1995 850 cranks but does not start

[seattle850]

Turbo sedan, 180k miles, starter cranks well, but there is no spark or very weak spark. It will start with ether after about 5-8 seconds of cranking but not reliably. Once it starts, it runs smooth whether cold or warm. I installed a used transaxle 2 years ago, and that functions, shifts fine.

"All Vovo", yes with no "L", a local independent late model Volvo specialist here in Seattle, replaced apparently every likely culprit part by part, including the ECU, all ignition relays, crank and cam sensors, vacuum lines, cap, rotor, wires, and plugs, and could not determine the problem. It does have 43psi at the fuel rail and with the noid tester each of the injectors is pulsing. After 7 hours of work they told me the problem was a weak spark, likely (but not certainly) because the transaxle bell housing mating surface was not cleaned properly and this was causing an improper ground to the crank sensor. They said I had to clean the housing on the transaxle to get a proper ground, but they were not convincingly certain. That sounds unlikely to me since the starter is grounded there and it seems to me that it clearly it is a good ground or it wouldn't crank the starter.

Starting with ether apparently works because a weak spark can ignite it. What should I try next? Please help.

[Juan62]

Sounds like fuel related. My 1998 S70 did the same thing over a year ago, replaced my fuel relays in the fuse box that did the trick for me. Mine has two, one red and one black fuses in the engine compartment fuse box.

[Ozark Lee]

On the list of parts that have been thrown at it I didn't see a coil but with weak spark that would have been near the top of the list. My guess is that the coil just didn't make it to the list of things you posted but that it has been changed.

You have 43 PSI at the rail, which is perfect, but what is the fuel pressure after the key is turned off? Does it hold or does it quickly fall to zero? A bad check valve in the fuel pump can cause the hard starting that you describe.

...Lee

[seattle850]

Ozark Lee and Juan, Thanks both of you. I should clarify that it still is very hesitant to start, even with the ether. Interestingly, without the ether, it will not start at all. I'm going to look into the coil, fuel pump relay, and check valve in the fuel pump. If it holds pressure and is not apparently fuel related, I'll swap the coil. I'll let you know what happens. I'm crossing my fingers, but I would think that mechanic did check the output at the coil.

Thanks again.