Checking for spark

[blr]

Hi guys,

I just finished installing TFS heads on my 393W and now the car won't start. The engine ran fine with the old heads, but I can't get it to fire now. The engine turns over well when I hold the key and I can see gas spray into the carb when I pump the throttle. I tried testing for spark by holding a plug in the plug wire and grounding it to a head bolt then turning the engine over and also with a spark testing tool. Both times, I saw spark only briefly after releasing the key (ie: no spark when the key was held in the "start" position but 2-3 quick sparks after the key was released). I then put the spark tester on the wire coming from the coil to the distributor and the same thing happened, no spark when the key was in the start position but a few intermittent sparks after I let go.

So, what the heck is going on here? Do I have a bad coil or connection? Has anyone had a similar problem?

Thanks in advance,

Ben

 

[HISSIN50]

The issue, or at least this issue, isnt a component like a coil.

Check that your ignition is powered while cranking. It sounds like it only is energized in the run position. When you let off the key but the inertia of the engine keeps it turning over, you're getting a gasp of spark.

Also let us know the year and mods (ignition type, etc) if you need more specific info.

Good luck.

 

[blr]

Thanks for the help, your interpretation sounds pretty right on.

My engine consists of a Coast high performance 393W stroker kit, TFS track heat heads, edlebrock performer RPM cam and manifold and holley 650 double pumper carb. The ignition is the stock 1985 mustang duraspark ignition and the distributor is stock too. The coil is a crane cams model.

How would you suggest that I check when the ignition is powered?

Thanks again,

Ben