I have a 76fj40 with a "Con ferr" or "MAF" type aux gas tank installed by the previous owner. I have still not figured this thing out yet. The rear aux tank actually works ok, ( I get fuel to the engine anyway)... The problem is ...I can't figure out the correct operation. I run on the front tank because I have the fuel gauge to view. When I run out of fuel on the front tank I switch the dash mounted switch to the operate the rear 22 gallon tank. The stock fuel gauge still shows empty front tank, which is correct . There is no gauge on the rear tank, but I know there is 22gallons in the rear. After switching the solenoid to the rear tank, (after 30 minutes) the front gauge now shows 1/4 to 1/2 tank of fuel. Is the rear tank siphoning the fuel into the front tank? Is that the standard procedure/design? Do I just keep filling the front tank from the rear tank? I thought I would just be running off the back tank because there is a fuel diverter solenoid switch . The rear tank has a fuel line coming from the tank to the solenoid switching valve. The front tank is routed to that valve also. from the switching valve there is a short fuel line and then an electric fuel pump, then on up the the sbc v8. ( there is no mechanical pump on the v8). If anyone has suggestions or instructions from their install , I would appreciate it.

bennett

bennett,

It sounds like it is installed to run off either the front or the back. I have a confer 22 gallon tank in mine and I have run it both ways. Where I ran directly off the back I had a set up similar to what your describing. Now I use the back tank as a giant 22 gallon jerry can and I only pump fuel to the engine from the front tank.
It does seem strange that your gauge moves when you swap over to the back tank. what I would do is empty the front tank, premove and plug the line to the front tank from the switching solenoid. Then have a freind turn on the pump to see if there is fuel coming out the solenoid taht is being routed to the front tank instead of the engine, like it sounds.
I guess it is possable that the switching solenoid doesn't switch all the way over from tank to tank, but I can't imagine how fuel is pushed from one tank to the other since I would expect them both to be under a vacum to very slight pressure.

Be VERY careful of heat sources if you do try this...there is the obligatory safety first message.

Don't know how old your set-up is. Mine was purchased four years ago from MAF. The old Con-fer tanks included a sending unit and there used to be two configurations for combining the stock and 22 gallon tanks. One option used an electric pump to re-fill the stock from the auxiliary tank. The advantage of this set-up is that you only use one sending unit and that is compatible with your fuel guage.

The second set-up (the one I chose) had no pump. Instead, there was a solenoid which switched fuel supply to the engine between the main and auxiliary tanks. Some solenoids also had enough relays to allow switching the outputs of the two sending units to the dash fuel level guage. The sending unit that Con-fer used to send with their tanks was not compatible with post-'69 (approximately) guage and, therefore, the guage reads about 5/8 full when the auxiliary tank is topped up. But, at least there is a rough indication of fuel level. I use the auxiliary as my primary tank and the stock tank with it's accurate fuel information as my "back-up".

You can easily determine which configuration the PO installed, then, MAF and/or Downey should have the information you need.

Where does the fuel return line go? Your fuel pump give more fuel to the carb/F.I. than it needs, and there's a fuel return line that goes back to the tank, and yours must go to the front tank. No matter which tanks the fuels being pumped from. You could get another solenoid attached to the same switch on your dash and put it on the fuel return line, so it returns back to the proper tank