I have a 1994 ford f150 with an 300 - inline 6 engine. Cylinders 1 and 6 are not firing. Upon replacement of the two spark plugs they did fire for a few minutes. Then the engine went back to barely working. It's funny, it happened as soon as I started it up.

I took it to a mechanic and he said it has about 10 - 15 lbs of compression on cylinders 1 and 6. I've been waiting for 2 weeks now, and I was just wondering...

Does this sound like a cylinder issue with damaged rings or does this sound like a timing / valve issue?

I've been the one owner for 165,000 miles. It's been a rugged truck. The coil, rotor cap, wires and plugs are all relatively new.

Any feedback would be appreciated.

 

did the mech. do a dry and wet compression test? and leakdown test? that will narrow out whether its rings or not. if it changes then the rings are no good. if it doesnt change then you have a valve problem.

 

have a leak down test done, It will tell you if the rings are bad, intake valves or exhaust valves are no good. Anything more than 10% you should be looking at rebuild/replacement

 

With 2 low cylinders, why not just do a full rebuild on it and run it for another several hundred thousand miles?

 

165K on a 300, I seriously doubt something came apart in the bottom end. I'd lean towards a broken rocker arm, bent push rod, broken valve spring, etc.