Fuel Reservior, what can I do ?

[Howling.Wolf]

Hello Ladies and Gents,

got me a nice 1986 5.0 EFI 4x4 LWB with only 19387 miles on the clock.

Buuuut here we have a new problem.

The inline pump on the frame tries to transport fuel from the tanks to the engine.

But there is only air that flows out of the fuelpump unless the car stands downhill.

I disasambled the fuel filter reservoir which holds the tankswitch on top and changed the filter in the reservoir.

I have the feeling that something is wrong here.

Now I have 2 questions in my mind.

1st who tells the Tankswichreservoir which tank to be used ?

2nd do you guys have an idea how to replace this by a substitute one as I cannot find an original replacement ?

Thnx in advance and

Haveniceday.

Heinz

Sorry the pic is upsidedown

[85lebaront2]

There is an in-tank pump that may be bad, it is a low pressure one, if you have two tanks then there is a low pressure pump in each one. The tank selector switch supplies power to the selected tank pump and connects the sender in the selected tank to the gauge. I would try unplugging the frame pump, ground the tan/light green wire at the test connector and see if you can hear either of the in-tank pumps running and if so there should be a hiss of fuel flowing through the supply and return lines at the reservoir.

The reservoir contains two diaphragms one for each supply pump and they will move the supply and return shuttle valves to allow the proper flow to and from the tanks. One item, Ford changed the reservoir in 1987 doing away with the internal filter, but the later one should work (same system was used on EFI from 1985-1989) so maybe a 1987-89 might be available. To my knowledge the only difference is the filter in 1985/86 and none later.

[Howling.Wolf]

There is an in-tank pump that may be bad, it is a low pressure one, if you have two tanks then there is a low pressure pump in each one. The tank selector switch supplies power to the selected tank pump and connects the sender in the selected tank to the gauge. I would try unplugging the frame pump, ground the tan/light green wire at the test connector and see if you can hear either of the in-tank pumps running and if so there should be a hiss of fuel flowing through the supply and return lines at the reservoir.

The reservoir contains two diaphragms one for each supply pump and they will move the supply and return shuttle valves to allow the proper flow to and from the tanks. One item, Ford changed the reservoir in 1987 doing away with the internal filter, but the later one should work (same system was used on EFI from 1985-1989) so maybe a 1987-89 might be available. To my knowledge the only difference is the filter in 1985/86 and none later.

Thanx Bill,

I will try this if I find the test connector.

Speaking of the two pumps. Does this all also count if one them doesn‘t work?

Because the clock of the rear tank seams to be dead if I switch onto that one.

Have a great day.

Heinz

[myrl883]

Thanx Bill,

I will try this if I find the test connector.

Speaking of the two pumps. Does this all also count if one them doesn‘t work?

Because the clock of the rear tank seams to be dead if I switch onto that one.

Have a great day.

Heinz

The one that you have is the early design. The newer one, without filter, is still available. F1UZ-9B263-B

[Howling.Wolf]

There is an in-tank pump that may be bad, it is a low pressure one, if you have two tanks then there is a low pressure pump in each one. The tank selector switch supplies power to the selected tank pump and connects the sender in the selected tank to the gauge. I would try unplugging the frame pump, ground the tan/light green wire at the test connector and see if you can hear either of the in-tank pumps running and if so there should be a hiss of fuel flowing through the supply and return lines at the reservoir.

The reservoir contains two diaphragms one for each supply pump and they will move the supply and return shuttle valves to allow the proper flow to and from the tanks. One item, Ford changed the reservoir in 1987 doing away with the internal filter, but the later one should work (same system was used on EFI from 1985-1989) so maybe a 1987-89 might be available. To my knowledge the only difference is the filter in 1985/86 and none later.

Thanx Bill,

This helps a lot.

The Truck and I are getting to know each other more and more.

So if I got you right. Then I may expect some fuel spill coming out of one of theese pipe connectors once i turn the key and the green/tan of the testconnector is grounded an the switch is on front as the picture is from the front tank.

I surely can hear the frame pump as this is quite noisy. But unfortunately northing comes out of the tank.

Would mean I have an in-tank fuel problem.😩

I know check the rear tank as well.

Thanx

Heinz

[85lebaront2]

Thanx Bill,

This helps a lot.

The Truck and I are getting to know each other more and more.

So if I got you right. Then I may expect some fuel spill coming out of one of theese pipe connectors once i turn the key and the green/tan of the testconnector is grounded an the switch is on front as the picture is from the front tank.

I surely can hear the frame pump as this is quite noisy. But unfortunately northing comes out of the tank.

Would mean I have an in-tank fuel problem.😩

I know check the rear tank as well.

Thanx

Heinz

Good luck with it sir! BTW, if your frame pump is quite noisy it has probably been replaced with an aftermarket pump. The original was a Bosch, which from what I remember from my days in a Mercedes-Benz dealership, looked very similar to the one used on the D-Jetronic Mercedes V8s and the M110 DOHC in-line 6 once Daimler-Benz quit using that Solex Quadrajet. You can probably get one easier than we can here.

[Howling.Wolf]

Thanx Bill,

This helps a lot.

The Truck and I are getting to know each other more and more.

So if I got you right. Then I may expect some fuel spill coming out of one of theese pipe connectors once i turn the key and the green/tan of the testconnector is grounded an the switch is on front as the picture is from the front tank.

I surely can hear the frame pump as this is quite noisy. But unfortunately northing comes out of the tank.

Would mean I have an in-tank fuel problem.😩

I know check the rear tank as well.

Thanx

Heinz

Allright, I recon I need 2 new in-tank pumps and once I am on it, 2new tanks as well.

As the gas in them might be is as old as the truck.

Grrr.

I start with the sidetank.

Thanks for the help Bill.

Just one more question please what is the tan/lightgreen wire, once grounded, supposed to do?

Please have a nice sunday

Heinz

[Howling.Wolf]

Allright, I recon I need 2 new in-tank pumps and once I am on it, 2new tanks as well.

As the gas in them might be is as old as the truck.

Grrr.

I start with the sidetank.

Thanks for the help Bill.

Just one more question please what is the tan/lightgreen wire, once grounded, supposed to do?

Please have a nice sunday

Heinz

Will a Delphi sending unit and a spectra tank (19 gallons) be good ?

Or do you have any other suggestions ?

[85lebaront2]

Will a Delphi sending unit and a spectra tank (19 gallons) be good ?

Or do you have any other suggestions ?

I will answer both your questions here. The tan/light green wire is the control circuit for the fuel pump relay. It is grounded by the EEC to run the pumps. It is initially grounded when the ignition switch is turned to "run" which is why you hear the pump on the frame "pulse". after the initial pulse, the EEC needs to see a signal from the distributor telling it the engine is turning, there is also a signal from the starting circuit which may trigger the pump control circuitry in the EEC. Grounding the tan/light green wire with the key on closes the relay.

On your second question, as long as the tank is for a 1985/86 with EFI and the sender includes the pump, then yes, it is what you need. Physically any tank from 1985-1989 with the low pressure in-tank pump will fit in place and work, but, as Gary showed in his "Big Blue" thread, Ford changed the filler piping in 1987 to correct a fuel filling issue that was annoying at a minimum on the styleside trucks and a flat out pain on a dual rear wheel truck. If you can give me the PNs, I can check what you are looking at.

I just went to Rock Auto's site, the Spectra tank I come up with is PN F6B, Delphi pump (only) is FE0484, pump and hanger (includes sender) is HP10157. If you have the F6B tank and one of the Delphi numbers you should be good. Before I would condemn the in-tank pump, I would make sure I have power and a solid ground at the plug on top. Power will be the red wire and pump ground is the orange wire. The black wire is sender ground and the two of them are connected together in the harness near the frame mounted pump.

I hope you can follow all this, I don't have a good way to put this in German, although at one point I was pretty good at interpreting the instructions on my Marklin 1015 metal building set. I did have the English translation, but it was just text, none of the pictures, so it involved a lot of back and forth for a 12 year old.

[Gary Lewis]

Will a Delphi sending unit and a spectra tank (19 gallons) be good ?

Or do you have any other suggestions ?

I'm not Bill, but maybe I can help.

First, on the sending unit, tank, etc, I recently bought a new Spectra tank with the pump and sending unit included. It was for a '95 so is a different unit, but you might look for that combo for your truck as it was very cost effective and kept the shipping cost down.

But, to answer your question, a Delphi sending unit and Spectra tank will be fine.

As for what the tan/light green wire does, it is used to pull in the fuel pump cutoff relay. On Page 60 you'll see the blue triangle marked ZZ, and if you follow its wires back you'll find that it is powered by the EEC Power Relay in Run or Start.

That goes to Page 104 where the Fuel Pump Cutoff Relay is, and it supplies power to that. Then, on the other side of the relay is the tan/light green wire & another blue triangle marked YY, which goes off to Page 62. And on that page you'll see the ECA, which grounds the wire and, therefore, pulls the relay in. And that provides power to the pumps.