[V8] Fuel Pump noise

[Paul Jager]

The gauge of wire and the distance is going to drop the voltage a bit - that 
is expected. 12.5 you are fine. Corrosion at the terminals may cause voltage 
drop but the location of the V8 it's in the trunk so that I would not 
suspect to be an issue.

I found that possible causes of noise
filter restriction
mounting
or Bosch's are noisy! At least for 928's they are horrible, reliable but 
whiners.

When my RPM/crank sensors were on their way out sure felt like fuel pump 
issue. That is the first thing I replaced when it died on the highway due to 
those sensors.
No engine crank, no fuel pump go signal from the Motronic.




----- Original Message ----- 
From: "Professor GT gmail" <CavalloGT at gmail.com>
To: <v8 at audifans.com>
Sent: Wednesday, May 25, 2011 7:38 PM
Subject: [V8] Fuel Pump noise


> Allan,
>
> Low voltage to any motor will cause degradation of performance of the 
> motor itself, AND an increase in current flow in the circuit. The reduced 
> voltage (push) causes the motor to run slower. This then makes the motor 
> labor more (noisier). Because of both, the current draw goes up, which 
> increases heat in the motor, which shortens life. Now a fuel pump is 
> cooled by the fuel, so temp in this case is not typically an issue. But to 
> confirm all of the above a current draw measurement would be best. Then, 
> once full voltage is available if the pump is still noisy we'd have to 
> blame the pump itself, which if internal binding, poor brush contact, or a 
> tight pump itself is the culprit, again current draw will be higher than 
> "normal". The problem is getting a draw spec. Many times with things like 
> this, the only way is to measure a "known good" unit to use as a baseline. 
> I'm sure you have done this with other things, so I know you can relate to 
> what  I'm saying. Fuel pump noise can be a
>  challenge, as things like the intake sock being mis-positioned can 
> contribute to the issue as well.
>
> My V8s have been sleeping for some time now, and as I prepare to get them 
> out of mothballs, I hope I do not run into issues from rancid fuel. I'm 
> getting closer to beginning the 4.2 swap, and can't wait to get started.
>
> Unfortunately I was laid off this Monday, so my focus right now is on job 
> hunting. I hope to land something substantive soon, but in the meantime 
> I've has a few offers to spin wrenches and do some training as well. It 
> will be a trying time, but I have to stay positive. My solace is burying 
> myself in V8-ness! This takes my mind off the worrisome stuff, and gives 
> me a sense of accomplishment and pride, but you already knew that!
> By the way, you beat me to it, but the red engine parts look excellent. 
> Guess I'll have to go with blue anodize on mine!
>
> Gerard
>
> Message: 3
> Date: Wed, 25 May 2011 17:57:19 +0000 (UTC)
> From: allanvega at comcast.net
> To: Professor GT gmail <CavalloGT at gmail.com>
> Cc: V8 at audifans.com
> Subject: Re: [V8] V8 Fuel Pump
> Message-ID:
> 
> <1553510383.859210.1306346239323.JavaMail.root at sz0030a.westchester.pa.mail.comcast.net>
>
> Content-Type: text/plain; charset=utf-8
>
> After reading this, I decided to go out and check out why my new Bosch 
> fuel pump was so noisy. Voltage @ battery with engine off was12.6 volts, 
> with engine running it was 13.47 volts..
> Now @ the fuel pump I have 12.64 volts with engine off, and 12.65 with 
> engine running. That 12.65 jumps to 12.82 if I add a temp ground wire. I 
> stopped there because I ran out of time, but I suspect the supply voltage 
> to pin 30 of the fuel pump rely may be the culprit. I will continue 
> diagnosing either later tonight, and report back later. Allan
>
> Thanks,
>
> ProfessorGT
> (Sent from my iPhone4)
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