Hi everyone,
I will probably soon take the fuel pump out to replace the rubber part holding it (Audi 100, 1989). Since the pump has become quite noisy recently, I was wondering whether there is anything I can do to clean it or otherwise service the pump.
I did search on this group and found lots of threads where a noisy fuel pump is mentioned and the recommendations seem to range from "replace it before you get a problem" to just don't bother (cite: "Noise is not necessarily a problem. A 'varying' or 'hunting' noise (incessantly changing tone) usually _is_ a problem.")
I will try to give you the complete story, despite the fact that is is a bit lengthy:
1.) Almost two years ago, the engine was replaced with one from the scrap yard. After that, I had problems to start when it was warm plus there was a problem above ~5000rpm. The people who put in the engine sent me to the auto electrisian to check the injectors.2.) The auto electrician replaced something in the distributor and the check valve on the fuel pump. He also mentioned that the warm-up regulator had a slightly too high pressure, but there wasn't anything he could do about it. Anyway, the car seemed fine.
3.) Some time later, the car first cut out a few times and then stalled completely. It turns out I completely ran out of fuel, since the fuel gauge didn't work. I refilled the car and changed the fuel filter (was very impressed how dirty the fuel looked on one side of the filter and how clean on the other).4.) From then onwards, the car started to cut out occassionally when the fuel tank was still a bit more than 1/3 full. It always became worse until I filled it up again and then was fine up to a bit above
1/3. I think this was the first time I noticed noise from the pump, but only when it was close to cutting out. The car never stopped completely.5.) I went back to the auto electrician. They worked for a few more hours on it and solved the gauge problem. Apperently, it was stuck because the sending unit was not in the right way. The gauge worked again, but the cutting out was still there.
6.) Eventially, I took the pump out myself. I found some dirt in the tank, including a few pieces from what looked like a latex clove. On the other hand, the fuel tank seemed to be made from some sort of white plastic without any lining.In addition, I saw that the black rubber part holding the pump was close to disintegration and the screen on the pump inlet was really dirty. My conclusions: When the tank was full, the fuel just bypassed the sreen and ran from the top through the bad rubber holder of the pump. There were engough gaps there. When the thank was around 1/3, the rubber was not entirely covered in fuel any more and probably started to pull air. I couldn't get a spare rubber fast enough, so I just cleaned the screen and put it all together again. At least that seemed to solve the problem.
Since then, the pump has become more noisy. Therefore, I was wondering whether there is anything I could do when replacing the rubber part. Or maybe the noise has just increased because the rubber is not damping it any more as it used to? It's quite a constant noise, no variation or "hunting".
Two other observations, which are probably not related (but who knows):
- Recently, I have trouble again when starting. Sometimes, I need to crank it over for quite some time before it starts.
- The power seems to be a bit down, but I am not absolutely sure.
And while I am in there: When filling the car, the last 5 litres or so go in very slowly. It seems a ventilation hose is blocked. Is there an obvious place to look for a blockage?
Thanks for any help,
Christoph