The bike originally would not start. If I cranked it for a long period sometimes I could get it running. I put in new spark plugs, new injectors.  I have a couple of FI computers and a spare Ignition module that I have tried to no avail.  I followed your testing procedure in CrazyFrog's  article(test at the pins)  with these modules and found nothing wrong with the voltages.  I thought It could be out of time, and put in a new hall effect sensor, again nothing. ( I used your procedure for testing with a diode- tested at the connector).  When I try to start the bike, it doesn't  seem to start up  at a fast idle  even with the choke set to fast. The spark  plugs and injectors seem to be working - with the injectors I tested them with a noid light and with the spark plugs I used tester lights. I tested the FI relay and it seemed to be OK.  The spark plugs and injectors seem to be working which would indicate the FI relay is working. I did replace the FI relay with another one. Also, I cleaned the throttle bodies.
Everything I have tried to get the bike started has not worked. 

I have been trying to get the bike started all winter and have run out of options to try. This is something simple that I am overlooking, or I need a test procedure to test a "no start".

Any help would be appreciated!

Hi there, I would check the gas pump and filter, air leaks and the MAF.
Best regards
JAP

Greetings Maibsassy (what a mouthful in such a short word)   welcome to the forum.  
May be best to copy the post to a post in the appropriate heading as these types of threads tend to get very long and its not a good place to have them in the intro section.
However, sounds like maybe a stale fuel problem, first if you have not already done it remove all the fuel and replace with a litre or too of fresh then with the ignition on press the starter a few times to flush the injectors drain again and replace with fresh fuel, as much as you wish
I am presuming this is an 8 valve K100 or K75.
If that doesn't work get the injectors serviced. Mr Injector has a good reputation and good turnaround.  They could be just dribbling instead of a fine spray and when cold all the dribble does is put the fire out. Well sort off.

Check the electrical  connection into the gas tank. if you have the 4 way plug that connects in at the front left underneath it will cause this if the connectors are not making proper contact. You can use a small precision screwdriver to open the male pins  to make a better connection. After that follow the advice about gas pump and the filter and in tank fuel lines. Your mentions all the checks on the ignition system but not the for the fuel pump connection.

Tell us what you hear when you press the start button very shortly (normally the bike doesn't start, but you should be able to hear the fuel pump making a short run) and when you press it longer (If you hear a whine, but the bike doesn't start the starter clutch is suspect).

And put your bike details in your signature so we don't need to guess what it is :-)

Here is a simple question: Is the engine flooded after you try starting it?
If not, gas may not reach the cylinders. I maybe a problem with the fuel pressure regulator....
If the fuel pressure regulator is stocked open, you won't get any pressure in the cylinders.
If it's stocked close, your pressure will be twice what it should be and the engine will be flooded.

At this point, a fuel pressure test maybe the best way to go.

CF

1.The gas connection at tank is ok.
2. Injectors are new.
3.a fuel pressure tester is connected to the fuel tank, pressure is 35 psi
4. when I press the starter button on this bike, (early 1985 K100) the fuel pump
does NOT run for 1 sec to pressurize the fuel system. I have talked to a couple of people
and they said it doesn’t on this year??  I don’t know anything about the starter clutch, but
the bike seems to turn over.

On 2V K bikes (like yours) the fuel pump only runs when the engine is turning - when starting or running. Put your ear to the left side of the tank while pressing the starter button to turn the motor.  You should hear the fuel pump "whining."

As Duck says. If you just hit the starter the pump whine should be heard, but the bike won't start. Who said the pump had to run for a second? So did you try it are are you trying to be argumentative? ;-)

maibsassy wrote:1.The gas connection at tank is ok.
2. Injectors are new.
3.a fuel pressure tester is connected to the fuel tank, pressure is 35 psi
4. when I press the starter button on this bike, (early 1985 K100) the fuel pump
does NOT run for 1 sec to pressurize the fuel system. I have talked to a couple of people
and they said it doesn’t on this year??  I don’t know anything about the starter clutch, but
the bike seems to turn over.

As Duck said the fuel pump will run for 1.5 seconds when you touch the start button even if the engine is not turning. The ignition control unit (ICU) monitors the pulses from the sensors and if there are no pulses it continues to run for 1.5 seconds and then stops.
Lift the fuel tank cap and look inside as you press the start button you should see fuel flowing around unless the tank is brim full and you will hear the whir of the pump.
The couple of people you talked to apparently don't know as much about K bikes as they think.

I put in new fuel, but this didn't help

I did get the bike to start after cranking for a long while. The bike engine won't start in a fast idle even with the choke on. I've adjusted the choke, but this doesn't increase the fast idle speed. The bike only starts up at about 400-600 rpm, and when it is cold outside this isn't fast enough to start.

Also, when it was running white smoke was pouring out of the  exhaust.

Have you run the check on the fuel pump as Rick G has recommended? That is step 1.

maibsassy wrote:Also, when it was running white smoke was pouring out of the  exhaust.

Hmm...that could be cooling leaking into the combustion chambers, from (possibly):
- cracked or warped cylinder head
- cracked engine block 
- head gasket failure caused by overheating.

Wow, easy now..... :-)

Mostly white smoke comes from leaving the bike on the side stand or overfilling the crankcase, let's not get too 'dark' too soon.

This is sounding more and more that the fuel pump isn't running for some reason because a K will idle without the fuel pump going (when it is hot) as the vacuum is enough to draw some fuel through the injectors when they open and it sounds to me that it is trying to run but because its cold can't get enough fuel.
Quick fuel pump test is to remove the fuel filler and surround remove the line from the pump top to the filter at the filter then with your hand inside the tank and thumb over the end of the line turn on the ignition and touch the starter button, you should have a very difficult time stopping the fuel flow (don't let it spray out of the tank) then with the line facing into the tank press the starter again and you should get a really good flow of fuel. Not quite as strong as a garden hose but akin to that. If you don't get both of those then the pump is very worthy of a much closer inspection and will probably be cactus. If the pump does not run at all check the electrical connections. It is also possible to get a piece of foreign matter wedged in the pump which will stop it turning (8 microns will kill a rotor cell pump). Run the pump backwards by reversing the connections briefly and that may dislodge anything that is preventing it from running. Take care not to cause any sparks as we don't do rescue missions to the darkside of the moon.

RicK G wrote:
Quick fuel pump test is to remove the fuel filler and surround remove the line from the pump top to the filter at the filter then with your hand inside the tank and thumb over the end of the line turn on the ignition and touch the starter button, you should have a very difficult time stopping the fuel flow (don't let it spray out of the tank) then with the line facing into the tank press the starter again and you should get a really good flow of fuel. Take care not to cause any sparks as we don't do rescue missions to the darkside of the moon.

What Rick means is open your fuel cap and remove the 4 screws marked #9 in the first diagram. Then lift off the whole filler cap and base. It will come off in one piece (not like the picture).



Then undo the clamp on hose #8 where it connects to filter #10. This is done inside the tank unless the hoses are really long.
Hold your thumb over the end of hose #8 and hit the starter. Lots of pressure?
Keep the hose in the tank and with your thumb off the hose hit the starter again. Garden hose?



Sorry to steal your post Rick. I like pictures. And it is Friday and I am at work and bored.

And it is Friday and I am at work and bored.

I will tell your boss what's his number?

RicK G wrote:And it is Friday and I am at work and bored.

I will tell your boss what's his number?

07 4683...... 

Awwww He must live near me 

ReneZ wrote:Wow, easy now..... :-)

Mostly white smoke comes from leaving the bike on the side stand or overfilling the crankcase, let's not get too 'dark' too soon.

True. Being dramatic...

The fuel pump pressure is 35 psi, gauge is connected to the fuel lines. No white smoke.

The bike started today but still doesn't start up in a fast idle with the choke lever on. Tried adjusting the cable at the throttle and will test
the bike tomorrow after it cools down.

I moved the hall effect sensor plate clockwise(facing the bike) and this seemed to help starting the bike(timing is probably too far advanced); the manual says the base timing is 8 degrees BTDC and was wondering how you would determine this.

The hall sensor plate should be positioned like this and .5mm is very close to 1° on the outer rim of the plate

Hi, why don't you buy or download the BMW manual? Everything is explained with good pictures and it will save you lots of money by better understanding how the bike works and where to look when you have an issue. You checked that the 'choke' cable is properly adjusted?
BTW IIRC I thought the advance was 6 degrees originally.

hi. i had a no start problem a while ago. it was the fuel sensor which is in the tank. im told the plate corrodes and then the fuel pump ground wire does not earth properly. i replaced this part. problem solved.good luck

The fuel sensor in this bike is an electronic sensor.  BMW doesn't  make this part any more. Bought a a couple of used ones that seem to work.  You're correct that this was part of the problem about the ground not working.

I have a Clymer and Haynes service manual. In adjusting the Hall Effect sensor both manuals are not very clear as to what to do and the diagrams always don't correspond to the bike. In the Clymer manual the engine must be sitting on one end, not as if it is in the bike.
What manuals are you referring to? Is there an electrical manual ? Where can you download a manual, the one I saw was in Italian.

There is a rough adjustment where you make sure the cut-out in the sensor plate corresponds with the cut-out in the housing. That normally gets you a running bike. The correct way to adjust it is with a measurement tool through the spark plug hole of unit No.1, where you then check if a led of a tool you connect to the sensor lights at the right distance before the piston is in TDC.
When the moderator gives you access to the download page the official BMW repair manual is there and shows it all.

Do you think this is too far advanced or retarded?

Pocket light, anyone? ....it looks to far advanced.

I've got the same darn problem. been trying to get the thing started for weeks. have replaced quite a few parts, checked and rechecked all sensors, rebuilt the throttle bodies. 2 days ago the thing was running like a top. used a timing light to set the idle timing to the little notch on the spinning disk and watched it advance when revved up. never sounded so good. my hall plate looked too advanced like the picture a few posts back, but can't argue with a timing light (which I have been using for 40 years). next day, no workie. The intermittancy of it all is chapping my soul. will install replacement ignition and EFI modules when they arrive from ebay...probably start replacing wires soon. fuel pressure good, new gas, new plugs, all firing. WTF?

maibsassy wrote:Do you think this is too far advanced or retarded?

Post 22 shows how the half moon cutaway should be aligned with the v shaped cutout on the plate. If you do that it will be within 1-2° of correct

jeffeaby wrote:I've got the same darn problem. been trying to get the thing started for weeks. have replaced quite a few parts, checked and rechecked all sensors, rebuilt the throttle bodies. 2 days ago the thing was running like a top. used a timing light to set the idle timing to the little notch on the spinning disk and watched it advance when revved up. never sounded so good. my hall plate looked too advanced like the picture a few posts back, but can't argue with a timing light (which I have been using for 40 years). next day, no workie. The intermittancy of it all is chapping my soul. will install replacement ignition and EFI modules when they arrive from ebay...probably start replacing wires soon. fuel pressure good, new gas, new plugs, all firing. WTF?

Go to the portal page and follow the link to a troubleshooting guide to ignition flo chart.
Throwing components at it is a waste of time and quite likely money.  Also check out my previous post

I have been using that troubleshooting guide for quite some time...it is a great guide. I've just always valued a timing light over a diode tester since it's running at engine speed and also checks for spark.

The mark you are using to set the timing is a TDC mark not a timing mark and is used as the reference when using a dial gauge to set the timing. The only really accurate way to set the timing is to use a dial gauge and a LED to check when the hall sensors switch and the setting is 0.24mm BTDC.
As I said previously align the cutouts and the timing will be in a useable position. All I ever do is scribe a line and reinstall to that mark and I have never seen a K that is anything more than 0.5mm out on the cutouts when at 6° BTDC

Same here, agree with Rick. Rarely do you find or get to a set-up that's not very closely aligned with the cut-outs. Don't forget that there's electronic advance dependent on the revs as calculated by the ECU.

The bike will start only with the Throttle full open. If the the throttle is closed  the bike will not start.
The spark plugs are all firing. The full pressure is 35 psi. The fuel injectors are new. I set the timing plate back to where it is in alignment
with the slot.This is a new problem that has occurred after the bike wasn't started for a few days.
Also, there is slight back-firing if I do get the bike started.

Also, when I first tried starting the bike the 2nd from the bottom fuse blew and the fuel pump didn't run. Replaced fuse and the fuel is working.

I would suggest that you check the resistance through the coolant sensor.

Measure it at the Jetronic multiconnector, how to.......you find info about this in the troubleshooting guide at the portal...and heaps of posts if you use the search function.


Some info you find in this thread.

final report...replaced the EFI computer and back in business. I was mistakenly using the 2nd notch in the timing plate to set the timing with a strobe. that 2nd notch denotes max advance, about 28 BTC. moved it back to the forward edge of the TDC notch and all is well. used the #1 piston movement method and built a LED indicator box ala mr. crazy frog's troubleshooting writeup. The bike has never run this good and cranks on the first turn of the starter. hoping for another 70K miles.

Great to hear that the bike is running well. Good job.

Do you think the timing was the issue or the swapped-out EFI computer?

Would it be worth the trouble to put the old EFI computer back to see if the bike runs? If it does, then you have a spare.

My 2 cents worth.