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 the 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

--
Important: Emails sent to me which contain my full name
in the "to:" or "cc:" field will bypass my spam filter.
With most programs "Reply" should do the job.

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)
"Christoph Bollig" > wrote in message
...
> 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 the 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
>
> --
> Important: Emails sent to me which contain my full name
> in the "to:" or "cc:" field will bypass my spam filter.
> With most programs "Reply" should do the job.

Christoph Bollig wrote:

> 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.

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.
>
> 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.")

Yep.
>
> 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).

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.
>
> 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.

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.
>
> 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".

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.
>
> - Recently, I have trouble again when starting. Sometimes, I need to
> crank it over for quite some time before it starts.

Among other possibilities, it could be due to a bad fuel pump check valve. Could
have gone bad due to overheating with empty tank.
>
> - The power seems to be a bit down, but I am not absolutely sure.

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 : )

Hi Steve,

Thanks for your detailed reply.

> 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.

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/qu...04/062976.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.

> To check the condition of the pump, I'd do the pressure
> checks that are described in the Bentley Manual or www.sjmautotechnik.com

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.

> I'd shy away from the "auto electrician" - a few hours to find out that he
> installed the fuel tank sender wrong?

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>

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.

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

> I hope you didn't have pay him for
> his diagnosis.

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.

> Also the piece of glove in the tank - sounds like a careless
> surgeon who forgot a sponge in a patient.

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.

> 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....].....

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

> The cutting out you describe
> may be the screen getting blocked by the bits of dirt and glove/lining.

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.

> 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.

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
--
Important: Emails sent to me which contain my full name
in the "to:" or "cc:" field will bypass my spam filter.
With most programs "Reply" should do the job.

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)

Nedavno Steve Sears pise:

| I'm also
| going to be running new wires to the temperature sensors from the ECU.

Why?



--
___ ____
/__/ / \ ** Registrovani korisnik Linuksa #291606 **
/ / \/ /\ \ ** Registered Linux user #291606 **
/__/\____/--\__\ ** http://counter.li.org/ **

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)

"Yvan" > wrote in message
news:20050323161405.3113f79c@localhost...
> Nedavno Steve Sears pise:
>
> | I'm also
> | going to be running new wires to the temperature sensors from the ECU.
>
> Why?
>
>
>
> --
> ___ ____
> /__/ / \ ** Registrovani korisnik Linuksa #291606 **
> / / \/ /\ \ ** Registered Linux user #291606 **
> /__/\____/--\__\ ** http://counter.li.org/ **

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...


--
___ ____
/__/ / \ ** Registrovani korisnik Linuksa #291606 **
/ / \/ /\ \ ** Registered Linux user #291606 **
/__/\____/--\__\ ** http://counter.li.org/ **

Hi Steve,

> 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.

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.

> 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.

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.

> 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.

I think I will follow this up.

> 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.

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

--
Important: Emails sent to me which contain my full name
in the "to:" or "cc:" field will bypass my spam filter.
With most programs "Reply" should do the job.

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)

"Yvan" > wrote in message
news:20050323204220.7e2b0503@localhost...
> 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...
>
>
> --
> ___ ____
> /__/ / \ ** Registrovani korisnik Linuksa #291606 **
> / / \/ /\ \ ** Registered Linux user #291606 **
> /__/\____/--\__\ ** http://counter.li.org/ **