'86 PCM 351 won't start - no spark

[Graeme]

Hi,

Went to start my '86 Sunsport with a 351 PCM engine 2 days ago and there was no spark. In fact, the coil isn't even firing. I have 12.0 V going to the coil, but the coil isn't firing, it only reads 12 at the exit. The pickup in the distrubutor is working. I have a prestolite distributor with a magnetic pickup, and when I turn the rotor past the pickup the voltage at the input to the coil drops to zero then back up...just as it suppose to...but I still have no spark!

Anybody have any idea what is wrong?

[lively]

Check your breaker , and do u have a noid light ? Clean your cap and rotor , but I would double check that coil too ... Lol they tend to like messing up on me ...

[michael hunter]

Connect a test light from the neg side of the coil [Distributor side] and ground . Crank the engine and watch the light it should flash . What does it do?

[DKJBama92Mariah]

Coil is suspect. Google "how to test an ignition coil" and use your multimeter to test it.

[86 century]

If you have 12v at the high voltage or where the wire from the cap goes then the coil is most likely bad.

[Graeme]

K, we've replaced the coil. We tested, and even took the ballast resister out of the circuit. The voltage across the poles goes from 0 to 12 and the pickup goes by. I could put a light on, but it would flash. Have I replaced a bad coil with a brand new bad coil??

[michael hunter]

If the voltage is going from 12 to 0 with each pass of the pick up that rules out the primary circuit . The only thing left is the secondary [Coil,Cap,Rotor and Spark Plug Wires. Have you ohm-ed out the coil wire ? How are you checking for spark?

[86 century]

This is kind of a redneck test but.
Pull the coil wire out of the cap and stick a sparkplug in the wire. Make sure the plug has a good ground.
Make sure you have 12v or somthing close to that at the + side of the coil.
Connect a wire to the - side of the coil ground the other end for a few seconds.
Then watch the sparkpug when you pull the wire off of the ground.




The coil charges when it has power and ground will only send voltage out of the high tention side when the circuit opens.

[Graeme]

Sometimes life throws you a curve ball...I tested the replacement coil just direct to the battery and it was dead...a brand new one from NAPA. So I went back to the old coil, and it started firing...the more it has been used now the stronger it is getting.

All seems to be good now.

I HATE working on electrical problems!