CJ7 running oddly

rtormet · 05-31-2012, 04:41 PM

Let me start witha little back story. I have been looking through the forum for a few days now trying to find someone who has had the same problem but have had no luck.

I bought my 84 Jeep CJ7 with a few problems with the intent of fixing them all.
My valve cover was the stock plastic one which leaked oil like crazy - replaced it with a cast aluminum one.
My water pump went out on the drive home after purchase - replaced it.
The stock carter carb ran OK at best - so i replaced it with a 1.08 Motorcraft 2100 that I got from ebay. I did a rebuild and made the custom brackets for the throttle linkage.
I started it up with the vac gauge attached and everything looked great. Ran smooth and it measured at about 19. Throttle response was great and all the power was there. Ran it down the street with no issues. Thought it was done and perfect.
BUT THEN i reved it up to maybe 2500 and heard a pop from under the engine compartment. The engine started to run roughly and the vac gauge was bouncing back and forth. I tried to see if there was anything obvious under the hood but nothing stood out. THEN after a minute or two the engine calmed down and got smooth. The vac reading went back to normal. I tried driving it around a little bit but under load the engine seemed to want to cut out. I had to feather the clutch and give it lots of gas.

I checked under the valve cover for a bad spring but again nothing stood out. Everything seemed OK.

So im stuck. Has anyone ever run in to anything like this before?

Thanks for the help!

**keman** · 05-31-2012, 04:57 PM

Still running stock ignition? For some reason, I would check the vac advance unit on the distributor. Not really sure, but that's just what came to mind first.

Did you bypass the ECM when you changed carbs? If not, a simple bypass will allow you to remove 90% of the ridiculous unneeded vac system. Research Nutter bypass, or take it one stop further and replace the distributor with an HEI diz. Thunderchicken has new ready to install units for a great price. Mine was under $80 shipped.

rtormet · 05-31-2012, 05:03 PM

Quote:

Originally Posted by keman

Still running stock ignition? For some reason, I would check the vac advance unit on the distributor. Not really sure, but that's just what came to mind first.

Did you bypass the ECM when you changed carbs? If not, a simple bypass will allow you to remove 90% of the ridiculous unneeded vac system. Research Nutter bypass, or take it one stop further and replace the distributor with an HEI diz. Thunderchicken has new ready to install units for a great price. Mine was under $80 shipped.

Ah i forgot to mention that all of the vac stuff has been removed by a previous owner so there is nothing to worry about there.

And im not sure about the ignition but I dont think it is stock.

Vac advance is running fine from what i can deduce but i will check out the distributor tonight anyway.

**Matt1981CJ7** · 05-31-2012, 05:09 PM

Get some pictures of your engine compartment posted up, so that we know what you are running.

And fill out your profile as completely as you can. That will help a bunch.

Matt

rtormet · 05-31-2012, 05:11 PM

Here are a few pics of the engine bay.

http://imgur.com/a/W9sPK

**keman** · 05-31-2012, 05:17 PM

Looks like you already have an HEI diz. Where is the vac advance getting it's vac from? Make sure it is a manifold vac source.

rtormet · 05-31-2012, 05:34 PM

Quote:

Originally Posted by keman

Looks like you already have an HEI diz. Where is the vac advance getting it's vac from? Make sure it is a manifold vac source.

Right now we had the vac advance coming from the carb - thats where it was attached on the stock carb when i bought the jeep so i just assumed thats where it went.

rtormet · 05-31-2012, 07:42 PM

just checked the rockers - each one was tightened to the proper spec - over the weekend ill remove each one and inspect them more closely
the distributor looked fine but i cleaned all of the contacts just for kicks

Mickey_Mouse · 05-31-2012, 07:54 PM

your Cam could need to be replaced

rtormet · 05-31-2012, 08:11 PM

Quote:

Originally Posted by Mickey_Mouse

your Cam could need to be replaced

Wouldnt a bad cam give me a constant problem not just one that went away after a few minutes?

BagusJeep · 05-31-2012, 08:16 PM

Looks like the Teamrush upgrade on the Motorcraft dizzie with something on the coil end. Hard to say exactly how it is plumbed togather but I would hazard a guess that your timing is governed by a basic Motorcraft setup, same as a standard CJ. If you have Motorcraft stamped on the vacuum capsule on the dizzie then it is for sure. The Motorcraft dizzie is a good piece of kit and worth keeping but checking for full operation and wear, you can buy quality parts to rebuild it if needed.

The symptoms you describe sound like a foreign object in the intake passing through the valves. When you had it all apart did you cover the inlet? It is awfully easy to drop a nut down there and it will pass through the engine once the revs build up. I would suggest a compression check on all cylinders to verify the cylinders and valves are within spec.

**keman** · 05-31-2012, 08:20 PM

Quote:

Originally Posted by rtormet

Right now we had the vac advance coming from the carb - thats where it was attached on the stock carb when i bought the jeep so i just assumed thats where it went.

Switch it to manifold vac.

I have had a vac advance diaphram tear in the past, caused all sorts of odd problems. Put a short hose on it and suck hard (no bad jokes guys). If it passes air, it's bad.

rtormet · 05-31-2012, 08:21 PM

Quote:

Originally Posted by BagusJeep

The symptoms you describe sound like a foreign object in the intake passing through the valves. When you had it all apart did you cover the inlet? It is awfully easy to drop a nut down there and it will pass through the engine once the revs build up. I would suggest a compression check on all cylinders to verify the cylinders and valves are within spec.

Hmm yea i tried to keep everything covered and never lost a part or anything into the intake. Compression was fairly consistent on all cylinders. 120 on all except #5 at 110

not exactly sure what spec is for compression tho

Mickey_Mouse · 06-01-2012, 02:03 AM

the cam and distributor go hand in hand. if you heard a loud pop, I would say a bearing in the motor. never over-rev a motor: in any gear: if anything else, check the carb again. did anything look odd with the distributor cap? bearings, springs, contacts?

BagusJeep · 06-01-2012, 02:44 AM

Factory specs were 120-150 psi with max variation 30psi. Sounds like your compressions are good, were these measured after the episode?