I have an 87 F150, 4.9L, EFI (Calif model), 3-spd with O/D and two tanks. I have had front tank replaced, and both in-tank fuel pumps replaced. Have had selector valve (6-port) removed and cleaned. Mechanic said he did continuity check on switch and that the switch was OK. Same mechanic who did the in-tank pump/filter work and removal and cleaning of the selector valve said both tank fuel pumps "clicked" when selector switch was moved from Front to Rear, etc, and gave him the impression that the switch was selecting each tank correctly as selected.

Problem: Only the Rear tank is in service, regardless of switch position. Gas gauge reflects normal movement when in the Rear position, but does not move when in the Front tank position. Also, no gas is used from Front tank. It remains full.

Any help would be greatly appreciated. Thanks.

 

I know this sounds weird, but if there is a problem with the front fuel pump when the rear tank is selected the returned fuel winds up going to the front tank. Does it seem like this might be what is happening? Are you able to use the front tank at all?

 

Thanks for your comment hanky. I can't draw from the front tank at all as I can tell anyway. If the back-flow you mentioned is the case, it'd have to be only a very small amount of gas (like < 0.2 gal per 100 miles). I suspect a bad switch but I don't know. I'd hate to have to take it to a dealer.

 

In any case it might be a good idea to check if they would be able to get parts for your vehicle due to the age. There is a check valve in each fuel pump module that is supposed to prevent fuel from going into the wrong tank on return. We don't know for sure if this is what is happening. I believe you are on the right path by trying to get that front pump working properly.None of this could be happening so just take one thing at a time and check around. Some dealers can locate parts from a place called ,"Vintage Parts" located in Beaver Dam , Wisc.

 

Thanks, hanky. The search will continue. Without that front tank my restoration project for this old friend is not going to happen.