CJ5 Won't idle (only runs while pumping throttle)

This is on my 1963 cj5 134 4 cylinder, with a carter YF carburetor.

The original carburetor leaked fuel out of the throttle lever (I believe the actual term is the pump lifter link) and I was told the only way to fix that is to have it sent out to be rebuilt.

Soo, I took the carb off my 65 parts jeep, and bought a rebuild kit for it and installed it. Now I have done these before, so it was nothing new. But on this one, I can not get the jeep to run right.

It will run as long as you sit there and really pump it hard, and it will run forever like that, and run well at that, doesn't even hesitate. But as soon as you leave the throttle in one position, or try to let it idle, it dies.

What is cause this, and how can I fix it easily?


Thanks very much for the help!

 

sounds like the idle circuit is clogged. Did you ensure all the passages were open and cleaned out?

Will it run on the choke?

 

Never tried it with choke, I can tomorrow though. I doubt it, its acting like its not getting fuel except when I pump it.


I too thought there was a hole plugged. I got tired of taking the thing on and off not finding the problem, so I blew air into the line, and air comes out of the holes in the carb mouth, so it seems if air is then fuel should be too.....?

 

I think I migghtt have it. I put the old carb back on it, and was doing the same thing. Then I put my finger over the vacuum wiper hole, and then it ran a lot better. Still not running real well though, Ill keep yall updated

 

Would this type of engine have a mechanical fuel pump? Your description leads me to think its the diaphragm in the fuel pump not holding sufficient fuel pressure.

 

vacuum leak would definately cause some symptoms you describe. And with the old carb there were problems to begin with.

fix that vacuum leak and then try again.

 

Is there some way to check pressure? sure seems to have a lot to me when I un do the lines

 

if it has enough to run while pumping it has enough to idle on it's own.

Is the vacuum leak fixed? any other vacuum leaks? easy to check by spraying an aerosol like carb cleaner around all the seams, manifold, throttle shafts, etc. If RPM changes, then you have another leak. Until you get rid of all the vacuum leaks, you'll chase your tail.

 

The fact that it runs better when you plugged that hole is a major clue. It has an air leak and it's running too lean (among possible other problems.)

There is something that is almost never checked but should be on any OLD carburetor. How loose is the shaft that the butterfly valve rides on? I have seen carburetors that were so used and worn out that the hole that the shaft rides in was worn oversized and leaked air into the carburetor. The symptoms and results was exactly the same as leaving off a vacuum hose. The engine idled rough (and usually too fast) and the idle air adjustment had little affect. In addition, the worn out holes will also cause the butterfly valve to not close enough or sometimes too much and either will cause more problems. Check to see if that shaft is loose. If it is, then you CAN get the holes bushed and rebored but that means that you have to remove the butterfly valve from the shaft and those are preset at the factory to leave a small gap in the bore and not fully close and if you change that gap it will be very difficult to make the carburetor run properly so I usually just pitch those carbs.

 

I just found this article http://www.film.queensu.ca/CJ3B/Tech/Carburetor.html. It explains the problems with worn out throttle shaft holes and how they can be fixed. I hadn't even thought of the tiny "corners" left when putting square ended bushings up against a round hole! But according to them, even those tiny openings can cause problems. This article also explains some of the problems with using a generic rebuild kit or having the carb rebuild by lesser quality shops that don't use the exact part for that application. I can also tell you this from experience, you need to get a GOOD quality kit and the exact, correct parts for your carburetor and rebuild everything exactly the way that it should be and with all the right clearances, settings etc. At one time I used have a lot of time on my hands and I rebuilt cards and made small changes and then road tested them. Then take it back and change something else and try it again. I found that even minor changes usually made a huge difference (usually for the worse!) You can't just slap a carburetor together and have it work WELL. Just about any carburetor with any setting will run on an engine but everything has to be right for it to work WELL.