sweet!

I see that few of us have the same musical taste.
I just spent 1 hour on Youtube looking a videos of Dire Strait and Mark Knopfler (even playing with Clapton).

How's the troubleshooting working on the K75?

alas - I am in one location - the bike is in another - and the tank in yet another!
I've been trying to rally some support all day but so far have failed. really regretting selling my truck.
I'll let you know soon tho!
thanks,
b

looks like I'm not going to get to the bike until tomorrow - will start by switching tanks/fuel pumps and see what happens - if no love then I'll have to rent a pickup, and I'll be asking for more advice!
thanks for all the help so far - VERY friendly and helpful list you guys have here. much different from the BMW-Tech mail list where I'm leery of posting anything since I always just seem to get flamed.
so hats off to you all.
b

Good luck Bob,
Let us know how you get on.
Regards,
K-BIKE

ok - so here's the update, I'm really hoping you all can help because I'm really not sure what's going on. I finally got the bike towed over to my house and did the following:

• switched out the tank with the tank from my other K75, who's pump I know is good. No dice - still NO pump noise under ANY conditions (kill ON or OFF)
  
• checked and confirmed that - with the IG ON - I get 12V at the hot wire on the 4pin plug that runs to the fuel sender unit (green/white). which means power IS getting to the pump (all my Ground connections were measured at the frame unless it was specifically stated to measure at battery).
  
• confirmed that the ground wire in the 4pin connector (brown) has continuity (0 Ohm resistance) to ground.
  

so - I have a good pump, getting power with a good ground, that isn't pumping. perhaps there is some kind of issue with the fuel system being depressurized? or does the pump need some kind of vacuum from the fuel flow regulator to operate or something?

anyway - I went back to Crazy Frog's diagnostic flow chart, and when I checked the "Ground from pin #7 of the ECU to pin #85 of the relay" I found that there was NO continuity between the two under any conditions (IG ON/Kill ON or OFF etc).
I wasn't 100% sure what "Ground from Pin... etc" meant - I assume it meant continuity between the female connector to the ECU and the female receptacle for pin #85 where the FI relay plugs in (i.e. with the FI relay removed).

this made me suspicious so I turned to Crazy Frog's ECU test table - note that all these tests were done at the female pin connector with it UNPLUGGED from the ECU*

• Pin #1 to Ground: Expected Value is ".5 max" (not sure if that's Ohms, kOhms, or mOhms); I show 8 kOhms.
  
• Pin #2 to Ground: Expected Value is 12V with IG ON; I get 12V.
  
• Pin #3 to Ground: Expected Value is 0 Ohms; I get 0 Ohms.
  
• Pin #4 to Ground: Expected Value is 0 Ohms resistance; I have INFINITE resistance - no continuity at all.
  
• SKIPPED Hall Sensor Pins #5 & #13.
  
• SKIPPED Pin #6.
  
• Pin #7 to Ground with IG ON: Expected Value is 12V; I get 0 (none).
  
• Pin #10 to Ground: Expected Value is 12V with IG ON; I get 12V.

I SKIPPED all Pin tests where starter is running - Pins #6, 7, 8, 9, 10, & 11 because I'm not sure HOW one tests the ECU connections with the starter running since as long as it's unplugged the starter won't crank.

anyway - that's where it stands for the moment... I'm not too sure I'm doing all the tests correctly, and even if I am I'm not sure how to interpret the results.
so I could sure use some help!!
thanks alot.
bennett

*this is something else I'm confused about - if these tests are all done with the ECU disconnected then it can't be the ECU I'm actually testing right? just the connections to the ECU... is there some way I'm supposed to get at the pins from the back side while the pin connector is plugged in? because I tried that and it seemed insanely difficult.

bobthebob wrote:
[*]switched out the tank with the tank from my other K75, who's pump I know is good. No dice - still NO pump noise under ANY conditions (kill ON or OFF)
[*]checked and confirmed that - with the IG ON - I get 12V at the hot wire on the 4pin plug that runs to the fuel sender unit (green/white). which means power IS getting to the pump (all my Ground connections were measured at the frame unless it was specifically stated to measure at battery).
[*]confirmed that the ground wire in the 4pin connector (brown) has continuity (0 Ohm resistance) to ground.
[/list]
so - I have a good pump, getting power with a good ground, that isn't pumping. perhaps there is some kind of issue with the fuel system being depressurized? or does the pump need some kind of vacuum from the fuel flow regulator to operate or something?

This doesn't make any sense! If you get power to the pump and it's not turning, it must be something wrong with the second pump.
Have you tried to have it running when hooked to the battery?
Remove the pump from the tank and plug it on the battery (just for 1/2 second). if it works, take 2 wires with crocodiles clips and hook the pump directly at the plug going to the tank. see it the pump is turning when hooked outside the tank (again only a short time as the pump won't be cooled down by the fuel)

I know - it's baffling... what are the odds of both pumps being bad?!? Especially since the second one was working perfectly when I pulled the trans off that bike a few months ago...

so before I pull the pump out of the tank I'm going to try just jumping the voltage from the battery straight to the tank 4pin connector and see if that happens.

question: that 4pin connector to the fuel sender unit (which connects to the pump) has 4 wires.
the green/white has power with the IG ON, the brown is the ground... so what do the other two do? I assume that at least one of them goes to the "low fuel" light yes? what does the other one do? I noticed that one of them (the white one I think) is powered when the starter is engaged...
but then again the fuel pump itself just has the two - power and ground - so maybe these other two are irrelevant.

a related question - how dangerous would it be to hook up jumpers to the fuel pump when it is still inside the tank? the power wires to the pump don't appear to be insulated - does that mean there is no danger of a spark etc?
it would be a lot easier than pulling the pump out - but explosions are... well, undesirable ;-j

thanks
bennett

also - what about these readings from the ECU pin connector:

Pin #4 to Ground: Expected Value is 0 Ohms resistance; I have INFINITE resistance - no continuity at all.
Pin #7 to Ground with IG ON: Expected Value is 12V; I get 0 (none).

could they be relevant?

bobthebob wrote:also - what about these readings from the ECU pin connector:

Pin #4 to Ground: Expected Value is 0 Ohms resistance; I have INFINITE resistance - no continuity at all.
Pin #7 to Ground with IG ON: Expected Value is 12V; I get 0 (none).

could they be relevant?

Pin #4 is the shielding for the Hall sensors
Pin #7 is providing the ground to the Fuel injection relay. If the green/white wire at the pump gets power, this proves that the FI relay is energized and its coil gets the ground from pin #7 of the ECU.

Have a look at the Interactive diagrams (ckick on the fuel pump tab).

I would not try to plug the pump with loose wires inside the tank. Remove it to test it.

ok - I hooked up some hot leads directly from the battery to the 4pin connector and my second pump is good. it whirs and turns no problem.

with the second tank tho - when I hooked up the hot leads all I got was some small <clunk> type noises and the leads kept arcing slightly at the pins... no nice whirring sound.
which leads me back to the original assumption - the fuel pump is seized!

as far as why the other pump didn't work when connected I have to try and see - it might be a bad ground or perhaps something shorted and it's not getting enough voltage under load or some such...
I'm going to start testing again after lunch.

thanks for all your patience so far.
bennett

On the K100, the 4 pins connector is a known problem. Quite often you get a bad connection between the male and female connector. To fix it, you have to pull out the individual connectors and squeeze them with a pair of pliers.

aha! that would explain alot... getting closer and closer!
really appreciate the help Crazy Frog.
especially with me being a sort of a lurker here since I don't even OWN a K100!
/=D

bennett

Unfortunately you are in the worst situation of trying to fix one problem and introducing another which just sends you round in ever decreasing circles.....

The important thing is to stay on one theory until absolutely proven otherwise. I know easier said than done.

As for being a lurker we will just have to accept you as a K100 owner with one cylinder fallen off.

bobthebob wrote:
With me being a sort of a lurker here since I don't even OWN a K100!
bennett

I don't think you are a lurker... lets say that you are a biker riding a K!
Even if you were riding a Russian bike, if we could help you we would.
One day, I stop to help a biker stranded on the side of the road (he was riding a Honda CBX)
He told me that he was very surprised that a "BMW guy" would stop to help a rice cooker rider. It turned out that this rider was the owner of the biggest Japanese bikes dealer in my area. Hey, if I ever need a service, I hope he will return the favor!
If I wave at you when riding, I will also provide assistance if you are in need.
Don't be shy, you are part of the family and like another member said part of the band of brothers (Thanks to finally_A_K for this appropriate remark!)
Here, we don't flame! This is against our code of ethic. We accept everybody wanting to be "a good brother (in law)". As such, we can argue but always respect each others.
Enough about this, go back to your troubleshooting (your slacking off!)

And if you think you have a lot of problems, what do you think of this?

despair.
I don't know what is going on...
Because I found that I can attach hot leads directly to the 4pin connector to the pump and hear it spin I figured I'd try and 'hot-start' the bike like that just to see if I could get it to turn over.
so I ran the hot leads (pos->gr/w and neg->brown) got the pump spinning and then proceeded to hit the starter and see if I could get the bike to at least burp... no dice.
the battery was pretty low at this point but there was enough at first for a few healthy cranks.
I'm charging up the battery now so perhaps that will solve things.

nonetheless I still can't figure out why I can read voltage at the pin connector but still can't get the pump to spin (without hot-wiring it)!

could it possibly be caused by a poor connection - one that reads 12V but 'under load' doesn't deliver enough current to the pump?

also - I'm curious, what keeps the fuel pump powered after the engine is running and the starter button is no longer being pressed?

I'm ready to tear my hair out at this point. anyone live in the SF area?
I'm willing to buy a case of good beer!

Bennett,

You wrote:
"ok - I hooked up some hot leads directly from the battery to the 4pin connector and my second pump is good. it whirs and turns no problem.
with the second tank tho - when I hooked up the hot leads all I got was some small <clunk> type noises and the leads kept arcing slightly at the pins... no nice whirring sound.
which leads me back to the original assumption - the fuel pump is seized!"
Is that the original pump that was seized when the bike quited?

The power to the pump comes from the FI relay. It is a simple circuit.
The coil of the FI relay is energized by the ICU and the emergency cut off switch.
If the relay is energized but you don't get enough power at the pump connector, here is few possibilities:
- bad FI relay
- bad ground at the pump
- bad positive connection from the battery (Red)
- bad wire coming from the relay and going to the pump (Green/red)
- bad wiring inside the tank.
Have you tried to replace the fuel injection relay?

Since you burned fuse #6 , I tend to think that you may have a problem in your wiring loom or the internal wiring of the pump. If the pump was seized, the wire in the loom may have overheated and be damaged OR the contact of the relay may have burn.
Do you have a spare relay?

I agree it sounds like a FI relay problem - but I replaced the relay with one from my other K and measured voltage to the Green/Red wire coming off the relay (measured at the fuse block).

I'm going to go back through the electrics today and see if I can track anything down.

BUT STILL - why wouldn't the bike start with the fuel pump 'hot-wired' and spinning?!?
there must be something else going on now. maybe I messed something up while I was working by the side of the road.
I'll have to check for spark again and see what's going on.
But still - the pump isn't spinning...

ahhhhhh!!! my HEAD is spinning. =((

still - I could have real problems like the guys in the picture.

I don't know if this helps but I had similar problems so first checked
the fuel injector electric leads with a diode when cranking, they all worked, then removed the injector rail and cranked it (BEWARE FUEL Spits out) found 3 of 4 not working. I had them ultra sound cleaned and it started after 2 goes. Of course you then find something else wrong, like black smoke. The clean cost me $160.00
but was worth it to find out.
Cheers RT.

Hello all - after walking away from my bike for a few weeks I'm back to it and still trying to solve the mysterious lack of FUEL issue.

Right now - all I want to know is this:

I have another FI Module from my other 87 K75 that I know is good. what are the dangers involved with swapping out the units??

do I run the risk of frying my good module?

swapping them would be *very* easy and would answer a lot of questions all at once, but I don't want to do it if there's a chance I could fry my good one.

let me know.

thanks everyone.


PS - just for giggles I cranked the engine over a few times (about 4 sec) and then pulled a plug and checked it - dry as a bone, no fuel smell at all.
I'm getting good spark but with the 'choke' all the way out wouldn't there be at least a little smell of fuel on the plug??

PPS - Crazy Frog, I know you wrote that article about the FI system describing some tests for the FI unit connections - but is there a bench test for the FI unit itself???

Can't comment on swapping the FI module as it is a two edged sword. As for the "choke" it is purely and simply a fast idle so no enrichening capabilities or additional fuel unfortunately.

In theory if you are getting a spark then the FI module should be getting a pulse from the ignition module to fire the injectors. I can't remember seeing if there is a test for that and which pin it would be present on?

It is amazing how common and similar this thread is to others including club-c's K100 problem and yet there just does not seem to be the magic answer to fix it.

Being a technician I like things really broken or fixed. If there is a burning smell I want to see a fire I can put out but mysterious and intermittent problems are not my favourite.

yup - I agree. this problem has been driving me crazy for quite a while now - the only upside is that it frustrated me so much I returned to my other K-bike and have almost finished putting her back together.
that - at least - was a 'fixable' problem - input spline/clutch plate meltdown.

anyway - I would surely like to see this issue resolved so I could have something to ride tomorrow but it just isn't going to happen.

the bottom line is that I CAN'T hear the FP come on - not when I hit the starter button or after I let it go or ever really - and I know the pump is good AND I know that there's voltage going to the pump so...

I don't know. just don't know.

assistance?

BTW Phil, could you post a link to 'club-c''s thread?

I am reading this with interest. Here's the link. I am still not starting either...

http://k100rt.aforumfree.com/engine-and-transmission-f10/another-no-start-condition-t1371.htm

Looking this over I would really suggest you pull that original pump out and see what that's all about. With all the extra effort you've been putting in, it won't take you that long to pull the pump and test it. And I'd do it on the bench, not in the tank. It is amazing how fast those vapors can ignite (ask me how I know ). If you can establish the pump has failed, you are well on your way to the solution.

I'd also respectfully suggest Bert splits Bob's thread off the original posting from gabriel, so it can be searched a bit better later on by those that will come after us. It kinda took on a life of its own here.

yes - I agree about the post. I never intended to hijack this thread - it just worked out that way.

re: the FP, I ran some hot leads to the appropriate pins on the 4pin connector to the FP/tank and confirmed that the pump is seized.
but that was one of the first things I swapped out. the pump/tank I've been using this whole time is a working pump from my other K75...
but perhaps I'm missing something?

Funny how these bikes can follow us home. I too have two Bimmers...

I know the connection to the fuel pump on my K100 is a bit finicky, there is power at the plug but you have to sometimes hold your tongue a certain way while you stand on one foot to make a good connection to the pump. I think you are so close to a running bike. Wish I was...

I'll jump around on one foot and see what happens - maybe I can channel some mojo your way. ;-j

In theory (make that bold and in capitals) if you have a known working pump and it is not working when you press the starter the only fault can be in the wiring.

The fuel pump is directly connected to the FI relay via fuse 6 so essentially confirm the FI relay clicks when you press the starter switch.
Secondly check you have power on both sides of the fuse when you press the starter.
3:) Check for power on one of the connections to the tank when you press the starter.
4:) Check for continuity between the fuel tank connection to the pump.
5:) If all of the above are correct then you must have power at the pump when you press the start button.
6:) The other side of the pump connects to earth i.e. back through the tank connection.
7:) One of the pins of the tank connection has to have continuity to GND and therefore the pump must also have continuity so confirm that is the case.
If all of the above are correct the pump has to work.

If you were to hotwire the pump (through a switch) then the bike should start. If it does then it will confirm a wiring issue.

In addition if you can confirm you have 12V on one side of the injectors when you press the start button you also confirm the FI relay works and for all intents and purposes you have confirmed 12V to one side of the Fuel pump fuse.

Thank Phil,
I have performed many - but not all - of those tests.

BUT - before I go through all that - ONE THING I just thought of:

how long should it take to re-pressurize the fuel line/injector system?? it's been totally depressurized, will it need to be cranked for a while to re-pressurize? I could just run the pump for a minute using the hot leads if you think that might be the issue.

Just look at This post. I just replied to Club-C and he has a similar problem to yours.

Re-pressurizing the circuit should take only few seconds.

Bert

Just to throw a cat amongst the pigeons re fuel pressure. A while ago I had my tank off the bike and disconnected for a week and I was testing the starter circuit and the bike attempted to fire twice! so I don't imagine there was much fuel pressure left just a bit of residual in the injectors.

In theory, if the relief valve is tight and not leaking, it should hold the pressure for a long time. In practice, due to internal leaks the pressure will drop over time but the lines will still be full of gas (unless the injectors are leaking).
A short run of the fuel pump should re-establish the pressure as it doesn't have to refill the line.

so I just put my *other* K75 back together and something has occurred to me:
this bike had been sitting for a few months and the fuel lines had been off and as such the system was *totally* dry and (obviously) depressurized. when I went to start her up it took about 2-3 min of cranking to get her started (~15 sec max crank time with the same interval between - don't want to cook the starter!).

seeing this bike take so long to pressurize the fuel system I'm wondering now if that has been the real problem all along!
the hypothetical timeline goes like this:
1. pump seizes
2. I check fuses, plugs, spark, FI relay etc
3. I realize the FP is seized and switch tanks with my other bike, the bikes are not close to each other so this takes several days during which fuel system is totally depressurized and all fuel evaporates since the fuel lines are not hooked up.
4. I try to start the bike with good pump/tank and get nothing, when I check plugs it seems they are getting no fuel.
5. I try about 20 more things on the assumption that it is an electrical problem with the FI circuit.
6. Epic Fail.

so - perhaps it's as simple as not giving the FP enough time to pressurize the system? I think the longest session of trying to start via continuous cranking was maybe 1 min - not long enough apparently.

what do you all think? sound plausible? now that my other bike is running I don't really feel like messing around with switching tanks (rather be riding!), so I'd like to hear your opinions before I get back into it.

or perhaps someone has a FP they'd care to donate to a worthy cause? ;-j

cheers,
b

Hey guys ,
I am having a similar problem with my 75c. Ran lousy in May, replaced fuel filter no change. Checked and replaced hall sensors first ,then replaced water temp sensor ,spark plugs. Found vacuum leak and repaired still not running. Would run good for short 5-10 miles then start to sputter and run very rich. Ran engine with TPS removed ,no change. Checked spark plug leads only to find out they emmited spark but showed infinite resistance when checking with ohm meter. Now it is flooded to the point where gas is running out of the exhaust. I had it started for a short time then it shuts off as if you switch the ignition key off! Checked MAF which turned up somewhat different than Bert's published chart but still had resistance changes with the doo closing and opening.pin7-5 = 108, 7-8=361, 8-5=363, 8-9=189. Is this acceptable? I have checked and cleaned or repalced every ground. Replaced the battery, had the alt checked etc. I don't know what to check next. FP=36...BMW dealer near me has no solution! FRUSTRATED!!! Haven't ridden all summer!
HELP1

Welcome 8675k. I would suggest you start a new thread with your issues rather than jumping in on this one. It makes things very confusing if folks are giving diagnostic info on more than one bike at a time on the same thread.
Cheers,
clubbie

OK Didn't mean to muddy the water!

After reading all of the above. Particularly the first half and having all the problems mentioned.
After doing all the basics it occurs to me that the bike will be hard to start with the petrol air thingy sitting on the block out side the air box. (Air box not on bike).

A couple of good laughs gents.
"Hold a small blow torch to plug hole to get ride of extra petrol" true but dam......!
And the comment about the guy that may have ridden off into the sunset or suffered a massive cardiac arrest due to contact with plug leads. .... been there.... How the hell can they still get ya when motor is not turning over, the bastards? That got me........
i will put air box vack together and soldier on.....

All advice above and,   definitely do not try and start the bike without the air box in place a the mixture control unit working and connected - Maybe it is only me - I slept on it and thought "you boof head" of course she wont start with out proper air intake control.......

She lives again.......

Has BobtheBob mentioned if he had a good reading through the earth pin in the 4pin fuel connection, as he pressed the button to start the power goes through the pump and back to that point and then? I cant see where it is confirmed it goes back to the FI connector? Anyone see a post that confirms that? 

I'm right aint I that the pump gets an earth through the FI connection. that makes the pump work.

The FI relay gets the earth from the ICU but the pump has an earth to the frame under the tank

8675K sounds like a dodgy injector, try to clean them as one may be sticking partly open, other than that the temp unit needs to have a good connection to the bike to deliver correct readings is it thread taped to the max? may not allow a good connection. Charlie spoke of this last year to someone cant remember which thread though. Just my thoughts.

RicK G wrote:The FI relay gets the earth from the ICU but the pump has an earth to the frame under the tank

Ah OK was thinking the pump has a more convoluted pathway in the start function. Taa rick