no compression - rings or valves?

[tmbfi]

My '92 Exploder w 144,000 miles has been running lousy and getting bad fuel mileage. For kicks i checked the compression: all checked out between 175-185, except piston # 5 which had no comopression at all. I put in a little oil and rechecked it...but no change. I took off the valve cover and watched a few rotations of the engine (with a remote starter) and everything looks fine. So is it my valves are bad or are my rings shot? And do have any recourse besides taking the heads off (internal engine degreaser, sea-foam, etc.)?

 

[Billy177]

try again because it is very hard to get 0 pressure but if this is in fact true thrn it is probrally valves

 

[aldive]

If when you added oil to the cylender, the compression had gone up, it would indicate bad rings.

Sounds like you have valve difficulties.

 

[justsearching]

The rest of the engine will appreciate it if you keep the 100% unburnt fuel mixture out of your oil. Pull the fuel injector harness from that cylinder's injector. If you had any compression I'd say run without the plug. Doesn't sound like it would matter.

Dave

 

[Maniak]

It can also be a cracked head... Our x had a cracked head between the valves on the #5 cylinder...

We had about 20psi compression on that one...

since the compression didn't go up with the oil you most likely don't have a lower end problem (unless you have a hole in the piston)... The problem will be from the head gasket and up.. That means heads and valves.. In my case, not only were the heads cracked, but the valve seats were pretty much gone.. (due to the cracking between the valves).. I got a new set of heads (with valves).. I think I ended up paying $550 for a pair, and I only got I think $150 for the core on one of my heads (the other one wasn't worth anything for a core)..

If you do need to replace the heads, get a set of 93tm heads (it says it on the heads).. They are for the '93/94 explorer and are supposvily(sp?) better than the ones that came on the '91-92 (they are all interchangable).

~Mark