Help diagnosing an engine problem.

[stoney bones]

This has been going on forever and it is driving (lol) me nuts.


Started very shortly after purchasing jeep. It will be running seemingly fine, then what seems to be randomly, the motor starts to bog down and want to stall.

Doesnt matter if vehicvle is warmed up or not.

You can hold the throttle at say 1/3...the motor starts reving up smoothly..hits somewhere (im guessing) around 2000or so rpm then its like the gas cuts out...all the way down to an almost stall. sometimes without moving the gas pedal it will jump back up to an idling rpm (all still with foot help at 1/3) then it ill climb smoothly and repeat. It will usually stall unless you kind of bounce your foot on the pedal and you can work the rpms back up.

I will drive it around the property like this for an hour trying to figure it out...get mad park it a few days then when I come out again it will work fine again...for a random amount of time, like hours, or days, then it goes back into it.....

When this first started happening I got on here and learned of the MC2100 upgrade....I thought it was my carb so I switched out.

Ran fine at first..then right back to the same problems.

I took the jeep to a friends dad who is a mechanic. I had him go through the carb, give it all a tune up. He never duplicated my problem. Gave it back to me and it ran great for a couple days. Parked it for about a week and it was the same old same old all over again.

Ignition is all new. I had it checked over as well as having the timing adjusted.

new fuel filter...the fuel pump is working (at least sometimes)..i can tell that much...

What can I check now? This kills me...All I want to do is drive my CJ!!!!





edit to add:

just the other day I was driving around well over an hour flawlessly....then all the sudden it started doing it again...started bouncing the throttle to keep it running like always and limped it back to her bed....before I even got to park it, it just started running normal again...all the way from to golden and back again within a matter a mins...normally takes days or weeks.....i dunno if that helps at all.

and i have changed out the gas multiple times...been through 4 tanks of gas (at least) with this problem persisting the whole time intermittently. I do use stabil when I know it will be sitting any amount of time.

 

[73CJ]

I would check the fuel pressure at the carb. Was there a lot a in the fuel filter? The gas tanks like to shed rust inside and can plug the fuel pickup tube inside the tank. When she acts up, check the pressure.

Have you dropped the tank and cleaned it?


http://www.harborfreight.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/i/m/image_13661.jpg

 

[Old Dog]

I'm with 73cj here. I'd rig up a pressure gauge I could read while I was driving to see what happens when it acts up.

 

[mtnwhlr]

I agree also you my need to drop the tank and check the sock on the pickup tube and make sure there isn't a bunch of in it.

 

[Torxhead]

I am another one who seems to agree with the previous posts. It very well could be in the fuel system. A lot of crud can develop in the fuel tank after 30+ years, thats why there is a filter sock. That crud can also work its way into the fuel fump causing more problems. Some guys make a door in the bed at the fuel sender location for future access when they pull a tank to clean it out to get at that sender. Let us know how it works out.

 

[Barry2]

Cutting out a square in the floor above the fuel sender/pump saves tons of work and frustration. A patch and a little silicone and short metal screws will seal it back up. Done this with all my stuff.

You can access the filter sock, pump or fuel sender all in short order.

 

[stoney bones]

I knew where this was going...I was just hoping not. But, afterall it can only be so many things I suppose.


What should be normal running fuel pressure? I will start there and start looking for a new tank. I want everything re done eventually so if this is coming out, it is not going back in unless new. Or unless it can be made into like new condition.

With that said, any fuel tank suggestions? I am building this with the end goal being an expedition vehicle. I would like higher capacity if its out there.

Wish I could find my Chiltons.

 

[Torxhead]

Your normal running fuel pressure should be around 4-5 psi at idle. If you want a new tank, I would suggest one of the poly 20 gal jobs. You can also add a rack for the rear to hold two 5 gal gas cans.