Fuel Tank Check Valve
 

Howdy,

I have a 1985 F250 6.9L IDI. It has a bad rear fuel tank leak. I was told that fuel is flowing from the front to the rear, and that is also why it is so hard to start. I was told there was a recall on that in 85 but I can not find anything about it. Is there a kit to fix it? What could be wrong? http://www.misterfixit.com/dualtank.htm I read on this site about what could be wrong. Please help.

is your tank leaking or overflowing.
do you use rear tank or is it getting fuel in from front tank.

knash0727,
Welcome to FTE and the IDI diesel forum.

The hard start is probably an air leak in the return lines or bad glow plugs.

Is fuel going from the front tank to the rear tank?


Please give more info on how the hard start acts.

When I was putting fuel into my rear tank, it was not full, and just started pouring from the top of the tank. When I was driving it today, it blew fuel into the bed. My bed was covered with fuel. What I mean by hard start is that it takes about 25 seconds before it cranks for the first time in a while of not running. Just replaced the glow plugs, and I think there is air in the lines. As far as knowing if fuel is getting into the rear tank, it is. It was near empty now it is near full.

Sounds like the FSV (fuel selector valve) not working right. You can move up to a FSV from any dual tank ford up to 97-98 at the wreckers, best to ask for a 93 year if your getting new. You will have to splice the new connector for the valve into your existing wires......old color to new different color. So get the connector off the wrecker truck too. I do not have that schematic yet....... but someone will send it.

One other point might be the IVR (instrument voltage regulator) on the back of the dash cluster.. a little silver square tin that screws to back of the cluster. I would do the FSV first due to fuel diverting to wrong tank.

The fuel selector valve problem could also be corrosion in the electrical connector on the valve.

The hard starting problem on my 1987 F250 with 6.9 is due to the absence of the check valves in both tanks. A couple of years ago my truck was running out of fuel in each tank when there was still 4-5 gallons of fuel remaining in each tank. I took the bed off and looked in each tank. The plastic fuel pickup which contained the screen and a check valve had disintegrated in both of the tanks and was only picking up the fuel several inches from the bottom of the tank. I went to Ford and found I had to buy the entire pickup/float assembly at about $125 for each tank. That wasn't going to happen so I just cut a piece of fuel line at an angle and put it on the end of the line in the tank as the float gauge still works. This solved the premature running out of fuel problem but I still have the hard starting problem after it sits for awhile as the absence of a check valve is letting the fuel in the line to run back into the tank after it sits overnight. I've found an inline check valve I can put in the line just outside of the tanks but I don't know what diameter the ID of the hard plastic fuel line is. I can't order the check valve until I know the ID and if I cut the line to find the ID then I can't drive the truck until I order the check valve. Does anyone know the ID of the hard plastic line on my 87 F250?

That is not a check valve for the fuel.... it is a liquid fuel bypass for the screen should gelling occur. Opens to allow usable fuel when the gelled fuel blocks the screen.

Ok, I've learned something new. But why then do I have such a hard time getting the fuel up when it's cold? I check and/or replace my glo plugs about once a year. I replaced the fuel pump a couple of years ago just because of the hard starting problem although the old pump was good and it didn't change anything with the problem. I replaced the injector pump with a used but rebuilt pump. I replaced all of the injectors with new ones as well as replaced all of the return lines. After the glo plug light goes out it starts instantly but soon runs out of fuel and stalls. It takes a lot of cranking to get it started again but once it starts it runs fine and doesn't stall again all day. It starts instantly again all day long but if I let it sit overnight it goes thru the same old thing all over again. It appears to be losing the fuel supply to the engine and by cranking it alot it finally brings it back up. That's why I wanted to install an inline check valve to keep the fuel line full.

Do you still have the water separator in your truck? It could cause the same issue.

Brimmstone, no it was bypassed years ago as it had the usual problem of letting air in the system.

I had to ask because I just had to deal with a truck by me that had the same problem and that was where we found it.

The starting and then running out of fuel is a return line air intrusion problem.


Have the O rings and return lines been replaced recently?
Have they been disturbed since they were installed?

gov2mod....... I did not explain far enough in my post, there is a check valve,... but it is on the single return line....... it is shaped like an add on pencil eraser.... tapered. Now if it has fallen off or disintegrated that could cause air intrusion possibly..... as long as it is below fuel level things should be fine. Tunnel vision at that time on my part....

Dave, I replaced the injectors, o-rings, and return lines about 150 miles ago. It runs a lot better but it didn't change anything with it's starting problem. However, I only changed the return lines between the injectors and on top of the engine. I didn't replace any return lines from the engine to the tanks. But, if a return line had a leak in it wouldn't it also leak fuel out on the ground?