I just replaced my fwd fuel pump w/ aftermarket oem replacement(bosch). Now my aft tank fuel is transfering to the fwd tank when fuel is put in the aft tank. Ive verified this twice.
Tank selector worked fine before the new pump installation. I think it is related to the new fuel pump. Any ideas or suggestion on how to test this?

 

Why did you replace the pump in the first place? Was the fuel transfer problem there before? Did you replace the entire Fuel Delivery Module or just the pump?

 

I replaced the pump body only(white plastic body that plugged into the 4-5 metal tubes attached to the coverplate and hoses) after it quit working.
I was driving w fwd tank and 1/2 tank of fuel and it sputtered like it was out of fuel,then transfered to other tank and it kept going. Fwd pump was always noisy and didnt run anymore after this. I believe its original ford pump 180,000 miles

 

You need to replace the front one again.
About a year ago someone reported this problem with some brand of pump (DFM) but I do not remember the brand or were they bough it anymore.
If you take it back get a pump from another mfg.

 

I got the Bosch because I read the Bosch was a good one! doh! it acts like that way though! thx Kansas(boy I dont miss that heat up here in AK!)

 

I called the auto store, I have a warranty on the bosch and they have the Delphi instk so I will get it and return the bad from stock one. I asked for the OEM and paid about $50 more for the part but the chic(keyword maybe?)stated the Delphi was the oem so who knows? its hard to get it right these days.

 

It may have been Bosch that had a bad run with bad check valves.
I had to take back three Delphi once because they made too much noise.
I think I wound up with Airtex.

 

I just got back from the parts house. They say my pump they sold me and I put on was for a Ford Truck w/ a plastic rear tank I have metal. So they sold me the wrong pump!
I hope I dont have probs w/ Delphi pump!
I wonder what the real difference is? They look identical except the o ring it came with was the correct size unlike the previous pump.

 

I replaced my new Bosch(henche in Brazil) fuel pump w/ a Delphi(made in USA) and I have no more problems. No more fuel transfer to other tank. Thanks Kansas for the input. I hope Carquest refunds my incorrect p/n(used on plastic rear tanks not steel) and bad fuel pump for $180.00 like they said they would. I sure hate doing things TWICE!

 

I too have recently replaced my rear pump and now have fuel transfer problems. but i have no front tank so mine just leaks on the ground..