87 dual tank issue
#1
#2
More info: 1987 2.9L FI ext. cab dual fuel tanks
This has me totally baffled. Truck has been sitting for 5 years. I siphoned all old fuel out from both tanks, replaced battery, changed oil and put 6 gallons in the front tank. After repressurizing fuel system, sprayed some starting fluid and she started right up. I let her warm up for several minutes. Even though tabs are expired, I couldn't resist taking her out for a 2-3 mile drive around the neighborhood. Next day I repeated the same scenario but noticed fuel gauge needle dropped significantly. I thought that's weird but shrugged it off to an electrical quirk from it sitting idle for for 5 years. Next day gauge needle read E and she wouldn't start. No leaks under truck, so I figured someone siphoned it. Bought locking gas cap and 2 more gallons of fuel She started right up after pressurizing I let her idle for several minutes and again took her out for a drive.
Next day the tank is empty again, locking gas cap not tampered with so I sat down in a lawn chair and gazed at the truck and tried to figure out what was going on. For S&G's, I checked the rear tank. It was supposed to be empty but now there was 5+ gallons in there. WHAT THE HECK IS GOING ON HERE?? I've never heard of this situation before. Anyone have any guesses as to what is causing this?
Next day the tank is empty again, locking gas cap not tampered with so I sat down in a lawn chair and gazed at the truck and tried to figure out what was going on. For S&G's, I checked the rear tank. It was supposed to be empty but now there was 5+ gallons in there. WHAT THE HECK IS GOING ON HERE?? I've never heard of this situation before. Anyone have any guesses as to what is causing this?
#3
I’ve had some posts about my truck running good one day, stalling out, letting it sit, and then it will fire right up and run like nothing ever happened for a while.
I suspect it’s a fuel issue, so I was thinking it was a fuel pump problem. I know the previous owner, so I asked him if he ever had issues with fuel, and he said yes, he said it siphons from one take to the other, so you don’t ever want to run one tank empty. I did a search in the threads, and there was a thread from back in 2004, and it looked like it was related to tank switching valve, but it never really said if that fixed the problem or not. I thought maybe other people have run into this and have found that the valve is the problem. I was ready to pull the box off and switch out all the fuel pumps/sending units, so any info on this “tank siphoning” problem would be greatly appreciated.
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Old 03-07-2011, 09:59 AM
smashclash smashclash is offline
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it's most likely the fuel tank selector valve. look underneath on the drivers side frame rail a little north of the front tank and you'll see a round and square black thing about the size of a fist with 4 lines running toward the rear and 2 running to the front. That's the valve and there's a 99% chance that's your problem. it's pretty common. i had the same issue with mine, replaced it, and i've been fine since.
__________________
1986 F-150 XLT Lariat 4x4. Shortbed, 5.0, AOD, Limitied Slip rear, EFI, dual tanks, A/C (Still R-12)
I suspect it’s a fuel issue, so I was thinking it was a fuel pump problem. I know the previous owner, so I asked him if he ever had issues with fuel, and he said yes, he said it siphons from one take to the other, so you don’t ever want to run one tank empty. I did a search in the threads, and there was a thread from back in 2004, and it looked like it was related to tank switching valve, but it never really said if that fixed the problem or not. I thought maybe other people have run into this and have found that the valve is the problem. I was ready to pull the box off and switch out all the fuel pumps/sending units, so any info on this “tank siphoning” problem would be greatly appreciated.
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#2 (permalink) Add to smashclash's Reputation Report Post
Old 03-07-2011, 09:59 AM
smashclash smashclash is offline
Elder User
Garage is empty, add now
Join Date: Apr 2010
Location: South Jersey
Posts: 858
smashclash is starting off with a positive reputation.
it's most likely the fuel tank selector valve. look underneath on the drivers side frame rail a little north of the front tank and you'll see a round and square black thing about the size of a fist with 4 lines running toward the rear and 2 running to the front. That's the valve and there's a 99% chance that's your problem. it's pretty common. i had the same issue with mine, replaced it, and i've been fine since.
__________________
1986 F-150 XLT Lariat 4x4. Shortbed, 5.0, AOD, Limitied Slip rear, EFI, dual tanks, A/C (Still R-12)
#4
My first post is a cut and paste from a guy with an F-150 & having the same problem as you.
Looks like the tank selector valve is your problem.
BTW, I have the exact same truck as you an 87 2.9 dual tank with a 5 speed manual trans. The 2.9 & the manual trans is an XLNT combination and a kick to drive.
It would be a terrible waste of a good engine if it had a slugomatic behind it.
Looks like the tank selector valve is your problem.
BTW, I have the exact same truck as you an 87 2.9 dual tank with a 5 speed manual trans. The 2.9 & the manual trans is an XLNT combination and a kick to drive.
It would be a terrible waste of a good engine if it had a slugomatic behind it.
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