928 s4 cut out while driving over speed ramp

[dave944cab]

Hi

Driving my s4 low on fuel and drove slowly over a speed ramp and then the anti lock light came on and the car came to a hault.

Suspected fuel so put 20 litres in. The car will just about start up but cuts out after 1 second or as soon as you attempt to give any throttle.

Just towed it home as to late to mess but any ideas appreciated

Thanks
Dave

[Normy]

Well, if it starts at all, the fuel pump is working.

LH-Jetronic: What will cause this system to start to work, but then shut down. It sounds like it is giving start enrichment, but as soon as that disappears...the engine stops.

The long and short: You've probably a wiring issue, and I suspect it is on the central electric board under the passenger foot well.

Hmm.... now that I think of it...the fuel pump may be working, but it is possible that the relay is burnt/overheating/funkalated, and as such won't allow the pump to run. Have you tried a new relay?

We're with you! Folks, it's time to circle the wagons-

N

[EIPtuningR32]

Originally Posted by Normy

We're with you! Folks, it's time to circle the wagons-

N

circling

[Dean_Fuller]

Were ther ANY the less bit odd behaviors before this?? Some electrics working when not on, windows not rolling down some times, ect....

[dave944cab]

No all was working fine,

car going very well....

going to check the basics spark and fuel later, test the fuel pump relay..

Thanks

[Xlot]

Your primary fuel pump has probably failed. Exact same failure happened to me in the same way.

If you're lucky its just jammed and you can clear it by applying voltage both ways in short bursts, running it both forwards and backwards.

The in-tank pump will pressurise the system giving it enough gas to turn over once or twice, then it runs out of fuel and dies as it can't supply enough to feed the engine.

[dave944cab]

Great

Whats the location of the primary fuel pump?

[Xlot]

Originally Posted by dave944cab

Great

Whats the location of the primary fuel pump?

Backside of the fuel tank - there's a metal cover with two 10mm nuts (M6) that are just above the rear bumper. You can remove the pump without lifting the car up in the air.

Pull the cover off, and you'll find the pump and fuel filter. Annoyingly, the fuel filter is on the other side of the pump from the tank, so any sediment and crap in your tank gets to bust up your pump before its filtered

Then:

1. Disconnect the battery ground strap so you can't generate sparks by accident
2. Stick a hose clamp on the line from the tank to the pump, and then undo it - you'll still need to catch about a half pint that'll drain back out of the pump and filter.
3. Undo the hard line from the filter to wheel well
4. Undo the electrical connectors
5. Take off the whole pump/filter carrier with 4 more 10mm nuts, to try un-jamming/replacing the pump on the bench