fuel pump pumping, but no fuel!

alright the truck is at it again, fuel pump is pumping fine, both tanks have gas, switch works and clicks over,. sit there and crank it nothing. prime it it will run on the gas in the carb and die <of course> but i dont get it! could it just be blockage? being an 80 this is a nightmare to many fuel lines!:LOL: whats the best way to clear it out? each tank has a to-something and a return line, plus the ones that go from the twin tank switcher to the fuel pump and a return line. how do ya do this without making an incredible mess <the real question> whats the easy way!





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"its never THAT easy":LOL:

Probably a bad valve? Dunno, must be something simple, usually is.

should bought an old international? OOOOOOOOOOOOOOO i better hide for that comment! :LOL:

i'd check the valve on the tank switch..... i've seen them freeze up before, i'd go through every single place the lines have a connections and see where you get flow to, and find out where the flow stops.... might be a little messy, but with full tanks you at least can do it with using the pump

I agree, it's usually the electric valve. Even if they click, they don't necessarily work. They didn't work for all that long when new, I'm amazed that there's an '80 out there with one still on it!

i use those tanks isnt there a manual switch <wait of course there is> where the heck do you get them?

take one line loose from the valve fuel should run out.

I useta put a Tee fitting in, run off both tanks all the time.

No idea what kind of truck you have, or if it is FI, TB or Carb, but you said it is an 1980 ... any chance you have neoprene lines in the fuel system (supply lines) somewhere with metal brackets holding them in place?

I see the flex lines on front brakes "plug" at the metal clamp often enough. Clamp at the strut (or on the upper control arm) rusts and pinches the line, thus stopping any fluid from passing through.

Just a shot in the dark.

Easisest way to check is pull the feed line from the Carb (SFAETY SAYS to extend the lines with oversized line into a bucket or something) and turn the key on. See if you have flow from the tank to under the hood.

its carbed it has all metal lines from the tanks. to the motor and from the tanks to the solenoid. i use the tanks on road trips though

So much for that theory ....

If it was me, I'd see if there was gas at the carb from the feed line. If so, I'd be pulling the carb apart. Check to see if the floats and needle is working right. Always a chance the float is stuck "up".

there is no fuel from the pump to the carb, i ordered a new tank switch block those are notorious for going out on these trucks and even if thats not the problem it's a good idea to change it. and i am going to just take and air nozzle and blow the lines when the block is off.

we skipped puttin the solilnoid <whatever> on and blew all the lines out checked them for cracks both tanks has fuel and it still wont start. and the fuel pump is pumping! what the heck? anybody want a free truck this is ridiculous. i have never seen a cam do it but could the fuel pump lobe be flat?

Try the dangerous route....run a hose from the fuel pump inlet to a small can of gas and see if the pump will draw from that. If it will, the problem is in the lines/valve/tank. If it doesnt pull, the problem is in the fuel pump/line to carb/or carb inlet.

Be careful, gasoline vapor will ignite!!! Liquid gasoline will not burn but it's darn hard to get rid of the vapor layer on the surface!!!

mike in tucson

i like essplosions :LOL:

Scooter, you say the pump is pumping but is it pumping at full pressure? I once had a pump that seemed to be pumping, but the spring under the arm had broken in two and it wouldn't keep up.

took and stuck an air nozzle in the tank with a rag and pressureized it about 30 times, of pressurize and release at first very little fuel to the filter then it start filling it i let it run for about 15-20 minutes to see if it was a fluke or not at varied rpm's then drove it around the block thought cool parked it left it running got back in drove around the block again and it died again! i really dont get this?????? edit interject>i am on my 4th brand new fuel pump.........

i shoulda stayed with gut instinct, it was the cheesy old tank switcher after all! shoulda known they are notoriously cheesy!

Pour some gas into the vent tube of the carb. eng should start. .I am in the middle of replacing a fuel tank on a truck that sat for 4 yrs. when i pulled the tank and could get the feed line out it would not let fuel run thru. you could pressure it and it would pass. i cleaned the fuel line and am replacing the tank in the am.

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Originally Posted by gassersrule_196

i shoulda stayed with gut instinct, it was the cheesy old tank switcher after all! shoulda known they are notoriously cheesy!

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hmmmm. If I remember right, a defective valve was one of the first replies when you started this thread~~~~:LOL: :LOL: :LOL: :LOL:

quiet you :LOL: :LOL: :LOL:

the small things that cause the biggest problems are often missed by even the best..... i've done it plenty of times at work, you just start instantly thinking for the worst.... specially when the car is a piece of junk though, like a mitsubishi or any chrysler product of the newer junkier era