Another dual-tank problem
Thread Starter
|
5th Wheeling
Joined: Sep 2011
Posts: 43
Likes: 2
Another dual-tank problem
I've done a lot of reading, but need some help...
The truck ('96 F250, 460 Auto) will not start or run on front tank. When switched to front, the gauge pegs above Full. I can hear the pump when cycling the ignition key, but the sound is odd; it has a deeper tone than I'm accustomed to hearing. I've only added a little fuel to test as prior owner advised it did not work.
...so I drive on the rear tank. Gauge works and truck runs well...but, after the truck sits for about 8 hours, it takes an extra "half crank" to start. I'm confident it's losing fuel pressure as if I cycle the key, it starts right up.
I believe I have two problems. 1) the front pump & sending unit are smoked 2) the rear FDM is somehow failing. Thoughts please...thanks in advance!
The truck ('96 F250, 460 Auto) will not start or run on front tank. When switched to front, the gauge pegs above Full. I can hear the pump when cycling the ignition key, but the sound is odd; it has a deeper tone than I'm accustomed to hearing. I've only added a little fuel to test as prior owner advised it did not work.
...so I drive on the rear tank. Gauge works and truck runs well...but, after the truck sits for about 8 hours, it takes an extra "half crank" to start. I'm confident it's losing fuel pressure as if I cycle the key, it starts right up.
I believe I have two problems. 1) the front pump & sending unit are smoked 2) the rear FDM is somehow failing. Thoughts please...thanks in advance!
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
Replace the front FDM first and see what that does, stuck check valve often correspond with a dead pump.. possibly because they get varnished from lack of fuel flow, and if that happens your working tank could be losing some fuel pressure into the front tank which would explain the extra long cranks.
Logistics Pro
Joined: Mar 2011
Posts: 4,197
Likes: 558
From: Central Wisconsin
Here's my thought, my truck did a similar thing when I bought it, but from the rear tank. The PO insisted that the back tank pump did not work. with the truck off, switch it between back and front tank really fast. Sometimes the switch gets dirty from lack of use and that will clean it up a little so that it might work. Otherwise just replace the unit and see what you get. I dont know about the second part
Senior User
Joined: May 2004
Posts: 125
Likes: 0
After dealing with nearly this exact thing, here is my findings.
My truck didn't run on the front tank when I bought it either. After rebuilding the engine (for other reasons lol) we decided to get the front tank working.
After pulling the bed off for access, we tested the pump. It wasn't working, so we removed the assembly and found the pump and the tank completely gunked up. We spent hours cleaning the pump, the assembly and the tank. We also replaced the filter. Now it runs good on either tank.
Not sure if that helps you or not, but its a place to start.
My truck didn't run on the front tank when I bought it either. After rebuilding the engine (for other reasons lol) we decided to get the front tank working.
After pulling the bed off for access, we tested the pump. It wasn't working, so we removed the assembly and found the pump and the tank completely gunked up. We spent hours cleaning the pump, the assembly and the tank. We also replaced the filter. Now it runs good on either tank.
Not sure if that helps you or not, but its a place to start.
Fleet Owner
Joined: Aug 2005
Posts: 23,667
Likes: 301
From: Easton,Ks
I would go by what Paul (Conan) O'Brien (Conanski) said above.
A pegged gauge past full means an open circuit somewhere between the gauge and ground. The ground for the gauge runs from the gauge to the selector switch then on to the fuel gauge sending unit (float unit) and from there to a screw on the left radiator support on the drivers side. The fuel gauge sending unit changes the resistance to ground for the fuel level indication on the gauge. The fuel gauge sending unit has the resistance of 145 Ohms for full and 22.5 Ohms for an empty reading on the fuel gauge.
The reservoir/pump unit:
The fuel gauge sending unit:
The fuel hanger:
The FDM/Pump/Sending Unit as an assembly:
The selector switch:
/
Thread Starter
|
5th Wheeling
Joined: Sep 2011
Posts: 43
Likes: 2
Thanks all for the awesome input! I'm going to drop front tank, confirm ground and check assembly/tank cleanliness before swapping. If that seems to be the problem, I'll return the assy.
Edit: I've been looking at available Motorcraft assemblies and see three options: 19 gallon, 2 port; 19 gallon, 3 port; 17 gallon (pic looks like two port, but who knows if the pic is a fair representation).
Each of these three have unique part numbers. Being that I have never filled the front tank (and do not wish to do so prior to dropping), I do not know how large the tank is.
Subford, the pic you posted of the front hanger looks like a three port...
I'd like to buy in advance...any recommendations on how to select a pump before starting? Thanks again!
Edit: I've been looking at available Motorcraft assemblies and see three options: 19 gallon, 2 port; 19 gallon, 3 port; 17 gallon (pic looks like two port, but who knows if the pic is a fair representation).
Each of these three have unique part numbers. Being that I have never filled the front tank (and do not wish to do so prior to dropping), I do not know how large the tank is.
Subford, the pic you posted of the front hanger looks like a three port...
I'd like to buy in advance...any recommendations on how to select a pump before starting? Thanks again!
Trending Topics
New User
Joined: Feb 2012
Posts: 3
Likes: 0
Thanks for the Pic's ... Like they say worth a 1000 words. They answered a few of my questions about my trying to remove a damaged rear tank that I don't really need
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
New User
Joined: Feb 2012
Posts: 2
Likes: 0
hey guys im new here and im having the same problem. my rear tank works great on the gauge but when i switch it to the front tank it goes past full. i dropped the front tank and it was shot so i bought a new tank/sending unit/fuel pump. but when i hooked all that up except the tank it still goes past full. im going nuts trying to figure this out. what i have is an 88 f150 xlt lariat 5.0. also my sending unit looks completely different then the pics above.
Fleet Owner
Joined: Aug 2005
Posts: 23,667
Likes: 301
From: Easton,Ks
reaper88,
Passed full means you have an open circuit between the selector switch on the dash an through the tank fuel sender and back to ground.
The ones above are for a 1990-1996 stile and yours is like the one below:
/
Passed full means you have an open circuit between the selector switch on the dash an through the tank fuel sender and back to ground.
The ones above are for a 1990-1996 stile and yours is like the one below:
/
New User
Joined: Feb 2012
Posts: 2
Likes: 0
thank you subford
i cant tell you how thankful i am for the help lol ive been trying to figure this out for awhile. the wire between the switch and tank was/is bad. what i did is ran a separate wire from the switch to the tank and that fixed it. i think a mouse may have gotten to that wire. the truck i have i am re-building. it was an old farm truck that was sitting in a field for a few years so ive got alot to do
but once its done its gonna look nice as hell
but once its done its gonna look nice as hell
Cross-Country
Joined: Sep 2013
Posts: 64
Likes: 1
From: boonies, central TEXAS
There is also a Ford recall relating to separation of the tanks. You might take it to the dealership and claim the recall. While they are doing the fix, they might see "something else" wrong and let you know what you need to fix.
Elder User
Joined: Feb 2013
Posts: 856
Likes: 3
From: Livonia, MI
I'm having fuel issues as well. Tanks pumping fuel back and forth, fuel pressure differences, fuel gauge reading wrong, etc. Since it's difficult to pinpoint a diagnosis, I'm just going to replace the whole system: Both tanks, both fuel modules, seals, straps, etc. Yes, it's going to be expensive ($600 or more). But these components are almost 20 yrs old. Even if I was able to pinpoint the exact problem, I'm not going to remove the bed and fix one small part of the system, only to have another part break down in 6 months and have to repeat the process.
Thread
Thread Starter
Forum
Replies
Last Post
samr.820
1987 - 1996 F150 & Larger F-Series Trucks
21
Mar 11, 2019 09:31 PM
61BBF100
1987 - 1996 F150 & Larger F-Series Trucks
8
Oct 19, 2012 05:04 PM
