Simplespeed

89 f150, 5.0, 5 speed, dual tanks. I just bought the thing and noticed when the switch is flipped one way it reads empty. Flip it the other way and it reads waaaaay past full. I have no idea how much fuel is in either tank. With the top of the switch pressed in, which tank is selected? Is this a common problem?

grilljames

up=front down=rear. As for your 2nd question i dont know...

short stack

i have a 92 that reads empty on the front tank when key is on and 1/4 full when key is off. seems to run ok on that tank

Simplespeed

Anyone know the capacity of the tanks?

And maybe any tips or tricks to find out how much is in there?

short stack

i think like 17 in the front and 14 in the rear

BrianH

16 in the front, 19 in the rear.

Simplespeed

SO, my truck is still running and i have no idea how much gas is in either tank, and iv been driving a lot. I went to add gas to the front tank and it wouldnt take any. I kept trying and it started overflowing. So, front tank is full even though i have had the switch on the front tank. Maybe the front tank isnt being switched on when i flip the switch? Are the tanks connected to where the rear tank could flow into the front tank keeping it full?

I added 15 bucks to the rear for now. I guess im going to run the rear tank until the truck dies and then switch to the front tank and see if it runs. If it does, ill see how many miles i can go until it dies. Id like to be able to track my fuel by mileage until i have the time to drop the tanks and get it all figured out.

badger1115

Long bed will have a 19 gallon front tank. Short bed will be 16. Rear tank will be 19 gallon for whichever bed you have. Flip the switch up for the front tank and down for the rear. I would just fill up the tanks and then run one until its empty and keep track of the miles.

scoby41

That's what I was doing... until my speedo and odo stopped working, DOH! I'm thinking it's the little contraption that re-calibrates the speedo for larger tires. Hopefully removing it will get my dash back, albeit a little off.

Simplespeed

So the rear tank ran dry and it died. I walked to a station and brought back 5 gallons in a fuel tank. I tried putting it in the front but it started to overflow right away. The truck wasnt cranking with the front tank selected. Its possible that i didnt give it enough time to get fuel to the motor. I put the 5 gallons in the rear tanks and cranked away, it fired up and was running again. I stillhas the fuel cap and door open to the front tank and it began to overflow once the truck was running again. So, this has got me thinking that the rear tank is pumping fuel into the front tank.

Iv done some searches and it seems like there are a couple different systems based on year model. Lots of talk on check valves and vent valves, selector switches and of course the pumps themselves. Im kind of lost, can someone point me in the right direction? Or at least explain how the system is set up to work so i can begin to diagnose all the problems. Mine is an 89 5.0l 2wd 5 speed short bed.