I have a 1991 with 340,000 kms on it. I still can not figure out the stalling problems
which are intermittent and driving me crazy. My mechanic has replaced the coil, the
spark plugs and the crank shaft sensor. Also the fuel filter has been changed along
with the fuel pump relay. Oh and the distributor cap was also changed.


I was recently on the highway going around 110kms and felt the car all of a sudden
lose power. I pulled over and let it sit a bit. I tried it several times and the engine would
start but would not keep going. I finally got it started again and it ran for about half
a mile and stalled again. I finally had to get it towed as it finally would not start anymore.
This could be that I finally drained the battery after so many tries. Well I was told it
may be the throttle bottle; but who knows. I am frustrated with all this intermittent
stalling.
Totally frustrated and looking for some answers

Hello,
Your 740 should have an on-board diagnostics box to check for codes. Have you retreived any? Sounds like you have had just about everything related to fuel/ignition replaced. When it is not starting you should check to see if you are getting fuel to the rail and wether or not you have spark. It may be your ignition/fuel control unit.

Hello, I have almost the same problem but no solution so far. Have you any ?
Reginald

OP, ever figure out your problem ?

My 1991 740 has the same exact issue.

I have the Regina-Rex ignition system. New fuel pump, with new filter. New crankshaft position sensor.

Does the Regina system have different trouble spots than the Bosch system?

Hi there...

I had a friend who has a late model 740, which is actually a 940 base model but in a 740 shell. As far as I can tell (in Malaysia), most post 1990 740 were actually 940. You can tell by the dash console which looks semi-circle instead of the square-ish type of old.

He had the same symptoms and after a couple of tries & a new fuel pump, he found out that there was a wire which runs to the injection system from the injection relay panel.

All that about was a loose joint. Got that wire soldered and all was well.

I called him and he described the injection system which was something like an EZ116K - with fuel railing (early common-rail.?). You could also check the ignition control unit as mentioned earlier.

:beer:

Hello There,
My symathies. I am having the same issue. I had my 1991 740 taken to my mechanic and had the fuel filter and fuel line replaced then drove the 30 miles home with no problems. The next morning I left for work and 4 mile from home it stalled again. Had to have it towed as I could not get it started again.
If you figure out the problem let us know. I am out of ideas and cash.

I've been told the air mass sensor can cause that. I'm not sure if your model has the AMS.

I have a similar problem on my 740 but, so far it has only stalled at a stop, not on the freeway. Unfortunately, I switched out the AMS and still have the problem. It's very intermittent, maybe once a month.

I'm still searching for the answer too. Good luck.

Hi everybody...

All of our problems stated above seems to seriously point to the electrical side of things.

As far as I know, if it's fuel - the car's gonna jerk and shudder, while any mechanical side would be readily visible or audible.

According to the electrician friend, such cases are mainly due to the loose joints or disintergrated wirings, resulting in short-circuits.

These take a long time to suss out.

I just got back my 1992 940 which had all the wirings for the headlamps, fog-lamps (front & rear), brake-lamps etc...etc...etc...mixed up by previous half-baked air-con installers. The car was at the workshop for 3 weeks and my friend had the head-spinning job of individually testing each wire...!

Grateful - I made him sign a small advert sticker "This Volvo was re-wired by XXXXX", and was he proud...!

List of items that should be checked :

1) Ignition coil

2) Ignition control unit - a.k.a. Engine Control Unit over here.

3) Relay Control Board - especially the fuel injection relay switch

4) Air Mass Sensor (Air-Flow Sensor) connections. A little WD-40 on small screw-drivers to clean the pins - careful you don't bent them. BTW, if this is damaged, you can actually "limp" home although a higher RPM is needed - it'll stink due to the wrong air-/fuel mixture.

5) Alternator (this one's going to baffle everyone) - warm up the engine with all lights and air-con (or heater) switched on. Up the bonnet and touch the alternator body (careful now..!). You should be able to stand the heat up to 3 seconds or more. If it's less than that, get it changed 'coz it's gonna fry your system being insufficient supply.

6) Timing Sensor cable (if there's one)

7) Ignition switch - although I doubt it much.

That's about all he could think off based on his experiences.

P.s. I've been reminded time & again that when starting the car, it's recommended that we wait till the little orange light near the fuel gauge goes out, or at lease up to 5 seconds or more. This will allow the on-board system to be fully powered up and stabilised before cranking.

Loads o'luck. :thumbsup:

"When you hit rock-bottom, the only other way is to go up" - Atlantis, Lost Empire Movie

I have had a few Volvo's so far and the first one I had symptoms exactly like the ones in the first post.
A quick and easy way to eliminate a dozen possible problems: check the air mass meter. It is located right after the air filter and is in the 3" diameter air intake tube. It's about 6" long and has one plug on it with wires that go to the computer. When the engine stops running right, unplug the air mass meter. There is a little metal clip on the wiring harness - push this clip in to unplug the wires and unplug them.
If the engine starts up and idles roughly after a few moments, when it would not idle at all before, then the air mass meter is bad.
Once the engine is idling without the air mass meter plugged in, plug the air mass meter back in. If the engine dies in a few seconds, then the air mass meter is definitely bad!
A bad one will look exactly the same a s a good one!
A new one from the dealer will cost a few hundred!
Try to get one from a junkyard with a warranty, so that if that one is bad, you can exchange it for another one.

I changed almost everything related to the ignition and fuel systems before I found out about the air mass meter.

In case you are wondering what the air mass meter does and why it can totally kill the engine, here is a quick explanation: The air mass meter determines how much air is flowing past it. The more air, the richer the computer will make the fuel mix. Too much fuel and the engine will flood out and stall and cough and almost start and almost run and do many weird things, including black smoke out of the exhaust pipe from too rich a mixture. If the air mass meter is faulty, then it will send the wrong signal to the computer and the mix will be way off.
When the air mass meter is unplugged, there is a pin on the plug that will let the engine computer know that it is unplugged and the engine will use ba standard "default" fuel mix that should let the engine drive somewhat normally until you can get it somewhere to get fixed. This is called the "limp home" mode.

Hope this helps someone!! :thumbsup:

Cosmislobster,

I know that the AMM has filaments like a light-bulb and it heats up like one. The thing is rather warm (if not hot) after a few minutes.

Is this some sort like using the heat to measure the air temperature..?

The one that was previous changed on my 940 had a little screw which someone said that it was used to adjust the O2 (?).

The new unit didn't have this but works just fine. Perhaps the older unit WASNT the correct one and this has resulted in it's demise..?

:blush:

P.s. COSMICLOBSTER - great name, how'd you come by it...?