My fuel pump went out and I gotta get the gas out of the tank and I was wondering if I can still drive with the front tank down and run of the back....or.r they connected? ..1991f150

 

Not 100% on the gasser, however on the Diesels, from the FSV forward it could care less what tank it's on or even if the non used tank is even there ...

I suspect the gassers are the same, So, yes, you should be able to pull one tank, run on the other.

I do suggest wrapping up the lines to prevent filth from entering while off.


-Enjoy
fh : )_~

 

You cannot disconnect and leave open the fuel lines on one tank or the other without it dumping fuel on the ground with this vintage gasoline truck.. There is no fuel selector valve like the earlier trucks and diesels.

You could plug the lines and be safe.

 

so plugging the fuel lines with do fine?

 

So on the gasser you cannot switch from front to rear tanks ??

Then the tanks are tied together ??
If that is the case, then the missing tank lines need to be plugged.

-Enjoy
fh : )_~

 

No,you can switch between tanks....lol im confused

 

Yes, you can switch between the front and rear tanks on a gas truck.

Here is some theory on how the fuel system works:

The electric fuel delivery system used on the 4.9L, 5.0L, 5.8L and 7.5L Electronic Fuel Injection (EFI) engines consists of a fuel delivery module (FDM) assembly. The FDM unit includes a high pressure fuel pump, venturi jet pump, supply check valve, and a shuttle selector valve located internally to an in-tank reservoir assembly mounted from the fuel tank sender flange.

The following provides a brief description and function of each of the FDM internal components.

High Pressure Fuel Pump: The high pressure fuel pump is located inside the flange-mounted, reservoir assembly internal to the fuel tank.

Shuttle Selector Valve: The shuttle selector valve opens the return line to the tank and the return flow is directed to the appropriate tank on vehicles equipped with dual tanks.

Supply Check Valve: The supply check valve, which is normally closed, opens when the outlet pressure from the energized pump exceeds the opposing check valve spring force. When the pump is de-energized (i.e., engine is shut off), the supply check valve closes to maintain pump prime and fuel supply line pressure.

Venturi Jet Pump: A portion of the high pressure flow from the pump is diverted to operate the venturi jet pump. The venturi pump draws fuel from the tank into the ITR reservoir to augment the engine return flow. This process ensures an adequate fuel supply to the pump during extreme vehicle maneuvers and steep vehicle attitudes with low-tank fill levels.

A visual from Steve83:




Without someway to block fuel flow, to (check valve) and from (shuttle valve) the engine, fuel will be pumped out of the open fuel lines of the disconnected tank. That is why you need to plug them until you install the new tank.

 

ok i just got the tank down i just need to know what ones to block off and what should i use ??? and it wont build up pressure if blocked off?

 

ok so i started the truck with them unplugged and they do have gas coming out of them

 

You need to block off the fuel supply, fuel return lines. I would also block off the tank vent line as well, just to be sure.

What to use to plug them temporarily is a good question. The vent should be easy enough. The fuel supply and return lines are going to be difficult because you do not want to destroy the existing fittings.