Random Stalling when at Running Temp

[Chadryan]

Guys, my '87 Grand Wagoneer has started having a random stalling issue once it warms up to running temp. Other than the fact that it only does it when the engine is hot, I cannot come up with any other factors that are consistent every time it stalls.


When it is "cold" (I live in Florida) it runs fine. The first time it stalled was on a very rainy day when there was a lot of water on the roads (no idea if that has anything to do with anything but worth noting). The first time it stalled I was accelerating up an on-ramp to the interstate. I managed to get it in neutral and it re-started pretty quickly but ran poorly most of the next couple of miles to work. Since then, it has stalled when idling in park (after warm up), when driving consistent speeds, when coasting, when accelerating, all conditions. The only other thing that I have noticed is that sometimes when I try to re-start it soon after it stalls, I swear I can smell something like a hot wire. It isn't smoke necessarily, it is faint and I can never track down the source. I don't think the smell is coming from under the hood and I have stuck my head up under the dash when I smell it and there is never a strong smell under there.



When it stalls, it just cuts off. Not really any sputtering or backfiring which leads me to believe it might be an electrical problem. The Jeep will re-start after sitting for a few minutes (I assume it cools down enough to start). Sometimes it starts back up easier than others. Sometimes it really struggles to turn over.



What I have done since it started stalling:
- Checked the wires to the coil (I did find a slightly loose wire at one of the spade connectors which I fixed.)
- Plugged in my spare (new) ICM. Still stalled so I went back to the ICM that was in originally.
- Replaced the Ignition Switch
- Replaced the coil
- Replaced the fuel filter
- Looked over the wiring that I can see. I did notice an orange wire coming out of the ignition switch that had a couple bubbles in the insulation. I also discovered a small bad spot in the insulation on one of the wires in the group of wires that runs over the top of the passenger valve cover. It looks like the heat from the valve cover may have damaged it. I wrapped it up and put some loom and insulating tape around that group of wires.



I did all of these things one at a time to see what item was causing the stalling. None of them fixed it.


A couple of background notes and things that have been done in the last 6 months:


- Oil pressure is good and is usually around 35-40 while driving around town.
- The Jeep runs around 190 degrees most of the time. If I am in traffic it goes over that but stays well within the acceptable temps. (I have two temp. gauges)
- I have replaced (upgraded) the spark plugs and wires.
- I have upgraded to the larger distributor cap/rotor/GM coil. I have not replaced the actual distributor.
- I have replaced the positive battery cables with a heavier gauge set.
- Last week the gas tank was dropped, soft lines replaced and everything cleaned up prior to install. I did this because of a fuel leak, it was stalling prior to this and is still stalling after.
- Replaced the fuel pump.


None of these things, or any other work, happened less than 3 or 4 weeks before it started stalling. Honestly, it was running pretty good when it started this new stalling issue. The only work that was done about a week prior to this starting was I had a shop replace the motor mounts and some of the soft transmission lines.



Any thoughts would be appreciated. This is my daily driver currently and it really sucks when the engine cuts off and I have to steer this thing to a safe location without power steering.

[wiley-moeracing]

So is the distributer original or a aftermarket gm style?, sounds like the pick up in the distributer may be the problem or you have a wire connection that is getting hot and expanding and looses contact till it cools off? Check this things next then let us know.

[Chadryan]

So is the distributer original or a aftermarket gm style?, sounds like the pick up in the distributer may be the problem or you have a wire connection that is getting hot and expanding and looses contact till it cools off? Check this things next then let us know.

Thanks. I have not replaced the distributor since I have owned the vehicle. It may be original. I have a new one on order which should be here tomorrow. I saved this part until last because the process of pulling it and meshing the new distributor gears (I know to put my old gear on the new distributor) makes me a little nervous to be honest. I am pretty mechanical but am by no means an expert.

[wiley-moeracing]

Chances are the distributer has been replaced/upgraded if you installed a larger cap or gm coil. Should be ford style cap and rotor and a round cylindrical coil separate.

[Chadryan]

Chances are the distributer has been replaced/upgraded if you installed a larger cap or gm coil. Should be ford style cap and rotor and a round cylindrical coil separate.

I mis-spoke when I mentioned GM. It was all Ford parts. This is what I followed when I did it: http://www.grimmjeeper.com/J-Truck/tfi.html. I did not change the actual distributor at the time.

[Full Size Jeeper]

It sounds like you are changing a lot of stuff and that's fine. I'am sure most of it was old and getting some of those parts replaced are upgraded can't hurt in the long run, but it has not fixed the problem. The next time it does it, have some fuel that you can put down the throat of the carburetor, if it starts, you might have a fuel problem and more specifically, Vapor Lock. ( IF YOU TRY THIS, MAKE SURE YOU HAVE A FIRE EXTINGUISHER IN CASE OF A BACKFIRE THROUGH THE CARB. My two cents, good luck!

[wiley-moeracing]

check the pick up inside the distributer, this can cause the problem as well a vapor lock issue. the vapor lock issue can be checked with a can of brake cleaner to see if it fires up after it stops on you, but be careful and not blow yourself up, this will eliminate a fuel related issue.

[Chadryan]

check the pick up inside the distributer, this can cause the problem as well a vapor lock issue. the vapor lock issue can be checked with a can of brake cleaner to see if it fires up after it stops on you, but be careful and not blow yourself up, this will eliminate a fuel related issue.

10-4. I always carry a nice big fire extinguisher with me =). Unfortunately, the jeep has not picked very convenient places to stall... I am usually driving in very congested areas in Tampa and I can't just hop out to check the carb. I will get flat run over. I am going to start it up at my office and let it idle this afternoon and see if I can get it to stall. Then I will check for fuel at the carb.

[babywag]

check the pick up inside the distributer, this can cause the problem as well a vapor lock issue. the vapor lock issue can be checked with a can of brake cleaner to see if it fires up after it stops on you, but be careful and not blow yourself up, this will eliminate a fuel related issue.

x2
The wires can break down internally from decades of flexing.
The "wiggle" test can sometimes replicate the issue.
If testing and stalls a quick ohm reading of the pickup will show infinite resistance(usually).

Pickup assembly is cheap & easy to replace. Can be done w/o removal of the distributor.

[Chadryan]

Ok guys, a little change in direction here...


I just drove to lunch and then let the GW sit idling at my office while I ate. The thing sat there for almost 20 minutes idling away with perfect gauge readings just as happy as can be. I couldn't believe it. So, I pulled it around into a different parking lot and sat in it with my foot on the brake and the jeep in drive. It took about 3 minutes and it sputtered and stalled. I tried to restart it right away and it would crank but not fire. I grabbed a can of starting fluid and shot some in the top of the carb. It then cranked and fired for just a couple seconds until the starting fluid was burned up. I repeated the steps... No starting fluid = no fire. Starting fluid = fire (the good kind).


I stuck my finger in the carb and pushed on the throttle cable... no fuel. After everything cooled down for a few minutes, I pushed on the throttle cable and it started spitting fuel again.


So, what would be some common causes of lack of fuel or vapor lock while driving? Weak fuel pump (it is only a moth or so old)? Clog in the line? Like I mentioned, last week I had the tank out and replaced all of the soft hoses and the grommets on the vents. The sending unit is about 6 months old.

[Full Size Jeeper]

From what I have read on the subject of vapor lock, it really all comes down to the boiling point of the gas in your car, and that number can vary a lot. Straight gas (no ethanol) Has a higher boiling point than gas with ethanol. Gas today is full of ethanol so older cars that ran fine on straight gas back in the day are now having problems running on this new blend. Here are some numbers I found with a quick search on the net.
Boiling point of straight gasoline 95 degrees F
Boiling point of gasoline with 10% ethanol 80 degrees F
Now you say, even when these were first built, it was well over 95 degrees under the hood. True, but AMC is sending more fuel to the engine than it can use and that is one of the most important reasons for the return line. It keeps fuel moving through the hot lines and sends it back to a cooler part of the car, the fuel tank.

[Full Size Jeeper]

What I did to fix my vapor lock problem, I removed the mechanical fuel pump and went with an electric Holley pump. You may ask how changing the way fuel is delivered to the engine compartment going to stop vapor lock. The number one reason is the increase in volume of fuel through the line, more fuel running through the line means it has to bypass to the return line faster and moves out of the hot fuel line at a higher rate. Another theory is that the electric fuel pump, because it is mounted in the rear at the fuel tank, and because it runs at a slightly higher pressure, brings the boiling point of the fuel up a bit, thus less chance of vapor lock. Liquid boils at a higher temperature under pressure. (Ron Burgundy says it's science.) Now, is any of what I just said true, I'am not 100% sure, but the electric fuel pump stopped a similar problem I was having.

Good luck!!!!!

[Chadryan]

Thanks for the suggestions. I may end up going to an electric pump eventually. I did just disconnect my fuel lines (front and back) and blow them out with about 15lbs of compressed air. I also pulled my sending unit to inspect it. I discovered that the little bitty filter that came on the end of the aftermarket sending unit was largely clogged with fine debris. I blasted that all out with the hose and dried it out with the compressor. It looks nice and clean now. We'll see how the ride to work goes tomorrow...

[nograin]

If you think its fuel, then check the carb. If its a bad fuel line to the carb, it would not be restarting. (actually the one that goes is the rubber hose connecting to the fuel pump.)

Anyway. see if enrichening the idle mix helps. If turning the idle mix screws does not effect the idle - then almost certainly the idle passages are gunked up.
Then work back.. If you think fuel level is a problem, remove the the top of the carb and check. If its your first time, take your time.

[nograin]

The pick up tube in the tank should have a pretty big meshlike filter on it (aka sock).
Since the fuel tanks in the 80s and 90s are plastic not metal, its possible youre getting charcoal. If so, look in the archives about how to open up and put new foam in your charcoal cannister.