LONG STORY SHORT: Front tank runs great, rear tank sputters and stalls

So I have a 1994 7.3 IDI Turbo.
The beast ran just fine until about a month ago I decided to fill her up and take her through the car wash. This is when my problems started.

I ended up overfilling the rear tank, causing it to leak everywhere. Now whenever I run off the rear tank I get surging, sputtering and stalling. Front tank works fine.

So far I've eliminated
-Vacuum situation in the rear tank (ran with no gas cap, still problems, took the drain off the top of the tank, still problems)
-Felt the selector valve move when I switch from front to rear, so that seems to work

I think it could be either water in the tank (car wash) or there's air getting in there before the selector valve (because the front tank works great). It could also be a clog.

I have 0 experience with fuel systems, so does anyone have any suggestions on where to start? Thanks!

 

The cone of failure(i.e. suction cone inside the tank) failed?
You'll probably need to pull the tank(use a jack under it), drain it, and see what's up.

 

I took the bed off. I removed the sending unit and it looks OK, other than it looks like they repaired it with solder at some point. When I disconnected the fuel lines they were both dry (no fuel came out). Is that normal?

 

Update: Took the rear sending unit out, everything appears good. No clogs, minimal rust. One thing I noticed was that the supply line quick disconnect doesnt snap on, it's just sitting on. I wonder if that could be the problem and if so, how do I fix it.

 

it sounds like it is sucking air.
what i would do is remove the line from the lift pump, or the rear tank line from the selector valve and block it off with a bolt and hose clamp. then pressurize the pickup with around 5 lbs air pressure and look/listen for leaks.

 

I've narrowed it down to the rear sending unit. When I put a tube straight from the fuel line into the tank I can see no bubbles or issues. When I put the tube onto the feeder on the sending unit it goes all frothy and pulls bubbles. It can't seem to pull fuel through that thing anymore.

 

I had the cone of failure with both tanks. When I replaced my tanks, I noticed plastic pieces were logged in the fuel supply line. I think these pieces could eventually clog the line or work their way up to the switching valve and cause a failure.

 

I found a pinhole leak in the sender by submersing it in water and blowing on it. W00p! It was 15mm above the round plate part, on the outside. I'm gonna JB weld it and finish tomorrow. Such a small hole causing so many problems... I couldn't even see it, all I could do is see the air coming though.

 

In my case it wasn't the cone of failure, it looks like that part was replaced at some point. It's a little warped but otherwise perfect.

-Also, it helped immensely that the previous owner installed an electric fuel pump. It allowed me to pump fuel without mashing the starter.