dual tank issue
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From: utah
dual tank issue
ok so I just bought a 1993 f150 5.8L 4wd. and it only runs on the rear tank. I was told by the seller that the front tank drains into the rear tank. I flipped the switch and the truck quickly dies. the gauge moved to the half mark(not sure weather its actually half full or not though). anyways im assuming its one of the valves in one of the fuel modules. the question is which one would it be? I don't want to be buying the wrong one and be out $130 with the same problem. the seller also told me the truck has a new fuel pump, not sure which one though.
any help at all would be great, one small tank isn't going to work well for me.
also shouldn't the truck still run even if it is draining into the rear tank?
im not sure what all is true about what the seller told me, I just know that the front tank definitely doesn't work.
any help at all would be great, one small tank isn't going to work well for me.
also shouldn't the truck still run even if it is draining into the rear tank?
im not sure what all is true about what the seller told me, I just know that the front tank definitely doesn't work.
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the fuel tank selector valve on the frame rail under the driver door is bad. i got the same problem with my 88 f150, but it is rear tank to front tank. you can either take it apart and clean it up or buy a new one and replace. i am going to try to clean my up before i spend the big money for a new one. do a search here and you will find a post that will have a link on how to open it up and what to look for. ford had a recall on the 89 and 90 models for a fix. don't know about 93. my 88 did not have a recall. but it should have, it has the fuel tank selector valve as the 89.
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From: Sedalia MO
[quote=tonyjklh;14126285]thanks for the reply
I believe I read that after 1991 that they no longer had the selector valve? that they have the "FDM" in each tank instead.[/quote
Begining in 1990 gas engine trucks had FDM.
Frame mounted reservoir/selector valve ended with 1989 model year.
Been my experience tank that is being filled has defective FDM check valve. Also will be hard to start when cold on tank with bad check valve--looses line pressure while sitting causing extended crank time.
I believe I read that after 1991 that they no longer had the selector valve? that they have the "FDM" in each tank instead.[/quote
Begining in 1990 gas engine trucks had FDM.
Frame mounted reservoir/selector valve ended with 1989 model year.
Been my experience tank that is being filled has defective FDM check valve. Also will be hard to start when cold on tank with bad check valve--looses line pressure while sitting causing extended crank time.
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From: utah
I think i might just change both pumps now. what the seller told me doesn't make any sense now. he said the rear tank has a new pump installed. but if it had a new pump then the front tank wouldn't leak into the rear, right?
i also found know now that the front pump doesn't work at all, so again how could it be leaking into the rear. so now its either change just the front pump and see if it leaks to the rear, or change both. im also finding it hard to believe that the rear pump was changed. the bolts for the tank straps are very bad, i don't think they have ever been off. and although the bed bolts aren't as bad as the tank bolts it doesn't look like they've been off either
i also found know now that the front pump doesn't work at all, so again how could it be leaking into the rear. so now its either change just the front pump and see if it leaks to the rear, or change both. im also finding it hard to believe that the rear pump was changed. the bolts for the tank straps are very bad, i don't think they have ever been off. and although the bed bolts aren't as bad as the tank bolts it doesn't look like they've been off either
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From: Sedalia MO
I think i might just change both pumps now. what the seller told me doesn't make any sense now. he said the rear tank has a new pump installed. but if it had a new pump then the front tank wouldn't leak into the rear, right?
i also found know now that the front pump doesn't work at all, so again how could it be leaking into the rear. so now its either change just the front pump and see if it leaks to the rear, or change both. im also finding it hard to believe that the rear pump was changed. the bolts for the tank straps are very bad, i don't think they have ever been off. and although the bed bolts aren't as bad as the tank bolts it doesn't look like they've been off either
i also found know now that the front pump doesn't work at all, so again how could it be leaking into the rear. so now its either change just the front pump and see if it leaks to the rear, or change both. im also finding it hard to believe that the rear pump was changed. the bolts for the tank straps are very bad, i don't think they have ever been off. and although the bed bolts aren't as bad as the tank bolts it doesn't look like they've been off either
My tank strap bolt's, front and rear, were extremely rusty and scaly. Surprisingly threads looked ok (no pits or gauld) when I got them out. I slathered em good with anti seize at reassembly. Soaked all bolts with PB day before and they came apart just fine.
For me worst part was positioning front tank while starting strap bolts and taking care not to pinch wires and lines at final tightening of straps . I have no building (yet) to work in so everything is on the ground in my back yard.
Good luck with your pump replacement project. Let us know how it goes.
PS in 1st post you said " . . .front tank definitely doesn't work". When I did mine I was bringing front tank back into system-it was previously bypassed. Originally I assumed a pump would do the trick. I discovered tank selector switch was bad as well as tank/pump being junk. My point being, before condemning PO or pump in your front tank, may be prudent to verify voltage to pump.
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Freshman User
Joined: Mar 2012
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From: utah
My tank strap bolt's, front and rear, were extremely rusty and scaly. Surprisingly threads looked ok (no pits or gauld) when I got them out. I slathered em good with anti seize at reassembly. Soaked all bolts with PB day before and they came apart just fine.
For me worst part was positioning front tank while starting strap bolts and taking care not to pinch wires and lines at final tightening of straps . I have no building (yet) to work in so everything is on the ground in my back yard.
Good luck with your pump replacement project. Let us know how it goes.
PS in 1st post you said " . . .front tank definitely doesn't work". When I did mine I was bringing front tank back into system-it was previously bypassed. Originally I assumed a pump would do the trick. I discovered tank selector switch was bad as well as tank/pump being junk. My point being, before condemning PO or pump in your front tank, may be prudent to verify voltage to pump.
For me worst part was positioning front tank while starting strap bolts and taking care not to pinch wires and lines at final tightening of straps . I have no building (yet) to work in so everything is on the ground in my back yard.
Good luck with your pump replacement project. Let us know how it goes.
PS in 1st post you said " . . .front tank definitely doesn't work". When I did mine I was bringing front tank back into system-it was previously bypassed. Originally I assumed a pump would do the trick. I discovered tank selector switch was bad as well as tank/pump being junk. My point being, before condemning PO or pump in your front tank, may be prudent to verify voltage to pump.
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Freshman User
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From: Sedalia MO
Used jumper wire at fuel pump relay in order to provide continuous voltage (ECM shuts pump off after few seconds when key is moved to run position), 0volts at plug.
Next I visually checked wiring up to fire wall while under there-nothing obvious, seemed ok
Next test was tank selector switch, BINGO, dead on front tank side of switch. Luckily new switch provided proper voltage to pump plug-no wiring issues.
Good luck
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Freshman User
Joined: Mar 2012
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From: utah
so just an update to my tank issue. I dropped the front tank and it turns out there was a bad connection in the tank itself for the pump. the pump still worked but I changed it anyways so I wouldn't have to do that again. also found out that the truck has the external check valves from the recall that ford had on these trucks.
so far everything is working perfect! haven't driven long enough to know if the tanks are still cross filling but so far all is well.
so far everything is working perfect! haven't driven long enough to know if the tanks are still cross filling but so far all is well.
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Joined: Dec 2013
Posts: 35
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From: Sedalia MO
so just an update to my tank issue. I dropped the front tank and it turns out there was a bad connection in the tank itself for the pump. the pump still worked but I changed it anyways so I wouldn't have to do that again. also found out that the truck has the external check valves from the recall that ford had on these trucks.
so far everything is working perfect! haven't driven long enough to know if the tanks are still cross filling but so far all is well.
so far everything is working perfect! haven't driven long enough to know if the tanks are still cross filling but so far all is well.
Good call installing new pump, especially since you already had it. Dropping a tank isn't worst project on these trucks but I do not see a need for practice either haha. Recently noticed pump in rear tank of my 90 f250 sounds suspect when I turn key to run-doesn't have that high pitched "whirrrr" that it once did (my 95 f150 has same issue as well as hard cold start). Need to check fuel pressure, may be dropping two rear tanks soon for possible new FDM's
. I cant complain though, 90 rear pump was used freebie cpl yeas ago and 95 had new pump in front tank just before I bought it. "keep your powder dry"
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Freshman User
Joined: Mar 2012
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From: utah
Congrats! Good call installing new pump, especially since you already had it. Dropping a tank isn't worst project on these trucks but I do not see a need for practice either haha.
Recently noticed pump in rear tank of my 90 f250 sounds suspect when I turn key to run-doesn't have that high pitched "whirrrr" that it once did (my 95 f150 has same issue as well as hard cold start). Need to check fuel pressure, may be dropping two rear tanks soon for possible new FDM's. I cant complain though, 90 rear pump was used freebie cpl yeas ago and 95 had new pump in front tank just before I bought it.
"keep your powder dry"
Good call installing new pump, especially since you already had it. Dropping a tank isn't worst project on these trucks but I do not see a need for practice either haha. Recently noticed pump in rear tank of my 90 f250 sounds suspect when I turn key to run-doesn't have that high pitched "whirrrr" that it once did (my 95 f150 has same issue as well as hard cold start). Need to check fuel pressure, may be dropping two rear tanks soon for possible new FDM's
. I cant complain though, 90 rear pump was used freebie cpl yeas ago and 95 had new pump in front tank just before I bought it. "keep your powder dry"
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