940SE 16V Auto Engine cutting out/not re-starting

I have had an ong-oing problem whereby the engine randomly cuts out and will not restart immediately. I took advice from a fellow member (Ian Fewtrell) to clean the throttle housing. This was indeeed dirty so I cleaned it as advised. However, the problem is still occuring.

The problem presents itself either as an engine stall at low speeds (often while idling) or at higher speeds while the engine is on load. In both cases, the car will not re-start unless I wait for at least 2 or 3 minutes. It turns over OK and sometimes it splutters but dies. As a basic mechanic, it seems like either fuel starvation or too much fuel preventing ignition. I'm at a loss at what to do next other than replace the fuel pump relay. I've already replaced spark plugs and ignition leads. I've a feeling it's been getting worse since I've been using the air-conditioning more frequently in the hot weather. I'm hopeful that someone can pin down the problem.

Many Thanks - Dave Harper, London

[Peter Milnes]

Ian should have mentioned to clean the Idle Air Control Valve if fitted. This device maintains sufficient fuel mixture flow to enable the idling speed to remain constant. The other problem may well be the ubiquitous fuel pump relay. Solution is to either change it or resolder the connections inside the relay which become dry-jointed mainly due to vibration and heat.

All the best, Peter

Thanks Peter

I cleaned the Idle Control Valve and no further cutouts so far but I've only driven a few miles. However, the difficulty in starting within a short period of stopping the engine still remains. My wife is getting very irritated when I pick her up at the station. After leaving the car for 5-10 minutes it takes another 15 to eventually get it going again.

I've located the fuses, relays etc. behind the ashtray but cannot work out how to remove the shelf to allow access to the fuel pump relay. Swedishbricks mentions two screws although all I can see is a bolt on the left next to the cigar lighter.

Cheers - Dave

[Peter Milnes]

Prise out the lighter surround panel which is just clipped in being careful not to break the clips. This will expose the two screws. Remove them and withdraw the shelf and you are there.

All the best, Peter

[Grizlyadams]

My 945LPT did the same thing, change out the Fuel pump relay and/or the powerstage (above the battery), should solve it.

Griz

I checked out the fuel pump relay and it looked as good as new - it must have been replaced recently (I've had the car 10 months). Since refitting it, the car seems to start OK. Maybe it was a loose connection. I'm not sure what the powerstage is, but I'll check the manual tomorrow and have a look.

I've still had two recent instances of the car just stalling while driving at low speeds although it restarted again immediately on both occasions. Perhaps the two problems are un-related. I'll monitor the situation and keep my fingers crossed.

Thanks - Dave

[Grizlyadams]

Can be called the ignition amp, just above the battery, hidden in the harness. You need the exact part number from unit (small and quite flat with typical electrical connector (like the amm plug) to get the correct replacment.

Griz

I'm grateful for all the help. After replacing the fuel pump relay (something I should have done earlier), the problem disappeared, so I guess this was the cause.