96 850 turbo no spark, most of the time Topic is solved

greg850r · Post by **greg850r** » 09 Mar 2018, 11:20

If I wanted to invest in one that played well with Volvos, what would you recommend?

greg850r · Post by **greg850r** » 01 May 2018, 10:05

I'm just now getting back to this one and was wondering what the chances were that an ignition switch could cause it to crank with no spark?

Post by **abscate** » 02 May 2018, 03:43

greg850r wrote: ↑01 May 2018, 10:05 I'm just now getting back to this one and was wondering what the chances were that an ignition switch could cause it to crank with no spark?

Very possible but easy to test. Look forvvoltage at the coil while cranking, it should be right at B+ voltage it won’t be the same as the rest battery voltage while cranking but if it’s really low there’s A problem.

greg850r · Post by **greg850r** » 04 May 2018, 08:04

I have good voltage at the coil while cranking. There is no signal though. I already pinned out the ecu plug and checked all the grounds. Going to replace crank sensor and cam sensor again (3rd time). Sooner or later it has to work

greg850r · Post by **greg850r** » 17 May 2018, 18:19

Hi all, I'm back to looking at this one. I found this:

The ECM delivers the 5V reference and the CMP sensor grounds it to yield the 0V for that crank revolution. The CMP signal is needed by ECM to sort the firing order. 5 cylinders do not fire the various cylinders at the same location relative to the flywheel on each of the two crank revolutions it takes for all cylinders to fire (even cylinder count engines do have synchronous firing events relative to crank position on each rotation). There is no faking it. If the blue wire to CMP sensor has 5V with key on, engine off, CMP unplugged then all is good with ECM for that circuit. The red wire needs to have 10.5 to 12 V and the black wire must have good ground connection. Check the ground wire with ohmmeter battery ground cable off batt post. Or check the ground by backprobing at CMP connector engine harness side with starter cranking engine over, should be 0V to at most 0.2V.

Here:

www.matthewsvolvosite.com/forums/viewto ... st#p214687

I unplugged the cam sensor and the plug coming from the ECU shows 1 volt on outer Red striped wire, zero volts in the middle on the Blue striped wire, zero on the other outer black striped wire. Ohmmeter shows good ground on outer black striped wire and the other two not grounded as it should be.

Put in a different ECU and got different results on voltage test as follows:
I unplugged the cam sensor and the plug coming from the ECU shows 4 volts on outer Red striped wire, 2 volts in the middle on the Blue striped wire
Where to look next?

greg850r · Post by **greg850r** » 30 Jun 2019, 18:19

Well I finally pulled this one off the back row and it's back in the shop. Still no spark and still looking for the reason. (tried multiple cam and crank sensors last time). I did a sensor ready test with my obd2 scanner and all show grey on the screen. They don't show 'not ready' or 'ready', just grey like not there. I swapped another ECU from the same model and year and all I could get was 'failure to connect', so I put the other one back in.

tardcart · Post by **tardcart** » 30 Jun 2019, 20:02

with the blinking arrow, Ive heard a bad transmission computer will disable the ignition. Try swapping the trans computer.

greg850r · Post by **greg850r** » 02 Jul 2019, 06:48

tardcart wrote: ↑30 Jun 2019, 20:02 with the blinking arrow, Ive heard a bad transmission computer will disable the ignition. Try swapping the trans computer.

I think I did but it has been so long that I'll try another one, Thanks. Here's a picture of the scanner on a different car when I do a ready test and also what it shows on this one. You can see in the second pic that the reader simply sees nothing there on the individual sensors.

I just noticed something else, thanks to this advice; every other car I plug my scanner in to gives me a control module screen first and I need to select 'engine' or 'A/T' and then it goes to that diagnostic screen. On this particular car I never get the control module screen to choose engine or A/T, it just opens with the diagnostic screen like it isn't seeing the trans module.

UPDATE: I just replaced the fuel pump relay above the radiator and scanner behaves normally now, though still no spark.

greg850r · Post by **greg850r** » 08 Jul 2019, 16:22

Did a voltage check to CMP and coil and all looked well so I pulled the coil wire at the distributor and had my son crank it while I held it close to the negative battery terminal. 3 sparks, then nothing. I had him turn it off and try again; same result. Each time it sparked 3 times and then cranked the rest of the time with no spark. Can anyone shed any light on this? Is it a normal function that stops the signal for some reason?

I also noticed a second male spade on the solenoid with nothing connected. All my other 850s only have one, for solenoid engagement. I've seen plenty of two wire solenoids on my Pontiacs. The the plate in the solenoid contacts the other one when it hits the big starter motor feed and is used to supply 12 volts direct to the coil while cranking. (Turning the key on powers a resistor wire that supplies 6 volts to the coil while running.) I have no idea if this is relevant.

tardcart · Post by **tardcart** » 08 Jul 2019, 18:00

did you swap the trans computer?

96 850 turbo no spark, most of the time Topic is solved

Re: 96 850 turbo no spark, most of the time