Dual tank issue, fuel out the fuel cap.
 

Ok bought this 96 yesterday. Dual tanks, front tank gauge sender inop, rear tank gauge sender works. Filled both tanks. Selected front tank, to run it down to empty (getting idea of range on front tank for the future) then switch over the known full tank. I put on 90 miles yesterday }> the P.O. had obviously cleared the check engine light because as soon as I finished the second drive cycle on goes the CEL. EGR insufficent flow not related to this issue.
Ok get home today, I smell fuel. Fuel is dripping out the rear fuel cap. Crack cap to release pressure and it wants to run fuel out on the ground. Lots O' fuel.
Not cool. I owned a 93 dual tank extra cab before, never had this issue.
Does the fuel injection return to the rear tank only? It is 90 here today and it is sitting on black pavement. Heat expansion maybe. I only fill to the first click. Any ideas? I have it running outside on the rear to burn that fuel up. I cant recover it. I sure dont want toast my new truck.
Steve

Now while I was writing time was ticking. I am on my 3rd 10 min interval now with it running. It is still steady dripping with it running, and when removing the cap it pours out. Could it of tried to do a tank pressure test and got airlocked under the fuel in the neck? This is a very odd situation to me. Fire extinguisher is out and ready but dang this isnt cool at almost 4 a gal.

Ok it ran for over 30 mins on rear tank. Still under lots of pressure, fuel still dripping. Removed cap and got a fountain of fuel, looks like about 2-3 gallons at least. Its everywhere. Siphoned out the filler neck and down into the tank to remove 3 gallons of fuel into a red jug. Tank still reads full. I guess I will run on the rear tank untill half, then run front empty, then back to rear. OR MAYBE I have a magic gas tank that makes its own fuel.

Iwant one of those tanks! :-huh

LOL I dont think you do. LOL

I believe I have found my answer. Quoted from this site.

The filling tank always has the bad valve in its FDM.
The Fuel Pressure Regulator was bad for the 1993 year truck as they had a bad run on them and it let the fuel pressure go too high.
The check valve was going bad because the supply line pressure was way to high so this took out the valve in the non running tank.

From reading a lot of posts on this site it now seems shortly after a check valve goes bad the pump also stops working. This leads me to believe that something is coming apart in the FDM maybe from the pump and the debris is getting under the check valves seat. So now this tank starts to fill while on the other tank and its pump on the filling tank soon quits.


So my rear tank has a failed check valve and is about to fail. Replace rear pump and such and be cool. Seem like the answer to me.

This problem ( Tank cross flow ) caused by a bad check valve . Ford did have a recall that installed an external check valve. Mine and many others have this issue. Before I replaced my Fuel Delivery Module, I just watched tank fuel levels so one tank did not over flow. It's what I called The Fuel Fairy, meaning my once empty tank now had fuel in it . Or the fuel B!^ch that leaks fuel out of my other full tank.

Yes that's it. And I'm Old you type faster than me :-hair But complete failure of the pump does not happen all the time. Before I took off my bed to fix this and some other PM , Mine was still working for 12 months and still worked when I replaced it. But to be safe you have to watch your fuel levels .

Before I took off my bed to fix this and some other PM , Mine was still working for 12 months and still worked when I replaced it. But to be safe you have to watch your fuel levels .

[quote=92 Black Nite;12206375]Before I took off my bed to fix this and some other PM , Mine was still working for 12 months and still worked when I replaced it. But to be safe you have to watch your fuel levels .[/quote


I only have a rear tank gauge that works. So I guess never over half on the rear unless I am going to run it first.

Do I have a fuel selector valve problem, or a check valve problem? It looks like from the post I had found, my fuel pumps have built in check valves? Is that right? Neither one of the Airtex (my favorite brand of fuel pump) say anything about the check valve.

Check valve problem Yes , Your rear tank overflows use it first. Then when you use the front tank the fuel fairy will refill the rear .And from what your saying you will need a FDM and a sending unit . I used a FoMoCo pump. Here is the info about the recall look at the 2nd recall details.
1992 Ford F-150 Recalls | Find Used

The problem actually goes back further than that. The 90 parts truck I bought had the recall check valves installed on it. I kept them when I replaced the FPM in the front tank.

The FPMs do have the valves in them, there is also a shuttle valve that is supposed to close the return in the inactive tank.

Be aware that a lot of replacement FPMs have a glitch. I have one NAPA and one SPI in my truck. On the original Ford modules there are 4 pins, fuel pump power (red for front, brown with white stripe for rear), fuel pump ground (orange), fuel gauge (dark blue with yellow for front, yellow with light blue for rear) and gauge sender ground (black). The pin the black wire goes to is directly grounded to the metal body of the FPM, on both my aftermarket units, the pin is insulated from the body like the other three. What will happen is your fuel gauge will read over full since the other end of the sender isn't grounded. If this occurs, you will need to run a ground from the tank to the frame.

Do you have a part number for the FDM? I've been searching high and low for one.

Thank you both very much. I am not trying to be obtuse. I have worked as a service advisor for midas for several years, but now work in another field, so no more alldata. I want to make sure we are talking about the same thing.
By Fuel Pump Module (FPM) you both mean the pump assembly. Correct? I am not super concerned about the fuel sending unit failure in the front tank.

I am talking about the electric pump motor, with the plastic spring loaded houseing as the pump assembly.

My brother still works at midas so I guess I should just run by after work and see a nice exploded diagram and go from there. They also have NapaFix which is a rocking awesome chunk of info.

Basicly my understanding of what is going on is this.
Fuel pressure on the return line is overpowering the failing check valve in the rear pump assembly. It is allowing fuel to return to the path of least resistance which in my case is the rear tank. If I replace the pump assembly I will get a new check valve that will make the system return fuel to the tank that is selected. If I have it jacked up PLEASE tell me. :-X22

Fuel Delivery Module
http://i54.photobucket.com/albums/g9...-seriesFDM.jpg
courtesy of subford

There is an outside chance the Fuel Pressure Regulator (FPR) mounted on the fuel rail could be bad. One failure mode is no regulation at all...full fuel pressure is applied to the fuel injectors and return. This will also over-power the shuttle valve. Ford had a batch of bad FPR's in 1993-94. They had a recall because of it. Other symptoms would be poor fuel mileage, rich error codes and probably a strong fuel smell in the exhaust.

Rockin awesome man. Only code is EGR low flow. One rear fuel pump coming up next payday. LOL