I have a 1987 F150, 300-6 cyl with dual tanks. The fuel gauge does not work on the front tank. Only had the truck for a few months, so I have been using the front tank. I used the rear tank last week and went through the tank of gas in 70 miles, so I knew there was a problem. I found out the problem when I filled both tanks then ran it on the rear. Gas started flowing out the front tanks filler cap.

Is this a problem with the tank switching valve or maybe the tank vents.


Ed

 

Your problem is a bad check valve in the front tank/fuel pump. The valve is built in to the pump. When it fails, unused gas returning from the engine to the tank goes into the tank with the faulty valve cause the valve ain't working. Had the same problem on mine. Ford had a recall on this...check with your dealer. They might be cooperative and then the onus/job is off your back. I had to do it myself. Ain't hard to change the front tank's pump, but a replacement pump will cost around $200 and it will take you about 2 hours. Rather than dropping the tank to gain access to the pump, consider taking your bed off or moving it back on the frame. Ain't as hard as it sounds. Remove your tailgate, get the bed bolts/nuts out, loosen the clamps on both fuel filler hoses, and disconnect your tailights under the bed close to the bumper. Now get a buddy to help you: each of you lift the bed up and back, gripping at the top of the wheel wells. You only have to move the bed back about 2 feet to gain access to the front tank/pump. First, depressurize the fuel system (check your Chilton's or Haynes manual). Then, remove the wires going to the tank/pump, unscrew the metal ring that locks the pump down to the tank, pull the pump and put the new one in. Same holds true for the rear tank/pump, only you'd have to take the bed off. The bed ain't that heavy, especially for two guys...or just one BOB (big ole boy) like me.

 

Well, I got smart and popped off before I noticed your truck is an '87 model, which may have three fuel pumps...a low-pressure in each tank and a high-pressure on the frame rail. My comments fit for my truck, a 90 model with just a high-pressure pump in each tank. You might run a search, on fuel cross flow or something similar in this forum or the 1987-96 forum. I know I have seen discussions on both types of trucks with the same problem. Or, maybe someone who reads more carefully than I can chime in and tell you whether my advice fits for your year model.

 

I got a recall on mine but mine hasn't went bad yet they told me it has to be bad or 150 000 on the truck. Before they would fix it for free.

 

I had the same problem on a 88 F-150 it was the tank selecter valve was bad. On these year trucks if I remember right it controls the fuel return line also. There should be 3 fuel pumps low pressure in each tank and a high pressure pump on the frame rail at least thats what I remember from mine.

Mike