Running Issue

[Thumper168]

Ok guys, I took my 84 Wagon for its first ride today and everything went well for about 45 minutes, once it warmed up good it stalled and sputtered and lost power but it never actually died, It would drive fine up to a certain rmp and around 30 mph but once you cross that spot it sputtered like it was loosing fire. I have allready replaced the pick up coil and im leaning towad the firing coil, any ideas?? Once it cooled down it seemed to run fine again.

[FSJ Guy]

Since it won't go above a certain rpm, that sounds like either a bad float adjustment (if you still have a carb) or a clogged fuel filter in the tank or in the engine compartment (regardless of fuel delivery system).

When it cooled down, however, would it run well over 30 mph?

If the symptoms went away after cooling down, then ignore.

[Thumper168]

It ran fine after cooling down, it was running bad and I came to a car wash and the motor needed washing and it was running bad anyway not to mention I was only about a mile from the shop so I washed it, fired it up after and it ran just fine all the way to the shop. Tomorrow I plan to replace the igniton control module, the coil and a new fuel pump not to mention I need a new fuel sending unit so Ill check the screen and replace the inline filter as well. Anything else I need to replace or check?? Could it be vapor locking?

[FSJ Guy]

OK, it it truly ran better once cooled down, it's probably your ignition module. You can replace it with a (duh) replacement or wire up a GM 4 pin module to fire your ignition and gain some reliability, too.

Google will bring up several wiring diagrams. Just be sure to provide the module with a good heatsink and don't be stingy with the heatsink grease.

[Thumper168]

Thanks for your thoughts! Im new to the FSJ scene so Im learning as I go!!!! I also want to avoid a few future problems by replacing a few of the 26 year old parts that I know will fail at just the right time when Im in BFE.

[FSJ Guy]

Some people report good results with a parts store replacement module. Others report that they poop out (sometimes literally) fairly quickly.

Consider it an item to keep in your spares box.

[Joe Guilbeau]

OK, it it truly ran better once cooled down, it's probably your ignition module. You can replace it with a (duh) replacement or wire up a GM 4 pin module to fire your ignition and gain some reliability, too.

Google will bring up several wiring diagrams. Just be sure to provide the module with a good heatsink and don't be stingy with the heatsink grease.

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[Skeeter74]

Or, just get rid of the "box" and go HEI. They can be had for well under $100 and only have 1 wire to install.

[rocklaurence]

It could be Vapor Lock. The fuel in the lines going to the carb get too hot and turn into vapor-strving the carb of fuel. I cured this by covering the metal fuel lines with rubber fuel hose.

[Thumper168]

Ok, I repleaced the ICM and the coil and the problem is still their doing the exact same thing it was doing before I replaced them. What is the next thing in line to check? Im getting a little frustrated with this Cold it runs fine but once it heats up it will not run over about 30 mph and bogs down but will not die if you let off the gas. ?? HELP lol

[cavicatz24]

I agree with lawrence - sounds like vapor lock.
I was experiencing the exact same symptoms with Bessie. However, I usually drove her to the point of stalling.
I went the electric fuel pump route with great results. You can also use an inexpensive Mr. Gasket electric pump as a booster pump only - wire it to a toggle and put the pump in-line before the mechanical pump. When she starts bogging or acting like she's starving for fuel the just back off the gas and flip the switch. Only downside to this method is that if your mechanical pump develops a hole in the diaphragm then the electric pump will fill your crankcase with fuel!
You can also try insulating the fuel lines in the engine compartment - Jeg's and Summit both sell silver adhesive insulating tape or ready made sleeves. The hard fuel line from the pump to the carb runs really close to the block and intake and heats up really fast.
Also make sure that your fuel filter is clean and oriented in the proper position - the small return tube should be at the 12:00 position with the outlet to the carb being the center of the clock.
Lastly, make sure your fuel lines are clear. My factory line was badly clogged, thus restricting fuel flow to the carb. Poor flow+low pressure+hot fuel=vapor lock! You can blow it out with compressed air or replace it completely. I replaced mine with 3/8" steel line and never looked back.

[tgreese]

If it runs ok when cold and runs poorly when warmed up, I would suspect the difference is the coke is open when warm. This could point to a really big vacuum leak, which makes the engine run very lean. It could also make the engine run like it's starved for gas. If it runs ok below 30, that suggests that the fuel pump can't keep up with the demand for fuel at highway speed, and it's starving.

Another possibility - there are several emissions-related devices (EGR, TCS, among others that are temperature dependent. The factory manual for 1984 Jeep would help with this... I would examine each system - that's it's hooked up right and that it's functioning properly. If the emissions gadgets are't connected right, you can get all sorts of weird symptoms.

I'd also check the plug wires, examine the plugs, and do a compression test. Visually checking the plugs along with the compression test will tell you something about the overall condition of the engine.

[tgreese]

Regarding vapor lock, do the simple stuff first. Make sure none of the steel lines are touching metal in the engine compartment. Make sure all the rubber hoses are in good condition. The fuel pump is supposed to circulate fuel from the gas tank, up to the fuel filter and back to the tank. This flow of fuel keeps the fuel cool. Your fuel filter should have 3 nipples - inlet, return, and to the carburetor. Also, if the filter in the tank is plugged, that could slow down the flow of fuel and and promote vapor lock.

The mechanical pumps work fine if they are in good condition and the lines aren't plugged or leaky. Check the simple stuff first!

I worked for a Jeep dealer in southern California in the '70s, and I do not recall vapor lock being real problem with these cars. I'm skeptical ... especially this time of year. Maybe at high altitude, where gas boils more easily, but not on the plains in winter.

[Thumper168]

Ok, I may be a doop!! All the emission stuff was disconected, its still on the motor but just not hooked up any longer. It was all taken loose right before I purchased it, I never thought much about it being dis connected but could this be the issue? Ive read that the cat could cause this problem as well once it heats up? I really appreciate all your help here,

[REDONE]

I agree with the posts about regarding the choke.

Everybody here answers based on their experience, and since everybody has different experiences that makes this forum ROCK!

In my experience everytime I've had the warm-gutless-wonder symtoms like you're describing on EVERY carbureted engine it's happened to, from my FSJs to Dodges and Ramblers, it's been the choke closing for some odd reason. The choke on my PowerWagon is still gagged open with a piece of coat hanger from when I had this same issue last summer, haha!

EDIT>>> You posted while I was typing. A big honkin' vacuum leak from loose emissions parts could definitely cause this too!