The van runs well...just not much power. Feels more like a four cyl than an 8. Shifts well. Oil pressure good. I pulled the plugs and they are as black as black can get so Im hoping my issue is a stuck valve(s). But I drove it to my place yesterday and the only noticable issue is that i get an intense steering wheel shudder at about 45 mph. Goes away above and below. So, I'll post compression values later this morning.

Thanks,
-G

 

Ok, I'm stumped. Here are the values:

Front of Vehicle
Cyl. 1: 150 psi 2: 150
3: 135 4: 0
5: 135 6: 150
7: 140 8: 155
Rear of vehicle

So I cant see why the one dead cyl would have two fully functioning cylinders next to it. I pulled the valve cover and no broken springs and while running everything moves as it should. I feel as though my compression values are good (except the 0)--they seem to be within 10% of the mean. The one dead cyl did not get any better with a wet test which makes me feel the rings are ok. There is no audible knock indicating a broken connector. Aside from the loud exhaust it sound real good. Am I on the right track? Any ideas?

-G

 

try this,disconnect the coil.(you do not want the engine to start) pull number 4 plug( or the cylinder with no compression) put your finger over the plug hole.have some one turn the engine over.(or remote starter switch if you have one) see if you can feel suction or pressure in the hole. if no suction or pressure you have a broken connecting rod.if you do feel suction or pressure you have a valve problem.(stuck or burnt) you will need to pull off valve cover then rocker assembly tap the valves with mallet to see if they are stuck its hard to see if valve train is working correctly with everything running

 

I don't know who told you this, but it is not an accurate diagnostic method. Whether a piston is not moving or a valve is stuck, you will not get compression (or suction) in either case. As long as there is no visible damage to the rockers, the head has to come off to know exactly what the problem is, there are no shortcuts.

 

I have seen broken piston rings be the problem.

A few years ago when I was working on small aircraft we had a plane come in for its annual checkup. This aircraft flew in on its own and though engine ran, it was not as powerful as it should be. We ran a compression test and found only one cylinder with a low reading, it read 0, we even looked through a bore scope and did not see any obvious problems. We removed the problem cylinder and found that the piston rings had broken into many pieces.

After you remove the head and if it checks out fine and the piston moves in the cylinder then have it removed to see what condition the rings are in.

 

Think you would want to know exactly where the problem is before you remove that head. You can look down the spark plug hole or follow it with a stick to confirm the piston is connected and moving up and down. If the rod is broken or disconected you will definately know that just from the racket you'll hear. You need to pressurize that cyl. with air with the valves closed and check for leakage. Burned valves or something stuck (unlikely) in them is what to look for. If you did the wet test and nothing changed it kinda points to the valves. Going to be pretty time consuming leak testing those valves with the head off.

 

Wasn't too concerned about that (we only have those old Sea Kings).
Still feeling my way around this site...........got severly reprimanded over at another for even suggesting such stuff. Feel better anyway, thanks.

 

with no compression, on #4
popping "backfire" in intake manifold?
any evidence of fuel in oil?
with engine running remove oil fill cap holding your hand @2-3 inches over fill hole, do you feel blow by?
intake vacuum steady?

IF no is common answer sounds like a exhaust valve burnt or ?

 

Ok, stupid question but how do I know the valves are closed on that cyl when I go to pressurize?

This is all extremely helpful stuff--thank you very much and keep it coming. Im stoked to see that the condition of the engine is not as catastrophic as Dodge made it seem. I need to get this thing back on the road and touring again. Thanks!!!

-G

 

Ok, verified that the piston is moving up and down no problem. I guess the next thing is pulling the head??? Im dreading it but if thats what needs to happen to get to the promised land of rock then so be it.