so before you watch the video, let me give you the history. I bought this truck two months ago or so and am slowly tinkering with it, working out all the bugs. it sat from jan 2008 - mar 2010. changed the fluids and popped in a new battery and it fired right up. i bought it from my moms cousin. i call him uncle jay. he told the not to trust the fuel gauge when using the front tank because it dances around (as posted in my other thread) and the rear fuel pump was bad so dont even bother messing with it.

so i would drive around using the front tank but was getting terrible fuel mileage. i had heard of fuel spilling out to the rear tanks in these two tank trucks so in the back of my mind i always kept that in mind but never checked. so today my wife and i get home and she tells me my truck smells like gas. i walk over to it and smell old fuel. i notice that there "dried fuel stains" on the paint that wasnt there earlier because i had washed the truck this morning. i opened the fuel door and gas was slowly spewing out sides of the cap. i opened the cap and a flood of old gasoline started puking out (just like when a radiator overheats). this has never happened to me. i didnt know what to do. i grabbed my phone and shot a few seconds of video as a resolution reference.



YouTube - ‪010.3G2‬‏


why did this happen? how did this happen?
\is there a way to cap off the line to prevent the front tank spilling over to the rear tank?

any light on this subject?



p.s....my collegues with the city helped me clean it up. i love my city.

 

You need to replace the rear Fuel Delivery Module (FDM), it has a bad check valve in it.

 

^^^^^Agreed. I just went through that with the front tank on my 94. don't just replace the pump though, replace the whole module.

 

Thats a first for me! i have never seen that ever happen

 

I have the same thing happening to my 96 f250. I'm shopping for a FDM. don't
seem to be cheap either $200ish

 

it was the weirdest thing ive ever seen. i stood there with no idea what the heck to do. it literally blew out about 5 gallons of old fuel. thats no exageration.

 

It was not old fuel, it was new fuel that you put in the front tank.

 

I bought one (rear tank) for my 96 from Global Automtive off of e-bay for $50 last year. I haven't had any issues with it. It's just the pump, so you have to splice the wiring, so I used heat shrink.

I had the same issue about eight years ago and took it to the local shop who charged me $500 to change the front pump, which I believe contains the switch. That's why I decided to do the rear one myself.

 

You need to follow Subford's advice. Your "crossflow" issue from one tank to the other is what I call the "fuel fairy" who fill's your empty tank up for free. Then turns into the fuel bitch that overflows the tank, risking blowing up your truck. To say the least this is dangerous. Replace the FDM as Subford said.