Dual tank issues...

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Jun 17, 2007 | 06:52 AM

CaptGuz

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From: Cary/Rocky Mount NC

Dual tank issues...

Ok so i thought both tanks worked but found out when i almost ran out of gas this morning they dont. Here's the sitch...

I have gas in front and rear tank. The gas gauge for the front works. I believe the guage for the rear works also cause when i add gas it goes up. When i flip the switch to use the rear or front tanks, the guage also changes. But i dont believe it changes which tank it pulls gas from, i think it stays pulling on the front.

How i figured this out was I had about half a tank in the rear, and a full front tank. I ran off the back for a week or so and it just never really moved. This morning i switch back just to make sure i have a whole tank and i'm sittin at 1/8th.

Any idears? I ran half a tank of SeaFoam in front and rear, and i know its gone through from the front but i'm sure the rear still has it in it. Didn't know if this was a common easy solution or what. I hope to have a new bed on the first, so i should be taking this bed off right after the first of the month (if anyone wants to help !!!!)

Jun 17, 2007 | 07:09 AM

ridgerider3

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Looks like, in my trusty Haynes book, on page 12-29, that both gauges will work when the "FUEL TANK SELECT SOL" fails.
It is the BRN/WHT wire out of the switch.Hook up a jumper to 12v positive, and jump the switch for this wire, and see if you can hear the solenoid cycling. If it does, bad switch. If not...........

Jun 17, 2007 | 09:18 AM

scottddove

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From: North Georgia

all you have to do to verify if the in tank pumps are working is get under the truck and listen when you switch the tanks back and forth. that should tell you if things are working properly. If the front tank pump continues to operate all the time that is a starting place. Good luck with the bed I did mine myself with a chain hoist with a four way connection to all four corners of the bed coming to a central point and it was easy as could be.

Jun 17, 2007 | 10:31 AM

CaptGuz

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From: Cary/Rocky Mount NC

so while the truck is running get under it, or just while its turned to ACC? How does the engine switch from front to rear tank? i'm thinking its something with that device that isn't actually switching over, or do you think its setup where if the rear pump goes out, the front will stay on all the time?

Jun 17, 2007 | 10:56 AM

geezer43

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The tank switch is inside the left frame rail just back of the drivers side door. Have someone switch tanks on the dash while all is on and you are under vehicle (properly chocked and tires blocked, etc so you don't get made into flat person)

Replacement for my switch was about $45 (15 years ago) and would be more today.

Geezer43
84 F150 sb I6 231K, one owner

Jun 17, 2007 | 11:05 AM

kc5gxl

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So Capt:

Are you running fuel injection on this 1981, or are you talking about another truck? If you are not running FI, then you probably have a mechanical pump on the engine, and only a valve that switches the tanks. You should be able to hear the solenoid click. If the gauges are changing, then it is probably not a bad ground, and most likely it is a bad solenoid/switch.

Good luck,

Dan Harriman 84 f150 351W lwb
Orange, Texas

Jun 17, 2007 | 11:43 AM

CaptGuz

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From: Cary/Rocky Mount NC

engine is the 351W with a 2BBL Carb. i will check to see if i can hear the solenoid switch when i'm under the truck... try that out tomorrow at work. I'll also try and get behind and try the jumper on the br/wh wire. sorry also, i hadn't seen that post when i made my last one. All good information - i just hate having half a tank of gas go bad when its something easy lol