Fuel Problem

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PeterCS
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My E21(s): 82 BMW Baur
Location: Oakville, Ontario Canada

Fuel Problem

Post by PeterCS »

Fuel does not appear to be getting to my carburetor.

Background:
- after starting very reliably for several years, the car suddenly would not start, the engine turned fine.
- determined that it was not pumping fuel

Attempted Fix:
- i bought a replacement fuel pump (used)
- installed a new fuel sender

Sadly, no fuel is getting to the carb. The fuel filter remains empty. I have checked that the fuel line back to the sender is not blocked.

Here is a picture.

Thoughts?

Thx PeterCS 82 315 Baur

Image


Peter Churchill-Smith
Wilmo
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Re: Fuel Problem

Post by Wilmo »

If you attach a handpump (or if you are as me, can you suck) fuel out of the tank? Maybe the fuel line to the pump is blocked.

If you feed the fuel pump directly with a hose and a filter out of a jerry can, does the pump fill the filter and carb?



My first problem with my 315 was that the sending unit was blocked because of a dented tank... Therefore I removed the mesh filter.
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ZenderE21
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My E21(s): '82 318i
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Re: Fuel Problem

Post by ZenderE21 »

Have you checked the lift pump also? It’s an internal tank pump, is always good to catch you out.
1983 318i - Sapphireblau Metallic, 5spd
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Jeroen
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Re: Fuel Problem

Post by Jeroen »

Wondering if Peter found a solution already indeed. Apart from a rare few models like the AUS spec 323i and the early US 320i I believe, there aren't much models that have an in tank pump fitted. Think I'd fit an electrical pump just to test if that delivers any fuel. If that's the case you can fit a alternate supply (from a jerrycan for example) to the mechanical pump to see if it's working at all.
Regards/groeten, Jeroen
Mark3
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My E21(s): 1983 RHD 1.6 manual

Re: Fuel Problem

Post by Mark3 »

I had this problem after my E21 had sat for several months and the fuel lines had become dry. The mechanical diaphragm pump was not strong enough to pull fuel all the way from the tank. As Wilmo suggested, priming the system (by a suction pump or sucking, i used the latter - not nice!!) was sufficient to let the diaphragm pump work.

Also check for perished pipes or loose jubilee clips. The pump sucks fuel from the tank, if there is an air leak it will suck air and not fuel. Replacing your fuel pipes may solve the problem.

Good luck :)
PeterCS
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Re: Fuel Problem

Post by PeterCS »

In the end, I discovered that my weber 32/26 was completely gummed up and need to be rebuilt. All is good now.
at first, I thought it was the sender, then the filter, then the pump ... until I got to the problem!

thanks for all the help, PeterCS
Peter Churchill-Smith
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Jeroen
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Re: Fuel Problem

Post by Jeroen »

Good to hear you're up and running again!
Regards/groeten, Jeroen
javibcnpar
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My E21(s): 323i EU June 1981

Re: Fuel Problem

Post by javibcnpar »

Hello

I did not introduced myself (sorry for that) but in order to provide my 5 cents to this topic, i share my experience, in case if may be useful for someone else:

My case:
I replaced all fuel lines from/to the tank to the pump, and from the pump to the suction unit (for a 323i) and also the ones from pump to metal pilelines (feeding and return lines). Also the vent hose which links the top of the two tanks as well as the hose which goes to the expansion vent tank and the one which links the bottom of the two tanks. In summary : 100% of rubber pipes were replaced and also fuel filter. So the tanks were removed and installation became dry.

My issue:
Once everything was put in place it was impossible to start car. Engine was crancking but it seemed that it had no intention at all to start. In a first check, I could see that there was no pressure in the fuel lines. Since the installation was "dry" for about 3 weeks, i suspected that the pump could have gone out after spending some weeks in "dry" (being a 38 years old pump, i was really not surprised)

The solution:
This morning i found the solution: I tested the pump "isolately": I removed fuel pump relay , and put a cable in the relay socked linking the terminals 30 and 87 (with caution and ready to retire the cable immediately just in case there was a shortcut). I started the contact -without crancking the engine but completely connected- and I could then hear the fuel pump turning. After about 15 or 20 seconds i could hear bubbles inside the fuel lines and also hear liquid fuel moving around the pipes.

After couple of times doing that (intervals of 5-10 seconds in order not to overload the pump), i could see that fuel pump noise started to be slightly different (some kind of noise change difficult to explain now, but a kind of noise that tells you that the pump is now turning with liquid inside and not empty anymore). So i put relay again in place and I started engine. It started-up without problems. Just to mention some erratic idle at the first 30 seconds, probably due to the air bubbles in circuit, so quite normal situation, and after that everything is running perfectly again.

The conclusions:
So definitely it seems that it's needed to prime the fuel lines when these operations are done (in other old Opel cars i worked with L-Jet, this was not necessary but here it seems yes, it is)

As mention, I share the experience here in case it may be useful for someone else.
Regards!
javier
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Jeroen
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Re: Fuel Problem

Post by Jeroen »

Thanks, that may be helpful indeed. As you noticed, it can take quite a while until the fuel lines are all filled up correctly again!
Regards/groeten, Jeroen
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