Have an 86 F250 w. 7.5L and dual tanks. Rear tank sending unit is bad and it looks like there are two options, one sending unit only and one that has an in tank electric fuel pump. The Side Tank does not use an electric pump in tank. Why does the rear tank need one?

 

Most 460 trucks use the electric pumps. Are you sure your truck hasn't been modified in some way? What type of fuel pump do you have?

 

The rear tank hook up appears to be original and did have the pump inside. I bought the truck about a year ago and have been clearing up little problems. Getting to the rear tank now. Have been running off the side tank. The truck has an aftermarket electric fuel pump up on the front frame rail.

 

There you go. These trucks seem to have a lot of problems with their fuel systems when they get old, we have a ton of questions on here about the 460 fuel systems and trucks not running. Someone added that pump and bypassed the original system.

If your switching valve is still hooked up and still works, there is no reason why you could not buy the sending unit only for the rear tank, and then modify it so the fuel can be picked up without the fuel pump in the tank. I have never done this before on this particular unit, but I am guessing you could add a piece of fuel line to take place of the missing electric pump on the sending unit so the aftermarket pump can suck the fuel out of the tank.

The original system had a return line system that went to the switching valve also. With the aftermarket pump you probably don't need the return system, so you will have to figure out which line is which at the selector valve.

 

Thanks...I have a new sending unit w/o the pump on it and will test it on the ground before I install it in the tank and hook it all back up and put the tank back in place.

 

Welcome to FTE

There are two different aft axle fuel tank sending units for these trucks...they are not the same!

E5TZ-9275-KA .. Aft Axle Fuel Tank Sending Unit-Use with 19 gallon steel fuel tank / Obsolete

E5TZ-9275-LA .. Aft Axle Fuel Tank Sending Unit-Use with 19 gallon plastic fuel tank / Obsolete

Applications for both senders: 1985/86 F250/350 351W & 460 without EFI

 

all you have to do is put in a electrical fuel pump and get a pet **** for a carbed motor and put it in your tank there with be a return line from the motor put another fuel pump for the return and return it into the tanks

 

Thanks....I have a steel tank. Can get the correct part from LMC. Just wasn't sure why the rear tank had the electric fuel pump inside and the side tank does not. The person who had the truck before me said he removed the mechanical fuel pump from the engine and mounted an electric pump up near the front frame rail by the front left wheel.

 

the reason for the in tank was because it was a tight fit for a fuel pump in the rail and without the reture you will flood the floats

 

Ford officially calls this system "hot fuel handling". That leads me to believe it was to keep the fuel cool and prevent vapor lock. The fuel pumps in the tank pushed the fuel up front to the carb where there was a orifice with a return fitting and line. This continuously circulated the fuel from the tank through the fuel lines back to the tank to keep the fuel cool. The orifice was designed to let a portion of the fuel into the carb, and the rest back to the tank.

 

Your truck originally did not have a mechanical pump on the engine. If it did, then it's not the original engine. You have the remnants of the hot fuel handling system, so that's what the truck originally had from the factory, as did most all 460 equipped pickups did in the 80's.

 

That actually makes more sense. The guy I bought the truck from must have installed the external pump rather than drop the tanks to replace the failed pumps inside the tanks. The plumbing up at the carb has a split off for the fuel return to the tank.

 

It all depends on the applications whether these trucks came with a mechanical or electric fuel pump...as both were available.

The two aft axle sending units I listed in post #6 were used with mechanical fuel pumps, because... If with electric pumps, the fuel tank senders were only furnished with them.

1980/89 Ford Light Truck Parts Catalog / Text, Section 93, Page 22:

EOUZ-9350-B = 1980 E350 460, except CA / 1981/85 E250/350 460 & 1983/85 F250/350 460 .. Mechanical Fuel Pump-includes mounting gasket.

E5TZ-9350-E = 1986/87 E250/350 460 & F250/350 460 .. Mechanical Fuel Pump-includes mounting gasket.

Text, Section 93, Page 2:

E5TZ-9H307-E .. Electric Fuel Pump & Sending Unit Assy-Use with Aft Axle Plastic Fuel Tank = 1985/86 F250/350 460.

E5TZ-9H307-F .. Electric Fuel Pump & Sending Unit Assy-Use with Aft Axle Steel Fuel Tank = 1985/86 F250/350 460.

E5TZ-9H307-L .. Electric Fuel Pump & Sending Unit Assy-Use with Mid-Ship 19 gallon Fuel Tank = 1985/86 F250/350 460.

 

He said his rear tank has a electric pump. That means his engine DID NOT have a mechanical pump on it originally, unless someone swapped in a tank from another truck. He also said it has the return system at the carb inlet.

 

If the sending unit is available by itself, the tank could not have an electric fuel pump inside, because w/an electric pump, the sender is not replaceable by itself....it's only furnished w/the pump.

And, since the OP bought an aft axle fuel tank sending unit (for a steel fuel tank)...there is no way on God's green earth his truck has a electric fuel pump & sender assy.

Post #12: The way I read it, someone installed an autoparts store external electric fuel pump on the OP's truck, why I couldn't say.

The OP is only guessing, because an individual fuel sender cannot be installed in a fuel tank that came with an electric fuel pump/sender assy, because there is no provision for it.

The on going problem is...that you are aware of...is that people swap parts around, do not record what they come from.

Then when the part fails, they or a subsequent owner has no clue what the part is from and/or where to get it.