What does "No compression" mean?

With a piston moving up and down in there you have to expect it to push some air. No compression means very little compression. Did they do a compression check? Or was that a guess? First off check to see if you didn't happen to get the #2 and #3 spark plug wires mixed up when you changed the wires? I would also check and see if you have some stuck valves. If there really is no compression that would probably be the best case scenario. Anything else is going to involve major surgery.

-jim

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Probably a blown head gasket between those two cylinders, allowing air to escape from one cylinder into the other. If it were just one cylinder, then it could be a stuck valve, but two side-by-side hints at a blown head gasket between the two cylinders.

No, because that's just air moving in and out at atmospheric pressure. IF the compression were good, all the cylinders would read the same and it would be in the neighborhood of 130-150 psi.

Why in God's name would you JUNK an engine for something like a blown head gasket? If it had two holed pistons, or a cracked head, then yeah maybe. Or if its otherwise a russtbucket, but Jeep Cherokees generally hold up really, really well over the long haul. On a Jeep 4.0, its a relatively simple job to pop the head off, look things over, and install a new gasket and have the head milled if necessary. Even if you didn't do it yourself, it would be under $1200, and I dare you to find a replacement car that you'd trust for that little.

I agree.

I had that just a few weeks ago on a 351 Cleveland.

The cylinder balance test in the EFI indicated that #7 and #8 didn't contribute properly, and a compression test showed that these cylinders had only half the compression of #5 and #6.

A piece of the head gasket between the cylinders was just gone.

Runs fine now with new head gaskets.

A Cleveland with EFI?

You can buy an inexpensive compression tester and check them yourself. As others have mentioned, having two side by side bad normally means a popped head gasket.

Have you overheated it recently? That is one way they pop, other times they just up and go. I bought a Jeep I 6 engine with 40K km on it that had been used hard and it had low compression between a couple cylinders. I removed the head and sure enough, the gasket was popped. I don't know if it was overheated, but I suspect it. That was 8 years ago and that engine is still running strong.

Mike

I would like to see the setup on that one. It sounds like an interesting project for mine.

Lugnut

On an inline 6 like yours, my money is on a blown head gasket between the two cylinders. Not uncommon. When this happens, they pretty much just shuttle the air/fuel charge back and forth between the two cylinders. Your only option is to pull the cylinder head, have it checked for sealing surface damage and flatness by a machinist. This would also be a good time to decarbonize the combustion chambers and resurface the valves. Some shops have a flat rate for a complete rebuild plus replacement parts if you hand them the head. There are also those parts suppliers that can provide a rebuilt exchange head at a decent price with a warranty. You have no option as far as removing the head and replacing the head gasket. If you ignore the other recommendations, you are simply rolling the dice that no other problems exist that caused it to fail in the first place. If you plan to dump the Jeep pretty soon, just do the minimum to get it going. Bars Leak probably won't work on a case like yours.

Lugnut

I also think it's a gasket problem. However, after reading about they blindly repalce fuel injectors for no good reason:

"Unplugging 4 of them made the engine start to die off right away but the #2 and #3 injectors didn`t seem to change anything when I unplugged them. So I figured those injectors were dead and replaced them"

I have to wonder about their automotive skills (or lack thereof).

Thanks for all the quick input..I will replace the head gasket this weekend..As far as my automotive skills I will admit that I lack a lot of "determining what is wrong" skills but I have the mechanical skill to be able to replace most anything on the engine short of actually pulling it and taking it apart internally.

That's fine if you have a 2 vehicle family, but myself, I only have 1.

When you have 2, you can fetch parts and take your own time. When you only have 1 like myself, something like this can rise to the Crisis level rather quickly.

I'm sure I can change my headgaskets also, given the rest of Autumn! See, that's the problem on my end. Only 1 vehicle, as to be done quickly. Lucky you if you have more than 1 truck or car.

Nick

I used to have at least two or more vehicles.About two years ago I sold all of them except my 1978 Dodge van and my 1948 Jeep.Jeep needs a total rebuild from the ground up.My 1978 Dodge van isn't in running condition right now.Last Sunday I bought a 1983 Dodge RV Conversion Van.I will work on my 1978 Dodge van when I get time.I am too fat to get behind the steering wheel of my old Jeep.It is nice to have at least two vehicles to drive. cuhulin

One cheap fix that has gotten pretty good reviews is this stuff called Blue Devil. I've only seen person come back saying the stuff doesn't work, but I've sold a lot more where the people say it fixed thier leaky head gasket etc. Just make sure you follow the directions to the letter. It costs around $62 a bottle and it has enough for 2 applications.

I'm also eliminating the distributor and will go EDIS. I now have all hardware done, and it just needs to be installed and wired up.

I have also installed a new Bosch 044 fuel pump, larger fuel rails, larger injectors. I'm also using a TwEECer for tuning, and was running on E85 at the time the head gasket blew. I don't think that had anything to do with it.

Thomas

Btw, it was featured in FordMuscle:

I saw some products like that but all of them seemed to talk about the radiator etc..It seems the head gasket leak on mine would be between the 2 cylinders and away from the coolant parts..I see no sign of any coolant in my oil etc

I have known about your car for several years. The conversion looks very professional. IIRC, the last I saw, you were still working out some minor gremlins but, the overall result was impressive in terms of fuel consumption and performance for a 351C. Keep in mind that head gasket failure on the 351C is fairly common because of the fairly close cylinder spacing and their tendency to detonate. They tend to need a lot of ignition lead to perform at their best. It can be a fine line when you are leaning on it.

I'm glad to hear you are still working with it. Cheers and good luck with it. I'll keep an ey open for your progress. I need to get back to work on my project so I can drive it after I retire in a year or so. Then, on the other hand, I may need an excuse to stay out of the house.

Lugnut

Having just become a Jeep owner within the last 6 months, I've become VERY impressed with the ruggedness of the 4.0. I'd always heard good things about it, but delving into more detailed reading and also hands-on has really made an impression on me. The thing is practically slant-6 tough.

Even when you have 6 and two are awaiting restoration, things can rise to Crisis Level more often than one might think... :-/

I have a theory that cars sit around the garage all night and make a plan on what they're going to do to us next. "OK, tomorrow you blow a cooling fan motor, I'll split a radiator seam, and you there... the red Jeep. Try to at least chatter the clutch a bit, will ya?"

Steve wrote in news:v5CdnRVir8lmjUHVnZ2dnUVZ snipped-for-privacy@texas.net:

You have to buy a Honda. Hondas spend their free time thinking about how much /better/ they can run the next day.