Does not accellerate well??

[Trigger]

I recently finished a repair job on my 79 CJ5 w/AMC 304 V8 where I removed the timing chain cover to replace the front seal (I just hate oil leaks). This was a big job for just an average shade tree mechanic, and I was very proud of myself. When done, it started without trouble, and I was able to get the timing set perfectly (never done this before). My wife and I took a drive since it was such a nice day, and it ran great for about 30 miles. I got to my turnaround point, turned around, and the jeep wouldn't accellerate under a load. I couldn't get it to run in third gear, so I drove home very slowly in second gear. I can't figure out what is wrong. When I did the work, I changed the fuel pump, and all of the fuel lines while I was working in the area. I checked all of them, and there are no leaks. I cannot find a vacuum leak either. Any suggestions? Really dissapointed....

 

[Trigger]

Forgot to mention that it idles fine.....I can even press the pedal all the way down, and it revs up great. Just when it is under a load?

 

[alpha6]

It is a timing problem. Did you remove the distributor? Is it backfiring?

 

[Trigger]

It isn't backfiring. It worked fine for 30 miles. I checked timing as soon as I got it home and it was still dead one

 

[Trigger]

Runs great at an idle....can give it all the throttle I want w/o backfiring

 

[alpha6]

It has been awhile since I worked on a timing chain, but, I found this and it may help you...as while it looks like the timing is correct, the mark may not be in the right place. { One thing (probably the most important, actually) I forgot to get a pic of is to verify the timing marks by rotating the engine (use the HB bolt in the front of the crank snout again) until the timing mark on the cam sprocket is at 3 o'clock. Once there, stop rotating and count the number of chain pins between it and the timing mark on the crank sprocket. There must be 20 pins. If you didn't move anything when you took the old sprockets off, and installed the new ones with the chain taught, you shouldn't have a problem. If you don't have 20 pins, you have issues, and you'll have to start all over again.}

Whole procedure is at this link.
How do you change a timing chain on a Jeep 4.0 liter Inline-6 cylinder engine It has been used in Wranglers Cherokees and Grand Cherokees.

 

[Trigger]

I didn't change the timing chain.....just pulled the cover

 

[alpha6]

Oh sorry...misread your first post. Scratching my head on this one.

 

[Trigger]

Reminds me of a fuel supply issue. Checked filter and it is ok....going to let it cool and check timing once more. Whoever had the jeep before me did away with the fuel return line. I may go get another filter and rehook up the return line. I am scratching my head too

 

[Barry2]

While you're checking things check for smashed exhaust pipe or maybe in the muffler and lastly The cat converter coming apart inside.

 

[Trigger]

I have exhaust headers w/dual exhaust. Mufflers are simply glass-packs.....from what I understand, they shouldn't plug

 

[Trigger]

Ok, so I hooked up the return line and replaced the fuel filter, although I didn't think that was it. When I started the engine, I left the timing light to check the timing advance and t worked. I have it some gas with the air cleaner off, and fire flashed out of the top of the carburetor....that ought to help troubleshoot but I don't know what to check????

 

[alpha6]

It really is sounding like a major timing issue. While replacing your cover you did something to the timing chain or your distributor somehow advanced...either way you have to get that under control...hopefully someone with more experience will jump in here...you don't want to keep running it like that...can't be good for the engine.

 

[Trigger]

Thanks. I am starting to think the same. I noticed my timing chain seemed to have a lot of slack in it. Maybe it jumped a notch at mile 30? If anyone knows a sure way to diagnose the timing chain issue before I take all of this apart again I would appreciate it

 

[Torxhead]

When you check the ignition timing with a timing light and notice the mark on the vibration dampner is bouncing a lot when the light hits it then it is time to change the chain and gears. To see if the chain has skipped a tooth, put the #1 piston at the top of the compression stroke and the mark on the vibration dampner should be reading zero on the scale. I once skipped two teeth on a chain and it ran pretty bad. I wonder if a broken advance spring in the distributor could case the problem.

 

[Barry2]

Check your exhaust system for a restriction, the cat converter ( if you have one) may be breaking up inside.

 

[Trigger]

Have exhaust headers and glass packs....no converter

 

[Trigger]

Torxhead - I like the timing advance spring idea. I checked the timing while I reved the motor, and I felt like it advanced to quickly. I have a simple timing light and couldn't check it, and I couldn't watch the tach at the same time. I'll have my wife watch the tach tomorrow and compare it to the timing curves. Fingers crossed! This would explain why it happened all of the sudden......

 

[Trigger]

Torxhead - I checked the timing advance spring, and it seems real tight. I'm not sure what elese do do to check it. I have a question about your suggeston to diagnose a slipped chain. The harmonic balancer is directly attached to the crankshaft with a key way. Won't it always show TDC when the #1 piston is at TDC?

 

[csuengr]

Won't it always show TDC when the #1 piston is at TDC?

It will be close, unless the outer part of the balancer has slipped. About the only way to check for a shipped chain is to pull the timing cover off.

The fireball out of the carb indicates either the ignition timing is way advanced, or the cam timing is wrong.