At this point, I would suspect the carb. Provided that the choke is fully open when the engine is hot (You have an elec assisted choke cap but the heater will still open the choke fully it will just take longer) and you have confirmed that you have spark during the no start. These Chinese knock of carbs are notorious for having issues, I would R&R the carb and replace it with quality rebuilt original unit.

 

Well, sorry it didnt help in your situation. I was 95% sure I had carb issues. My truck sat for nearly 15 years before I started tinkering with it. In the end, I didnt do anything but spray carb cleaner in mine. Thought I'd try the heater pipe before I tore into the carb - has run like new ever since. Hopefully it still runs fine when it gets cold here again. I cant tell you how surprised I was that stupid little thing made such a difference. Good Luck!

 

+1 on that. In the vintage Jeep world, many models also used an earlier variant of the same carb used on your truck. The aftermarket replacements are all over the map as far as quality. Some guys said they worked fine right out of the box, but other examples were nothing more than expensive paperweights.

As far as rebuilding, a professional's touch is the way to go. On my truck (different carb than yours), I had "rebuilt" the carb several times over the years. My efforts were basically nothing more than a good cleaning, new gaskets, new float valve, and wishful thinking. I had an off-idle stumble I could never clear up no matter how many times I "rebuilt" the poor thing. Finally, out of desperation, I purchased a true professionally rebuilt carb. The improvement was like night and day.

What about the carb that was originally on there? I think you said you could never get the engine to run correctly, so you replaced the carb. Were the symptoms the same? If different (sounds like they were), I'd suggest reinstalling the original for giggles, and then see if the symptoms revert back. Even if the engine still won't run properly, if the current fault clears up, you'd know your new carb unfortunately is part of the problem. This is free troubleshooting, costing only your time.

Could you swap the float and float valve from the original carb to the replacement?

One last though on the fuel pressure. How exactly did you test it? Did you disconnect the line at the carb inlet and measure the pressure while cranking the starter? Or did you tee into the line and measure with the engine running? The latter is much preferred, as it is more representative of what the carb actually sees. If you only measured while cranking the starter, this is at a lower speed, maybe 400 RPM or so. But once the engine runs on it own, the speed jumps up around 700 or 800 RPM, nearly double the speed. It would be very rare, but perhaps your pump is defective and the pressure is within specs at the lower speed, but rises too high once the engine reaches normal operating speed. Once again, you can rule out this unlikely scenario with just a few minutes of time and a tee fitting.

 

Does the engine shut off like a switch being flipped, or does the engine stumble for a short time, then quit?

 

It stumbles just for a few seconds before it stops.

 

I took the line off the carb and put the tester right into that. I guess I could get a tee fitting and try it that way, it couldn't hurt. How do I go about returning the carb? I bought the carb that I posted the link to in my first post, but I bought it through the Walmart website just in case anything went wrong. But it's been over the 30 days since I bought it, so I dont think I can return it. Besides, now that Ive taken it apart, wouldnt that void any warranty there might have been?

 

I seems from what you have said (multiple times I know) that the carb is allowing too much fuel into the engine. While you are out there experimenting with the fuel line off and then the fuel line on, you need to get a flashlight and look down the throat of the carb. When you hook the line up and get it started, and you know it's going to quit, while it's still running shine the flashlight down the carb throat. You should see nothing, just hear air hissing. If you see fuel droplets or liquid fuel dripping into the engine, the carb is overflowing. When you take the line off, and then start it, if you saw it overflowing, it should eventually quit dripping, the engine runs great and then it stops because it ran out of fuel.

The above is just a guess, but you can look down in there and verify if it's dripping or not. If it is dripping, then you have verified the problem, and I would get in there and adjust the float.

 

Well. The new carb was just straight spraying fuel into the motor. I know it's supposed to be richer when the motor is cold and the choke is closed, but JESUS. So I put the old carb back on. It sat there and ran for a couple minutes before it started missing and cutting out for just a split second at a time. Then it died. To be fair, I didnt have any of the electronics on the carb at all. Dont know if that would have made a difference. At this point Im almost ready to get an old YF carb without all the electronic crap and a vacuum advance distributor. Get back to the basics. Very tempting

 

Well have you pulled codes? Sounds like the ECU of the air mix stepper motor could be faulty The ECUs are at the age now where caps and the like will have started to crap put.

 

The electronics only add or subtract air. If they were failing it would only run a little rich, it should not stall. I am running a electronic carb with none of the wires hooked up and it runs fine. From what you said above, one of the carbs was pouring fuel into the engine, obviously that is not correct. You have been swapping carbs and swapping floats around, what do you have now? You said it still stalls after awhile, is it still dripping our pouring fuel into the engine? Take a look and see.

When the engine is cold, the choke blocks the air entering the carb, and increases the signal to the fuel venturi, which is what they use to help the engine when it's cold.

 

Putting on my Sherlock Holmes hat and lighting my pipe. Reading between the lines, after you said the new carb was spraying lots of fuel, do I understand correctly that the new one is not doing so? If that is the case, this means the two carbs are behaving differently. The symptoms changed. Ding, ding, ding! You should hear a bell ringing, alerting you this is a major clue. The new one is obviously bad, spraying all that extra fuel. The old carb is also bad, but in a different manner. Replacing the old carb should have fixed it, but you had the misfortune to get a new part that was bad out of the box. Rare, but it happens. Or maybe there is some other undiagnosed fault, but based on the sputtering with the old carb, that sure sounds like a fuel-related problem.

Now you get to decide what to do. It all depends on your wallet and tolerance for risk. None of us can make that call for you. Can you take the (hopefully) good float and float valve from the old carb and swap it to the new carb? Or maybe gamble on a used carb from eBay? Some sellers offer guaranteed parts, so this something to consider. If you can get a used carb from a running vehicle, you have very good odds in your favor. Or do you want to have the old carb professionally rebuilt?

For the moment, I would advise against swapping to a non-electronic system, etc. It's not just a matter of swapping the carb. The poor computer wont be happy if it can't talk to the carb. Other computer-controlled aspects, such as ignition timing, may revert to to default positions, with a huge loss of power. It can be a big can or worms. We've seen plenty of examples of people "ripping out all that pollution crap" and making things much worse. I'm not saying it can't be done, but it's fairly involved to do it correctly.

 

There's a way to pull codes on this thing?? Wow. Could you tell me where the connector would be so I can try?

 

That makes sense. From what I can tell, the old carb is not spraying nearly as much fuel as the new one. I wont have access to the truck again until next friday, so looks like I can try then to swap the needle/seat and float assemblies and see what happens! So much fun... just in case I end up needing a new carb, does anyone here have a known good carb, preferably off a recently running vehicle?

 

After changing needle and seat, and before putting the carb top back on, turn the top over and check that the top of the float is even across with the carb top. That should get you close to being the right fuel level.

 

I was recently reminded of something that may help with your troubleshooting. I've been working on the fuel tank on one of my old Jeeps. I needed to move the vehicle while the tank was out of commission, so I rigged up an outboard motor fuel supply. It's one of those small portable tanks with a squeeze bulb to prime the line.

I've got this external tank feeding directly to the Jeep's engine-driven fuel pump. When I squeeze the primer bulb before starting, fuel flows through the pump check valves and up to the carb. When the carb float chamber fills up, the float valve closes and I can feel the increased resistance at the primer bulb. The flow of fuel stops and the bulb becomes more or less rigid.

If you've got a similar outboard tank handy, you could try the same thing with your carbs. They don't even need to be installed, as long as you keep them upright. I bet you will find the old carb stops the flow properly, but not the new one. You'd then have extra confirmation of the problem, which should help deciding how to proceed.