96 Volvo 850GLT: Crank No Start

[bmdubya1198]

A failed crank sensor should kill spark. Those normally cause intermittent hesitations/misfires when they're on their way out. Unlikely to be a cause in this case, being that you still have weak spark.

That does look pretty bad though. Maybe not enough to kill spark, but I guess weak spark is a possibility. I don't think I've ever seen that much metal in a distributor cap.

[abscate]

Definitely new cap and rotor , then test coil by looking at spark at a plug right off the coil.

[erikv11]

Be sure to get Bosch only on the cap and rotor!! That's Robert Bosch from a reputable vendor, not Rupert Busch from eBay.

Check under the dust cap, behind the rotor. How do things look back there, is the metal plate rubbing on something?

[RickHaleParker]

Battery in good condition?

Pull the rotor off the shaft and check for cracks. Do the same with the cap.

What color is the spark coming straight out of the coil? ( to ground, not to the cap )

Disconnect the Camshaft sensor and see if it will start on the lookup tables. You would need to do a long crank to get it started the first time on the lookup tables .. If the Camshaft sensor is the problem.

[bmdubya1198]

That's Robert Bosch from a reputable vendor, not Rupert Busch from eBay.

Gotta watch out for ol' Rupert Busch. He'll get ya when you think you're getting good parts.

[erikv11]

I don't think an 850 will ever start with the cam sensor disconnected. That may be a valid concept in auto repair but in practice I've never heard of anyone doing it on an 850 (or any P80 Volvo). Worth a try but I'd hesitate to interpret anything from the test if the car fails to start.

[RickHaleParker]

That may be a valid concept in auto repair but in practice I've never heard of anyone doing it on an 850 (or any P80 Volvo).

I have done it on two white blocks. A '98 2.9L S90 & a '03 1.9L S40. It was the problem that brought me to MVS. The '98 S90 would start with the camshaft sensor disconnected but not with the camshaft sensor connected.

Jimmy57 deduced the the blocking cup was 180° out of alignment. Connected the ECM could not get the timing right. Connected it could get the timing right enough using the lookup tables.

The 03 S40 would not start after doing a timing belt that had jumped. Disconnecting the camshaft sensor forced the AI to rethink the startup condition. After I got it started one time on lookup it would start with the sensor connected.

One could say it is a way of doing psychotherapy on a ECM that not right in the head.

[LanceBoyerVLVO]

Ok so upon futher inspection and checking the spark; im getting 2 different colors at the same plug. I get bright white on half and red on the other half; does that narrow it down to weak spark? or do i need to keep digging?

Yeah I'll likely buy a new cap and rotor, the contacts inside are good/smooth but the amount of crud in there makes me want to get a new one anyways. Not sure where the metal shards are from, I noticed that as well when I removed it. Don't seem to be from the rotor and with smooth contacts I can't figure out what its from. Did a spark test after cleaning the rotor and I get a mix of red and white sparks in each plug... not sure what that means but I know red is weak; so now the question is whether its the crank sensor or maybe an ignition coil?
I read that a bad crank sensor would cause no spark thus a no start but I get spark. I can test that in the morning though...

Well frankly that looks like crap. I can't see if there is tracking on the contacts, but based on all of the metal particles I'm guessing there is some.
To those who know, would a bad crank sensor cause the no start problem ?

[RickHaleParker]

based on all of the metal particles I'm guessing there is some.

Could be crossfire arcing. Same effect one get when the inside of a cap is not dry. He could try wiping the inside of the cap clean and dry.

[erikv11]

And pull that dust cover and plate, and check the cam seal.