'96 850 T5 (B5234T, M56H): Crank, no start

[erikv11]

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Is it possible for sensors to struggle under high temp scenarios? Yesterday's ambient temperatures were 27'c when the hot-start failure occured. Temperatures since have been approx 10'c lower. I'm still not entirely trusting of either that fuel pump relay or the CPM.

Yes, failure of electronic parts under heat soak is a classic problem. Just remember the temp swings in the engine bay are what counts.

I'm also thinking "just jumper the FPR until you are sure the problem is elsewhere."

[Cookeh]

Any long term issues associated with jumping that relay? Presumably not given its being recommended, but worth asking! Keeping fpr jumpered certainly would help in the elimination of issues.

[erikv11]

People have reported keeping it jumpered for days at a time, I would use a wire for that not just a paperclip etc. And I would remove the jumper when shutting the car down for peace of mind and to keep me paying attention to it.

[Cookeh]

Noted, thanks. Its reassuring to hear that it wont have any significant impact. I've made a jumper cable from 14gauge wire and two spade connectors, so that shouldn't be a problem either.

[Cookeh]

Interesting. Rechecked codes today (Im doing it after every drive), and although I had no hot start issues or any starting issues whatsoever there was a DTC314 code - which is a missing or defective CPS.

I'm assuming now that in addition to a bad fuel pump relay my CPS was on its way out too. Im now hunting for a used CPS (only finding aftermarket items new currently - mostly PPS branded). I'd like to confirm this by either seeing the code again, or by it not starting when using a relay jumper - but then I can't wish the car to fail either...!

Tomorrow I'll recheck the wiring harness for any obvious and potentially reparable damage.

This brings me back to one of my original questions. The part number listed on the current sensor is Volvo 9146108 and Bosch 0232 101 023. Looking for replacement parts, the search of Volvo 9146108 brings up plenty good used parts, but they have a different Bosch part numbers (0232 101 030) - are they compatible?

[RickHaleParker]

but they have a different Bosch part numbers (0232 101 030) - are they compatible?

0232 101 030 is the Bosch catalog part number for 1996 850 2.3l L5.

[erikv11]

yes both styles are compatible, black plastic cap or aluminum cap. NA and turbo are all the same CPS, 95-98.

[Cookeh]

Thanks all. I have ordered a replacement. Tomorrow I have to drive 253miles, so I have a potentially very stupid question.I do apologise if it is stupid, I don't fully understand the role of the sensor (I know it is used to ascertain when to fire sparkplugs as crankshaft rotates twice for every camshaft rotation, but thats it).

Is the cam position sensor only used for starting the car, or is it in constant use throughout the drive cycle?

If it is being affected by heat, does that mean its potentially liable to cause a loss of spark whilst driving, or only when starting? To date I havent done more than 20mi in a single drive cycle since the start of these issues.

[scot850]

You need the CPS at all times. If it is faulty or engine loses signal engine will shut down.

I had an issue with a CPS n a 93 850 GLT and the engine would randomly just lose power for a few seconds or just die. If it died, I'd have to wait a while and then it would start right up.

Replaced the part with OE and problem persisted. What I figured out was the way the cable had been routed ran it too close to the distributor. The spark in the distributor was enough to kill the CPS signal. Re-routed it and no longer an issue.

Neil.

[Cookeh]

Replaced the CPM today, 5 drive cycles later and I have not had any codes or studying issues yet. With a bit of luck that will be the end of it. I'll be looking out for a spare for future incidents, along with spares of the fuel pump relay, and crankshaft sensor. I will also be looking for a few other relays, I guess.

Thanks all for your help, thus far.