Fuel Pump Relay question
ekellock at gmail.com
Mon Jun 6 13:08:23 EDT 2005
Coupe GT? How about this... may be a long shot. On my 87 several
years ago I had a borken post on the battery and over time battery
acid leaked down into the main wiring harness which routes downward
through the firewall behind and under the battery tray. I had similar
bizarre cutting out behavior, accompanied by backfiring. Finally gave
up and took it to a dealer (before I knew of the "quattro list", this
was 1993 or so). Anyway, they happened to be fiddling with or near
the ecu and it stalled. They found that the battery acid had gotten
down into the wiring harness and was eating away at the wires. $400
later they had it fixed and I haven't had any issues since. My one an
only happy and very thankful dealer service experience. THAT guy did
a helluva job, one I would not have wanted to do.
On 6/6/05, Chris Hall <badcomrade at gmail.com> wrote:
> Jim Jordan wrote:
> "the backfire is raw fuel that got to the cat and/or muffler. When we
> were kids, we used to blow the guts out of mufflers by turning off the
> ignition briefly letting the raw fuel pass through the engine, then,
> while still rolling in gear, turn on the ignition with a big bang."
> That doesn't make any sense to me.
> I always thought that if a car backfired, that it meant un-ignited
> fuel hanging around in a cylinder was being detonated at the wrong
> time by a mis-fired spark plug when the exhaust port was open in that
> cylinder. You seem to be saying it only happens when too much fuel
> goes in to the engine, passes wall in to the exhaust system, and the
> heat within the exhaust ignites the fuel and goes out the muffler.
> How the hell would gas -in the cat or muffler- as you say, POSSIBLY be
> ignited when the ignition is switched back on? It'd HAVE to be near a
> spark plug to do that... and I sure as hell don't have a spark plug in
> my exhaust system that would ignite fuel in the cat / muffer when I
> switch the ignition on.
> Would it be a safe assumption then that my ECU is cutting power to the
> coil, the fuel pump keeps pumping gas for a second or two in to the
> engine (I've witnessed this while observing the fuel pump relay with
> it's cover off after the engine dies), and when the ECU cuts back IN
> (for what ever reason) sometimes, that it's igniting gas in cylinders
> who's exhaust ports are open? As I said, I sure as hell don't have
> any spark plugs in my cat or muffler that would ignite un-spent gas
> when the ECU switches the ignition back on the same way you did as a
> kid to cause a backfire... and I'm sure you cars didn't either.
> My friend used to do the same thing in his old Chevy truck. Turn off
> the key, keep it in gear so the wheels spin the trans which spins the
> engine and the mechanical fuel pump, feeding gas to all cylinders,
> then switch the key back on, and BAM.
> On 6/6/05, Jim Jordan <superba at comcast.net> wrote:
> > Hi Chris,
> > Well, as I said before, the backfire is raw fuel that got to the cat and/or
> > muffler. When we were kids, we used to blow the guts out of mufflers by
> > turning off the ignition briefly letting the raw fuel pass through the
> > engine, then, while still rolling in gear, turn on the ignition with a big
> > bang.
> > Something is dumping huge(relatively) amounts of fuel in the engine at
> > times. The waiting period, ~10 minutes as I understand it, is consistent
> > with letting a flooded engine clear out. The next time it does it, remove
> > the coil wire and clear it by 4 or 5 15 sec on and 15 sec off start tries
> > with the starter.
> > HTH.
> > Cheers!
> > Jim Jordan
> > >
> > >
> > > By the way... there can only be -so- many things that will
> > > cause the car to BACKFIRE like it sometimes does when it's
> > > stalling, right?
> > > Anyone know what those things are? I imagine that'd help us
> > > narrow it down...
> > >
> Chris Hall
> badcomrade at gmail.com
> "making girls cry since 1974"
> quattro mailing list
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