1974 bronco stalls out after 3 mile drive like starving for fuel

[dar359]

1974 bronco with a 302 engine and new 2 barrel carb, new fuel line, fuel pump, and carb. gas tank was dropped and cleaned. had this issue a few monts ago and went away. it is worse now, i start with 2 pumps and high idle and kick down. drive for about 3 miles and stalls and wait 15 to 30 mins and it restarts. i tested for spark on coil and spark plug and was good. i pulled the gas line at carb and gas came out. i took the gas cap off and i am at a loss, it seems to be a fuel related issue??

 

[SteveL]

Vapor lock? Any of those new components ran closer to the exhaust?

 

[Broncobowsher]

When it stalls, do you still have spark? or are you checking for it when things are cool?
Do you have a tach? A thing to try is get up to speed and keep the RPMs up and let it die. You should be able to tell if the engine is still spinning (engine braking). In an automatic you will have to be in manual 1st or maybe 2nd gear before the engine stalls. Watch the tach, does it still read RPM? If it drops, you have an ignition issue. At least an ignition trigger issue.

Fuel check. You pull a line off and have fuel there. Look down the throat of the carburator and cycle the throttle, do you see the accelerator pump shot down the throat of the carb? No? there isn't fuel inside the carb. Yes? You have fuel, it is possible to keep an engine running off that pump shot. Too much fuel is harder to check,

 

[El Kabong]

When you popped the gas cap off, was it right after it died? If so, was there a woosh of air? Sometimes when a tank isn't vented properly, air can't get into the tank to replace the fuel that's being pumped out. The tank builds vacuum & won't allow fuel to be pumped out.

Another thought is a clogged fuel filter. I know you found fuel in the line, but even when it's not flowing enough to run you can still find fuel inside there.

 

[dar359]

thanks for the responses, there is spark and appears gas in the line . there was woosh of air like a suction when i took cap off. i think it is a vented cap and will get a new one. there are 2 small nipple evap nozzles that come out along the side of the tank that i have capped off. im at a loss, doesnt even start now.

 

[Broncobowsher]

Things are actually better now. Chasing intermittent problems is very difficult. But when it is just broke, it is a lot easier to figure out.

Appears gas in the line, that doesn't mean anything. Fuel in the line is useless, it needs to be in the carburator. Go back and do the accelerator pump shot check I mentioned before. Cycle the throttle, does it squirt gas into the carburator?

The vented gas tank issue isn't a problem at the moment. It can be difficult to tell the difference between a little air rushing in and a little rushing out. The starving for fuel with an unvented cap is generally an issue when you draw a large amount of fuel out of the fuel tank and lack air to take its place. Take more than a couple miles of driving to draw enough fuel for that to be an issue.

 

[DirtDonk]

But either way, those two vent tubes are not supposed to be capped off.
You don’t actually have a vented cap available for your 70 or newer bronco. The only style that fits is the correct one-way type for use with a charcoal canister setup.

Remove at least one of the caps and see if the problem goes away.
Easier still is just remove the gas cap and drive it.
That will tell you if it’s the problem.

 

[dar359]

thanks, ok just to confirm one of those evaps holes should be vented? I think its the carburetor and i had it rebuilt twice already. any thoughts on a good carburetor

 

[DirtDonk]

Yes one is fine as a vent.
The original set up would’ve had both attached too plastic hoses that ran up to a plastic tank behind a panel next to the drivers shoulder. It’s a condensing tank where when enough vapor condenses to liquid it drains down through the other hose back into the main tank.
The auxiliary tank (when so equipped) only had a vent since there was enough room in the main tank for liquid from the much smaller aux tank.

To minimize the smell of gas in the garage or driveway you can run a hose up into the wheel well and loop it around once or twice.
Or there are other methods as well, including reconnecting it to a later model charcoal canister.

 

[dar359]

thanks, going to expose one of evap hoses off tank and cap the other. there doesnt appear to be fuel going into carb when pumping gas as suggested. it appears to be at the filter right before the card. i had the carb rebuilt twice. any suggestions?

 

[Broncobowsher]

Sounds like a pump issue.

 

[sprdv1]

thanks for the responses, there is spark and appears gas in the line . there was woosh of air like a suction when i took cap off. i think it is a vented cap and will get a new one. there are 2 small nipple evap nozzles that come out along the side of the tank that i have capped off. im at a loss, doesnt even start now.

never fails right

 

[sprdv1]

Sounds like a pump issue.

Thought crossed my mind as well

carb should definitely be good now

 

[dar359]

update, i resolved the intermittent stalling issue after all this time. I installed an electric fuel pump and it runs like a champ. thanks for all the input.

 

[fluffybunny]

What electric fuel pump did you go with?

 

[dar359]

carter p4070

 

[sprdv1]

update, i resolved the intermittent stalling issue after all this time. I installed an electric fuel pump and it runs like a champ. thanks for all the input.

outstanding..