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Thread: Explain how my dual fuel tanks work. Help???

  1. #1
    Senior Member
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    Explain how my dual fuel tanks work. Help???

    I have a 1992 Chev Kodack. 366 gas. No problem for years. It has dual fuel tanks and no manuel switch. My normal procudure is to fuel the left tank as I can see when pulling up to pump and dont have to walk around. I do fill the right side sometimes when a pump is conivenient on the right side. The other day I was going out on a job and I seen I had just slightly under 1/2 tank. I normally get gas then. I pulled into the pump and filled the right tank. Fuel gauge showed just over 1/2. A short time later the truck shut off and I had to have it towed. Evidence led me to believe that there was a problem in the distributor. (weak spark) After replacing the module, cap and rotor it seemed ok. Back to the job site run ok for about 30 miles. Shut down again. Another tow. Begin to check fuel system. Ran a stick down iln fuel tank. Left tank was compeletly empty. Found that engine pulls off that tank. Right tank was 3/4 full. Did some checking and found that the right tank pumps fuel to the left tank and fuel pump wire on right side was not making good contact. How does this switching system work. Lets say you have 3/4 in your left tank and fill your right, what prevents if from pumping it all into the left? I am hesitant about fillling the right tank now. I hooked a wire and pumped all the fuel out of the right tank, then took it to the gas station and filled the left tank till it was full. (fuel gauge showed just above half) Drove the truck for a couple of loads and took a stick and checked the left tank. Down some. No fuel at all in right tank. I am tempted to just only fill the left tank and use off that tank but it is nice having two tanks as I can fill up when gas price is down. So how does this switching system work? Is the fuel pump on my right tank running all the time now that no fuel is in it? Dont want to burn it up. Called Chev. garage and they were no help. Is there a relay some where that makes the right tank pump only on demand (when left tank gets empty)

  2. #2
    Senior Member
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    My experiance has been that trucks that do not have a switch draw from both tanks equally. So the left tank running empty allowed the system to suck air and lose prime. It sounds like the cross-over line has a check valve that's stopping fuel from going to the left tank.

  3. #3
    Senior Member rare ss's Avatar
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    we have a nissan patrol which runs dual tanks down here which does the same, they have a main tank and sub tank, the fuel is drawn from the main tank 100% of the time and the sub tank pumps fuel into the main tank when you press a switch on the dash, once the sub tank has filled the main tank the transfer pump suts off automaticly

    you should be able to hear the fuel pump transfer fuel if you turn the key on and get you ear close enough to the secondary tank, i wouldn't think it would run all the time unless there was a fault with the system?

  4. #4
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    Since asking about it in this thread. I have talked to a couple of other chev. truck owners who had the same trouble at one time or another. They said they never could get a answer from or even get the problem fixed by going to a chev. dealer. Seems lilke that there would be a section in a Chev. truck repair manuel that would cover this trouble shooting problem. So far I am just filling the left tank, as it draws off that tank. Still cant figure when and how the right fuel pump kicks in. There is no check valve of switch between the fuel out let in the right tank and where it goes into the left tank. From what I see it is just one line that runs from the right to the left. And just three wires going to right tank fuel pump. One ground, one fuel gauge and for the fuel pump. Cant figure what shuts it off, lets say your left tank is full and you fill the right tank, what keeps it from pumping into the left and overfilling it. Must be a preassure valve somewhere as there are, I think, four lines running to the right tank and three to the left tank. I think the three on the left tank, one to fuel filter, one from the right tank and one to vapor canaster. Its hard to trace all of them on the right tank. When I get time I will try and get under there and trace all them out. Sucks, if gas keeps going up, might never afford to ever fill the right tank again. When gas fluctated up and down .40 a gal, it was like money in the bank to fill the right tank when the price was down.
    Last edited by John White; 03-05-2012 at 09:27 AM. Reason: spelled word wrong

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