Weak orange spark 1995 850 2,0 10V

[Kokonradus]

I have measured everything and It´s all fine. So problem have to be in spark plugs. I will try the volvo 3 prong plugs (propably original for this model) and add a final post.

If would someone have same problem as me, start with measuring the power supply to the coil.

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ATTENTION ignition coil in this car is not grounded by its body, it is grounded by black wire to the car body. Make sure that ground is perfect. Measure the voltage on battery and then on the coil contact with blue wire and battery +.

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I try to describe what I studied about this topic last days from basics.

By turning the key to 2nd position you send current from 15 contact to the overload relay that activates and let the + from battery go through 40A fuse into the ignition power stage (on your coil). Than the current flows through the red wire to primary coil, from the end of the primary coil current flows through blue wire to power stage and than through black wire to the ground and circuit is closed.

When you turn the key to 3rd position the ECU start to cutting the circuit of coil by interrupting the signal to power stage in frequency of engine strokes (taken from crank sensor and cam sensor). Power stage is basically a transistor. (component that needs tiny amount of current and voltage to interrupt or regulate the bigger and stronger current and voltage like primary coil circuit). The interruption of primary coil circuit causes a magnetic field of primary coil to collapse and produce a high voltage pulse on a secondary coil that goes through cables and makes spark on your plugs.

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[jreed]

Best wishes for figuring out the source of the problem.
You mentioned that you replaced the spark plug wires with Bosch leads. I don't know if there is any difference in specification or performance between Bosch and Bougicord, but at least for the 20V car, Bougicord is the original spark plug wire. Have you already measured the resistance of the lead between the coil and cap, and between the cap and spark plugs?

[scot850]

Do you still have the original spark plug leads. Many times I have read of issues with aftermarket brands of leads, Bosch being one of those. As jreed suggests, checking the resistances of the new leads is worthwhile. If you have the originals try even one of them and re-fit it and see if there is any difference.

Did you also check that all the grounds are good, the main battery cables, especially the ground cable is good?

Neil.

[Kokonradus]

Do you have resistance values that the leads should have? What is the proper way to measure resistance between cap and spak plugs? I can check if originals make a difference. Will take the ones from my 2,5 20v 850.

Yes the ground of body and engine is good. But maybe I measure it wrong way. I placed one lead on battery positive and other lead on the engine, or on the car body. The multimeter shows me exact same voltage as it´s between battery terminals (+-0,01).

[jreed]

For the Bougicords, this info is located here ( https://rwblock.net/en/resistance-of-ig ... volvo-850/ )
"Resistance of ignition leads Volvo 850
Resistance of new ignition leads designed for Volvo 850 2.5 10V B5252S (Bougicord PN 6469):

cyl. #1: 4,97 kΩ,
cyl. #2: 4,47 kΩ,
cyl. #3: 3,58 kΩ,
cyl. #4: 3,13 kΩ,
cyl. #5: 2,58 kΩ,
to ignition coil: 2,72 kΩ.
If measured resistance is not in spec, then ignition leads should be replaced."

[800artfreed]

Sorry if I missed it but did you change the coil? My 98s have a coil mounted on the strut tower drivers side. This supplies the high voltage to the cap center lead. Good luck.

[Kokonradus]

Yes, coil is new with proper resistance. Thanks
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Resistance of my new BOSCH 0986357054 cables (OEM 9135701)

cyl. #1: 1,40 kΩ,
cyl. #2: 1,25 kΩ,
cyl. #3: 0,95 kΩ,
cyl. #4: 0,85 kΩ,
cyl. #5: 0,60 kΩ,
to ignition coil: 1,22 kΩ.
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Resistance of my used NGK cables:

Almost same as the bosch ones
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Resistance of my worn Bougicord cables:

In general, 2 or 3 times higher that should be by the original Bougicord specifications.
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I am unable to find Bougicord ones in my country, but I will try to find somewhere in europe and order. Than I let you know if that fixed the problem.