Date: Mon, 28 Jun 1999 23:21:58 -0700
Reply-To: Coby Smolens <cobys@WELL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Coby Smolens <cobys@WELL.COM>
Subject: Re: one last question from Woody
In-Reply-To: <199906280642_MC2-7B09-3909@compuserve.com>
Content-Type: text/plain; charset="iso-8859-1"
First - have you been able to restart it? You've probably pulled the plugs
to check for soaking? Pulled the intact injectors rails off the intake
manifolds to see if fuel pours out of the injectors?
Are you talking about the main battery ground cable or the fuel pump ground?
Oops, never mind - I just rechecked the diagrams and it doesn't make a whit
of difference. The ground on the pump is direct to the chassis, as is the
battery ground. A break in either one is not going to power the pump. In
order to create the problem you describe, 1. the pump has to be running and
more importantly 2. an open path must exist for the fuel to travel between
the pump and the engine.
So,
1. The pump gets its power from the pump relay which gets its power from the
battery via a "30" terminal connection at the starter. The relay is
activated when it receives voltage from the ignition coil, when the key is
in the "on" or "cranking" position. The other side of the equation (i.e.,
the decision at to when the ground will be given for the relay solenoids to
operate) is handled by the computer. That's why, if you turn the key to the
"on" position without starting the engine, the pump is supposed to run for a
couple seconds and then shut off. This is a safety feature built into the
ECU, so that in the event of an accident wherein the engine stalls the pump
doesn't keep on running. If there were a broken fuel hose you'd not want the
pump merrily spewing fuel all over the place. SOMETHING KEPT THE PUMP
POWERED UP, GROUNDED PROPERLY AND RUNNING when it wasn't supposed to. I
don't see how a broken ground cable at the battery or the pump could do
that. Check the main FI harness for damage. It is possible that a ground
wire in the harness is bare (melted through at a hot place?)and making a
ground connection which shouldn't be there (in effect making a decision to
give ground to the pump).
2. The gas has to get into the engine. The most likely avenue is the
injectors. Did you pull the spark plugs or the injectors and check for
soaking in the combustion chambers? If that was what you found, then the
injectors had to have opened. The only thing which normally opens the
injectors is the ECU. They get power from the same relay that runs the pump,
but their ground wires go straight to the ECU, and they are 4 separate
wires, so it's not likely that all of them got ground at once through a
fault in the harness, unless there was a major internal meltdown (I don't
rule this out - check the harness by the Bentley pinout diagram in the FI
section).
In conclusion: If you don't find a major fault in the harness, the ECU is
probably the culprit.
> -----Original Message-----
> From: Woody Halsey [mailto:WoodyHalsey@compuserve.com]
> Sent: Monday, June 28, 1999 3:42 AM
> To: Coby Smolens
> Subject: one last question from Woody
>
>
> Do you think that a broken main ground cable could cause a fuel
> pump to run
> amok? That is the explanation of my (very smart) mechanic; but some on the
> list are skeptical. I don't understand electrical systems well enough to
> know if it is a plausible explanation for the fact that my fuel
> pump dumped
> a tank of gas into the engine and exhaust when the key was off.
>
> And I meant "anti-sway bar," not "strut bar."
>
> TIA,
>
> Woody
>
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