Troubleshooting

Had a friend with a '93 F150 5.0L call me yesterday asking for help.  He'd started the truck and headed to work, but it started bucking violently so he went home.  I went over and, to make a medium story short, he had a pre-heater hose to the throttle body leaking and squirting coolant - on the distributor.  

The parts store where our member DeWayne works didn't have quite the right hose, but they had a hose that would work.  We put it on, filled up the cooling system, and fired it up.  Yippee!  Oops?  It initially ran well, but then started dropping one cylinder all the time.  And a quick drive proved we still had a problem, albeit not nearly as bad.

Today he brought it over and we started checking things, including pulling plug wires and plugs.  Got to #6 and the wire came off way too easily:




Well, let's see the plug:




That mark at the top is where the spark has been going, and you can feel it with your fingernail.  Notice the porcelain blown out right above it?

The spec's call for ASF42C's, and I had none.  But I did have an ARF42-6, that I think has a resistor in it.  But otherwise it was the same reach, heat, etc.  So we put it in.  Problem solved!  

I love happy endings!

There's been more than a few times I've found an errant spark leaking to ground somewhere it's not supposed to.  

That was an astute observation, and easily missed.  Thanks for sharing it for collective databases.

To make a distributor less-sensitive to water, add dielectric grease inside the cap as indicated here:



...and a factory V8 boot (which will also work on I6 distributors).



Silicone grease is also recommended inside plug boots, but NOT on the metal contacts.