Hey Bobby! Thanks for the input! I always hate going out on a limb to spend money on a part that I am only relatively certain that it is causing the problem. However, I can't find any other part of the fuel delivery system that could be giving me this problem. I removed the line (at the fuel pump) that runs from the tank to the fuel pump. I removed the sending unit and put air pressure to the tank. Let's just say the fuel is flowing freely...very freely. I replaced the fuel pump, and it is running at a constant 6 psi. I replaced the line running from the fuel pump to the carb, the in-line filter, and added a pressure gauge. There is little to no air in the fuel lines. From all of the testing we did on Friday, I see no other alternative than getting a new carb.

 

Wow, it sure sounds like you have covered all the angles.

So, it will start and idle smoothly, run at rpm without a load with no problems at all? but once you try to drive it will die out and be hard to restart? Can you make it die in your driveway by power braking it? or does it have to be running down the road?
When it dies have you checked the carb to see if it has gas? looked down the throat of the carb to see if the accelerator pump will give a squirt?

Have you pulled a couple of spark plugs (I think Ross mentioned #3 or #4) after it dies to see if they are wet or dry?

Interesting problem
Bobby

 

It will start and idle smoother than a baby's bottom. It will rev for a very, very long time, but eventually the symptom will show itself after continual revving. It will just cut out and you have to feather the throttle to keep it alive, then it will idle fine again. The accel pump is working just fine. I haven't pulled any plugs to see the condition after it dies, and I really don't like to pull/replace plugs when the block is hot.

 

I understand about the plugs. After it dies is there gas in the carb bowl? can you see the accelerator pump squirting when you work the linkage?

It sure sounds like its not getting enough fuel. Is the truck an automatic or manual? The reason I ask is that with an automatic you could possibly duplicate the problem by power braking the truck which would make diagnosis alot easier being able to work in your driveway instead of on the side of the road.

If it were me I'd rig up a small gravity feed fuel can to the carb and see what happens. I find it hard to believe that the carb itself would cause this kind of problem. If the needle and seat is hanging up it could cause it but from what you have said, there isn't any problem there.

Bobby

 

It is as, if not more, strange than it sounds. I have checked and double checked every part of the system and I can't figure it out. I can't tell if there is gas in the bowl as it dies, because the bowl is metal. The accel pump is operating just fine and the truck is a manual, so replicating the problem under load is difficult without moving.

The only thing I can think of at this point is perhaps there is a hairline fracture internally in the carb. The situation is mind-bending. I am going to replace the carb totally to either confirm my sucspicions, or further deepen the mystery.

So Bobby, do you know which part # would be correct for my application?

 

Chris,
Sorry man, not a clue on which carb you need. If no one chimes in with the info you might try asking NumberDummy. Bill is an old Ford parts guy that really know his stuff.

Its easy to tell if the carb has fuel in it even with the metal bowl, if the accelerator pump will give you a squirt of fuel then the bowl has gas in it.

I can understand your frustrations, I think we have all been there at some point. I'll keep my fingers crossed that the new carb will solve all the problems.

Bobby

 

Thanks Bobby! This is by far the oddest situation I have ever run into. I am relatively new to rebuilding classic cars, but it seems that I have been handed an odd one with this truck. I am hoping the new carb will solve my running problem, and if it doesn't, the world goes on.

If anyone could help me with the correct part # for the reman carb, it would be great! NumberDummy, any input?

Thanks again Bobby!

 

There is an axiom you may want to consider:

"90% of all carb problems are ignition problems"

Sometimes you hear it the other way around, but; if you have eliminated the fuel system believe your results! It isn't the fuel system. I haven't ever heard of a carb doing what you describe. They will sputter, or sag, or run crappy, but they don't do what you're describing.

So, look at your ignition system.

Condensers are notorious for being junk for 6v cars. Especially brand new ones. They give very similar symptoms. Do you have access to a scope by any chance?

What is happening on your truck happened to a Triumph Spitfire of mine, right after a tune-up. As soon as I put my foot into it, it outright died, but would idle perfectly. I had replaced the screw on the condenser or points, and the new screw was a little longer, so when the vac advance kicked in, it shorted the points to the wire underneath the points plate. Guess how long it took to figure that out?!

A bad coil might be OK at idle but it won't carry the load.

Are you sure there are no vacuum leaks?

Before you spend the bucks on a new carb, I'd exhaust all possibilities!

 

Thank you Ross!!!!!!!!!!!!!!!!!!!!!!!Good wisdom from the desert. Have a great day,chuck

 

Well, another door of possibilities is opened. I had the same feeling at first, however, myself, my father-in-law, and 4 of my nieghbors (all classic car buffs from every genre, who I actually trust as knowledgeable mechanics) all went thirough the ignition system and it seems to be operating perfectly. My outlook on the carb, is I really don't mind getting a new one if it can help. I will be going through and replacing everything sooner or later, and am looking to get a new wiring harness while I get the carb. If the new carb doesn't make a difference, then I will return it, or maybe keep it just in case. I am going to be getting a new condenser anyway, as I will need the truck to be relatively reliable within the next two months. (My father is coming out from Detroit and I will be putting my motorcycle in the back and heading out to Las Vegas to meet him)

So, does anyone know the correct carb from the list on the previous page?

P.S. Albuq, I really appreciate the input. This has been bothering me, as the previous owner managed to make the existing wiring system a rat's nest. I am going to go through and replace every system one at a time. The condenser is the top priority for me.

 

Chris, I re-read your initial post, and, did you mean to say that you THOUGHT the bowl dry, or the bowl WAS dry? Is the engine hot when these problems crop up, or does it do it cold as well? Almost sounds like vapor lock. If it's when hot, try clipping a dozen wooden clothes pins to your fuel line at varying locations, (heat sinks) unless this poss. has been eliminated. Ross's suggestion is also plausible I'll spare you the details, but I once had a similar problem that I was CERTAIN was carburation, only to find that when I changed to a new ignition solenoid, I mixed up two small post wires, (distributor and coil) and the truck would run like poop after a few minutes. So like Ross said, be SURE it's not electrical.

 

I just wanted to update the people who have helped me so far through this problem. I just replaced the carb today with a reman from NAPA. I am writing this post from my girlfriend's house which is about 15 miles from my own. The truck ran like an absolute top the whole way over here. Needless to say, I am very happy.

 

Glad you got it figured out

 

That's great news, Chris! Congratulations. That was a brain cramp situation. I'm glad the new carb fixed it.

Now, wipe that smile off your face. You want it to stick that way?

Happy driving!

 

Chris, I'm glad you got your truck running right. Kurt G.