New to the site, recently purchased a truck, scanned the messages for info regarding pros/cons. Ended up with a 1999 FL70, 6-spd man., ISC engine, air brakes. Just drove the truck on a 500 mile trip, topped off both tanks(dual 45's) before leaving. Pulled in to re-fuel once needle gauge reached "E"...found out that the driver's side tank was still full to the brim and passenger side tank held 32 gallons to re-fill to the brim. Any suggestions from you guys regarding the driver's side tank remaining untouched?? There is a toggle switch and green led on the dash...but doesn't seem to operate anything. I know on these trucks the gravity fed crossover line has been replaced. Looking at the top and back of the tanks, I see matching fuel lines and the pass. tank only has a sending unit mounted to the top...the drivers side tank only has a blank plate mounted in place of the sending unit. I greatly appreciate any assistance regarding this problem...the small town I'm in doesn't have any repair facilities...thought I'd try to tackle it myself before going to the "big" city.
Fuel tank crossover??
- Thread starter swrjr71
- Start date
Did you notice a shutoff valve on either tank? The previous owner may have run truck on one tank only. The issue of tank and gauge reading inaccurate is not uncommon, you may need a new tank sending unit. If you do it yourself be prepared to calibrate the sending unit float. Good luck, and I hope this helps.
rode2rouen
Expert Expediter
By your description it sounds as though your truck has a "Dual Draw" system. That's why it has only one sending unit. The fuel should draw evenly from both tanks as well as return evenly.
In order for a dual draw system to work properly both of the suction and return lines must be the same length from the tanks to the "T" fittings from where the lines continue to the engine. I have seen instances where someone replaced a defective line to one of the tanks but did not measure the replacement correctly and the system would only draw from one tank.
Also, I have seen defective standpipes (the steel pipe that is inside the tank)that have cracked or even fallen off the fitting cause a unit to draw from one tank. These problems are usually accompanied by rough running complaints as the engine will be sucking some air.
It's good that it's drawing from the tank with the sending unit, or else you'd have been thinking "Man, this truck gets AWESOME fuel mileage!!!" about the time the tank without the sender went dry. That would suck!!! (I know, nasty pun, but I couldn't stop myself.)
Do the overhead lights in the cargo box come on when you flip the toggle switch?
Rex
In order for a dual draw system to work properly both of the suction and return lines must be the same length from the tanks to the "T" fittings from where the lines continue to the engine. I have seen instances where someone replaced a defective line to one of the tanks but did not measure the replacement correctly and the system would only draw from one tank.
Also, I have seen defective standpipes (the steel pipe that is inside the tank)that have cracked or even fallen off the fitting cause a unit to draw from one tank. These problems are usually accompanied by rough running complaints as the engine will be sucking some air.
It's good that it's drawing from the tank with the sending unit, or else you'd have been thinking "Man, this truck gets AWESOME fuel mileage!!!" about the time the tank without the sender went dry. That would suck!!! (I know, nasty pun, but I couldn't stop myself.)
Do the overhead lights in the cargo box come on when you flip the toggle switch?
Rex
rode2rouen
Expert Expediter
Another thing to look at: Check the vent for the tank that remains full, make sure the hose (if equipped) isn't kinked or plugged.
Rex
Rex