Rear Sending Unit Troubles

[kcnicolle]

Hey all!

New to Oilburners and I like it already. I have a 1994 F350 7.3 IDI longbed, 4door. Recently, the rear sending unit has not been working correctly. The front tank works like a charm. The rear...not so much. Just replaced the main fuel injection pump a few months ago, and took both tanks out to run new lines. When I flip the switch to the rear tank, the truck sound like there is a wrong mixture of fuel...more smoke coming out, sucks down fuel unbelievably fast, and spits and sputters while idling at around 6-700 rpms. I swapped fuel lines on the selector switch to see if the switch was bad, but it ran fine using the front tank, while the rear tank was selected on the switch. Sounds like a new rear sending unit right? Tried local parts shops all over the map, and they all told me the rear tank doesnt have a pump on it just the sending unit. When I initially had the problem I dropped the rear tank, took out the pump, and bench tested it. It spit fuel running off of my little battery jumper like it should. There is DEFINITELY a pump back there but all records show it doesnt exist! Searched all over online and still no luck.

Can anyone offer suggestions of where to find this part or if I'm doing something wrong if it's still good? Any replies appreciated!

Thanks in advance!!

 

[rattleonby]

Hello and welcome to Oil Burners!! Now I have never heard of a rear tank pump for a DIESEL either.....I'm gonna go out on a limb and say its aftermarket. The previous owner may have installed it for better cold start priming is my guess??? Either way your going to have to replace it with something of the similar or eliminate it and put in-line and mount it on the frame rail somewhere like alot of members do here. Another question arises in my head is do you still have a functional pickup fuel pump on the front paasenger side near the bottom of your block?

 

[PackRat239]

Sounds like a gasser sending unit or tank.

 

[lotzagoodstuff]

+1 on the gasser rear tank. Definitely shouldn't be a pump in either tank, you're lift pump is the mechanical one on the engine, unless you've got an aftermarket electric. Go scour the bonyards and see if you can find a rear rank with a diesel sending unit.

Good luck and welcome to OB