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1987 K75C 58,381k Karibic Bleu requesting fuel supply troubleshoot help

I am not sure what black substance is at issue. I do know that the OEM black rubber damper mount that holds the fuel pump will dissolve in ethanol added fuels. When new it feels like a tire. When damaged it feels soft like a marshmallow. When destroyed it is gooey and sticks to your finger when you poke it. Bob's BMW has commissioned aftermarket alcohol resistant dampers, and has them available. I am not sure who else might also have the aftermarket part.

Hi Paul,
I dismantled the pump clip assembly. The damper was in perfect condition. This is some type of plastic jammed between the metal housing that holds the pump and the left side of the tank. I've never read anything about this being inside of the tank, but it is clearly there on both the front and rear of the pump housing metal assembly. My initial thought was that it was there for structural support so the pump housing doesn't bend downward and rub against the inner left side of the tank.
 
Any opinion on the pictures of the plastic inside of the tank?

IF I get a chance today, I'll check out some of my spare tanks. I do seem to remember something in there to keep the pump shelf from rattleing, since I don't belive the outer edge of the shelf is welded to the tank skin.

You can reseal the outside of the sending unit with silicone.




:dance:dance:dance
 
IF I get a chance today, I'll check out some of my spare tanks. I do seem to remember something in there to keep the pump shelf from rattleing, since I don't belive the outer edge of the shelf is welded to the tank skin.

You can reseal the outside of the sending unit with silicone.




:dance:dance:dance

Thanks Lee. I was going to re-phrase the question as to whether the outer edge of the shelf was intended to be welded to the tank skin. I could see no other reason for needing to have something wedged in there. I too have another K75 (White 1988 that I tried to give to you years ago and glad you didn't accept) that I didn't think to check myself. I will do so on Monday to see what is going on with that shelf. For all I know that "plastic" is really hose that does not meet fuel standard requirements and became hard a brittle.

Thanks for the silicone tip. :):wave:dance
 
Pete,

Looked at my spare tanks. All the tanks have it. It is a HARD plastic piece. It is round with a slot cut in it to slide over the edge of the pump shelf. The pump shelf is welded to the tank floor, then the floor is welded to the tank top skin along the lower seams. The plastic prevents rattles.





:dance:dance:dance
 
Pete,

Looked at my spare tanks. All the tanks have it. It is a HARD plastic piece. It is round with a slot cut in it to slide over the edge of the pump shelf. The pump shelf is welded to the tank floor, then the floor is welded to the tank top skin along the lower seams. The plastic prevents rattles.





:dance:dance:dance

Hi Lee,

Really appreciate you checking that. Look what I found! Your response to this very topic in 2014. https://forums.bmwmoa.org/showthread.php?71787-Rubber-protectors-in-fuel-tank-K75

If my plastic is completely deteriorated I may be able to fabricate some fuel hose of the correct diameter after making a slit to wedge in there. Just checked my 1987 K75C and it had sleeves exactly as shown in the 2014 post. Much fresher looking than what is left in my 1988 K75C tank. :brad:wave:)
 
Final shelter-in-place update.

The sending unit replacement solved the fuel pump intermittent failure problem. I had difficulty diagnosing the problem for several reasons.

1) The fuel pump intermittent failure started within days of completing the ignition switch and start/kill switch dismantling and cleaning. I suspected one of those was the cause, even knowing they should be starter related, instead of fuel pump. Chalk that up to a shoddy workmanship bias.

2) Failing to aggressively wiggle the connections to try to induce failure on the initial ohm connectivity test (after 1st tow) lead to a good connection result. I found the connection failure after Paul Glaves got me refocused on the sending unit with his accurate guess as the probable cause. After the 2nd tow the connection failure was discovered. The 2nd tow took about an hour wait that allowed me to positively determine that the pump was not working. Once the K75 was delivered off the tow it immediately started. This time I more aggressively wiggled the sending unit wires to find the failure.

The 210k growling alternator was replaced with a rebuilt from Euro Motoelectrics that solved the ever-getting-louder growl.

As I researched the fuel pump mount bumpers inside the tank, I read that there should be fuel tank mounting post circlips for the rear mount. I ordered them and gained a much greater appreciation for why they were missing after failing to get them installed. I have some new ideas for my 2nd install attempt. Meanwhile I’m trying to grow fingers like ET.

Thanks to 98lee, 69zeff65, rich, & special thanks to PGlaves! :wave:wave
 
I am glad you got it sorted out. These intermittent issues that leave you beside the road are the worst.
 
I am glad you got it sorted out. These intermittent issues that leave you beside the road are the worst.

Indeed. Combined with the stuck starter relay I had 3 tows (1x on freeway), and 3 stalls to roadside (1x on freeway). Good learning experience on how to keep an eye open for safe roadside landing and avoiding freeway construction (with closed shoulders) on my commute. By the last tow it was no longer an anxiety producing experience. More like taking a time-out to slow down and take in the surroundings. Noticed my wallet did feel lighter! :lurk
 
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