try to do a thorough drying of the coils. Pull the wires off and hit the plugs and the terminals with a hair dryer. Clean any dirt on them as well. You want them spotlessy clean and dry.

If you have access to replacement coils, it might be worthwhile to try swapping them.




The spark plugs are brand new and gapped correctly. I have those flashing caps fitted between the ht lead and the plug for testing so know the plug is getting the power but I haven’t got a donor set of coils to test with unfortunately.
The last time it was rode was back in May so whilst it was very wet at the time it’s had plenty of time to dry out as it’s kept in a heated garage.

    

16Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sun Dec 20, 2020 6:31 pm

bigminiandy

bigminiandy
active member
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@MartinW wrote:It looks like you are over fueling, you need to check the temperature sensor connector at the sensor and at the computer. There is also another connector under the fuel tank which is often overlooked. There are posts on how to check this. It is also important not to use thread tape or sealant on the sensor threads, it seals with the washer on the sensor body. Using sealant or tape can stop the sensor from earthing.
Regards Martin. santa rendeer

I’ve replaced the sender and checked the wiring. To be honest I can’t remember if I used PTFE tape of not as it was a few months ago. It’s easy enough to test tho, guess I could temporarily earth the sensor to the block with a carefully placed piece of wire 🤔

    

17Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sun Dec 20, 2020 6:34 pm

bigminiandy

bigminiandy
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@Laitch wrote:
@bigminiandy wrote:. . . there’s good compression . . . There’s plenty of fresh fuel . . .  changed the fuel pump . . . a new fuel filter, fuel hoses and fuel regulator . . . replaced the water temperature sensor, changed the ecu . . . and the air flow meter. The battery is in great condition . . . The coils I believe are sound . . .The leads are in the correct order . . .  the computer . . . I’ve tried a donor one and cleaned all the contacts . . .The injectors are working as they should having tested them into a container . . .
We're approaching ancestral curse territory now. Have you done a thorough geneology?

Yup, I agreed it seems cursed. I’ve tried everything I can think of over the last few months, I'm hoping somebody will pop up and say have you tried......

    

18Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sun Dec 20, 2020 7:44 pm

Laitch

Laitch
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@bigminiandy wrote:Yup, I agreed it seems cursed.
I was implying that you might be cursed but you've raised an interesting point. Perhaps you should replace it with a Moto Guzzi and see how that goes.

You believe the coils are sound. Does that mean you've tested their resistance, or looked for sparking around them and their wires by running the starter in darkness?


__________________________________________________
1995 K75 81,000 miles
Starting problems 86 k100 8v Usa-lo10
    

19Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Mon Dec 21, 2020 12:00 am

RicK G

RicK G
admin
admin
The K100 coils especially the old black/dark grey ones are a big problem. I have only ever seen one set that was truly good and tested perfectly.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki
    

20Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Mon Dec 21, 2020 5:21 am

92KK 84WW Olaf

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I have had that coils issue and everything 'looked' good but not the case. No arcing or sparking along the coil, but definitely a sparking issue under compression.

Having more Ks a change of coils took place, sure enough one dodgy one. 

Rain does not really access any of the places that can kill a K engine except for the Hall sensor cover if the gasket is not good. 

Testing components is fine too BUT is does not necessarily identify if a corroded or poor connection to or from it is the issue.

Plug bobbins ok too?


__________________________________________________
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 37,190 miles
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles.
    

21Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Mon Dec 21, 2020 6:13 am

bigminiandy

bigminiandy
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Yes I’ve tested the coils, couldn’t tell you what the results were as it was a couple of months ago and I’m not at home to retest them plus my memory has slipped. I remember the results were the same for both coils and guessed that both wouldn’t have failed/deteriorated to exactly the same level at the same time so they must be good! However I’ll be very happy if I’m proven wrong. I’ll find some donors and report back. For the info they are grey in colour so guessing they could be the originals.

    

22Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Mon Dec 28, 2020 2:22 am

Lucky

Lucky
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Sounds like a problem I had a couple years ago. I had fuel dripping from the exhaust pipe after only a few attempts at starting, banging etc. Too much fuel for the amount of starts I attempted. Had me scratching my head for a while. I went through all the usual suspects such as temp sensor, fuel pressure regulator etc etc. I checked the injectors and they 'appeared' to be working fine. Upon closer inspection I realized it was more of a constant spray than a pulse. (I can't remember exactly but I have a feeling only one of the injectors was not pulsing. It was open constantly. Letting way too much fuel through the injector). Luckily a mate of mine recently acquired a K so I  borrowed his ECU and plugged it in. My bike started almost straight away. I subsequently bought another ECU and all has been good ever since. 

I realize that you stated that you changed your ECU already. I would have put money on it that it was your ECU that was the problem but it appears it may not be.... 
Maybe try another? Very quick and easy to try if you know somebody with one that you can borrow to try from a working bike.  

For fuel to be dripping out of the exhaust, something is allowing an injector or injectors to stay open longer than necessary and let way too much fuel through. A lot of fuel. Maybe try pulling injectors out while still attached to the rail and note how much fuel is coming out of each one. Should be a fine mist not a long heavy spray. Are they putting out the same amount of fuel? That's what I noted on mine anyway....

Other than that, I have no idea for a fix but the problem seems very familiar to what I experienced. 

Hope you find the problem and I'd like to hear of the fix out of curiosity.

    

23Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Mon Dec 28, 2020 12:07 pm

bigminiandy

bigminiandy
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I’ve replaced the coils and have exactly the same problem - no change.

    

24Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sat Jan 02, 2021 12:43 am

JSFR80

JSFR80
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I had the same problem on my K75. It turned out to be a faulty fuel injection computer. You say you changed the ECU. Do you mean the one under the tank for the ignition or the FI computer on top of the battery? You might also try pulling the fuse for the fuel pump and if the bike starts quickly put the fuse back in.

    

25Back to top Go down   Starting problems 86 k100 8v Empty No go on Sat Jan 02, 2021 1:08 am

daveyson

daveyson
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Jsfr80

If you still have your faulty computer don't throw it away. Believe it or not, with the help of riders on this forum you might be able to fix it.

Bigminiandy

I can't seem to tell from your replies how much fuel is being supplied. My money would be on Martin's suggestion about tape on the temperature sensor.

There are quite a few other causes of overfueling not mentioned yet. A quick easy test is to listen for a ticking sound from an injector while cranking.

If you hear it ticking, ignore my post. If it doesn't tick, you might for example have an injector earth wire earthing out, causing overfueling. I know that sounds weird, an earth wire earthing, but I've had that problem. In this case the problem would remain, even after replacing the fuel injection computer.


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

26Back to top Go down   Starting problems 86 k100 8v Empty Re: Starting problems 86 k100 8v on Sat Jan 02, 2021 6:29 am

nino

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Did you remove tank recently. Last time I had same symptom I broke brown ground wire under the tank. Didnt notice that. Its only one wire and check it carefully. After quick connect bike started as usual even it was flooded with gasoline.
Best regards

    

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