No start when at warm temperature Topic is solved

[122sPhil]

I have a boat that has an issue which i htink may be similar to described above. it has a coil for each cylinder. and in that case it also has a trigger.. anyway the cause can be that the coil is encased in plastic, the plastic degrades and it cracks, resulting in the fine wires shifting, one becomes broken ( interittently open)
my old speedboat will go 1 mile from the dock and then die. I think what is happening is that the coil ( or perhaps in my case the coil in the flywheel) has a break such as mentioned. initially it is ok it is closed, runs fine..
heat cuses things to warm and expand then the coil which has a break in a wire , which I cannot see, stops sending a pulse to make a spark.. in my case it is the spark generated within the flywheel, in this case the cars's ingnition system, perhaps.

different parts in a boat ignition system, sure, but I this may be a similar similar "type of" intermittent.

a coil may have many fine strands, one may have a break and be "almost sorta connected" but inconsistent.. heat may cause such a fault to "appear and disappear" as parts grow and shrink..

coil failures in older cars were usually quite rare but possible. offshore ones, I guess they may fail more easily, I assume more plastics are used now. old ones might have been potted in tar. I think the actual cause of this may affect many devices, may be pastic degradation. shrinkage, like how a dash cracks in time. the plastic is not dimensionally stable over the long term. planned obsolescence. the part was designed to work reliably for x number of years. It served its function.

[Pavel9]

Thanks 122sPhil... you have given me a lot to chew on. I'll start by checking connections - grounds. In another week we change over to our winter vehicle, the Rover, so the need to solve this Volvo problem now recedes.

BTW, I had a 1969 122s that served me very well although I remember the under dash windshield wiper motor used to get super hot...

Also notice you are a Vancouverite!

[Pavel9]

Finally had time (April 2026) to get back to the 850 Volvo. Nothing had changed so I plugged in my little scan tool and it read P0103 "MAF" this time. This was a different read out from originally when it read "Air Flow circuit high input". I do not understand why the scanner would read the same P0103 diagnosis but a different description.

Replaced the MAF sensor (Walker brand from Rockauto $65 Cdn) and now the engine starts when warm again. I have the impression the engine runs a bit smoother also. It's great to have the vehicle back fully functional again.

Thanks to everyone for their advice! Pavel.

[Pavel9]

I checked my notes more carefully and discovered the first code I recorded last year was not P0103 but rather P0445 - Evap valve signal. This Evap code no longer shows up. Very strange, but at least I know why I was not alerted to the MAF problem. Mischievous Greek God intervension? The old 850 runs fine!

[scot850]

That is great news. Thanks also for getting back and closing the loop on this one.

Neil.