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Hello Again:
You may remember the posts I placed based around the "Sparkless Green Bitch", a 1995 960 wagon that consumed many weekends, and finally ran again. My wife owns a 1995 960 sedan, that we had used to test components on. So, you can guess what happened... the no-spark virus populated her car. The symptoms were a bit different. It would run fine than die for no apparent reason. Pull off to the side of the road, start it up, and it would run fine till the next episode, sometimes 2 or 3 days apart. Well, it started doing it more regularly, so off to my favorite Volvo Master tech, Dave Motteler at Topping Volvo in Olympia, WA.
Dave traced and eliminated a whole bunch of things, and was concerned because it would be difficult to diagnose it when it was running fine. Methodically he went thru test after test checking out all of the components and connections. Miraculously, it failed the crank position snesor test while he was working on the ignition computer. He pulled off the connectors, and noticed that they were ever so slightly blackened with oxidation, and the female connectors seemed to be spread aprt more than usual. Now, you will have to have a very sharp eye to notice these conditions. The male prongs are silver plated, (the female connectors may be silver plated also).
The factory recommends you not disconnect the crank sensor more than four times, because this scrapes off the very thin silver coating, leads to oxidation, and renders the connection less than deisrable. The oxidation was so slight that I had not noticed it, and even after he pointed it out, I could barely see it. I think a magnifying glass would have shown it better.
I had also slathered a bunch of dielectric grease on the connectors, as I thought this would help make a better contact. I was advised to use only the Volvo recommended contact spray, as it will not cause deterioration of the silver plated connectors. A substitute spray is made by Wurth, and is called "Contact OL, Oxidation solvent". Description is: "Oxidation loosening cleansing agent for electrical contacts of all kinds".
Dave put in a new crank sensor, replaced both female connectors, and she has run fine with no problems for the last 3 weeks. Knock on wood.
If you are having intermittment sparking problems, or no spark at all, I'd look first at the crank, and second at the cam position sensor male connector contacts and make sure they do not have any black oxidation (silver tarnishes) or dullness on them. You may want to examine them with a magnifying glass. They should be shiney, not dull at all. If you notice dull connectors or some black oxidation, you can scrape off the oxidation and reassemble for a temporary fix, but I recommend replacing the sensors and their female receptacles. I know of no way to examine the female connectors without disassembling the connector, spreading open the females, and peeking inside. If you have gone to the trouble of getting it apart, you might as well replace the females too. Of course the female connectors require a special tool because they are so tiny.
Good luck with your 960.
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