Engine problems, Please help!

Well I have had my Jeep parked in the garage for the last two months while I was replacing suspension and steering components. This morning I went to start it up and the battery was dead. I went ahead and charged it up. When started it up it would idle OK but whenever I tried to drive it the Jeep would stumble and die. I had to tow it back to the yard as it would not drive back. Up until I parked it for the front end work it ran great except for a minor stumble when the motor was cold which went away as soon as it warmed up.

This is what I know so far. I was tapping the exhaust and believe the cat may be bad as there is a bad rattle in it. I thought this might be the drivability problem so I disconnected the exhaust at the manifold and started the jeep and have the same symptoms so even though I know it most likely needs a new cat it do not believe it is the reason for the drivability issues.

When I start it the fuel filter (clear plastic one) is 3/4 full and after it runs a few seconds it is about 1/4 full. Should it be full to the top when running? When the Jeep is idling it is fairly smooth but as soon as I try to give it some gas it stumbles and dies. If I play with the peddle quite a bit I can get it past the stumble and rev it out fairly tight however I did not hold it at that RPM as I did not want to hurt the motor. I noticed that the stumble is in the peddle travel area where the primary on the carb would be and I can sometimes get it to run if I can get past that poing and into the secondary before it stumbles.

I am thinking that it may be fuel pump not pumping sufficient fuel or fuel filter (it looks clear) clogged, or possibley a carb problem. The Jeep is a 1980 CJ5 with the 151 CU 4 cyl. The thing that concerns me it that it ran great up until 2 months ago and now this problem. I have not done any engine related work to it. Any help and suggestions would be greatly appreciated.

Thanks
Frank

 

i'd be looking into the reason for the fuel filter dropping down to one-fourth full. seems like a fuel-starvation problem. could be that while sitting, some "gunk" settled to the pickup depression in the tank, and then when you started it, it sucked some "stuff" into the line.

 

Should the filter be full with the engine idling? Should I be able to see a stream of fuel going into the top of the filter. It seems to only be a dribble....

 

I had a similar problem with my jeep a few weeks ago. The thing would start up and idle fine but anytime I mashed down on the throttle it would bog out and stall. Sure enough the carb wasn't getting any gas. Mistakenly I was convinced it was the fule pump so I went ahead and replaced the pump and filter...same problem...no gas. Finally, after working aft and dropping the tank I found that the two foot section of fuel hose running from the tank to the rigid hose on the frame had rotted out (probably the original hose) so that when I tried to accelerate I was only sucking air, but at idle, with less demand on the system, it idled fine. The only way to check that section of hose is to drop the tank.

 

That's fine in the filter.. It's probably just how it is in there. If you want to test that, disconnect the fuel line at the carb and stick it in a clear bottle. Than disconnect one side of the coil wires so the Jeep won't start and crank it over for a few seconds. you should get a pretty steady flow out of the hose. If it's just a little trickle then there's a problem.
What it really sound like to me is that the accelerator pump in the carb is not working.
Take off the air cleaner, prop open the choke butterfly, and twist the throttle plates (like pumping the pedal, but right at the carb linkage). you should see a "shot" of fuel go into the venturies. If not, then the engine will fall on it's face when you try to throttle up while driving.
Probably some fuel has gelled in the accelerator pump and its stuck.

 

Guys, Thanks for the ideas. I will try to test the pump this week and if it is OK will move on to the carb and see if the accelerator pump is workin correctly. If it is jelled up is it possible to free it with carberator cleaner or is it just time for an overhaul/replacement? I am a little nervious about removing the carb on this jeep due to the endless number of vacume lines attached everywhere. I do not want to mis-route them. Hopefully the carb cleaner might clear things up?

Thanks
Frank

 

The accelerator pump is inside the carb, so you're gonna at least have to take off the top to inspect it.
If you have to take the carb off, do something to mark the vacuume lines. Either draw a diagram on a peice of paper, or buy a paint pen at the parts store and mark the line and a spot on the carb with a corrasponding number of dots (or whatever) so you can see where they go back. Or light the area and take a bunch of digital pictures.
Best of luck

 

i have the same year and engine, fuel filter is about 1/4 to 1/2 full when i drive mine. i took the fuel sending unit out and replaced it. the tube was almost closed up with gunk all the way up it. also, could you have a kink in the rubber part of the line?

 

interestingly enough I had the same problem with different symptoms. Mine would run great but let it idle for a little it would stall and can't restart for a little while . Problem was simular, a pinhole leak in the fuel line. It would let in air at a set rate so if I was driving, I was sucking a lot of gas so the small leak didn't bother anything. However at idle I wasn't sucking much fuel and there was more air in ratio to the gas being sucked in so it would eventually hit a spot were it was sucking more air than fuel and the engine would die.

Stainless lines won't let that happen again.

 

here ya go,this will help.
http://www.jeeptech.com/engine/carter.html

 

I don't know much specifically about the 151, but I'd anyway like to offer some suggestions that I think may be useful.

First, whenver there is a sudden no-start or no-run problem, only loss of fuel or spark will cause that. It is very, very seldom that other problems happen suddenly.

You must approach the problem systematically. Sometimes you can get lucky and find the problem without some diagnosis (especially if it's a common problem specific to your vehicle), but often you'll waste your time following hunches.

First check for fuel by looking down the throat of the carb (not running!) and turning the throttle briskly. You should see a stream of fuel ejected from the accelerator pump.

If you see fuel, next check the spark by pulling a plug wire and holding it about 1/4" from the engine block. Be careful - hold the wire with something that's well insulated. There's also a fire hazard - take the obvious precautions. You should have a strong, blue-white spark.

Got fuel? Got spark? Then it's time to start looking more closely at the two systems. Check the timing. Check how much fuel the fuel pump is delivering. Don't just try stuff - instead, think of tests that will narrow down the source of the problem. Read the manual - not becasue it will tell you what to do, but because general understanding how your Jeep works will give you the best tools for solving such problems.

hth!