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1984 CJ7 will not stay running
07-25-2011, 10:03 PM
Post: #1
1984 CJ7 will not stay running
I have a 1984 Jeep cj7 2.5 4cyl 150 ci 4spd. It backfired out the tail pipe and spit fuel out the carb. I got it running but it ran rough, I gave it a tune up, plugs, wires, cap, rotor, got it running checke dthe timing its fine. I found the vacummn advance canister on the dist was rust frozen, so it is new and working fine. It idled fine I took it for a ride and it backfired again and died. I got it started but it ran very bad spitting and back firing all the way home. It made one loud backfire through the tailpipe and then wheezed and died spitting fuel back through the carb. It will not start. I replaced the fuel pump, Ign modual, rebuilt the re-man carb and checked for spark at the coil. Still it wont run. What am I missing? Can my carb just die? did my distrib die? is my ECM computer fried?
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07-26-2011, 11:34 AM
Post: #2
RE: 1984 CJ7 will not stay running
Could be a bad ignition module or coil but I would check the cam timing first as a worn timing chain can throw you a curve ball as it may jump one tooth at a time (advanced or retarded) and keep screwing with the dist timing in the process.

Let us know what you find.
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07-26-2011, 02:32 PM
Post: #3
RE: 1984 CJ7 will not stay running
(07-26-2011 11:34 AM)Rupe Wrote:  Could be a bad ignition module or coil but I would check the cam timing first as a worn timing chain can throw you a curve ball as it may jump one tooth at a time (advanced or retarded) and keep screwing with the dist timing in the process.

Let us know what you find.

I replaced the timing chain, gears and tensioner 2 years ago. I can't believe it could jump a tooth. Any other electronic issues I can look into that would affect timing? Fuel?
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07-26-2011, 08:45 PM
Post: #4
RE: 1984 CJ7 will not stay running
OK, you didn't mention that but keep it in the back of your mind as you go through the basics again.

Starting from scratch and now that it's not starting....

Are you missing fuel or spark?
Is the spark consistent and blue / snappy or weak / yellow?
Are all of the plug wires fully seated at both ends?
Are the plugs the proper heat range and gap?
All connections tight on primary wiring and connectors?
Ground strap from the engine / firewall / battery good?

Is there fuel up to the carb? (2-3 psi with a gauge and good flow)
Is there an accelerator squirt when you hit the gas?
Is the choke free and closed cold / open warm?
Is the choke pull-off working properly?
Is the air filter clogged or fairly clean?

While we are on the carb let's jump into other mixture basics...

Any major vac leaks at hoses, manifold gaskets, etc?
EGR valve sticking?
Carb base gasket blown out?
PCV valve blown apart?

Let's check the timing again as I have seen stripped dist gears and rotors that slip on the shaft, especially since you said the advance was frozen. There could be more "sticky stuff" inside the distributor.

Oh, one more electrical item, especially on an older vehicle...
Once you get it started check the charge rate at the alternator + terminal and see if it agrees with the battery voltage. I have seen poor grounds (alt to the engine?) and bad connections on the + side cause the alt to throw spikes into the electrical system and burn up ignition modules. (and other expensive stuff) If this has an ECM controlled carb it could also screw up the mixture once it's in closed loop.

Let us know if you find anything and we can chat more.
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