1995 850 Spark,fuel,compression and no start

[erikv11]

If the gauge is accurate (seems likely it is not at this point), then you have found the problem. At 120 psi you basically don't have compression, something is seriously amiss. I doubt it is just tired rings, pretty sure I have never seen or heard of an NA so low and 350,000 km on the engine is only average mileage (220k miles). Messed up timing would fit the lack of compression, I would look into that.

If the gauge is inaccurate and the engine actually does have compression then I would try getting junkyard CPS and crank sensors and swapping them in. Good idea on the fuel relay, just take it out of the equation. Since the problem is intermittent it is good to stabilize as many variables as you can.

[momentumbob]

I put in a new fuel pump relay just to eliminate that variable. I haven't tried the "lawn mower syndrome" gambit yet. The issue doesn't seem to fit with the intermittent nature of the problem but it's probably worth a try. If I can find a CPS in the salvage yard I'll try that. Not sure if I'd invest $250 in a new one.

Once again, thanks for the input
Bob

[FLXC90]

The check for "Lawnmower syndrome" is only the cost of some oil to put in the cylinders, and maybe 15 minutes. I'd say that is the cheapest, easiest step in your investigation. Go for the low-hanging fruit first!

[momentumbob]

The trouble shooting will be on hold for a while. Went out to the snowbank where the 850 has been resting, put the key in the ignition, turned it, car started immediately and settled into a smooth idle. Drove it around he block and it functioned flawlessly. Is anybody else confused ?

Bob

[erikv11]

I would test the compression gauge for accuracy, put it on your Expedition, that basic (key) question is still unanswered. So it still sounds mot like an intermittent cam sensor (or similar) problem.

[momentumbob]

Good idea Erik. I think I'll just make an adapter and check out the gauge on my air distribution system or take it to work and scope it out with a nitrogen bottle. The vehicle goes from absolutely dead to running well which, to my mind, points more toward an ignition problem. When I get it back in the shop I'll check again with the code reader and and the vehicles own on-board diagnostic. If it's the cam position sensor or the TPS it should set an error code. Stay tuned.

Thanks

Bob

[erikv11]

Hey just a heads-up: a bad CPS will typically not set a code. The car has to be running for the failure to register, so in a no-start situation you never get the code. Ironic, frustrating, but they way it goes. TPS will eventually set a code, agreed.

[Ozark Lee]

Just thinking outside of the box. In the process of trying to troubleshoot this have you removed the spark plug wires?

The illustration in the Haynes manual is dead wrong on the spark plug wire locations on the distributor cap and even the Volvo manual has the rotation backwards. If they are off, the ignition will fire but it won't fire at the right time.

The correct order is shown in this thread:

https://www.matthewsvolvosite.com/forums ... view=print

...Lee

[momentumbob]

Hi guys
Thanks for all of the input. It is time to square the circle. Despite visual evidence of spark on all plugs (checked twice) the engine would not respond to ether injection. Looks like no spark to me. I wasn't getting any error codes set. Ask me how i know a TPS error will explain a no start condition. I decided to go with a simple gambit on a part which would clearly not set an error code. I purchased and installed a new ignition coil. Problem solved. Car starts and runs reliably.

[abscate]

Did it go into no-start again? Glad you got this one done!!