The truck is a 99 Ram 1500 5.9. To give some background info, this is my dads truck that he bought a couple years ago. He had a ping and noticed he was burning a little oil after he bought it. He replaced the wires/cap/rotor and that seemed to help him out with the power/ping problem. This last november we fixed his leaking plenum. About a month ago he had a bad knock and a code, checked the code, said #8 misfire, and when he took out the #8 spark plug, the end had been completely burned or broke off. He replaced the plug but still has the misfire.
So I need some advice on a low compression problem in the #8 cylinder. He tested the #2 cyl and got 150 lbs and then tested the #8 and got 80 lbs. Is there any way to tell weather its a bad ring or bad valve(s)? If it is a valve problem, is it possible to pull the head and rebuild that part of the head for that cylinder? I need any advice you can send my way. Thanks

 

Our heads are known to crack around the valve seal.....so the head may be cracked....and at the #8 cylinder is typically the first to go....pull the heads and put some 2.02 iron ram heads on, and you'll be good.

 

Cylinder leakdown test will tell the tale. Need the right gauges, and an air compressor to do it though.

80 pounds is too low. Yer gonna have ta pull the head anyway....... and hopefully NOT find a hole in the piston.