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940 se injectors not firing (LH 2.4)

Hi

This car died on the motorway a couple of weeks ago and has been dead since.

Some info...

- The car won't start but cranks.

- I am getting spark which will jump 1/4 inch when tested against the block so I assume the problem must be fuel delivery.

- The fuel pump runs.

- The FI relay activates.

- The radio suppressor relay activates.

- The wiring from the injectors to the ECU pin 18 (injector signal) pin is OK.

- The supply and ground voltages at the relevant ECU pins are OK.

- The other pin of the injectors is getting 12v via the radio suppressor relay.

- I removed a spark plug and held a cotton bud in the cylinder as the engine was cranked -- there was no sign of fuel on it. Also, I used a long screwdriver as a stethoscope to listen at an injector... I couldn't detect any clicking.

- When I crank the engine the voltage read across the pins of all injectors remains 0.0v so it looks like the pulse signal from the computer isn't working.

All I can think of is a bad ECU... anything else I'm missing?

Any advice would be welcome.

Thanks

Bilko

Reply to
Bilko
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Yeah the series resistor pack for the injectors would seem to have become disconnected somewhere.

Cheers, Peter.

Reply to
Peter Milnes

Reply to
Bilko

Check the ballast resistor pack on the drivers side (i think) suspension turret.

Tim..

Reply to
Tim..

PS. You may not have a ballast reistor pack on this engine, some have, some haven;t- fingers b4 brain syndrome!

With the igntion on, and fuel pump primed, try grounding the injectors to ecu line to earth for a secord or so, then crank. If the engine fires you know spark and fuel pressure is fine, and 12v to the injectors is ok.

Then check very carefully all the ecu earth's.

Reply to
Tim..

No this car doesn't have ballast resistors -- it uses high impedance injectors.

I'll try as you suggest and see how it goes.

Reply to
Bilko

In article , snipped-for-privacy@bilko.com by Bilko dropped his wrench, scratched his head and mumbled,

Since the auxiliary fan relay and the radio suppression relay have the same P/N you can swap them and see if there's a difference. If you ground the fan relay at the radiator switch through a test light, the fan will run with the key on--easy way to check both relays for operation.

If that fails I'm afraid the control unit has left the building. That's the only thing left that generates an injector pulse.

Bob

Reply to
volvowrench

Yes, looks like you may be right and the ECU itself is the problem.

Tried everything else I could think of that would stop the injectors pulsing -- no RPM signal, bad wiring, faulty injectors, bad suppression relay, bad ECU supply or grounds, erroneous WOT signal from TPS putting the ECU in "clean start" (flooded engine) mode...

Luckily it's not my car... it's the father-in-law's. I think he's out at the moment looking for a car with a carburettor.... :-)

Cheers

Bilko

Reply to
Bilko

Apols for not being online lately- blasted Lovsan virus bolloxing my pooter!

Sounds like you have successfully eradicated any other fault with the car and it does point to an ECU failure.Makes a refreshing change that someone takes a logical approach to fault finding rather than just automatically blaming the ecu!!

It would be worth having ATP check your ecu on their bench testers local to you.

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just to be sure. This costs £35 whichis discounted if your ecu is faulty and you order a reconned or new one fromthem.

Tim..

Reply to
Tim..

Just to let you all know it was indeed the ECU that was at fault.

A free replacement was procured from a scrap car, plugged it in and the beast came to life with the first turn of the key... :-D

Cheers

Bilko

Reply to
Bilko

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