On my 89 E150 5.0 w/2tanks when I switch from the front to the back, the gauge shows the level of the rear tank but it still pulls fuel from the front. What's up?

 

Most of the time the fuel pump in the rear tank is bad.

 

My van has a frame mount external fuel pump. It has a vacuum switch to change the tank in use in line before the fuel pump and filter. Thanks though. . Ineed to investagate the vacuum source and if the fuel is even reaching the said vacuum switch

 

You are very welcome.
By the way you do not have a vacuum switch.
It is called a "Dual Function Reservoir" - 9B263 (base part number) also called a "selector valve". The "Dual Function Reservoir" is not electrically or vacuum powered, it operates off the fuel pressure of the running in tank fuel pump.
It is also a mechanical switching valve between tanks. One side of the DFR has 2 lines, a fuel supply going to the high pressure pump and then on to the fuel pressure regulator and the injectors, and a fuel return line coming back from the fuel pressure regulator (that will return unused fuel back to the tank from which it came). The other side that has 4 lines has a low pressure fuel feed from the front tank and a fuel return to the front tank, a low pressure fuel feed from the rear tank, and a fuel return to the rear tank.

As I said before it sounds like your fuel pump in the rear tank is bad.


Here are some diagrams and photos to chew on.

Fuel System Diagrams for the 89 F series:

Electrical:
http://i54.photobucket.com/albums/g91/subford/Fuel/fuel-sel1987-89FSeries.gif

Mechanical
http://i54.photobucket.com/albums/g91/subford/Fuel/88Fuelsystem.gif

Selector Valve 1:
http://i54.photobucket.com/albums/g91/subford/Fuel/dfres.gif

Selector Valve 2:
http://i54.photobucket.com/albums/g91/subford/Fuel/FuelRes1.gif

Selector Valve 3:
http://i54.photobucket.com/albums/g91/subford/Fuel/FUELRES2.gif

Selector Valve 4:
http://i54.photobucket.com/albums/g91/subford/Fuel/Fuelselectorvalve.jpg

In Tank Fuel Pump:
http://i54.photobucket.com/albums/g91/subford/Fuel/1989FuelPump2.jpg

High Pressure Fuel Pump + Filter:
http://i54.photobucket.com/albums/g91/subford/Fuel/FuelPumpFilter88.jpg

Fuel Pressure Regulator:
http://i54.photobucket.com/albums/g91/subford/Fuel/fpr02.gif

Fuel Manifold:
http://i54.photobucket.com/albums/g91/subford/Fuel/Fuelmanifold.jpg

Fuel Pumps test ground at the Test Connector:
http://i54.photobucket.com/albums/g91/subford/Fuel/DataLinkConn.jpg

Inertia switch location 87-89:
http://i54.photobucket.com/albums/g91/subford/Fuel/1989InertiaSwLocation.gif

 

I have an 82 E100 4.9 with dual tanks. Pretty basic setup with little electronics compared to later models. The main/rear tank does not register on my gauge but the front one does so I use it alot more. The back one will provide gas, though, if I toggle it (just will not register on the guage....sensor bad).

Yet if the main rear tank is empty with the front tank switched over to start with in the morning or whenever I decide to drive ....forget about getting it started. It will just sit and crank as if Both tanks were empty until some gas is put into the rear main tank. Something to do with the electrical reverting back to the basic main fuel system ..meaning the Main rear tank (I was told)....to start up with. So I keep my main rear tank close to half or just under....so it will start. (pump the foot feed after the key is turned on but not engaged yet.)

I am wondering if this is completely true or am I missing something here. Is there a good schematic of the fuel pump setup for my year van (81-82) someone could post? All I have is a Chiltons and Haynes but neither show much compared to what you have posted, Subford

 

VikingBabe

What you have is a very simple fuel system.
All that you have in each tank is a sock filter with a sending unit screwed on the side. From there the fuel goes to a solenoid selector valve on the frame. From the valve it goes to the engine mounted fuel pump, filter and the Carb.
I have the same system on my 83 and you can run either tank dry while driving and the switch to the other tank and it will start right back up.

The switch on the dash is a DTDP switch and will turn power on or off to the selector valve and also switch the gauge wires from one tank to the other.

I will post you some diagrams in a while but I will have to do some scanning and uploading first.

 

VikingBabe

Here is an electrical diagram of your system and if you can not read it PM me your email address and I will email it to you.

http://i54.photobucket.com/albums/g9...el/fuelsol.jpg

 

No this is not true, you should be able to start right up on either tank with the other on empty.
The carb should not be dry overnight and should crank the engine right up.
The float valve in the carb should still be closed in the morning and fuel lines should remain full of fuel.
Even if it sets for a week and they are dry it should start up after cranking for a short while with the other tank empty. If it does not then the selector valve is bad.
Make sure you have no fuel leaks as it sounds like you may have one.

 

Bill K Thank you for getting me out of the dark. You gave me more "correct " info than my local Ford dealership. They were the one who told me no pump in the tank. Thanks again.,Bill. I'll post my results.

 

subford, thank you for the jpg and the added information. Have a safe New Year's Eve!