Bad missing going up hill in third gear

Typically my stock '59 CJ5 runs great. I can easily get up to 60mph on flats. For a couple weeks it's been missing intermitantly going up hills in third gear (around 40 mph). Trying to solve the problem I changed spark plug wires, changed condenser, thoroughly checked out distributor and timed with timing light, flushed gas tank, replaced gas line (which had some pinhole leaks), replaced fuel filter, rebuilt the Carter 938 SD carb, checked out PVC valve, checked compression, cleaned oil bath air filter. Also went through all the ignition wirings to the switch. I haven't messed with the fuel pump or checked fuel pressure yet.

So the symptoms are that it only misses in third gear when it's struggling to pick up speed. At the bottom of the hill it's about 30-35mph. As I climb the hill and it slowly starts to hit about 40 mph it's as if the ignition is switched off. There's no power at all. I pull the choke, vent the gas tank, turn switch on and off testing if its a fuel fault but nothing happens. But if I let off the gas for a second and push it down again it will "catch" and keep going, but still sputter. Sometimes towards the top of a hill it will stall out,.,....I'll pump the gas peddle, but the jeep will still sputter for awhile (5 second or so) and then it will be fine. Doesn't really do this on flats or going down a hill.

I also can't get it to act this way in second gear at 40 mph up hill. RPM's are high and engine feels strong. But drop into third and it risks dying.

So after a few weeks of going through everything I can think of....I'm stumped. Next I wanted to try to observe the spark and gas and decide which one is dying on me but I can't think how to do it while driving.

 

I would say it sounds like the vacuum adance, but do you have one?

 

This sounds an awful lot like a gigantic thread I saw from a year or so ago. Must have had over a hundred posts in it, with all kinds of speculation. As I remember, in the end, the problem turned out to be a simple vacuum leak from one of the carb gaskets. You may want to really double check that you don't have a vac leak somewhere.

 

fuel pump or filter

 

Thanks for the replies. Here's an update: I found a couple small leaks in the gas line at the fittings. Tightened those up and repositioned the fuel filter. It started running much better and doesn't miss on the hills, but now when I come to a stop and check the clear fuel filter there's no gas in there. After it sits awhile it fills up 3/4 full. But now it's stalling when I come to a stop and I can't get it to idle anymore. So I think it may be fuel pump as well. That's coming out tonight. In any event, it seems I'm making some progress. At least it will pull the hills without stalling. Now to correct the stalling at the stops and get my idle back.

 

Why don't you test the pump before you pull it out?

 

Yep...I'll test the pressure before i pull it.

 

Turned out to be a simple problem: There's a brass T-fitting near the PCV valve and the cap that plugs the unused end was very loose. NowI have to take it for a test drive this morning.