Hi,

I have done some searching and found some answers, but I thought I would see if anyone has some advice before I actually get to wrenching.

The vehicle that I am having problems with is a 1989 Ford F-150 4.9L I6 with dual tanks. I have owned the vehicle for about three years now and it has basically been trouble free (few sensors had to be replaced at one time, easy enough). When I bought the truck the previous owner told me that only the rear tank works due to the front tank leaking. This was never really an issue for me as I live by a bunch of gas station and rarely take the truck on long trips. Starting a week ago though I have had a problem with fuel draining out.

The first indication of the fuel leak was when I went to drive the truck one morning and noticed the fuel gauge was on empty. I thought that was odd because I had just filled it up the night before and only drove it from the gas station to my house. I kind of assumed the gauge was malfunctioning or neighborhood vandals had possibly stolen my gas. So I went to the gas station and was able to put 16 gallons in my rear tank. I figured the gas was stolen and went on my way. [It may or may not be important, but I backed my truck into the driveway (something I rarely do) that evening - this caused the rear tank to be higher than the front tank] To my surprise within about 10 miles the fuel gauge was reading half full and dropping rather rapidly. I pulled into my destination and noticed fuel was leaking rather rapidly from the front tank filling cap. I waited a minute or so and it stopped dripping from the filling cap. I did not have time to mess around with the truck at this time so I left it in a friends driveway and got a ride home.

I went back to look at the truck today and it had not leaked any further gas. I took it for a quick drive around his neighborhood and parked it again. It was not leaking. So I figured maybe I would be able to drive it home...I was wrong. Now the truck would not start. After messing around with the tank filling caps for a while (I thought maybe it would relieve vacuum?) I was able to get the truck to start, but the leak came back from the front tank filling cap. I had to leave early than expected but have plans on going back tomorrow.

After reading some old threads I have come up with the following things I should try to do tomorrow.

1 - Put fuel tank selector to front tank to see if gauge works, if so see if the tank is full for some reason. The filler neck connection seems to go to the top of the tank so I would assume the tank has to be full to leak out of the filler cap area.

2 - Try running the truck with the selector on the front tank.

3 - Out of easy ideas after that....

The main thing I am trying to do is get the truck home (10 miles or so). I am moving from Minnesota to Virginia in one week and I don't think my buddy would appreciate a truck in his driveway.

Does anyone have any suggestions on what I can do?

Thanks.

 

over time if you dont run the truck on the front tank, it will slowly fill up from the rear tank... if the motor wont stay running on the front tank, replace the fuel pump. that should solve the problem... my front tank didnt work when i bought my truck and for every tank i filled up, as the truck runs it pumped 1/2 of that into the front tank. when the tank got full i'd siphon the front tank, and fill the back. after i replaced the pump, havvent had a problem since, put 25K miles on it since then

 

The return valve in your Fuel selector valve has a "O" ring stuck on the shaft and the return fuel from the fuel pressure regulator is going into your front tank.
You either need to replace the fuel selector valve or completely take the valve apart and free the "O" ring with silicone spray.

For more information go to this link:
http://www.stangler.com/motorsports/...alve/index.htm

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1) Yes, the front tank is dangerously overfilled. I advise AGAINST driving or even starting the engine until you drain it to a safe level (siphon it over to the rear tank).

2) If it'll run, that's by far the easiest solution. But I doubt it will, and if it does, you'll probably find another odd symptom or 2.

More detailed info on that valve can be found in the '84-89 Fuel Reservoirs album linked to the black Bronco in my signature. It also shows how to replace it with common solenoid valves & a more-reliable single-function reservoir.

 

Thanks everyone for all the help. I was able to run it off the front tank. After I found out it would run off this tank I siphoned out a few gallons and put them in the rear tank. I have been running off the front tank for the last few days. I am planning on doing some actual 'fixin' this weekend.

Thanks again.