940 B230FK occasionally losing power / stalling

[jonsoft]

Hi there,

Can anyone help diagnose a problem I'm having with my 1998 Celebration 940 estate petrol automatic?

It drives fine but then I'll suddenly lose power and the gas pedal will have no effect. Sometimes it recovers, other times it completely stalls with the various (normal) warning lights coming up on the dashboard indicating the engine has stopped.

When it does that, after rolling to a standstill it takes 10-15 minutes before it starts again. The ignition and battery are all fine (new battery from the RAC the last time it broke down due to this on the M1!).

I am thinking it's either the fuel pump -- which has never been replaced and the car has done 120,000 miles -- or possibly a dirty/broken MAF sensor.

Either part is GBP 200 to buy new, so I wondered if anyone has any thoughts what the problem could be before I go ahead?

Many thanks,

Jonsoft

[940volvoman]

Does it run roughly,at all?



used parts available from a Celebration to assist with fault finding/diagnosing before spending big bucks on brand new....

[jonsoft]

It seems to run really smoothly when it works. Ignition starts first time, it idles well and never idles out, and responds well to the acceleration. Or about as well as a vehicle of this size and weight and age normally would without any "tuning"! It makes me think it is fuel-pump related rather than MAF.

The last time we broke down, when it eventually started again, we left it idling. Every now and then, once every 5 or 10 minutes, you heard the revs dip momentarily, but it didn't cut out. After that we were able to drive it home OK.

940volvoman are you offering parts or suggesting I find them? I definitely think you're right, it's a good idea like you say to try out a cheap used part first while I find what the problem is.

[360beast]

It could be many things, it could be the fuel pump relay is getting hot breaking the contact, probably a dry solder joint that gets hot and then loses continuity until it's cooled down enough to resume normal service. You can test this one when it dies by quickly cranking the car by literally just flicking the key to start and instantly turning it off. Then turn the ignition back on and if the pump primes it's probably the relay, also put your hand on it (big white relay behind the ash tray) and see if it is hot.

My mate had a similar issue to yours that turned out to be the MAF but that was because it had an eBay special MAF on it, a used Bosch one cured it.

It could also be the crank sensor breaking down due to heat and then once cooled down it starts working again. An easy way to test this one is when it dies pull the king lead off the distributor and stick a spark plug in the end and rest it on the block then crank it, if there's no spark or a very weak (orange/yellow) spark then it will be the crank sensor.

120k miles is nothing for these, mine is on 197k on the original pump etc, the only sensor that's been changed is the ECT sensor.

[940volvoman]

Jonsoft,I am not offering the parts, only suggesting that P505DEF is currently breaking a Celebration.Be kind to him, he has some health issues.

Have you checked the basics, like plugs, leads dizzy cap etc?

Of course, If you are able to get used parts from P505DEF you can change parts, one at a time until you trace the fault guided by other experienced people on here. My Celebration has 175,000 miles and still has most original parts.

[Foeux]

I had precisely this problem and it was sorted by new distributor cap and arm.

It really showed off. Even with a brand new battery it would show 9v all of a sudden then behave almost like it was totally flat.

Come back to it, right as rain and totally unable to replicate the fault. Frustrating but rotor arm and distributor cap solved itm.

The cap is a little bit tight to get at as it is close to the bulkhead.

[Rversteeg]

A 1998 940 will have the improved impeller type fuel pump, which is far more durable than the pump model used in pre-98 cars. But even these pumps eventually fail. Mine lasted over 400K miles when it finally gave up. They usually refuse to start up and do not seize during running. A good whack on the tank gets you going again until the next start.
As you are experiencing hickups during driving, a faulty fuel pump would not be my first thought.
When losing power, does the rpm needle drop to zero while the engine is still rotating? If so, you have lost ignition on the ignition coil and you should look in that direction (crank sensor, power stage).
If the needle follows the engine rpm, then there is still ignition to the coil, but the coil (unlikely) or HT leads could still be faulty. As I tend to look at the fuel pump relay as a wear part, I would start by replacing it as it will fail at some point anyway. It could very well be the cause of your troubles.

[360beast]

Originally Posted by 360beast

It could be many things, it could be the fuel pump relay is getting hot breaking the contact, probably a dry solder joint that gets hot and then loses continuity until it's cooled down enough to resume normal service. You can test this one when it dies by quickly cranking the car by literally just flicking the key to start and instantly turning it off. Then turn the ignition back on and if the pump primes it's probably the relay, also put your hand on it (big white relay behind the ash tray) and see if it is hot.

My mate had a similar issue to yours that turned out to be the MAF but that was because it had an eBay special MAF on it, a used Bosch one cured it.

It could also be the crank sensor breaking down due to heat and then once cooled down it starts working again. An easy way to test this one is when it dies pull the king lead off the distributor and stick a spark plug in the end and rest it on the block then crank it, if there's no spark or a very weak (orange/yellow) spark then it will be the crank sensor.

120k miles is nothing for these, mine is on 197k on the original pump etc, the only sensor that's been changed is the ECT sensor.

That should say if the pump DOESN'T prime then it's probably the relay.