[s-cars] Fuel Pressure

[Jerry Scott]

The way I understand it, there is a check valve in the fuel pump and a 
FRP (fuel pressure regulator) on the fuel rail.  If both are working 
correctly, the line should hold pressure after the engine is shut off.  
My 93 S4 has a gauge on the rail and it will hold about 40 psi. for 
several hours.  If you are having a problem with this, try running a can 
B&G 44K ($24/can), through the gas tank to clear out any gunk in these 
two valves.  This worked for me and the pressure holding came back.  If 
the fuel drains back to the tank, you will have problems starting the 
engine, until it fills and pressurizes again.

Mark Strangways wrote:

> Nope,
>
> I should hold pressure, I was able to locate some spec's in alldata..
> Should hold about 36 PSI when cold...at the fuel rail to be specific.
>
> Enables nice fast cold / warm starts.
>
> Mark
> ----- Original Message ----- From: "matt ludwig" 
> <matt.ludwig2 at verizon.net>
> To: "S-CAR at audifans.com" <S-CAR-List at audifans.com>
> Sent: Saturday, May 07, 2005 4:08 PM
> Subject: Re: [s-cars] Fuel Pressure
>
>
>> Exactly what I was thinking!
>>
>>
>> On May 7, 2005, at 3:43 PM, Joe Pizzimenti wrote:
>>
>>> Um when the motor shuts off, so does the fuel pump.  Isn't this normal?
>>>
>>> On 5/7/05, Mark Strangways <strangconst at rogers.com> wrote:
>>>
>>>> Oh great Audi list...
>>>>
>>>> Riddle me this,
>>>>
>>>> Fuel pressure drops off like Pizzo's dates do just after dinner 
>>>> when I shut down the motor.. What part will I be replacing ?
>>>>
>>>> My first guess would be the FPR , second would be fuel pump.
>>>> Any BTDT's on Fuel pressure drop off ?
>>>>
>>>> Mark S
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