QuestionQUESTION: Hi Roland,
Per your instructions, I checked the coil 'driver' wire for voltage. I didn't see the initial 12V when the key is in "on" but it did seem to pulse at about 1V when engine was cranking. I'm not sure what else to do...
Thanks again for all your excellent help!
-Gabe
ANSWER: Did you say that you saw 12v on the single dark green/orange wire of the 2-pin plug when you turn the key to run, lasting for about a second? And when you crank it over does it still show 12v on that dark green/orange wire as long as you are cranking it?
If yes to both those questions, which indicates that the pcm is happy with the sensor signals and is thus closing the asd, then as
I think about it more I would agree that the 'driver' wire is probably spending most of its time grounded (and thus is putting energy into the coil primary) and then when a spark is called for the ground is lifted momentarily (thus the driver wire would show the 12v on the other end it momentarily) so I suppose that 'seeing' an average of 1v rms while cranking makes sense.
This being the case I can't explain your no spark unless the coil secondary winding is open or shorted to ground. But this is a new distributor, correct? If not, then measure the resistance between the coil tower and the ground pin (#5) of the 6-pin socket and verify that reads about 12k-18k ohms. If it does then I am stumped.
How are you testing for spark is the only remaining issue?
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Engine image
QUESTION: Hi Roland,
Yes, I am getting voltage on the single dark green wire. It was low but the battery was low so I replaced the battery and got higher voltage. I have been checking the spark by pulling a plug (tried 2 or 3 different ones) plugging it back into the wire boot and grounding the plug by touching it to part of the engine (two white arrows on the attached image). I finally gave up due to frustration and had it towed to a different mechanic who is now telling me the computer needs to be replaced. That seems weird since everything appears to be stopping at the distributor.
AnswerHi Gabriel,
The only reason to replace the computer would be if the spark driver wire is not pulsing, which we discussed earlier. However, we inferred it was pulsing from noting the rms voltage being around 1 volt, as opposed to 0 or 12v. It would be more accurate to look at that wire with an oscilloscope to see what it really shows. About the only other test would be to do the spark test right off the coil tower (remove and by-pass the cap and rotor) to see if there is any sign of a spark that way. I would expect the mechanic to show you that the driver is not actually driving the primary winding of the spark coil before opting for the computer.
One other possibility: Is the distributor ground wire on pin 5 of the 6-way plug well-connected to the rear of the front bank cylinder head? If that wire were loose or badly connected then that would cause the spark to be flaky or missing entirely.
Please let me know of any progress.
Roland
