Dual tanks
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Mountain Pass
Joined: Feb 2018
Posts: 192
Likes: 1
From: DEWINTON Alberta
Dual tanks
Question people,
I know my duel func res is not operating correctly. This winter project.
As a result I use only the rear tank.
I haven’t put any fuel in f tank since spring and when I looked at DFR I siphoned front tank out.
last 2 days I come out to the shop and big puddle of fuel spilled out over front tank. Stinky !
I suspected the return line to top of tank and removed for inspection.
Front tank is full to the brim.
What gives ?
I know my duel func res is not operating correctly. This winter project.
As a result I use only the rear tank.
I haven’t put any fuel in f tank since spring and when I looked at DFR I siphoned front tank out.
last 2 days I come out to the shop and big puddle of fuel spilled out over front tank. Stinky !
I suspected the return line to top of tank and removed for inspection.
Front tank is full to the brim.
What gives ?
Laughing Gas
Joined: Feb 2017
Posts: 991
Likes: 6
From: San Antonio, Texas
I've heard that the switchover valve can fail, and if you're parked on a grade, fuel from the rear tank can make its way to the front tank.
I've had it happen once. Between issues with my fuel senders in both tanks, and the fact that I somehow ran out of fuel in the rear tank on the highway when it should have been over half, I'm contemplating moving to a single tank from a Super Duty.
I've had it happen once. Between issues with my fuel senders in both tanks, and the fact that I somehow ran out of fuel in the rear tank on the highway when it should have been over half, I'm contemplating moving to a single tank from a Super Duty.
Thread Starter
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Mountain Pass
Joined: Feb 2018
Posts: 192
Likes: 1
From: DEWINTON Alberta
Duel tanks
Thanks
im parked in flat grade.
am I correct in the the rear tank is being used then surplus fuel is being dumped into the non functioning front tank?
Would it be a problem to plug off the return line for now to prevent this overfilling?
im parked in flat grade.
am I correct in the the rear tank is being used then surplus fuel is being dumped into the non functioning front tank?
Would it be a problem to plug off the return line for now to prevent this overfilling?
Lead Driver
Joined: Feb 2013
Posts: 5,006
Likes: 72
From: Roseville, MN
You don't say what year your truck is, and I'm not sure what years the dual tank system changed. But a common problem with the system used in at least '95 - '97 OBS trucks (and I'm sure a few years earlier) results in fuel going into the wrong tank. There's a valve in the Fuel Delivery Module that shuts off to keep fuel from going back into that tank when you aren't using that tank. But if that valve leaks, then fuel will go into that tank no matter which tank is being used. There are a lot of posts on here about exactly what you are dealing with. A bad FDM keeps someone from using a tank, and that same bad FDM then lets fuel go back into that tank.
The solution is to replace the FDM.
Edit to add: Based on the next two posts the truck in question here is too old for the dual tank system I'm describing. An '88 will have a different set of problems and solutions than my '95 and '97 trucks.
The solution is to replace the FDM.
Edit to add: Based on the next two posts the truck in question here is too old for the dual tank system I'm describing. An '88 will have a different set of problems and solutions than my '95 and '97 trucks.
Thread Starter
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Mountain Pass
Joined: Feb 2018
Posts: 192
Likes: 1
From: DEWINTON Alberta
Thanks Bob, sorry 88 5.0 f150
Ill do a little more digging and hopefully there is a FDM.
Man these old trucks... If it's not one thing ...
I know that the tank was empty early summer, it must pump a bit in every time I shut it off.
Anyhow tanks was so full of fuel it was spilling out the gasket that holds return line in.
cheers will dig further.
Ill do a little more digging and hopefully there is a FDM.
Man these old trucks... If it's not one thing ...
I know that the tank was empty early summer, it must pump a bit in every time I shut it off.
Anyhow tanks was so full of fuel it was spilling out the gasket that holds return line in.
cheers will dig further.
Mountain Pass
Joined: Nov 2014
Posts: 236
Likes: 11
That year model used a "dual fuel tank reservoir" that used fuel pressure from the tank being used to cause a switch-over to both feed the high pressure pump on the frame rail and to switch the return fuel to the tank being used.
Which sometimes didn't work so the return fuel went to the wrong tank.
The reservoir is not electrically operated, it's pressure operated.
Couple years back, I got a reservoir off Ebay or Amazon for reasonable. Just easily snaps into place.
Which sometimes didn't work so the return fuel went to the wrong tank.
The reservoir is not electrically operated, it's pressure operated.
Couple years back, I got a reservoir off Ebay or Amazon for reasonable. Just easily snaps into place.
Thread Starter
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Mountain Pass
Joined: Feb 2018
Posts: 192
Likes: 1
From: DEWINTON Alberta
Thanks Josie,
i suspected the DFR as I know mine is stuck in an up position inside.
This confirms why front is filling even though not selected.
Took the whole summer for it fill but now I know.
I may take stab at rebuilding if that's an option or try to track down new.
Funny how there is always something going on every time I get in truck.
oh well ...I wanted a project.
i suspected the DFR as I know mine is stuck in an up position inside.
This confirms why front is filling even though not selected.
Took the whole summer for it fill but now I know.
I may take stab at rebuilding if that's an option or try to track down new.
Funny how there is always something going on every time I get in truck.
oh well ...I wanted a project.
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Tuned
Joined: Dec 2005
Posts: 398
Likes: 56
From: Saskatchewan
I have a similar issue with my truck. I had removed the DFR and cleaned and reassembled the insides, but it failed again and I the same problem with the return fuel gong to the front tank instead of back to the rear. Sub-ford posted a bunch of pictures of the internal valves and description of disassembly. One of my internal valves had a damaged o-ring and I couldn't find a similar o-ring to replace it, but I don't know if that was my problem. My temporary, hack job solution was to Tee the front tank return line into the rear tank return line. I also cut and plugged the front tank supply line later as I still seamed to still get syphoning back through the supply line. New DFR's are very hard to come by and very expensive if you can find a listing, but likely the listing is out-of-stock, or discontinued.
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Mountain Pass
Joined: Feb 2018
Posts: 192
Likes: 1
From: DEWINTON Alberta
I'm on hold for a bit until some time off at Xmas.
I have been looking the past cpl weeks for a DFR as well online.
Only 1 was on Amazon at about $200 ish plus $50 shipping and I think in US funds. I'm in Canada so after exchange it adds up.
My plan is to once again pull existing DFR and dissaemble.
I had described a few months back that a rectangular piece under diaphragm was lifted up not allowing the diaphragm to go in the down position.
Other than that I followed some instructions I found to clean up inside to allow things to move freely.
I have no idea if the pile of O rings internal are ok.
I may be barking up wrong tree.
Id like to buy new.
If get in a bind and continue to just use rear tank I will do as you and T into line and route return fuel to the rear.
I'll post what I find out once I get into it again.
I have been looking the past cpl weeks for a DFR as well online.
Only 1 was on Amazon at about $200 ish plus $50 shipping and I think in US funds. I'm in Canada so after exchange it adds up.
My plan is to once again pull existing DFR and dissaemble.
I had described a few months back that a rectangular piece under diaphragm was lifted up not allowing the diaphragm to go in the down position.
Other than that I followed some instructions I found to clean up inside to allow things to move freely.
I have no idea if the pile of O rings internal are ok.
I may be barking up wrong tree.
Id like to buy new.
If get in a bind and continue to just use rear tank I will do as you and T into line and route return fuel to the rear.
I'll post what I find out once I get into it again.
Tuned
Joined: Dec 2005
Posts: 398
Likes: 56
From: Saskatchewan
I checked that Amazon listing and they indicate a few in stock. The price looks pretty good, compared to what I found when I was looking. I seem to remember the Canadian listings I found were for around $450 CDN, which is probably more than my truck is worth. At current exchange rates I'd guess that $250 US piece would end up around $340 - 350 Canuk Bucks, depending on what fees your credit card charges for foreign currency purchases. I don't like ordering from the States as it can be very uncertain what duties and brokerage fees will be, so I always look for Canadian sources and try to shop local as much as possible. I'll pay a little more for the convenience of being able to pick it up and return it, if necessary, on the way to, or from work. If you buy from that Amazon listing, let me know how it goes, as it seems like the best option going for a new DFR.
Found a listing on Amazon.ca, ~ $380 and another place with a Dorman Part at ~$280
Dorman 911000
Found a listing on Amazon.ca, ~ $380 and another place with a Dorman Part at ~$280
Dorman 911000
Mountain Pass
Joined: Nov 2014
Posts: 236
Likes: 11
The DFR can also be had from a Pick&Pull, even on-line, but that's gonna be chancey as might have same problem. But then could be easier to rebuild ?
Considering how many of these things go wrong, I'd think someone would find a sure-fire rebuild kit for them.
Considering how many of these things go wrong, I'd think someone would find a sure-fire rebuild kit for them.
Cross-Country
Joined: Jan 2019
Posts: 97
Likes: 0
I had the issue of both of my tanks just plain going out, but both about 2 months apart from each other. I spent tons of money replacing both of my pumps, didn't fix it. i then tried the relay and emergency cut-off, neither fixed it also. It turned out to be my selector switch that had caused the tanks to die.
1990 Ford F-250 XLT Lariat, 302 and 5 speed manual
1990 Ford F-250 XLT Lariat, 302 and 5 speed manual
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