AO

I have a bet with a friend. He has an '88 S4 and his fuel pump runs whenever the ignition is on. I told him that can't be. I always thought the LH killed the pump unless it received a signal from the Crank Position Sensor on all S4, GT, and GTS's.

But then I started to wonder if that feature was introduced the same time as the Ignition Monitoring Relay system in 1989 to prevent cat fires.

So if you have an 87 or an 88, and you are 100% certain let me know what your car does.

Thanks.

P.S. No money involved in this bet... just braging rights.

Rod Underwood

At least one of mine does. Funny you should post this right now.
Rod

aggravation

I have to jump mine at the relay to get it to run because it won't run in the accessory or on position, I don't know beyond that point what controls it.

dprantl

My '86 definitely did not (LH 2.2). Neither do my SAABs that have various versions of LH (2.2, 2.4, 2.4.x). And my '91 does not either.

Dan
'91 928GT S/C

michaelathome

Mine doesn't and I am absolutely positive. Engine needs to be running OR cranking, not just in the on position. How do I know you ask? I have a fuel pressure guage on my fuel rail and yesterday while troubleshooting a high beam issue that I have, I had the car on and off multiple times and you got it, NO pressure in the fuel rail. Rail doesn't pressurize until the car begins cranking.

Michael

BPG_Austin

Mine does NOT run unless engine is cranking. Positive.

chaadster

I've checked my fuel pump operation before, and it runs only when cranking or running. I've jumped it to get it to run in the ignition "on" position.

Actually, it might run for a second when ignition is first switched to "on", but it certainly does not run constantly, of that I'm certain.

Dean_Fuller

I just like voting.

Jim bailey - 928 International

One of the common early failures of the LH computer is not triggering the fuel pump relay many shops will then jumper the relay one way or another so the fuel pump runs anytime the key is on. Very very risky since all you need is a leaky injector and someone to have the ignition on too long and you fill the intake and or any cylinder with valves open with gasoline....liquid gasoline. Then hit the key have a couple cylinders fire and then the one full of LIQUID gasoline does the compression stroke but liquids do not compress , that can split the cylinder, lift the head and or bend the connecting rod....lots of bad things. Then there is the fire danger if you crash the car and the fuel pump sprays 2,500 cm3 per minute

AO

Well I don't think we have a statistically significant sample yet, but I find it interesting that a few 88's do not run (the way I thought it should be).

Let's let this one percolate a bit more.

And Jim... your explanation of why this is a BAD thing is precisily why I'm posting this poll. Lots of dangerous things can happen as a result...

worf928

When I got my '89 I noticed that the FP ran with the ignition on. Soon thereafter I found a mysterious black wire tucked almost-out-of-sight... that bypassed the FP relay to run the pump all the time.

I've done work on at least four '87s. None of them operated the fuel pump with the key on. So I voted...

UKKid35

Definitely top of the list of Truly Evil PO bodges - unless you fancy the idea of being trapped in a crashed car with hot exhaust manifolds and a continous flow of fuel through ruptured fuel lines.

I'd rather die because someone had tampered with my brakes, than burn to death because of that.

LightStriker

Mine has something fried beyond the fuse box.
Probably when that crappy anti-thief system was installed.

Anyway, instead I have a cable bypassing where there is normaly a relay.

It's in my list of thing to fix. Can be horrible in case of crash.

John Speake

I have handled more than 600 LH ECUs. Only one triggered the FPR briefly when igntion was first switched on. That had been rebuilt by someone else, but I has since seen several more of their rebuilds which didn't do that so that is one suspect LH in 600.

Deifinitely designed to be fail safe, as Jim said. Especially in the event of an accident - say car inverted, ignition on ; you wouldn't want to have the pump running then.....

If you get the wrong pins when trying to jump the FPR relay , then it is easy to blow up the FPR relay driver stage in the LH ECU, so that is probably why some cars have been doctored to run FP as soon as igntion on. (this can be repaired)

Can I post 600 "no's" Andrew ?

Rod Underwood

Crap, that was what I was afraid of...

Rod