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'85 K100RS Bad fuel pump or fuel pump relay?

117336

K-biker
Hi all,

I have an 85 k100rs that has been ok till now. Riding along and felt something knock between my legs like a slight vibration. Bike coasted to the curb and would not start. Thought it was the loose plug on the COMPUTER ECU ECM CONTROL MODULE BRAIN BOX and unplugged and re plugged it in. Have had this happen in the past. Put a zip tie on it to hold in position. Tried again but no start. All seems fine, starter cranking, battery power ok, gas in tank. Could it be the fuel pump relay or the pump? And how do I figure out which one? http://forums.bmwmoa.org/images/smilies/dunno.gif
 
Open filler cap. Turn on key and kill switch. Tap starter button. You should hear the pump (in the tank) run for a couple of seconds.

When you plug in the computer plug, you MUST remove BOTH battery covers and hold the rear of the computer with one hand as you are pushing the plug in the front with the other hand. You MUST hear a distinct CLICK when the plug locks into the computer.
The computer is rubber mounted, so just pushing from one side without holding the back side allows too much flex to get the plug properly seated.

IF you are sure the plug is properly seated, check your fuses especially #1 and #6. Check for voltage at #6 when the starter button is pushed. (only lasts a couple seconds, so have meter set up before pushing button. If you do have voltage, but pump doesn't run, you need to pull the pump and bench test it.



:dance:dance:dance
 
Does your bike still have the small battery negative cable (maybe 18 gauge)? If so, replace it with a later cable. The original, especially with some age, can give you fits.
 
Put 12v directly to the terminals. No fuel connected, just see if it runs (probably won't). The small terminal is positive. If the pump does not rum, try reversing the polarity. It might unjam it. But it usually is fubared.

A very cost effective replacement (I use these in all my bikes):

http://www.euromotoelectrics.com/BMW-R-K-VDO-Repl-Fuel-Pump-16-14-1-341-231-p/fp-231kit.htm


With the following adapter:

http://www.euromotoelectrics.com/BMW-K-Fuel-Pump-Foam-Adaptor-16-12-14-61-576-p/fp- 576foam.htm


If your vibration damper is going bad:

http://www.euromotoelectrics.com/BMW-K-Rubber-Vibration-Damper-16-12-1-464-628-p/fp-576damper.htm




:dance:dance:dance
 
bench test

Took out the pump and saw the err to my ways. I used a bead of gasket sealant (recommended by the garage I was in) that broke down in the tank and got into the pump. This raises several questions:
1. What can I soak the pump in to try and loosen/dissolve and reverse pump out the bits?
2. Did I even need the gasket sealant in the first place (to seal the gas cap gasket to the tank) and if so what is the correct one?
 
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The screen cup on the bottom of the pump should not have allowed any solid bits into the pump.

You might try spraying carburetor cleaner into the pump and then running it in reverse. Carb cleaner is flammable. Do outside. Solidly bolt wires to pump. Make/break connections with battery several feet away (sparks).

No gasket sealer should be used, but a new gasket would be a good idea.

16111453690 $8.37



:dance:dance:dance
 
A very cost effective replacement (I use these in all my bikes):

http://www.euromotoelectrics.com/BMW-R-K-VDO-Repl-Fuel-Pump-16-14-1-341-231-p/fp-231kit.htm


With the following adapter:

http://www.euromotoelectrics.com/BMW-K-Fuel-Pump-Foam-Adaptor-16-12-14-61-576-p/fp- 576foam.htm


If your vibration damper is going bad:

http://www.euromotoelectrics.com/BMW-K-Rubber-Vibration-Damper-16-12-1-464-628-p/fp-576damper.htm




:dance:dance:dance


Hey Lee; does your above statement mean that this fuel pump will fit/work in a K75S (with the foam adapter also mentioned)?

Just gathering info in case I need to replace my screeching, chirping OEM 1994 fuel pump.

Thanks!
 
Hey Lee; does your above statement mean that this fuel pump will fit/work in a K75S (with the foam adapter also mentioned)?

Just gathering info in case I need to replace my screeching, chirping OEM 1994 fuel pump.

Thanks!

Not exactly. That info is for the 52mm pump replacement. You have the 43mm pump. You can get a better deal by going with:

http://www.euromotoelectrics.com/BMW-R-K-VDO-Repl-Fuel-Pump-16-14-1-341-231-p/fp-231kitplus.htm

It includes EVERYTHING except a new vibration damper.

http://www.euromotoelectrics.com/BM...Damper-16-12-1-464-694-p/fp-231kdamper694.htm




:dance:dance:dance
 
OK, Lee; thanks for the clarification.

That EuroMotoElectrics is a great source---I bought my new Westco battery from them Friday morning online and the battery was at my door Saturday morning---well packed and ready to go!

Hope I don't have to replace the fuel pump but it (or it's pressure relief valve) is making such a racket I may have to do so soon.

I'll try replacing the fuel filter once more and see if that makes any difference beforehand, though.

Appreciate your help as always.:)
 
Good news!

Hey Lee,

Thanks for your help and wisdom. Good news the pump works. How should I clean it and make sure there's nothing stuck? Also what is the best way to clean out the tank. Seems there's particles from the first time I did it so my way didn't do such a good job.
 
The BEST way to clean the tank is to drain it, remove it and wipe it out. Then let it dry out, invert it and blow it out with compressed air. Inspect and repeat.


If the pump runs, there probably is nothing inside., but to be sure, you could fill a NON METAL pan (oil drain pan) with gas about 3" deep ( OUTSIDE!!!!!!). Connect LONG wires to pump and a LONG hose to the pump. Clamp end of hose so it will not whip around. Direct hose where flow will be contained (it will/should be at HIGH pressure). Run it, see what happens. Don't blow up the house. Keep fire extinguisher handy.


What is the condition of the cup/filter on the bottom of the pump??? That really should have stopped anything solid from getting in the pump.



:dance:dance:dance
 
The BEST way to clean the tank is to drain it, remove it and wipe it out. Then let it dry out, invert it and blow it out with compressed air. Inspect and repeat.


If the pump runs, there probably is nothing inside., but to be sure, you could fill a NON METAL pan (oil drain pan) with gas about 3" deep ( OUTSIDE!!!!!!). Connect LONG wires to pump and a LONG hose to the pump. Clamp end of hose so it will not whip around. Direct hose where flow will be contained (it will/should be at HIGH pressure). Run it, see what happens. Don't blow up the house. Keep fire extinguisher handy.


What is the condition of the cup/filter on the bottom of the pump??? That really should have stopped anything solid from getting in the pump.



:dance:dance:dance

Take video for YouTube. We want to see the fireball ! :thumb
 
done done and done

Thanks Lee. Managed to not blow anything up and ran the pump in a plastic bucket of gas with a hose clamped to the output and rubber banded to the pump body. All working as it should with unmeasured pressure. Cleaned out the tank with gas and air dried it then compressed air and some shaking to get all the crumbs out. Ordered a new strainer as mine had a tiny slit in it and I mean tiny but I didn't want to take any chances. I saw there were 2 kinds of strainer available: one with a hose attachment and one without. Mine had none and is an 85? Where would the hose on the strainer connect to in the tank if it is supposed to have that? Thanks for your help and the links to parts. This place rocks and is cheaper and faster than anywhere else!
Enjoy the long weekend!
 
hmmmm

Hi Lee,

So the pump is in with the new strainer, tank cleaned and just to be sure I did the key on and starter pushed quick test to hear her running. AOK. Put in some fuel crossed my fingers and ... same **** errrr. Starter oak, fuel check, clean air filter check, Got to check plugs next and maybe if there's a relay to check I will do that as well. Going to read my Haynes by the window and dream of cruising in the countryside. Could that have been the sound I heard when it quit? Maybe a relay popped or I need new plugs and wires?

before_after_wip1.jpg
 
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Hi Lee,

So the pump is in with the new strainer, tank cleaned and just to be sure I did the key on and starter pushed quick test to hear her running. AOK. Put in some fuel crossed my fingers and ... same **** errrr. Starter oak, fuel check, clean air filter check, Got to check plugs next and maybe if there's a relay to check I will do that as well. Going to read my Haynes by the window and dream of cruising in the countryside. Could that have been the sound I heard when it quit? Maybe a relay popped or I need new plugs and wires?

before_after_wip1.jpg

I'm not really clear what you symptoms are.

Does the bike crank?

Does the pump run?

Do you have spark? You can get a cheap in-line spark tester at HarborFreight or many car parts stores.

What is the fuel pressure? (tee in a gauge at the fuel rail).




:dance:dance:dance
 
tools

Hi Lee,

I need to get some tools and wonder if this will do the trick>
http://www.harborfreight.com/automotive-motorcycle/diagnostics/fuel-injection-pump-tester-92699.html
It says that it doesn't fit a bosch fuel injector but if I attach it to the hose before the injector it will test the fuel pump pressure and that's what I need I think.
and this:
http://www.harborfreight.com/automo...s/90-inline-ignition-spark-checker-69023.html
Will it fit?
Thanks in advance for your patience and help.
S
 
Hi Lee,

I need to get some tools and wonder if this will do the trick>
http://www.harborfreight.com/automotive-motorcycle/diagnostics/fuel-injection-pump-tester-92699.html
It says that it doesn't fit a bosch fuel injector but if I attach it to the hose before the injector it will test the fuel pump pressure and that's what I need I think.
and this:
http://www.harborfreight.com/automo...s/90-inline-ignition-spark-checker-69023.html
Will it fit?
Thanks in advance for your patience and help.
S

Both those SHOULD work just fine.

When taking fuel pressure measurements, it's easier to tee into the hose at the REAR of the fuel rail. That's the hose that goes to the fuel pressure regulator.


If your bike is cranking and the fuel pump is running, it's possible that the spark plugs are fouled. Clean, Dry, and regap.



:dance:dance:dance
 
Continued woes

Hi Lee,

Lapse in time due to necessary work schedule... Anyway got the tools and tested the spark to find 1 of the 4 not firing. Could be the wire or the coil, yes? Would that be enough to make it not start? Should I change the wires and test #1 again to rule out the Coils or is there a way to gap test the coils or try and check the wire? (I know your thinking... rookie)
Have not checked the pump pressure yet but know when I was testing it in the bucket it was pumping. Will test it this week.
 
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