1986 2.8l V6 won't run--HELP!

[Sam Thomas]

Hello all, I recently bought an 86 Cherokee Pioneer with a 2.8l and a 5 speed. It will not start. My dad and I have replaced: the cap and rotor, plugs, wires, oil filter, oil, fuel filter, and ignition coil. It has spark in all cylinders. The fuel pump works well. I'm afraid the head gasket is blown. When I was changing the plugs, the center plug on the driver's side was covered in oil. I'm not very experienced in this whole engine thing, but this cannot be good. Are the rings blown? Please help- I am leaving for college soon and would love to bring the Jeep with me. Thanks

[glennco1]

First, you will need to do a compression check on all cylinders, that will determine if it is rings or head gasket(s). If it isn't that, the issues could be timing etc.

Unfortunately the 2.8 was not a very reliable motor, in fact it is considered the least desirable motor ever put in a Jeep product.

[Sam Thomas]

I've got some good news! I spoke to the previous owner today and he told me to hold the choke open w/ a screwdriver and then to mash the gas when starting and it went. Now it starts, runs, and idles. It still runs hot, and I'm afraid that that one cylinder still could be a problem. Thanks

[MagicRat]

Originally Posted by glennco1

Unfortunately the 2.8 was not a very reliable motor, in fact it is considered the least desirable motor ever put in a Jeep product.

I strongly disagree.
I have had a 1984 Jeep Cherokee with a a 2.8. I bought it new.
20 years with a 2.8 tell sme that its by far the most reliable component of the Jeep. I have also had identical 2.8's in 2 Chevy S10 trucks (one had 411,000 km and ran fine when I sold it (too much rust). Also I had a 2.8 in an Oldsmobile. It is an excellent engine, strong, reliable, easy and cheap to maintain and (rarely) repair.
The Jeep 2.8 engine only sinned due to its modest power output, which is still better than hundreds of thousands of 4 cyl. Jeeps made over the years. Also there are many good performance parts available for the 2.8, some of which I have installed on my own vehicle.

[Sam Thomas]

Does anyone have any experience with spark plugs covered in oil? Only one of the plugs has this problem, so I think it could be the rings. Any help is greatly appreciated. Thanks

[frankensteinsCJs]

If the timing it correct and the compression check it good, and all cylinders read nearly the same pressures, you may have a cracked oil ring. Try running a little thicker oil, and maybe some STP oil treatment, see if the plug stays a little less oil soaked. This may buy you a little more time until you need to go in to the motor.

I agree with "MagicRat", as long as there is oil in the 2.8 and you keep it running cool, they will last almost forever. I have owned an 86 cherokee right from the dealer with only 2 or 3 miles on it in 1986, and it came with the 2.8 in it.

That 2.8 has lasted for over 392,000+ miles. The 2.8's are slow, and are very weak at highway speeds, but I don't think that there is a more reliable little motor under the 200 cid's.

that's my to cets.

frankenstein

http://www.delattres.com

[TimWestTx]

for sure you have either worn or broken piston or rings
or a valve guide or seal is bad.

do a compression test on that cylinder and 2 others to see where
ya stand there

then, with the oily plug cylinder at top dead center of the firing stroke (ease it up to top dead center just after the intake valve closes), do a pressure test, put compressed air into that cylinder,
about 40 or 50 PSI and see if you can determine if air is leaking into
the crankcase, or out through the valves.

you can make your own pressure tester cheap and easy

purchase a pressure guage that has a scale of about 0 to 100 psi (don't pay more than 4 to 15 bucks),
screw it into a "T" fitting, on another side of the T fitting,
screw in a grease gun replacement hose (wal-mart about 5 bucks),
then take an old spark plug that fits your jeep, put it in a vise,
knock the porcelain off the top, and grind the top flat down to where the top of the hex begins, punch out the inner porcelain,
then drill and tap all the way through with same size thread as the grease gun hose has (1/8" pipe thread i assume), but, an auto parts house or nuts and bolts supply house can tell ya the thread size.
The tap will cost ya about 5 bucks.
Last thinig is to get a lil simple regulator like at harbor freight
(about 6 bucks to 15 or 20 for nicer ones) and screw into the 3rd side of the T fitting.
And, an air quick connect into that.
Then with an air tank, VERY carefully add air.

start slow and easy and usually you can hear where the air is escaping, thus, then ya know where your failure is.
Also, you just added a nifty and inexpensive tool to your tool box.

You can also do aleak down test with the same tool,
pressure it up to about 50 lbs, then shut off the regulator to where
no air can go in or out on your compressed air adding side,
and see how long it takes for how much PSI to leak out.

I searched and found this sweet web page that shows how to make one and use it:
http://www.xs11.com/tips/misc/misc3.shtml

good luck!

[Cam7]

I had a 2.8 in a Chevy had to replace bearings other than that it wasnt too bad. If you need a Quick fix for the bad plug try a anti fouler a small socket like that screws onto your plug. If its not really throwing oil too bad it will keep up the oil from getting on the plug.