For starters the truck is a 1985 302 F150 with dual tanks, new to me as of about 2 months ago. have receipts showing that it had some fuels system work (new pumps and a new tank) done about a year ago... when I first got the truck I put half a tank of gas in the rear tank and have been driving off of the front tank ever since.... this leads me to today. Run some errands in the morning get home and I smell gas. Some investigating shows some gas on the frame rail near the rear tank... look a little closer and it also has some gas around possibly the sending unit? (I'll try and post pictures) so I go to pull the truck in the driveway to start pulling it apart and figure I'll switch it to the rear tank and see what is left, low and behold the tank is fuller than full on the gauge, way past the F... So any ideas? can the front tank pump into the rear tank causing problems? Thanks in advance -Tim

 

Is it possible that a faulty switch valve or whatever the name may be for it could be not closing all of the way pumping some fuel into the unused tank over filling it and causing it to leak?

 

Yeah thats sounds what is happening this is a very common problems with our trucks. You should have a fuel resservoir assembley that has a diaphragm that opens or shuts off the fuel flow depending on which tank your using or a selector valve.

 

Well its good to know that at least I was on the right track... may explain my less than desired mpg if fuel was just moving tanks as upposed to being burned. My question now would be this.. is the assembly in question on the driver side frame rail just behind the cab? if so i know what it looks like or is it near the leaky tank? and do I need to replace any seals on the leaky tank or shoud fixing the faulty valve be enough?

 

And would it be safe to use the rear tank untill I get off of work tommorow and have time to work on it? Might be goot to get gas out of the overfull one and possibly confirm a faulty valve if my front tank seems to magicly gain fuel?

 

Yeah you should be able to run off the rear tank. It's the seal that goes to the rear tank that is not sealing so you may be able to run off it and not put fuel into the front one.

 

Well more digging and the work will need to be finished in the morning but it looks like the fuel supply reservoir(?) is new as I got the receipt for it from the previous owner so it looks more and more like a faulty selector valve as it looks to be origional and with the level of crud buildup I doubt it is crossed return lines. So that leaves me with just the tank... if that valve caused a pressure leak at the tank (since there is only gas dripping there) what all seals should be replaced on the tank? or will fixing that valve alone be enough?

 

Well guys, I have a half update. I picked up a new selector valve but to to work schedual not lining up with times that its not raining outside I havent put it in yet, but here is the thing... I started running off of the back tank to empty it because I thought it was over full. Truck runs fine off of that tank and while on that tank it doesn't leak but after several days it still says I have a full tank and by now I should have seen a fair decrease. front tank still works and the gauge reads it correctly. This leads me back to my origional problem wondering if it is the selector valve that is actualy the problem... while running on the front tank the rear tank leaked from around where the sending unit enters the tank. while running on the rear tank no leak and the gauge says its full when it isnt. Looks like I am going to have about a week till I get some sunny days and would really like to get this sorted out then. Any new thoughs would be appreciated.