MagicMexican

So, last week I inherited a project Jeep. Or rather, my brother owed me $300 so he just gave me his Jeep instead. 94 Cherokee, 4.0L, red, manual trans, 4wd. He got it a few months ago, not running, and never got around to doing much of anything on it.

The PO was a kid from his church that knows next to nothing about cars. Word for word, "It doesn't work. I don't know why. It used to work, but now it doesn't."

My brother tried to jump-start it, said it started after a few tries, but ran like crap and sounded like it was misfiring. He shut it off and gave it a once-over, noticed that the radiator was dry and the hose to the reservoir was missing. Said, it's probably a head gasket, and never got around to doing anything with it.

So, now that it's mine, I figure before I try anything at all, I should check the compression. I used a cheap gauge from amazon, so I don't know how accurate the numbers are, plus the tick marks are in increments of 10 so I'm kinda guessing.

cyl 1 - 119
cyl 2 - 110
cyl 3 - 112
cyl 4 - 123
cyl 5 - 123
cyl 6 - 130

I figure since the 'normal' range is 120-150, and the odometer reads 202k, the numbers are barely within the acceptable range... maybe a leak between cyl 2 and 3? what do you guys think?

Anyways, my plan now is this: I'm going to replace all the plugs tomorrow since the ones I pulled were blackened and mismatched. Another thing I noticed is that even with a fully charged battery (fairly old, so maybe bad), no plugs, throttle body open, and no fuel, the engine/starter was cranking pretty slow. So I may also replace the battery and cables, see how it runs then.

I have plans to get it running and do Jeep things to it, so hopefully there will be a build thread soon...

Mouse4x4

Take spark plugs out of all cylinder and use compressed air to pressure each cylinder up. Listen for leaks either thru the other plug holes or out the radiator cap. That will tell you if there is a blown head gasket or not. The compression check can be misleading sometimes as the cylinders being dry and cold can also be off some.

Mouse4x4

Too do this procedure the fastest way is loosen all the rocker arms up so the valves are all closed.

BlueRidgeMark

Before you spend a lot of time and money on it, I'd give it an MMO soak for a few days, then repeat the compression test.

MagicMexican

Hmm ok that makes sense. I may do that, I'll see about getting a fitting for a compressor to the spark plug.

​​How would I go about doing an MMO soak/what would it do?

Remus Redbone

Marvel Mystery Oil. Plugs out, oil in.....

DFlintstone

Off the cuff here after a few beers...I wouldn't put allot of faith, or worry about those numbers. They don't necessarily show anything bad). Your battery, the cables, the temp the oil ect, your starter, all can affect the compression. Then after sitting the "thick plottens" "MMO" is Marvel Mystery Oil" Might have detergents that might desolve things to let the rings seat better and such. That or just a few table spoons of trans fluid in the plug holes won't hurt anything. (anytime adding oil to plug holes, a length of small, clear vinyl tube is handy. Suck in 2" or so in the end, put it in the hole, then blow)

I'd verify the oil was up on the stick and looks OK, then start it. Those numbers are not to low for it to start. You have been cranking it so it being "dry" is likely not an issue.

You should hear the fuel pump in the tank run for a couple secs after you turn the key on. After you do this two or three times, (or once), you should be able to see fuel spurt out of the Shrader Valve on the fuel rail, (like a tire valve) when you depress the thingy there. If you don't hear the pump, or nothing is spurting into the rag you are holding there, you have no fuel pressure.

You can pull ether the wire from the coil, or one from a spark plug insert a nail or screwdriver, and have your little brother hold it. If he falls over it's likely fine, otherwise set something up, (hold with insulated pliers or whatever) You want a crisp, mostly blue spark that can jump over 1/3 of an inch to any metal on the Jeep. (double that is OK to). If you are grounded to the jeep, and it gets you, it should feel pretty strong.

I you have spark but not fuel you can pull that stubborn rubber thing off the air cleaner and try it with starting fluid, at least see if it fires.

It's already yours. More complicated, (and meaningful) compression diagnostics can be done after she's been run.

cruiser54

Click MMO soak in Mark's post.

Agree with Flintstone. Numbers aren't that bad.

BlueRidgeMark

MagicMexican

Oh man. Sorry, guys! I don't know why I didn't realize that was a link. I swear, I'm not actually that dumb >.<

So, yeah, I guess I'll do an MMO soak, let it sit for awhile, and while that's going on, I'll drop the battery off at the autozone to get charged and tested, clean up, check grounds and maybe replace some of the battery cables.

There is oil on the dipstick. Who knows how long it's been there, but it's there and it's right below the high mark. The thick plottens... is that Hank the Cowdog I hear?

​​​Once I do the MMO soak and put in the new spark plugs, I'll see if I can't get it started. If it doesn't, I'll start digging deeper into fuel and spark and such.

cruiser54

Excellent plan. Keep us posted.

BlueRidgeMark

We all have our moments. Some of us have days.... and weeks...



I think I like this guy!

DFlintstone

Your battery, cables, and starter might be fine. I didn't explain well....It's largely the RELATIVE DIFFERENCE of the readings that tells the first part of the story. The actual highs of the numbers with everything all stretched out and warmed up does matter, but not so much. It's dependent on the RPM's. It might crank faster or slower depending on the rest of the business.

Nothing against it, but I've fired up well over a dozen old engines without knowing about any treatment. Cranking it (plugs out), with a little trans fluid or oil first is as far as I've gone.

MagicMexican

Well, I went to walmart and got the MMO and this cool little bendy funnel for 50 cents. I didn't want to just pour the stuff in and just guess, so I gave each cylinder a shot and a half.

I'll let it sit for now. Im busy tomorrow, so I think Friday night I'll put the plugs in and crank the key, see what happens. In the meantime, I've gone ahead and decided I'm gonna get this thing running or else.(if all else fails, there's a jeep place nearby that will sell me a completely remanufactured engine for $1300). It may take awhile, but I'll go over to the build section and upload some pictures of this giant piece of crap with my 'hopes and dreams' for it.

BlueRidgeMark

Make sure you spin it with the plugs out before you put them back in. You don't want a piston smacking up against an incompressible liquid on the compression stroke.