another mystery problem?maybe fuel system

[1970mule]

Ok, this is crazy, i am having a problem with my bronco just shutting off when i am driving. it sputters before it turns off like it is starving for gas. but i'll update those that don't remember what i already did. ok i have a new carb and i am sure that is ok. i just changed all the fuel lines and manual fuel selector for the 2 tanks. i checked both tanks for the filters inside. also i changed the manuel fuel pump. i have no idea what is going on, but inside the fuel filters i see no gas sometimes i do but not really. when i bybassed the tank and ran a gas can directly to the pump i saw fuel in the filter. so please help.

 

[1970mule]

anyone

 

[bludorbronc]

when the truck dies, if you take off the gas cap do you hear a swish of air into the tank. or take off the caps and then drive it ,the tank could be building a vacuum.

 

[1970mule]

yes i have heard that swish of air you speak of but only from the main tank.

 

[70_Steve]

1970 used a "vented" gas tank. The vent was built into the gas cap, and was more like a check valve that just an open vent. It would (should) allow air into the tank, to prevent a vacuum from being present in the gas tank (for any number of reasons) and preventing gas from being sucked from the tank by the fuel pump. But it does not relieve pressure from the tank.

So, if the swish was air coming out of the tank, that's OK. If the swish was air being sucked into the tank, get a new, 1966 to 1971, gas cap.

 

[1970mule]

ok will check, could it be something electrical from what i described teh symptoms to be?

 

[70_Steve]

With your description of it "sputtering" before it dies, I would think not. One way to check is, when it dies, take off the air cleaner, and look down inside the carb. Actuate the throttle and look for a squirt of gas inside. If no squirt, then it really is fuel related.

 

[1970mule]

ok will do.

 

[blubuckaroo]

To check the fuel delivery from the tank to the pump you can remove the inlet to the pump and pressureize the tank with an air hose in the filler neck sealed with a rag. You should get a good stream of gas fron the pump inlet hose. It might also be a good idea to check the vacuum of your fuel pump.

 

[1970mule]

anhhhhhhh, good point