She has a 95 850 NA. Occasionally it will not want to start. I went over to thier house to help diagnose this last time. It was getting plenty of fuel but it was getting no spark at the spark plug wire or coil wire. It did have 12.5 volts reaching the coil on the red wire, but as I said no spark coming out. I pulled the coil to have her father replace it - but, he just put it back in after I left and WALA it fired. He tested for spark at the coil wire and it had more than enough.

Is the problem an intermittent coil short or could there be another hidden problem.

 

Maybe it was a bad ground or something?

 

I thought the same thing, but would I have shown 12 volts on the weak side and no high voltage out before removing the coil if it was a ground issue?

 

a full tune up is in order it sounds like..

 

Coil shorts usually aren't intermittent (but possible). I would say you do have an intermittent issue though... Looking at schematic i would ck connections on something called the "DI Power Stage" which is mounted in front of left front shock tower; the two coil wires (red and blue) go into it.

Also could be the camshaft position sensor, or any number of other things; poor connection(s) at ECM, etc.

BTW: easy way to ck spark w/o pulling high tension wires is with inductive pickup timing light; just clamp pickup onto coil (high tension) wire and crank over and see if light flashes...

 

Thank you for the answers. I did not have my timing light with me so the spark and jump method had to suffice. Just to reiterate, when I tested it I found 12+ volts coming out of the "DI power stage" unit going into the coil via the red wire. If there was a problem with "DI power stage or any other sensor or the ECM would there have been power to the coil still? If the answer is yes I will have her take the 850 to a mechanic to run the diagonstic codes.

Oh, also there are no check engine or any other warning lights coming on.

 

A tune up isn't going to fix the issue of no spark at the coil. I'd say if it's intermittent it runs deeper than plugs, wires, and cap/rotor.

 

An idea....The coil has 12vdc supplied to it via the two small terminals contiuously (not controlled,in this car, by the ECU). the coil/inductor is an energy storage device that will charge then discharge when the rotor hits the spark plug gap in the firing sequence(long story as to why but if you've ever been on the end of an open circuit, charged capacitor an inductor is no different). I'd make sure the coil has primary(12vdc) and then replace the rotor, cap and after that the wires.

 

these things need to be ruled out first. and probably need to be done anyway.

 

The answer is yes; but what about the blue wire at the coil; do you have voltage there (key in Run position)?

If no, then you have an open in your coil primary (or possibly a faulty Power Stage unit; if this is the case, disconnect primary wires from coil and ohm out the primary).