1994 Volvo - Intermittent Stalling

At first it sounds like the imfamous "vapor lock" which tends to appear only when things get hot. I assume that your mechanic also replaced the fuel filter at the same time he replaced the fuel pump. I also assume that your mechanic checked to ensure full flow of fuel through out the entire fuel system when he changed the fuel pumps.

I'm not sure about the sensors on your volvo but it could be engine temp related. One way to test this is to block off the radiator airflow (put a peice of cardboard in just front of the radiator) and drive around the block for a few minutes to get the engine HOT... If nothing happens as the temp reaches the red zone then it most likely is not a sensor issue.

Still my first suspect is vapor lock which is the result of high temps and restricted fuel flow throught system.

Richard -

Thanks for your ideas. The stalling seems to occur at times when the engine is just arriving at operating temp. For example, the last time it happened I was about 4 minutes away from my house. I had been on the freeway for about 3 miles on a very mild day. It has stalled in a parking lot just a mile from my house. Higher temps don't seem to fit the scenario. Another clue may be that it stops immediately - no sputter or grandual loss of power that you'd usually associate with a fuel problem. It's like turning a light out. It doesn't falter or struggle at all. My mechanic did change the filter as well.

Still open for ideas.

Thanks so much for your time on this.

Dennis

When I say 'stall', I mean stop cold. It doesn't sputter for a second. Just stops, like you turned off the ignition switch.

I would suspect the electrical system. It could be heat related, or it could just be a loose wire.

When you do crank the engine, does it sound like it is firing, and then die when you put the switch back to the run position?

These days the ignition is handled by an electronic module. It used to be that there were 2 circuits for the ignition: Full voltage to the coil for a "hot" spark during startup, then a reduced voltage through a ballast resistor during normal run. They don't have that anymore, but the principle is still the same, 2 different supply paths depending on whether it is cranking or running phase.

This has happened so few times in the last few months, that it's hard to be absolutely certain, BUT... I don't believe it sputters or fires even a little. It's as though the last crank works, and it starts normally. I tend to add some throttle once it fires, almost as an impulse, thinking that it needs to be nursed along. But the engine really runs strong from the moment it finally fires.

Thanks

By 3rd time at cranking does the starter turn the engine the first two times?

Yes, the engine cranks. It just doesn't fire at all until the last successful crank. Then it seems to start normally.

Thanks,

Dennis

check for water in the gas tank.

gets sucked up at the strangest times.

My dear old Pappy said "There are only three things that stop a petrol engine from running. That's fuel, air and spark."

You mechanic can very easily check the fuel issue by removing the hose at the engine end and checking fuel flows freely through the system. (This then isolates fuel pumps, line blockages and such as the cause.) But I don't suspect this to be the case.

More likely is the pesky device known as the "body computer" that controls all circuits in modern cars. There is probably an intermittant connection INSIDE a chip in the control computer. When it is making contact, all is OK, but when it doesn't make contact, nothing happens.

There are a few cars notorious for this type of failure and the symptoms are exactly as you described. Complete and instantaneous engine failure, followed by frustration and then without any reason perfectly normal running conditions until it fails again and then eventually fails permanently.

Suggest your mechanic friend examine the body computer (BEM) or whatever you call it over there for signs of damage, and get a spare one lined up ready for when it fails.

(Words of experience, as I currently own one of the notorious models.)

Hall effect sensor inside the distributor is my guess - been there once.

Edmund

If your daughter is one (like mine) who runs with the tank almost always less than half full, you probably have a lot of condensation collected. Add Meths (denatured alcohol) to the tank, say a pint to a full tank, it should carry the water through and burn it. You may have to do it twice for a full fix.

One pint should suffice to carry enough water away that the car runs much longer between stalls.....if not for years......

In the future, only fill up fully........

That's an easy remedy to employ. Thanks so much, I'll give it a try.

I appreciate your time.

Dennis

My daughter lost her gas cap. Didn't replace it for months, or years. The car died at the strangest times.

After many new parts, they found a quart of water in the gas tank. Even in the desert it rains sometimes, and water found it's way into the tank.

It was fine after that.

She has her own children now. She'll get paid back.

Your intermittent stalling is symptomatic of a failing crankshaft position sensor (mounted on the top driver side of bell-housing, at rear of engine.) Takes 5 min to remove and replace, costs about $100. It is nice to you-giving so many warnings over time. It may continue to do this gradually getting worse--or the the next time maybe final act. Probability of this as cause-90%+

You dont say what model of volvo,but I had similar prob with 740/940.It stopped completely randomly, but of course at times to cause maximum embarrassment!

After 7 visits to dealer,changing sensors, ECU, etc changed fuel pump relay,end of prob.As it was fuel injected as soon as underfloor pump stopped immediate loss of pressure to injectors, and stops just as if ignition failed.I dissected the faulty relay and could find no fault,but the prob never recurred.

It's a 940 turbo. It doesn't falter, like it's running out of fuel, but I know that injection needs a high pressure feed of fuel. When it's cut off there's immediate loss of power. Fuel pump relay sounds good.

Thanks for your input.

First of all, welcome to the insanity.

Second stop guessing. There is a simple device that attaches to a spark plug wire that has a neon bulb in it that stretches far enough to allow the neon light to be seen from the windshield area while you are driving. This will you to see the light constantly as you drive. That way you will be able to isolate fuel from spark. Don't forget that the injectors are now electronic. If they loose power, they will stop injecting immediately, killing the engine just as fast as a dead coil does.

A more expensive tester is available. But it will give better results. It can plug into your OBD II test port. It will have a freeze frame function that can read all sorts of information that was present when the engine died. These testers should be around $400. It may seem a lot of money for a tester, but look at what a trip to the Volvo dealer is going to cost. And think about this that car is 15 years old. How many of their mechanics were even working on cars when yours was new? good luck.

Now that I think about it, your Volvo may not have an OBD II port. If you do not have the port, the OBD II tester may not read the earlier information. Check with the manufacturer of the tester before buying it. The good news is that if it is not OBD II it is a lot less complex to diagnose. More of the sensors were independent in their functioning.

Same problem with my '87 760 Turbo. My mechanic found two problems. One was a bad ground wire under the engine. Check all you wires, they seem to deteriorate over time. The bad ground fried my ignition Module. The shutting down while running - on freeway, at border crossing, rolling in a parking lot or just at a stop light - was frustrating. It got to the point that it shut off on the freeway and I had to have the car towed. It took the mechanic 1 week to find the problem and he had to bring in a auto electric (I live in TJ) to find the wiring problem. Now the car runs awesome. More power that it has ever had. Difference is like day and night.

If you want to call me, click here:

https://me.vonage.com/mglatfelterjr

Use this to call me toll free.

I think we found thwe problem. We replaced the fuel pump relay switch and the crankshaft position sensor (mounted on the top driver side of bell-housing, at rear of engine). I'll never know which one of those things it was, but it's been running perfectly ever since.

Thanks for your contribution.

Dennis