Question for you master mechanics

Logan · Jun 4, 2004

Check all of the vacuum lines to make sure none are loose or cracked. If one is bad the engine could lean out after the choke opens. One more thing check the ignition switch itself, bypass it with a straight wire job. I've seen one cause a similiar problem years ago.

Bird · Jun 4, 2004

That's a neat looking little Jeep, Rick. I know a lot of people sure were unhappy when they quit making them.

JerryG · Jun 4, 2004

Rick,
Looks like a fun little rig. You are right, the problem will be something that is awful simple when you find it. Those are the worse one. /forums/images/graemlins/frown.gif

JDgreen227 · Jun 4, 2004

I had a '79 F150 pickup with the 302 V8 that I installed an aftermarket Sun tachometer on, the tach was triggered by a wire attached to the ignition coil. After about a year the engine began cutting off at speed, it would surge, then die, and usually would not restart for a while. It drove me nuts trying to deduce what the problem was, it always started fine when cold and there didn't seem to be anything wrong with coil, electronic control box, etc. After spending too much money buying new parts which didn't cure the problem, I decided to disconnect the tach coil wire to learn if that was the cause.

Yes, that was the problem. /forums/images/graemlins/frown.gif

Every since then, when I have a problem with a vehicle not running properly, the first thing I do is disconnect any add-on electrical equipment.

"awful simple", yes.

JimR · Jun 4, 2004

Your problem sure sounds like it is fuel related. Start with some basics first. Make sure you have a good spark at the plug end of the wires. If not , then check your coil wire at the distributer end. If not, then work back from there to find the short or loose wire, bad electronics whatever. If you have a good spark at the spark plug wire end, then attack the fuel system. Check the fuel flow from the fuel pump when cranking over the motor if the pump is mechanical. Go north from there if the flow is good. If not, go to the rear. The Jeep will run with a stuck EGR valve. It just won't run smoothly. You can close it with a screw driver and unhook the vaccuum line to keep it from working. A stuck heat riser will not keep it from running either. It will cause the manifold to heat up more than normal. Good luck tomorrow with your problem.

bgott · Jun 5, 2004

Does that thing run a Ford blue grommet module? The Ford module is about four inches square, about 1 1/2 inches thick, aluminum, mounts on the wheel house or the firewall and it has a blue grommet where the wires come out. If it does, change it. They are famous for crapping out and the symptoms are the same as a bad fuel pump.

I worked a car lot that ended up with one of those Jeeps that had a 318 Chrysler stuck off in it. No top, no seat belts. It would carry the front wheels for a half a block. We couldn't retail it in California because there was no way it would pass smog so I used it for a shop truck with a dealer plate. That is, until the boss caught me doing wheelies up and down Miner Ave. one day. /forums/images/graemlins/cool.gif

RBManufacturing · Jun 5, 2004

Hi Guys, Thanks for all the ideas. I had planned to tear into it this morning, but wife noticed a water spot on ceiling last night, so I guess I'll be on roof today. It is suppose to rain heavily tonight. Maybe tomorrow I'll work on the jeep.

bgott, I talked to a guy in Alabama yesterday, and he has a 454 c.i. v-8 in his postal jeep. Has 10 inch wide slicks. Says it will do wheelie at 3/4 throttle. Has never had it to the floor. Says he is afraid it would go over backwards. Now that's carrying the mail. It has stickers on it that say "POST THIS YOU SISSIES!" And one that says "GONE POSTAL". Thanks, Rick

JDgreen227 · Jun 5, 2004

If that guy with the 454 V8 has the OEM rear axle in his jeep, no wonder he has never used full throttle.... /forums/images/graemlins/grin.gif

Likely has a narrowed Ford 9 inch instead. Good luck with the roof project....

RobertN · Jun 5, 2004

The AMC corporate axle is actually pretty beefy. They tend to have an issue with twisting the axle tubes though when big engines or tires are added. Seems they did not weld the tubes to the carriar section with welds big enough for extra hp...

The frame would easily be suspect as a 454's weight and tourque could twist it up /forums/images/graemlins/shocked.gif

bgott · Jun 5, 2004

You need to weld the hubs to the axles, too. They don't have a keyway, just a Morse taper and it can be overcome with enough torque.

RBManufacturing · Jun 9, 2004

Hi Guys, Well I checked the ignition wiring, installed a new magnetic pickup in distributor, and replaced carb AGAIN. I think we are getting closer. I did discover that the coil gets VERY hot after it runs for 5-10 minutes. It does not have a ballast resistor. I will put one on today, even though it does not require one. Also, the ignition module gets pretty warm. Not sure if it is suppose to. But as I said, the coil gets very hot. I don't believe it should. RIGHT??? I checked the altenator to make sure she is not overcharging and causing coil to overheat. Putting out 15 volts. What is the difference in a standard coil, and a heavy duty? I installed a standard. Could it make a difference in coil over heating? I can say one thing about all I have re-placed. When she does run, she runs Great! She will only run about 10 minutes though. Thanks for any help guys. A debt of gratitude, and a FREE tiltmeter to the one that comes up with the solution! This is getting expensive, and very frustrating. Besides all the parts, the wife makes me put a dollar in a CURSE word jar when I say bad words. The jar is overflowing! The neighbors are starting to take their kids inside when they see me raise the hood on the jeep. Thanks, Rick /forums/images/graemlins/confused.gif

gspig · Jun 9, 2004

This could be the same dreaded problem that happens to 8N tractors. The coil will fail when hot. You might try a ballast resistor with a NEW coil. If you are using the coil that you said is getting real hot, the damage is done.

California · Jun 9, 2004

Ok after you've tested and replaced everything else... Here's one of the most unlikely possibilities.

I had a similar experience with a 401 Wagoneer I bought from a 'mechanic' who held a smog cert license. Even he couldn't get it to run right. I think it had the same distributor as your 258-6.

After replacing nearly everything as you have done I discovered the real problem: the wire from the distributor's mag pickup went to a terminal, where there was another permanent wire that would rub against the distributor enclosure - but only when the vacuum or centrifugal advance rotated the plate that the pickup was mounted on. It was hard to identify the problem since the wire looked fine, had plenty of clearance when viewed with the engine off, and seemed to be mounted in its original position.

It had worn through the insulation so every time that wire grounded, the coil would fire an out-of-time spark to whatever cylinder the rotor was pointed toward. This explained why it would sometimes try to run backward when starting. Replacing that wire solved the problem.

Unfortunately that turned out to be #1 of about 50 difficult problems I discovered on that Wagoneer so I traded it to a Jeep/AMC dealer soon after. Then I started getting calls from a local agressive high-profile attorney who bought it at the auto auction and wanted to hold someone accountable for all the problems he discovered! I explained that's why I didn't sell it private party and he should look to the dealer who auctioned it. I think he called me three different times over the course of a year, angrier each time. The Jeep dealer must have hung up on him or something.

bgott · Jun 9, 2004

Coils and modules run hot. Electronics in general run pretty warm. What kind, as in make, of ignition system does your Jeep run? AMC never built their own electrical systems and they used different vendors all the time. It might help if we knew what kind of electronic ignition this thing has in it.

Ozarker · Jun 10, 2004

Are the ignition components not original.....ie......has someone converted it?

When I lived in Germany back in the 70's, a buddy of mine had an AMC with a HEI system........coil in cap. His distributor shot craps and he couldn't get another one in time to ship his car back to the states. So I pulled a conventional distributor and coil out of a junk AMC to get him running so he could ship the car the following month.

Two days later he called and it had quit running on him. The points were fried.

What I discovered, (if all else fails read the manual) was that the ignition wires for the conventional ignition had a resistance wire to the coil reducing the voltage to 9v. Cars designed for the HEI didn't have that resistance wire and V was delivered to the coil.

I replaced the points and installed a ballast resister from a junk Mercedes I had and it worked like a champ.

You may have the same problem if someone has converted your ignition components before you bought it.

RBManufacturing · Jun 10, 2004

Hi Guys,
The jeep is suppose to be original according to the third owner. However I do not believe he knew anything about it. He acted like he was not mechanically inclined at all. Not sure that was the case. When I bought the jeep, it had a replacement coil, electronic ignition module,ignition switch etc. According to the repair manual that came with it, it does not require a ballast resistor. But, the local napa store shows it requires a ballast resistor. I bought one, and a new coil yesterday. If it ever quits raining, I will be installing it. I am beginning to think we have a combination of non-compatable parts. I believe the old girl has been modified more than it should have been. Book shows a pollution pump. (not there).
Also shows a totally different type exhaust manifold, and egr valve set up. What I cannot understand is why she ran great for 2 months before deciding to quit. All parts I originally replaced were exact replacements for the ones removed. There is no makers name on coil, or number. No name on electronic module either. All parts I am replacing are what napa says it calls for. I'll keep you posted on new coil / ballast installation. Thanks, Rick

To20Chris · Jun 10, 2004

Check the vacuum operated emissions system parts. Thermal vacuum switches control much of emissions devices. If it runs until it reaches the switch temp, then it opens up a defective device (say a diaphragm with a big leak), then that could kill it. You’ll want a Jeep vacuum diagram. Look at the EGR, charcoal canister purge valve, spark advance system, air cleaner intake shut off (’76 may be too early for that), etc. Watch the engine temp when it craps out – if it is consistent, then I would strongly suspect the thermally operated vacuum control systems.

kensfarm · Jun 10, 2004

I had a old 76 CJ5.. w/ electronic ignition. I remember my Dad coming out one night telling me I needed to stop working on it because they were trying to sleep. I broke down more then I can remember.. once on the grates on the 14th street bridge coming out of DC in rushhour.. even caught fire one day cruising w/ friends in VA.. the car next to us was nice enough to tell us the jeep was on fire.. we didn't know.. until our buddy in the back seat stands up and screams.. "We're on Fire!!" One winter in college my Jeep top was an old Army poncho.. I had no money so I was sewing together a new top.

There wasn't much I hadn't worked on.. replaced.. or rebuilt on that jeep.. but I tell you.. those were some of the best times in my life.. man.. the memories.. wish I had it today to run around the farm in.

The electronic pickup sensor in the distributor is bad.. works until it gets warm.. then engine will shut down. I would replace that first.. then look at replacing the electronic module. This was the problem I had after installing a brand new distributor.