1981 straight six manual 4x4 project

[grumpin]

I think may have I jinxed myself by saying the truck wasn’t perfect but was getting by. I was hauling a load of household stuff yesterday and stopped for coffee on my usual route to I-17. Just as I pulled out the stalling was back. A few throttle taps and it cleared up and I was on my way.

But later on the I-17 it came back with a vengeance and was stalling more than running. But by the time I found a safe spot to pull over it cleared up again so I continued up the mountain. It was running fine for about 15 miles then went south. I managed to milk it to the off ramp at Munds Park coasted to a wide spot away from passing semi trucks. I mounted my spare carburetor and tried again... about 1/4 mile up the on ramp it was already stalling again. I backed up to a safe spot for some more checking.

I decided to replace the piece of fuel line between the tank and the hard line in the frame rail. I had not replaced this previously because it looked okay, and the stock one has a hard plastic liner. But I couldn’t think of what else to try. It did have some little cuts on the soft attaching ends, so I thought ah ha... I found ~a problem. The truck started and ran 145 miles with no stalling. I thought I had something. But as I came into Kingman I noticed by fuel was pretty low so I stopped and bought gas. About 1/4 mile up the road the stalling was back.

To re-cap. The sending unit is new. The soft line from the tank to the hard line is new. The tank selector is bypassed with a new piece of fuel line. The fuel line to the lift pump is new. I just replaced the lift pump, steel line, and inline filter to the carb and that didn’t change anything. And two different carbs just did exactly the same thing. It really feels like fuel starvation, but I am running out of ideas.

This morning I switched carburetors again, if for no other reason than I wanted the one that generally runs better.

I tried changing the DSII module, because they can do some weird stuff. (Still stalling).

I tried swapping on a spare ignition coil, as they can do some odd things as well. (Still stalling).

What am I missing? What should I try next?

Sounds like you are all over it. Frustrating! I don't remember all that you did, but have you checked the fuel tank vent?

I don't know if your truck is a vented cap or a vent line. Maybe drive it with the cap loose.

[Ford F834]

Sounds like you are all over it. Frustrating! I don't remember all that you did, but have you checked the fuel tank vent?

I don't know if your truck is a vented cap or a vent line. Maybe drive it with the cap loose.

Good idea! The truck had a charcoal canister, but I removed that and placed an open vent with the little plastic tip like they used for non-emissions and diesel models. Anyway, driving with the cap loose is very easy to try! 👍

[grumpin]

Good idea! The truck had a charcoal canister, but I removed that and placed an open vent with the little plastic tip like they used for non-emissions and diesel models. Anyway, driving with the cap loose is very easy to try! 👍

When I first got my truck the emissions were a mess. I found the vent line hanging there covered in dirt!

[Gary Lewis]

When I first got my truck the emissions were a mess. I found the vent line hanging there covered in dirt!

That’s a good test. But if it still falters you should look closely at the wiring of the ignition pickup in the dizzy. Then consider replacing the pickup itself.

[Ford F834]

Good idea! The truck had a charcoal canister, but I removed that and placed an open vent with the little plastic tip like they used for non-emissions and diesel models. Anyway, driving with the cap loose is very easy to try! 👍

Nice try but no cigar. Still stalling with the gas cap removed 😔

I sure don’t want to, but I might have to drop the tank and take a look.

[Ford F834]

That’s a good test. But if it still falters you should look closely at the wiring of the ignition pickup in the dizzy. Then consider replacing the pickup itself.

What exactly am I looking for Gary? I do have a spare distributor, maybe I should just swap and see what it does?

[Gary Lewis]

That’s a good test. But if it still falters you should look closely at the wiring of the ignition pickup in the dizzy. Then consider replacing the pickup itself.

What exactly am I looking for Gary? I do have a spare distributor, maybe I should just swap and see what it does?

Bare wires that might short when the vacuum or mechanical advance moves them.

And swapping the dizzy might be a good idea.

[Ford F834]

Bare wires that might short when the vacuum or mechanical advance moves them.

And swapping the dizzy might be a good idea.

Thanks. I don’t see anything obvious amiss there, but I think tomorrow I will swap distributors just to see what happens. It’s not a pristine unit, but it costs nothing to try it. The 4x4 donor gave me a lot of spare parts which can come in handy for troubleshooting.

[Ford F834]

Thanks. I don’t see anything obvious amiss there, but I think tomorrow I will swap distributors just to see what happens. It’s not a pristine unit, but it costs nothing to try it. The 4x4 donor gave me a lot of spare parts which can come in handy for troubleshooting.

I switched the distributor with my old spare and the truck would not start or run at all. I was very careful to find TDC, but I was hearing slight back-fire from the muffler while cranking. So I decided to try it 180* just in case I screwed it up. It would not start or run there either. I put the other distributor (that I have been running) back in and re timed it. It’s running again. I hauled a load of water and so far no stalling, but that’s the nature of an intermittent problem. I have not fixed anything so I know it will come back. I wanted to run and buy a new one, but of course no one here stocks it, and if I buy a new one I am thinking that I should choose carefully as there are other options besides the rebuilt stock ones. Mine looks to be in great shape, and honestly I don’t think it’s my problem since it does not run rough or misfire, but I’m running thin on ideas.

[Gary Lewis]

I switched the distributor with my old spare and the truck would not start or run at all. I was very careful to find TDC, but I was hearing slight back-fire from the muffler while cranking. So I decided to try it 180* just in case I screwed it up. It would not start or run there either. I put the other distributor (that I have been running) back in and re timed it. It’s running again. I hauled a load of water and so far no stalling, but that’s the nature of an intermittent problem. I have not fixed anything so I know it will come back. I wanted to run and buy a new one, but of course no one here stocks it, and if I buy a new one I am thinking that I should choose carefully as there are other options besides the rebuilt stock ones. Mine looks to be in great shape, and honestly I don’t think it’s my problem since it does not run rough or misfire, but I’m running thin on ideas.

It sounds like the pickup in the spare dizzy is bad. That's about all it could be.

And I agree you've not fixed anything, so the problem will come back. However, if you moved a wire that was broken or shorting then it might not come back until you move the wires again.

The pickup modules can start failing when they get hot. And from what I've read they quit and then come back again pretty quickly. But it is all or nothing. No bogging down as if running out of fuel. Just on/off.