7.4 Vortec 2 cylinders not igniting with spark.

[Squirrelizer]

I am at a loss right now. My 7.4 just won't run right. I have taken the spark plug out of the 2 cylinders and started the truck with them hooked to the spark plug wires. Both of them have spark but are not igniting. The truck still misses on the 2 cylinders. I have changed the 2 injectors out for those cylinders and also changed the wire harness for the fuel rail and still not igniting. These are missing on the same side. Has anyone had this problem? Please help!

 

[someotherguy]

Run a compression test yet?

Richard

 

[Squirrelizer]

Run a compression test yet?

Richard

Not yet. That is the next step. I didn't a tester handy. It is not igniting on the #3 and #5 cylinder. Are you thinking it could be a blown head gasket between the 2 cylinders?

 

[Squirrelizer]

So after pulling the heads I have found a big issue. I had about a half inch gap of burnt head gasket between each cylinder on both sides. I think it is time for some copper head gaskets. These only had 50 miles or so on them and a couple of sled pulls. It won the stock class but didn't run very good shortly after.