95 850 Turbo No Spark at Ignition Coil

[dtmmoore2]

I am checking for spark going backwards from the plug which had none. I have so far reached the coil and determined there is no spark there either. I do not have a replacement coil as yet but in the meantime assuming for the time being that the coil is still in working order, I suspect that the next component to be checked is the 4-pin coil connector but I don’t have a means to test it.

I would like to know what component or components should be checked working backwards from the coil connector. Thank you.

[RickHaleParker]

I suspect that the next component to be checked is the 4-pin coil connector but I don’t have a means to test it.

DI power stage it is right there at the coil.
You can check (+) & (-) with a Multimeter.
(---) with a Oscilloscope
All three with a computer safe logic probe.


(---) pluse from ECM.
(+) 12V power
(-) Ground.

[dtmmoore2]

Hello and thank you for the info. In reading up on this online and talking to an independent garage specializing in Volvo’s, I am getting the feeling that trying to solve this no spark on my own is far more complicated than I had initially thought. The final straw was when in discussing with the mechanic the fact that there was no spark at the coil, he jumped to the fact that just because I had fuel pressure at the rail, did not mean the injectors were actually getting the electrical current needed for them to work. He also suggested that if I don’t know exactly what I am doing, I could make it more difficult for him to find the problem.What do you think?

Unfortunately this mechanic’s wait time could be two weeks.

So what I think I will do before calling the tow truck is:

1. Switch out the cam sensor with a spare one I have (Robert on YouTube has stressed that a faulty sensor is very likely the culprit although I am not sure why a faulty sensor would not be a symptom rather than a possible reason for not having any spark at the coil. If there was a straightforward method of bench testing it to ensure it works before installing it I would want to do that since the spare is from my car’s previous engine and has bee sitting in a box of spare parts for the past 6 years, but I imagine I’ll just have to install it and see if it makes any difference.


2. Change out the coil (I have already tried replacing it with a spare used one but now will install a brand new one).

3. Replace ignition wires, cap and rotor. I assume one or more faulty spark plugs would not be a possible reason for having no spark at the coil so I will not replace them unless you think I should.

Thank you for any additional thoughts you may have.

[dtmmoore2]

One last thing. I asked what would be the next component to check working backwards from the coil connector because I have already swapped out the coil itself along with the DI power stage which comes along with it. Is it possible to post the full diagram of the circuit?

[dtmmoore2]

I just found it: http://brickspeed.net/VolvoDocs/850-Dia ... n_3_39.pdf

Never would have thought the set of wiring diagrams would run 198 pages!