1992 940 (B200FT) cutting out

[Sprog]

Hi all,

940 on works duty today with my other car in for work (940 usually goes out once a week otherwise) - accelerating up a hill (with the turbo in boost), the car suddenly cut out with the warning lights on. Pulled over to the side of the road and would start and run for a couple of seconds before cutting out.

On the last attempt before calling out recovery I gave it a little bit of throttle and it started fine and then idled happily and drove the last couple of miles to work with no further issues.

Fuel pumps sounds to be running, getting a whine noise from the rear of the car when i turn the ignition. Car was nice and warm and has about half a tank of premium liquid dinosaurs in it so can't think it's low fuel being an issue.

Any thoughts please folks?

Cheers,
Joshua

[griston64]

Originally Posted by Sprog

Hi all,

940 on works duty today with my other car in for work (940 usually goes out once a week otherwise) - accelerating up a hill (with the turbo in boost), the car suddenly cut out with the warning lights on. Pulled over to the side of the road and would start and run for a couple of seconds before cutting out.

On the last attempt before calling out recovery I gave it a little bit of throttle and it started fine and then idled happily and drove the last couple of miles to work with no further issues.

Fuel pumps sounds to be running, getting a whine noise from the rear of the car when i turn the ignition. Car was nice and warm and has about half a tank of premium liquid dinosaurs in it so can't think it's low fuel being an issue.

Any thoughts please folks?

Cheers,
Joshua

Initial thought was alternator but funny how it started and ran ok after. Belt sound ok ?

[Sprog]

No unusual noises after I lifted the bonnet when I got it to work - seems as happy as it ever has been!

Is it like to be crank sensor or fuel pump relay that I've read more than enough about on these forums?

[Laird Scooby]

Pull fuses #11 & #13 and clean the blades on them or renew them. The blades oxidise over time and eventually build up a certain amount that causes resistance and eventually once hot this stops the pumps running until the fuses cool down.

This is your first step in the diagnostic procedure.

Also invest in some IPA, meths or similar solvent cleaner and a tube of heatsink compound.
Locate the ignition amplifier module on the NSF inner wing (usually hidden either by the air filter or various induction pipework on turbo cars), remove it and clean both the back of the module and the mating surface on the heatsink bolted to the wing with the solvent cleaner - DO NOT use anything abrasive!

Smear some heatsink compound on the back of the ignition module and refit, giving it a wiggle to help spread the compound evenly.

This is your second step.

Third step, when it cut out, did the rev counter drop immediately to zero? If so, that usually points to the CPS but it can be the ignition amp module overheating (dealt with in the second step above) and shutting down until it cools.
If it cuts out again after doing those two steps above, make sure you note what the rev counter is doing as that will give some good clues to what's happening.

[TonyS9]

Could be a failing fuel pump (1 of 2), ignition amp, pump relay, crank sensor or injector relay.

Checking for pump noise is a good start, but you have 2 pumps so its hard to tell if one is faulty. I think lift pump failures will work to a degree but be unreliable especially at high power.

The other check you can do is look at the rpms when the engine fails, don't touch anything let the cars moment drive the engine until you have checked, then think about pulling over. (in my case with a failing pump, it actually came back on in a few seconds and worked for the rest of the journey). Does the rpm drop immediately even though the engine is turning or do the rpms show the true rpms? Its driven from the ignition coil so if there is an ignition problem the rpms drop immediately.

If you want more diagnostics wire up a pump voltage LED indicator. With this information, your ears and eyes you can diagnose most fail/no-start problems immediately.

Another problem is if you havn't desribed the symptom correctly. If its trying to idle after boost and just dies (eg you are stopping at lights) then there is a problem with the dump valve. Depending on how you drive its not always obvious these are actually the circumstances.

[Forrest]

My 280k mile Wentworth estate has had most of the problems described so far in this thread. Last month I finally fixed the bypass valve one described by Tony above.

In my case, the in-tank lift pump had failed and had been like that for about ten years. I’ve had several fuel pump relays during my ownership. Renewed the CPS once. Also plugs, leads, distributor cap and rotor arm.

Another recent problem not yet mentioned was a leaking heater valve squirting coolant into the distributor cap. This leads to running problems that clear when it dries out. It was quite hard to spot as not a big leak but the original heater valve crumbled upon investigation.