[s-cars] fuel pump switch

[Dave Forgie]

Its not just American cars.  My 1986 Jetta Carat (2L 16 v conversion mit 3 spd autogetreibe fur die frau) has the key on, engergize fuel pump, stop after 3 seconds relay.  In this case I use it (its now my beater) on cold mornings to compensate for a leaky check valve (somewhere) that I am too lazy to fix./  Dave F.

>>> <calvinlc at earthlink.net> 01/01/06 12:33PM >>>
One thing puzzles me, though.  Every American car I have driven has figured
out that you can activate the pump for 3-5 seconds with the initial
application of the key to the "on" position and then shut the fuel pump
off...a much better system than no pump "priming" at all.  This is
especially helpful when trying to troubleshoot fuel related issues so that
rather than having to jumper the relay or some fool thing like that you just
have to repeatedly turn the key on and off as many times as you need.
--Calvin


-----Original Message-----
From: s-car-list-bounces at audifans.com  
[mailto:s-car-list-bounces at audifans.com]On Behalf Of Dave Forgie
Sent: Sunday, January 01, 2006 12:53 PM
To: s-car-list at audifans.com  
Subject: [s-cars] fuel pump switch


Jerry: It would be possible but I would NOT advise it. Under the existing
protocols, the ECU triggers the main fuel pump relay (under the drivers side
knee bolster on North American UrS cars) ONLY after the ECU has received a
signal from the cam position sensor (or crank sensor) that the engine is
going around, i.e. being started.  The good thing about this is IF you are
in an accident that stops the engine, the ECU shuts off the fuel pump, i.e.
the risk of a car fire is decreased.

To do what you want to do, even if it was necessary, you would have to
engergize the fuel pump via a "hot" switch, pressurize the fuel system, and
THEN remember to turn the "hot" switch off and then start the car normally.
However, IF you forgot to turn the hot switch off, it could get real "HOT"
in an accident.

If there is a fuel line draining issue, its probably better (safer) to
replace the check valve which has failed, which in this case, I believe, is
in the fuel pump.  Fuel pump is probably due for replacement anyway.

A fuel pump replacement procedure that I wrote up is available at:

http://forums.audiworld.com/s4s6/msgs/86586.phtml  

Dave F.



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