Hey All I have a 1995 volvo 850 turbo that wont stay running. It starts and then will idle fine for 5-8 seconds then dies. I have replaced the fuel pump and filter. Fuel pressure is at 39-40 psi and stays there even when it dies. I have tried a new mass air flow sensor still same thing. I have cleaned the idle air control valve. Checked the plugs and wires cap and rotor spark is good but just looses spark after 5-8 seconds. Any one have any ideas? Oh and there is no codes.
Thanks

 

A few thoughts pop in my head:

A car needs air, gas and spark to run so it’s check the basics first. You got fuel pressure, so that should be ok.

"but just looses spark after 5-8 seconds" - you mean that literally? If so, it could be your ignition coil, alternator or battery.

What’s the gap of your plugs? Are they simple copper (which are best for our car) or those multi-tip, complicated unobtainium things?

Make sure the airflow is good; clean filter, throttle is clean, etc.

It’d probably be good to review the Stage 0 tasks while you’re under the hood:
http://www.matthewsvolvosite.com/200...hat-is-stage-0

 

Does it start right back up after it dies?

Assume you're cking the fuel pressure at the fuel rail?

Has the fuel filter been changed in recent history?

When you ckd the plugs were they wet/dry/black? Compression test?

Did this just start all of the sudden or any "events" precede it?

 

Literally the spark just cuts out after 5-8 seconds. I pulled a wire and put a spark tester on it and fired it up good spark for 5-8 seconds then just cuts out.
Fuel pressure was checked at the rail and filter was changed at the same time.
Plugs are copper gap is 35. The car does fire up right away when re started. Plugs were black when i pulled them so installed new plugs. Compression is 135-145 on all cyl. This problem just started one day no pre existing problems.
Someone please help.

 

Maybe something to do with ignition switch? Do you lose power on other components?

 

Hmm, a head-scratcher!

If the spark cuts out after 5 seconds then either the coil is going, or the thing that controls the coil is going - and I don't know what that thing is...

The plugs should be gapped at .028 - the car is quite picky about that!

 

First off your compression is on the low side but that obviously doesn't cause you to lose spark. And I agree the plug gap at .035" is too much; spec is .028 to .032". An interesting experiment would be to re-gap them at .028" and see if that changes anything; I suspect at a minimum it will run a bit longer than 8 seconds after that.

Loss of spark could be any number of things (e.g. a loose connection somewhere.. etc.) but to make spark the main components are the ignition coil, the engine speed sensor (top of the trans bell housing; senses crank rotation) and the camshaft position sensor (on back end of exhaust cam).

The resistance for the engine speed sensor (rpm sensor) should be between 200-500 ohms. But to really test it would need a scope; should see steady pulse train out of it that varies w/rpm.

The camshaft position sensor (aka CMP sensor) is a Hall Effect sensor; has 3 wires: 10v pwr, ground, and 0-5v pulse output on the Blu/Ylw wire. At starter cranking speed should see pulses from 0 to about 5v on Blu/Ylw wire. Again, best to read w/scope but this is slow enough that a decent meter may be able to see it.

But given the symptoms I would primarily suspect the coil; that's why I suggest the experiment above. Did you by chance recently do a compression test by cranking the engine with the key and not disconnect the primary side of the ignition coil? If so, you likely damaged your coil during the process. The other reason i suspect the coil is that faults in the other two components usually set DTCs (diagnostic trouble code) which you say you don't have. You can do resistance test on the coil but frankly those tests are inconclusive; I would swap in a known good used one or take it to a shop where they can test it under load.

Good luck and let us know what you find.

 

Ok so installed some new plugs at .028 still the same thing.I have 300 ohms of resistance at the crank position sensor. I checked the voltage on the blue yellow wire at idle and for the 8 seconds or so that it runs it switchs between 2.3v and 2.8v I don't have a scope to put it on but that is what i got so far. Resistance checked the coil and it is all good. Now did some experimenting and if i rev it up it will stay running for a bit longer as long as i keep reving it up. When it's about to die If i snap the throttle to the floor it will stay running until the rpm drops below 1500. then it just dies out. It always fires right back up and i don't loose power to any other components.
Any thoughts???

 

try replacing the engine coolant temp sensor located at the bottom of thermostat housing.

 

The computer is reading coolant temp at 18 degrees when it was 18 degrees out side. And temp readings do go up with engine temp.

 

Are you sure it is still losing spark causing it to die? Do you have an inductive pickup timing light? If so, clip that to any of the spark plug wires and observe; does the engine stop rotating about the same time you lose spark, or do you lose spark and then the engine stops rotating after that event?

Do the same w/CMP signal.

Are you monitoring the fuel pressure during all this? I ask because that's what it sounds like; but why it comes back immediately would be a mystery.

Like i said, only way to really test an ignition coil is to substitute in a known good one (or put on a load tester); same w/ignition pwr module under the coil. Shouldn't cost much at junkyard. BTW: I am not one to diagnose something by swapping parts; this is one of those cases though..

 

Not sure if it is cutting spark or just shuts down. Fuel pressure stays solid at 40psi even when it dies. Installed new cap and rotor today just to be sure. As well tried a new idle control valve. Still no go. Don't think it would be the coil since if I keep revving it up it will stay running. Well sort of when it feels like it's ready to die if i put it to the floor it will keep running. Still no codes. If i start it it will run from 8-10 seconds then die. It will fire right back up and do the same thing. Checked all the intake piping to make sure it was ok. Also checked the inter cooler to make sure it wasn't clogged. Its ok.

 

I forgot to ask, is it running rich when it does run (black smoke out the tail pipe and not running crisply)?

Oh yeah, have you checked the cam timing and belt tension?

 

Ok so checked the timing and it is dead on. Also pulled the cam position sensor to make sure the tone wheel on the back side wasn't loose. It was ok. Forgot to mention that i also changed the fuel pump relay when i did the pump and filter. It didn't change the concern but it is one more thing it can't be. Anyone please help. It runs good when it's running no black smoke or anything. Fires runs for 9-10 seconds and dies. Will stay running if you put it to the floor then can vary the rpm from 3000-4000 but as soon as you lift off the throttle it dies. Also tried a new idle air control and no go also tried to cut off the idle control and it wont run at all.

 

Oh and fuel pressure stays solid at 40-41 psi at the rail even when it dies.
Still no codes.

 

Have you started it with the MAF unplugged? If not, try that. It will surely toss a code then.

Sad to say that another guy was having the same problem last year and from what I know, never did figure it out. He had a '94 which had the problem (I think) and access to a '96 which he was swapping parts with. He was aware that some things changed between '95 AND '96, especially with the tranny. You may be able to search and find that thread.

 

Here is the thread I was referring to.
https://volvoforums.com/forum/volvo-...nth-ago-46403/

Not sure whatever came of it or if there were more threads about it. You can probably search all of his threads and find out more.

 

That sure doesn't sound like it's losing spark; really sounds like a big vacuum leak! Does your car have EGR? If so, I'm wondering if the EGR valve is stuck open... Again, are you sure the CEL is working (i.e. does it come in the key on light test position)?

 

Yes the cel is working it will throw codes if i unplug things. Like for instance running it with the maf unplugged. It did throw a code but didn't run any differently. I was thinking about the big vacuum leak but think i ruled that out when trying to start the car with the idle control blocked off. When I blocked it off it wouldn't start. The car doesn't have an egr valve so that couldn't be the problem.

 

Sorry dude; based on your input I'm out of ideas. Think it's time you get someone with some more sophisticated diagnostic tools (e.g. scope for one) on this; hopefully someone who knows how to use them too. A good tech with the right tools should be able to diagnose this in a couple of hours or less.

Keep us posted with any updates; conclusion may help a lot of folks!

If it is indeed losing spark before the engine dies then my guess is a sensor (most likely is crank sensor) is giving up. It just doesn't make any sense that it restarts right away every time.