Strange gas tank problem on my 72 1 ton

[flashed]

When I bought my flatbed dually truck I ran out of gas on the way home with it .I had a 5 gal can of gas with me that I dumped in to get me to the next station .When I got to the station it only took a few gallons to fill it up completely and the next day I ran out again even though it still had half a tank of gas .I went to the bodyshop that has my 72 1/2 ton and got the new tank and sending unit and installed it in the dually and it still will only run out half a tank and run out of gas even though it has a half tank. Any ideas what Im missing here ? The truck runs great otherwise ,just a weird situation.

[jackwalkeasy]

My 1st thoughts is the pump and filter. Did you flush out the gas line. And if thier is a filter been put in the line. Thier still might be a filter in the carburetor and it may be dirty. Sounds to me like trash could be building up. And ofcourse dirt could be building up in the carburetor.
Make sure the choke is working right. And put in a new air filter.

[haysonj]

Might also pull the sending unit and check to make sure there is not a hole in the suction line or not reaching the bottom of the tank.

[flashed]

The only fuel filter is the one in the carb which has been replacrd many times ,choke is working ,sending unit and tank are new and doing the same as the old original tank .I have not yet changed the fuel pump or the hard fuel line from rear of cab to pump but that is next. Rubber fuel lines are also new ,never had a situation like this .

[haysonj]

Is it possible it has the wrong gas cap and pulls enough suction at a half tank to overide the fuel pump.

[flashed]

I have wondered about that . My 1/2 ton truck had a vented tank and I believe the 1 ton was unvented . Im very confused by this but will figure it out eventually .

[volksworld]

check for crap in tank clogging pickup...you shut it off,pour in some gas,it stirs things up,and it can restart...also,if it dies,just take off the cap and see if it runs again..that 'll let you know if its a venting issue...also vapor lock,is there a gas line too close to exhaust or engine

[flashed]

There is nothing inside the tank as it was new and I looked inside before I installed it .The fuel lines are original in the stock positions so Im leaning toward the gas cap being my problem.

[PanelDeland]

This is just my first thought.Does it happen to have dual tanks or at least the valve for them.Maybe it's swapped to the other tank or partly.

[flashed]

In cab tank is all its got but that may eventually change if this problem persists .

[cdowns]

after you use the thing for awhile stop and take of your gas cap if you here the wooshing sound when you remove gas cap that is your problem // a badly vented gastank

[jackwalkeasy]

I,m Going along with the gas cap. But Are we sure it,s not a flooding issue. Ofcourse I guess you would smell gas.