1988 4.0l 4x4 5 speed - rough running engine. Need help

[absaroke]

I have a 1988 4.0l 5 speed 4x4 with 44,000 miles.  This Comanche has been in the family the whole 35 years.  I drive this vehicle everyday on the farm and into town 1 mile away.  Last month the engine began to run rough so I took it to my mechanic to check it out. I had him change the plugs and wires as I don't believe they were ever changed out.  When he took the distributor cover off, there was oil in the distributor.  As there is not "O" ring to replace, I had him install a new distributor.  I wasn't sure why/how oil from the engine would get into the distributor. This didn't solve the rough running.  He put on a fuel pressure gauge and could see a fluctuation in fuel pressure. He replaced the fuel pump, no joy, then the fuel regulator, no joy. He has a very busy country garage and really didn't have the time to devote to troubleshooting the problem. Like me, if I have fuel, air and a spark, it should run.  I now have the Jeep back in my work garage so I hope that someone here can help me.  When the mech did drive it with the fuel pressure being monitored, the engine would run smooth, then the pressure would fall and the engine ran rough.  The engine starts up and runs for a short time and then quits. Today I reved the engine and it seemed to start back firing before it quit.  Any suggestions as to where to start?  Why/how would oil get into the distributor, did something cause a blockage?  Is the distributor installed slightly off causing the engine to run rough?  Thanks in advance.  I love this old truck.

[Pete M]

have you cleaned up the rear ground behind the driver side taillight?  that's where the pump grounds and is notorious for causing issues when corrosion creeps in.  you should accomplish all of Cruiser54's MJ tips.  most are wiring related and cover the known flaws.  should be one of the first links in the link in my signature.  

[cruiser54]

www.cruiser54.com

 

Complete Tips 1 through 5 before doing anything else. And in your case, complete Tip 13

 

If the spark plugs weren't replaced before this time, I'm gonna bet the cap, rotor and plug wires have not either.

 

You can do all this stuff by yourself without paying a mechanic to do it. A few hours work at the most. 

[absaroke]

I'll look at it Tuesday unless we get the 6-12 inches of snow as predicted. 

[cruiser54]

It's never as bad as predicted. Mostly fear porn to keep the masses obsessed with the weather. 

 

Besides, with your head under the hood, you'll be fine. 

[absaroke]

OK, I have checked the main grounds, replaced fuel pump, fuel filter, fuel regulator, distributor, wires and plugs.  Starts right up, runs a minute and quits.  I've had this jeep since new. I'm old and want to find a new loving home.  Up until last month it was my daily drive. It has only 44000 original miles. Has rust. How much is it worth. It will need to be trailered to its next home.

[absaroke]

Believe it or not, while I was leaving this web site I saw some pictures of Ballast resisters. Thinking back to a problem 10 or so years back, another one of the mechs I use changed the ballast.  While going to feed the horses I stopped and removed the ballast and found that it was burned in half.  As the parts store was closed, I went back to my mech, he was open, dug through old new parts and found a ballast.  Put it in and the truck runs great.  Tomorrow I'll take for a run, more than backing it out of my garage and pulling back in.  $6 bucks on the box (it was very old) and seems as good as new.  

 

So now do I sell it or not.  I just started the hunt for a newer truck to pull a travel trailer.

 

Any takers, can have pics posted Friday as we will be on the road the next two days.  1988 4.0L, 4wd, 5 speed, 44,000 miles original, some rust but not bad as it could be.

[DAGAD]

I'm interested in hearing more about your jeep that you're considering selling:-)