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1996 850 Has spark, compression, fuel, won't start

Help, Advice and DIY Tutorials on Volvo's P80 platform cars -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, including 850 R, 850 T-5R, 850 T-5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

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regent
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Re: 1996 850 Has spark, compression, fuel, won't start

Post by regent »

Also, you could check for excessive current draw by the starter motor during cranking - this will create too much flux which will 'jam' the signall from the CPS (crank position sensor - it is quite close by and not well shilded). At the same time, the excessive load on the battery will pull the system voltage down a bit lower down than normal. (This is a known no-start with a seemingly working starter.)

Try to see if you can measure the draw while cranking.
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vmcrcr
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Post by vmcrcr »

Here's what it does without the plugs in the cylinders, just sitting in the plug wells.
Won't let me post the video I took.
The car does fire, shoots a small flame up from each cylinder for about 10 seconds of cranking, then stops.
If I put the plugs in and try and start it, it sputters briefly and then nothing. If I put my foot to the floor and hold it down it will not catch.

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Post by precopster »

You could have low compression due to cylinder walls no longer being lined with a film of oil known as "lawn mower syndrome"

The fix to restore compression is to place a teaspoon of oil in each cylinder. This restores compression and allows a start. While the engine is running, the splashed oil from crank counterweights allows cylinder re-lubrication.

If you measure compression before and after there is always a marked difference and also the starter will slow down as it encounters a higher load.
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Post by vmcrcr »

Did that. Have 200 psi compression in all cylinders.
Tried the oil trick.
Same results. A short little sputter then nothing...

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Post by regent »

Silly question here, you already know yor valve timing is fine. Your ignition setup is with a distributor cap. Can you doublecheck your firing order - this is all that remains: two or more plug wires are most likely crossed. Been there, done that.
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Post by vmcrcr »

Dist cap has not been moved.
It was running fine, and now has a no start condition.

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Post by Atis »

Just thinking loud and throwing in ideas...
Maybe your sparks are really not at the correct timepoint. Cam sensor can cause such a thing as well, although in that case you should have a code for that. Maybe somehow the ECU thinks that your sensor is OK not throwing a code.
With my previous car I had a similar issue ('85 Ford Orion), there the "amplifier" of the ignition system went wrong and although I had spark at the correct time, fuel and compression as well, but the spark was too weak. Oh and the real nasty thing was that as I have changed the ignition coil just as a trial, it killed that and after that when I put a known working amplifier in, it still did not worked because of the died coil...
Oh and one more. Did you checked the fuel pressure while cranking or in steady state? Maybe you have good fuel pressure in a steady state, but if you have a "blockage" in the fuel line, as soon as there should be fuel flow, your pressure is dropping.

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Post by vmcrcr »

Yes, we did check the pressure while cranking. Dropped a little, but not a huge amount. I'm beginning to think that the cam sensor failed. All the other threads seem to indicated that in order for the code to show up, the car needs to be running, and this one is not. I do have a couple of salvage yards reasonably close, with lots of inventory to pick through, might be worth a trip this afternoon to go get some cam/crank sensors and just start swapping stuff out....

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Post by Ozark Lee »

If the cam sensor fails you won't get spark. As I have glanced through this thread it sounds like you have everything you need to have a running engine.

One thing that comes to mind is that maybe you are flooding. If the fuel pressure regulator fails it can suck raw fuel into the intake manifold. Are the spark plugs wet when they come out after you crank it?

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vmcrcr
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Post by vmcrcr »

Sometimes. How would I test that?
The threads that I have looked at indicate if that fails I should have more than 40-45 psi at the fuel rail.

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