Delayed spark I’m losing my mind

garlendrix · Post by **garlendrix** » 25 Mar 2018, 18:54

If anyone could help, I’d be eternally in your debt. My 96 volvo 850 turbo is having an intermittent hard start issue. It will crank for about 5 seconds before finally getting spark and turning over. Once it’s running, I have no issues. This is what I’ve done so far:

Replaced ALL sensors and the ignition switch (coolant temp sensor, crank, cam, fuel pump relay, fuel injector relay and more I’m sure I’m forgetting)

I’ve done compression testing and that’s all ok, fuel pressure testing and that’s ok. Spark test and I get no spark for 5-10 seconds. Once I get spark, it fires right up.

Had two codes. One was for weak input from coolant temp sensor soI replaced sensor, cleared code and it hasn’t returned. The other was for a missing cam position sensor input so I replaced it and cleared code and it hasn’t come back.

Here’s where it gets interesting: I was moving wires ( to see if I had any that were broken) and when I started messing with the ones from the crank sensor, I noticed it started right up. Backprobed the signal wire and jumped it to a presumably good spot it the wire and no change. In fact even messing with the wire like I was stopped having an effect. Now the car was starting properly.

Started messing with the wires in the cam position sensor and it started reacting similarly only now by moving those I could make the car stall. I traced it down to the plug. By squeezing it, I could stall the motor. Decided to cut out the plug and hardware it to bypass any connection issues. Was very careful to connect the correct wires and suddenly, no start. The wires were twisted together and when I got the car started again, by touching the one bare wire with my fingers (keep in mind the wires had a solid connection) I could get it to stall. Got it started once again and started messing with the same wires but this time, they had absolutely no effect. Not even touching the bare wire could stall it. Nowhere else in the harness in the engine bay seemed to be effected when I moved the harness around.

I’m effing lost. I’m wondering if anyone knows what pins on the ecm would go to the cam sensor so I can run new wires to the cam.

Thank you guys for reading. I’m sure that got confusing and if you need me to clarify anything, please let me know

Post by **RickHaleParker** » 25 Mar 2018, 21:50

Which ECM, Jetronics 3.2, Fenix 5.2, Motronics 4.3 or Motronics 4.4?

garlendrix · Post by **garlendrix** » 26 Mar 2018, 05:19

I have a motronics 4.3 and a 4.4

Post by **abscate** » 26 Mar 2018, 06:36

You’ve got to get down and dirty and replace the wiring harness. The circuits are sensitive and if moving wires stalls the car you’ve got shorts or breaks buried inside

Post by **RickHaleParker** » 26 Mar 2018, 14:08

I have a motronics 4.3 and a 4.4

The three lines from the ECM to the CMP are:
Pin A36 Yellow-Red - CMP.
Pin A21 Blue-Yellow - CMP.
Pin A18 Brown-Black - ground to CMP via a junction shared with other sensors.

7/21 is the CMP.