Rear tank fills up front tank

[Howling.Wolf]

- deleted -

[Gary Lewis]

Heinz! Good to hear from you. How is Oberursel?

Sorry that you are having that problem.

I think you may have a problem with the tank selector valve. I've seen it before where it doesn't switch properly and returns fuel to the wrong tank.

In the page below you can see that valve. So I would check to make sure it is getting the voltages it is supposed to get, although if the right pumps are working then it should be.

[Howling.Wolf]

Heinz! Good to hear from you. How is Oberursel?

Sorry that you are having that problem.

I think you may have a problem with the tank selector valve. I've seen it before where it doesn't switch properly and returns fuel to the wrong tank.

In the page below you can see that valve. So I would check to make sure it is getting the voltages it is supposed to get, although if the right pumps are working then it should be.

Hello Gary,

good to hear from you and hope you all get around this stupid Covid-Virus.

Thanks for asking we are good here in Oberursel, life slowly becomes some kind of normal again.

Exept wearing the masks in shops and travelling outside of Europe

Thanks for the hints but I just cannot imagine where that tank selector could be.

My Bullnose got a fuel reservoir with filter instead (see pic but with 4 inlets)

If yes, there then is nothing to switch. But yes there are valves working pressurewise inside.

Best regards

Heinz

[Gary Lewis]

Hello Gary,

good to hear from you and hope you all get around this stupid Covid-Virus.

Thanks for asking we are good here in Oberursel, life slowly becomes some kind of normal again.

Exept wearing the masks in shops and travelling outside of Europe

Thanks for the hints but I just cannot imagine where that tank selector could be.

My Bullnose got a fuel reservoir with filter instead (see pic but with 4 inlets)

If yes, there then is nothing to switch. But yes there are valves working pressurewise inside.

Best regards

Heinz

Heinz - Sorry, but you apparently have the later version of the fuel system. The earlier version is shown in the first illustration and the later one is below that. (I'd much rather use Ford illustrations that LMC's.)

I don't understand how the later system works. I say that because I don't see how it knows which tank to return fuel to w/o the tank selector. Unless it uses different in-tank pumps with check valves. Maybe Bill/85lebaront2 knows? I'll tag him.

[myrl883]

This is all too common of a problem. We used to deal with it at the dealerships pretty frequently.

Your '86 should have a reservoir (9K044/9B263) with 6 ports, unless someone added a second tank and teed the lines together. The cause of your problem if all is plumbed correctly is the fuel reservoir.

Now, to answer Gary's question. On the newer trucks that have a "fuel delivery module" in each tank, the check valves are built into the modules. When this problem occurs, the tank receiving fuel at the wrong time has a failed valve, and you need to add an inline check valve (there was a recall on this) or replace the fuel delivery module. Trucks with FDMs can be identified by a 4 line reservoir, and the front and rear fuel lines teed together between the tanks and the reservoir.

[85lebaront2]

This is all too common of a problem. We used to deal with it at the dealerships pretty frequently.

Your '86 should have a reservoir (9K044/9B263) with 6 ports, unless someone added a second tank and teed the lines together. The cause of your problem if all is plumbed correctly is the fuel reservoir.

Now, to answer Gary's question. On the newer trucks that have a "fuel delivery module" in each tank, the check valves are built into the modules. When this problem occurs, the tank receiving fuel at the wrong time has a failed valve, and you need to add an inline check valve (there was a recall on this) or replace the fuel delivery module. Trucks with FDMs can be identified by a 4 line reservoir, and the front and rear fuel lines teed together between the tanks and the reservoir.

I do have a question, where would the reservoir be on a 1990 F250 with a 7.5L engine. All I found were fuel lines from the tanks to the filter and then the engine. There are a pair of tees outboard of the forward tank that all the lines go through.

There was indeed a recall, TSB 01M05 and is on this site here: https://www.garysgaragemahal.com/fuel-cross-flow.html

 

[Howling.Wolf]

This is all too common of a problem. We used to deal with it at the dealerships pretty frequently.

Your '86 should have a reservoir (9K044/9B263) with 6 ports, unless someone added a second tank and teed the lines together. The cause of your problem if all is plumbed correctly is the fuel reservoir.

Now, to answer Gary's question. On the newer trucks that have a "fuel delivery module" in each tank, the check valves are built into the modules. When this problem occurs, the tank receiving fuel at the wrong time has a failed valve, and you need to add an inline check valve (there was a recall on this) or replace the fuel delivery module. Trucks with FDMs can be identified by a 4 line reservoir, and the front and rear fuel lines teed together between the tanks and the reservoir.

I guess you are right.

My reservoir has 4 ports in and 2 out.

I will 1st check if I conneced the rear tank the right way. 2nd take it (the reservoir) off and see if I can do anything about it.

I keep you updated.

Thanks so far

Heinz

[Gary Lewis]

This is all too common of a problem. We used to deal with it at the dealerships pretty frequently.

Your '86 should have a reservoir (9K044/9B263) with 6 ports, unless someone added a second tank and teed the lines together. The cause of your problem if all is plumbed correctly is the fuel reservoir.

Now, to answer Gary's question. On the newer trucks that have a "fuel delivery module" in each tank, the check valves are built into the modules. When this problem occurs, the tank receiving fuel at the wrong time has a failed valve, and you need to add an inline check valve (there was a recall on this) or replace the fuel delivery module. Trucks with FDMs can be identified by a 4 line reservoir, and the front and rear fuel lines teed together between the tanks and the reservoir.

So the FDM's actually started in '86? I wasn't aware of that and haven't found it in the MPC. Apparently the base part number changed from the sender/pump combo so I need to look elsewhere.

[85lebaront2]

So the FDM's actually started in '86? I wasn't aware of that and haven't found it in the MPC. Apparently the base part number changed from the sender/pump combo so I need to look elsewhere.

No, Gary, they didn't, there was some confusion in there.

On the reservoir/tank selector valve, the ports for each tank are paired, from the picture it would be top two to one tank, bottom two to the second tank. Front pair, large to Bosch pump on the frame, small is return from engine. This system was used on all EFI trucks (Broncos only have one tank) through 1989.

1990 on use the FDM and many trucks from that era will have the recall check valves installed.

[Gary Lewis]

No, Gary, they didn't, there was some confusion in there.

On the reservoir/tank selector valve, the ports for each tank are paired, from the picture it would be top two to one tank, bottom two to the second tank. Front pair, large to Bosch pump on the frame, small is return from engine. This system was used on all EFI trucks (Broncos only have one tank) through 1989.

1990 on use the FDM and many trucks from that era will have the recall check valves installed.

Thanks for the clarification, Bill. I didn’t think the FDM came out in 86, but wasn’t sure.

Ford sure tried a bunch of different systems in that era. Makes it very confusing.