Can I "service" a noisy fuel pump?

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
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Christoph, I think that someone already has done an autopsy on a noisy pump on Audifans. The buzzing is caused by slack in the bearings, and they're slip bearings IIRC. To check the condition of the pump, I'd do the pressure checks that are described in the Bentley Manual or www.sjmautotechnik.com I'd shy away from the "auto electrician" - a few hours to find out that he installed the fuel tank sender wrong? I hope you didn't have pay him for his diagnosis. Also the piece of glove in the tank - sounds like a careless surgeon who forgot a sponge in a patient. It may be pieces of the tank lining coming off (does it look the same as the lining?), or.....[paging Dr. Electircian, your patient is crashing....]..... The cutting out you describe may be the screen getting blocked by the bits of dirt and glove/lining. The pump in my 5ktq is noisy - as is many others on Audifans, Audiworld, etc. I reduced the amount of noise by removing the metal screen from the bottom, but you can still hear the pump when the gas is below half tank, and you're parked. BTW, my fuel tank sender is hung up, it was that way when I got the car. I tried to fix it - it went from reading the upper half of the tank only, to the lower half of the tank only, then back to the upper half only. I gave up. Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)

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Hi Steve,
Thanks for your detailed reply.

I spent a few hours (which I don't really have) on audifans and couldn't find the thread you mentioned. I only found this one and a similar one mentioning that they cannot be taken appart:
http://www.audifans.com/pipermail/quattro/20021004/062976.html
<start cite> having just done an autopsy on a dead 5kt fuel pump, I would say there is no way that you would be able to rebuild it. We had to destroy it to get in there. <end cite>
However, I found a lot more advice, again ranging from "don't bother" to "replace right now". What I also saw is that some mention replacing the fuel filter would help, others say it won't. I might try this first.

Unfortunately, I don't have the fittings to do pressure tests myself. It seems those things are a bit harder to get in Soth Africa than in Europe or North America.

It actually took me some time to realise that the gauge was related to the repair he did previously. I only saw it mentioned on www.sjmautotechnik.com that you have to be very careful when reinstalling the pump not to mess up the gauge. I then went back and pointed this out to them. I think what took them so long was to take the whole lot out again and to put it in the right way. Generally the place makes quite a good imrpression. In South Africa, it's quite hard to find reliable garages and these ones seem to be the only ones in the area who can do full fuel ignitian tests. BTW, it's an authorised Bosch adgent.
Here is some more on the gauge problem, in case anyone is interested:
<begin cite>
Re: My fuel pump story ( http://www.audifans.com/archives/1995/03/msg00168.html )
The job took only 1 hr and 15 mins. Followed the sketchy procedure in Bentley augmented by the procedures posted here by others. BUT, here's the catch no one had alerted me to - the position of the fuel line connected to the pump is critical - else it will interfere with the fuel gauge sender's movement. I found out after I had put everything back together that the fuel gauge was now showing the tank as half full when I knew it was only about 1/8 full. So I spent another 3 hours inside the trunk practically redoing the job twice over to get it right. Although I was careful even the first time, I didn't realize that if the hose is off even 1/4" to the wrong side, the sender touches it.
Re: Buzzing noise from fuel tank ( http://www.audifans.com/archives/1998/12/msg03514.html )
I quite enjoyed replacing the Passat's pump. I parked the car behind the house in the sunshine, opened the rear doors and the hatch, and took out the spare wheel. I could sit very confortably with my feet in the spare wheel well, a tankard of cider and the toolbox, and work on the pump at leisure. With that much ventilation, fumes were no issue. I found the R&R pretty easy first time - much less than an hour. I made a mistake reassembling, in that I forgot/omitted to make sure that the hoses coming up from the pump to pass through the lid weren't fouling the fuel gauge float. I should have noticed that I'd done 300 miles on half-full _before_ it ran out.
So I lifted the lid again, and rearranged the hoses.
<end cite>
Another interesting one (too long to cite):
http://www.audifans.com/archives/1998/12/msg03370.html

As mentioned, I found the diagnosis and he only rectified the problem. But I didn't pay, only had to travel two times 20 km and wait quite some time. At least he gave me a nice desk where I could work on my old laptop.
I think part of the problem here is that in a good garage, there are a few qualified people who know what to do and how do the diagnosis. And there are a few not so qualified ones who do the actual job, supervised every now and again by the more qualified people. That takes longer, but the labour cost of the not so qualified people is probably quite small. A bad garage only has not so qualifed people. The agents are probably a bit of an exception, but they are quite expensive. Actually, it was the mechanic of the agent who sent me to the auto electrician. He said they can clean the injectors, at the agent, he would only be able to replace them.

The problem is I don't know whether that was during my repair or during someones elses job before. I only got the car a few years back and a lot of the trouble I have with it seems to be related to bad jobs done on it before. I would assume it was from an older job, since only the tip of a finger was left. I can't blame the auto electrician either for not finding it, since it was stuck in that flap between the tank and the fuel pump reservoir. I stuck my finger into that canal out of couriosity and found the pieces in there.

As mentioned, it was a white plastic tank without lining. Probably just after they discontinued the lining thing.

Last time I was in there, I cleaned the scean and since then it doesn't cut out any more. What's interesting is that this screen is a seperate part in my car. It's not permanently attached to the pump. It's like a metal mash in white plastic, which is moved over the pump. Dont' think I want to remove it.

Maybe twisting some of the pipes as suggested above might help. Or maybe it is just difficult and that's the reason the autoelectrician needed three hours to get it right after he messed it up the first time round.
Anyway, I have to run. I will get past an audi agent today, and I will probably just get that rubber part holding the pump plus a new fuel filter (if it is affordable from audi). I have this suspesion that the third-party filters they sell here might not bee of too high quality.
Thanks again for your help,
Christoph
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Christoph, I can see what you're saying about mechanics - when you find a good one, you've hit the jackpot. Sounds like the "Auto Electrician" is not as bad as they first sounded. We had a fellow working for us whose dad was a mechanic in Argentina. He often noted that where we in North America tend to take parts out and replace them with new ones, in South America there is a tendency to disassemble the part and fix it. Witness the quote I once got for repairing my squealing alternator - $100 - I took it apart on a weekend, pulled the bearings and replaced them for $20. With respect to the fuel pressure gauges, I got mine from JCWhitney in the US. They do offer international shipping, and the set cost $55-ish. In the spirit of DIY, you can often find a hydraulic shop that can make up a testing rig for a lot less than you could buy and import it for. The troubleshooting in the SJM web site is invaluable - I occasionally have the vapour lock problem as well and I'm planning to insulate the fuel lines as the rubber boot that originally covered them is long gone. I'm also going to be running new wires to the temperature sensors from the ECU. I'm suprised that the gas tank in your car is plastic - I've never seen a plastic tank, although I have seen tanks with various linings, and fiberglass on the outside that makes them look like plastic. Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)
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Nedavno Steve Sears pise:
| I'm also | going to be running new wires to the temperature sensors from the ECU.
Why?
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Yvan, I'm not getting a signal down one of the wires to the ECU temperature sensor - the wire's probably totally corroded and broken, so I figure that my best option is replacement. I'm just waiting for weather that I won't freeze to death in before I tackle the job - as well as lots of other "fun" wiring jobs - like the new Eurolights, front and rear fog lights, maybe even a CD changer! Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)

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Nedavno Steve Sears pise:
| I'm not getting a signal down one of the wires to the ECU temperature | sensor - the wire's probably totally corroded and broken, so I figure | that my best option is replacement.
Aha... I was just curious...
| I'm just waiting for weather | that I won't freeze to death in before I tackle the job - as well as | lots of other "fun" wiring jobs - like the new Eurolights, front and | rear fog lights, maybe even a CD changer!
Temperature hire is now high enough for working around the car outside, but since I solved my stalling problem (by disconnecting ISV) I am just going to change distributer cap (not changing rotor arm as it seems to be glued in place), and change oil and filters...
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Yvan, Lucky guy. It snowed here last night to add insult to injury...... Cheers! Steve Sears 1987 Audi 5kTQ 1980 Audi 5k 1962 and '64 Auto Union DKW Junior deLuxes (SPAM Blocker NOTE: Remove SHOES to reply)

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Hi Steve,

True, he is not as bad as it sounded, but still I had to go there twice, and in the end still do part of it myself. I'm considering to take it to him for a complete check of the fuel injection system in the hope that he finally solves all the small problems. But that will have to wait for a bit, until I have the money.

Here, they work more like the South American, except for the Agents who seem to replace just everything. There is a good garage here specialing just on clutch and breaks. I had a problem both with the master cylinder and with the slave cylinder within a relatively short time. They serviced both. I think altogether, I paid a bit under US$100 for this.

I think I will follow this up.

I will probably open it up again this weekend. IIRC, I was able to see light getting in throught the tank walls, which looked opaque. Maybe it's not the original tank, I don't know.
Thanks again for your advice,
Christoph
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Christoph Bollig wrote:

Replaceing is the only thing I have heard of. Shokane usually has a listing on Ebay for Pierburg replacement pumps for around $125. they are a good pump (I have one in my '91 100q). You must order off Ebay to get the deal. If you call them the price is higher.

Yep.
Running the tank empty can destroy the pumps becaue the gasoline is used as its coolant and that only happens when it is fully immersed.

It is now recommended to cut the straining screens from the pumps to allow them to pull the crud in where it is finally caught by the fuel filter.

Usually nothing can be done other than replacing. I have heard of one person who found a loose connection that caused intermittent operation and noise but I would beet it needs replacing.

Among other possibilities, it could be due to a bad fuel pump check valve. Could have gone bad due to overheating with empty tank.

Well, it is a 100 (like mine). My 100q 5spd has always seemed slower and burns more fuel than my former '87 5000q 5spd. I have doen all the thins you would expect but can not find a reason other than it is just heavier than the '87.
Tony '91 100q 5spd '98.5 A4 1.8TQ 5spd APR : )
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