92 960 cranks, but won't start. Fuel pressure is 44psi. Plugs all fire when laid out on top of engine. Component resistance checks look good.
IAC valve vibrates/hums with ignition on--engine off. Don't remember this happening before.
DTC's from former problems can't be erased using the Volvo manual instructions.
DTC 2 & 3 diagnostic checks won't perform. I suspect the ECM is bad. Any ideas out there? He-e-e-lp!

If this is the sticking valve problem, you can verify it by performing a compression test. You'll see low / no compression in the cylinder(s) that have the valves that don't close.

In that case, follow the procedures recommended in the faq about sticking valves. It describes the cause of the problem, immediate solution, and long-term preventive maintenance.

It's happened to me twice, and I've switched to Mobile 1 synthetic oil. Also always let the engine run at least two minutes whenever it gets cranked. Don't just run it long enough to move it in the driveway.

Good luck,

Robert

I had a thread going on this a while back. Check the archives under "6304 hard start 𖛼]󞩸]" for the whole story.
JD

The two times this happened to my 960 (6304 engine) it was because I started it and shortly (30 seconds max) shut it off again, after moving it from one side of my driveway to the other. These engines apparently do not like that kind of treatment, but need to be run at least a few minute before shutting off. Is this what happened to yours?
JD

Yep. Sticking valves after running it for about ten seconds (then shutting down). RWReagan put me on the right track. Basically, I just cranked it til it started. Lesson learned. No more very short runs to allow crud to stay on exhaust valves. And more spirited driving to preclude deposits. Good luck!

Lawn mower syndrome. Im not sure if this is the root of your problem although it is definitely a possibility. It hasn't happened to my car since I switched away from 10W30 to thinner 5w40 or even 0W40. Im sure 0W30 and 5W30 would have the same effect in colder climates. Good luck.
Justin