Re: Fuel pump roulette

[Phil and Judy Rose <pjrose@servtech.com>]

>Date: Wed, 15 Oct 1997 11:09:50 -0400 (EDT)
>From: QSHIPQ@aol.com
>Subject: Re: Fuel pump roulet
>
>In a message dated 97-10-14 13:11:31 EDT, you write:
>
><< All this talk about fuel pump noise, convinced to me to change mine on the
>86
> >5k. The beast ran fine for the first few days but now I have trouble
>keeping
> >it going after its been parked over night, after about 15 minutes of
> >operation every thing seems to be normal which is about the same amount of
> >time it takes me to get to my mechanic. Does the saying "If its not broken
> >don't fix it" come into play here ?
>  >>
>And another writes:
>>>So...the law that "a noisy fuel pump is a fuel pump that is
>>>about to fail" is one that may need to be taken with a _large_ grain of
>>>salt. Certainly some (most?) fuel pumps run quietly and get noisy shortly
>>>before failure, while others probably tend to run noisily for very long
>>>times.
>>Of course, a "very long time" for one person may be a major PITA for
>>another. But since in one sense all fuel pumps can be considered as being
>>"about to fail...

Whoops, that was me ;-)

>Some interesting thoughts, not sure I'd be content with that advice.  A fuel
>pump that is noisy after install can mean one of two things.  1) the fuel
>pump is noisy from the get go or 2) you have another problem in the system.
> The risk of running a 175 dollar fuel pump till it fails is this R&R (btdt
>to one):
>*  Rebuilt fuel head 63X = 750USD
>*  New fuel injectors = 450USD
>*  All Fuel lines/ pressure accumulator purge = 3hours
>*  New FP regulator
>*  Fuel tank drain and clean
>*  remove and clean Control Pressure regulator = most wrenches won't, just
>R&R
>*  3 Fuel filters in 1000 miles
>
>Sound expensive?  Guarantee, and a major PITA, I wouldn't want to be at
>either end of that repair again.  So, how bout some FP basics to help those
>now parnoid, and the naysayers.
>*  FP past 100k are on borrowed time
>*  FP are cooled by gasoline that is in the tank, no fuel = no cooling.  Good
>idea for warm weather folks to keep topped off tank
>*  FP work extra hard if the Fuel tank return regulator is clogged or not
>functoning correctly.  On CIS cars, this is the 16mm nut on the front of the
>FD, careful on R&R there are springs and o-rings in there.  A clogged or
>otherwise defective assbly, sends more fuel back to the tank than is being
>demanded by the CIS
>*  ALL in tank fuel pumps should have the lower screen removed per Audi TSB
>covering 1986-1991 5k and 200 model cars, ck archives, I already posted the
>procedure.

Scott --when the FP fails-- what happens that is able to get past the fuel
filter and cause damage to: (1) fuel head, (2) injectors, (3) fuel
regulator, etc? I understand crapping up the fuel tank, and I don't say the
rest _doesn't_ happen, but why? Seems the FP decomposes into microscopic
pieces that pass right through the filter?

Also, does Audi recommend permanent removal of the FP lower screen? Not
cleaning, or replacing with a new one? I assume the problem is that the
screen clogs up with crud from the fuel tank(?) If so, won't that stuff
continue to cause a problem--somewhere else?


>*  A fuel pump has a baseline noise.  Listen to it.  If it gets louder over
>time, there is a problem.  Find it.  The above repair is the risk, time is
>the bet.  Best to ante early.
>*  As a rule, if you bought a used car, replace the FP, you don't know it,
>why risk?
>*  Make sure you have good voltage at the pump, many Urq owners have already
>found this and relayed under the rear seat.  As with all vw/audi wiring, that
>is a pretty small wire that runs almost 16feet from the FPR to the FP.
>*  Check system and Control pressure before and after pump R&R
>*  R&R of FP should be accompanied by a system and CP ck, as well as a CO
>adjustment
>*  Save some diagnostic hassle, replace the FPR and the FF with the FP as
>baseline


>ANYONE who tells you that pump noise is "normal", isn't betting anything but
>the keyboard he's correct.

I hope I wasn't thought to be promoting the notion that _any_ "pump noise
is "normal"". But you do say: "A fuel pump has a baseline noise", and
that's all I meant to suggest. It sure seems reasonable (based on my
limited experience, i.e., none) that a significant increase in noise level
is to be considered as ominous. The $175 question is, "What is my FP's
baseline noise?"

>
>Trust your ears folks.

Easier said than done for a lot of folks. My wife, for example, has
profound high-frequency hearing loss--she cannot hear our smoke alarm at 3
ft! Ironically, I compensate by having extremely sensitive hearing, but
haven't a clue as to what a "silent" (i.e., good) Audi FP sounds like. Is
it desirable to evaluate the FP's sound with the engine not running?


> One that gets louder when it's hot out or under
>certain conditions is different from one that is getting progressively
>louder.  Also, my understanding is that a later model fuel pump (motorola I
>believe) supercedes the Bosch one at the dealer.  This is supposed to be a
>"better" pump design.  Also about twice the price of the good ol Bosch unit.

Seems like the newer pump might be money well-spent. Anyone have more info
on this model?
Thanks for the input, Scott.

Phil
'91 200q (probably gonna have its FP screen removed, pronto.)

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