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  • New (to me) TBI

    Just about done putting a Holley Projection system in my '72 SII /304. The system is off a wagoneer with an AMC engine (360?)

    We modified the 4 bbl base plate to fit the 2 bbl intake, installed everything, used the existing fuel line for feed & the cannister return for the return. Installed a petronix pointless ignition.

    Fired it up & it ran for a bit, then would die out. It would purr along and then start sputtering. After messing with it for quite a while, we unhooked the fuel return line & ran it to a gas can. After that it ran like champ.

    Found out the O2 sensor wasn't working & put in a new one. Works. Now we just have to run a better return.That's my first question. From what I've been reading, it sounds like there are outlets on the tank you guys use for the return.Would it be easier to drop the tank to get to it, or cut a hatch in the bed to get to it? I thought a removable hatch might be handy if I ever had sending unit problems or wanted to put a pump in the tank someday.

    I would appreciate any comments on any problems I might watch out for or advice.TIA

    Mike

  • #2
    Mike,
    I am running a Holley 4Di on my Scout with a 30 gallon aftermarket tank. I looked at several Scouts with FI and some routed the return line to the fuel filler overflow hose. They just spliced in a 'T' fitting and were done with it. On my tank there were 5 dummy fittings, tubes, welded to the upper edge of the tank. I just drilled one of them out and ran my return line to it.
    Mickey

    Comment


    • #3
      I did one of each. Use at least 5/16 line for the return. You can T into the tank vent like littledog suggested or if you have a later tank in your 72 it may have additional fittings on the tank.
      I used one from a 79 and it had about 4 extra fittings on it.

      Cutting a hole in the floor is an option but the extra fitting will not be right next to the fuel pick-up and sender.

      BTW
      I think my vent hose was 1/2in so you will need something like a brass 1/4 pipe female T. then use 1/2 barb fittings on each end and 5/16 for the return.

      Home depot or lowes normally has all you need.
      Remember if you block the return it makes the fuel pressure go up making it rich. If you restrict the feed the fuel press goes down which is lean.

      HTH
      Bill USN-1

      COMMITED TO TEACHING PEOPLE THE "PROPER" WAY TO EFI
      HAMILTON FUEL INJECTION
      May be the answer to all your fuel injection needs!
      Learn to do it right.

      Comment


      • #4
        Originally posted by Bill usn-1
        I did one of each. Use at least 5/16 line for the return. You can T into the tank vent like littledog suggested or if you have a later tank in your 72 it may have additional fittings on the tank.
        I used one from a 79 and it had about 4 extra fittings on it.

        Cutting a hole in the floor is an option but the extra fitting will not be right next to the fuel pick-up and sender.

        BTW
        I think my vent hose was 1/2in so you will need something like a brass 1/4 pipe female T. then use 1/2 barb fittings on each end and 5/16 for the return.

        Home depot or lowes normally has all you need.
        Remember if you block the return it makes the fuel pressure go up making it rich. If you restrict the feed the fuel press goes down which is lean.

        HTH
        I'm in the process of running my new lines.

        The reason you had problems using the canister line is it returns to the vapor collector. Most likely you filled the canister up and the return system became pressurized.

        I'm leaving the vapor line for it's intended purpose as a vapor feed to the canister. My old 5/16" feed line will be the return, I too am also tapping into the 1/2" vent line using 2 1/2 barbs, a 5/16 bard and a brass tee. I am running new steel 3/8 line for the fuel supply. I wish I'd read a little closer, I'd assumed that I needed 3/8 but 5/16 is preferred. We'll see if it causes any problems.

        Watch the vent line, I noticed that mine is brittle in a few spots and I had to repair a section with hose. The return line could see pressure up to 15lbs.

        Comment


        • #5
          Fuel Line Safety

          I just got my lines run new from tank to tbi.
          The return line that is required is 5/16.
          The fuel line that is required is 3/8.
          I would not use any of the original lines, just do to there age they should be replaced for safety let alone adding much more pressure than originally designed for.

          My fuel pick up sending unit was replaced with a unit from Super Scout Specialists do to leaking float, rotten sock and the gas gauge didn't work, it is the same as a factory unit. The problem is the fuel feed line is 5/16 so I ran 5/16 to the fuel filter than came out of the filter to the pump and to the tbi with 3/8.
          The return was 5/16 all the way to an extra fitting like Bill said the newer tanks have. We'll see how it works soon.

          I thought about the whole in the floor trick to get at the fuel sending unit but decided against it for safety reasons.
          In an accident it would be to easy for fuel to enter the passenger compartment.
          Just don't like the thought of that!
          And how often do you really go there?
          [CENTER]1994 Buick RoadMaSSter Estate Wagon LT1/4L60E. White and Woodgrain Sleeper...PCM 16188051 With SS/V4P/Custom Tune! WOT 12.9 AFR!

          1990 Chevy Suburban Silverado 5.7L 2wd ECM 1227747 HiWay Lean Cruise 18.5 MPG and 12.5 to 1 AFR at WOT!

          1972 IH 1210 Isky Cammed Balenced 345 4 speed PCM 16197427 Project!

          [SIZE=3][B][URL="http://www.gearhead-efi.com/"]GearHead-EFI.com[/URL] EFI Conversions and Chip Tuners![/B][/SIZE]
          [B]May be all you need to know about EFI![/B]

          and I still help local JustIH members (for fun) free! :cool: [/CENTER]

          Comment


          • #6
            Mike,
            The return line pressure should (must?) not exceed 5 psi per Holley. For fuel lines inlet or return, I think bigger is always better. Bigger line, less internal resistance, the easier it will be on the pump. On my Projection, with a 3/8" inlet line and a 5/16" return line, I typically see 2 - 3 psi on the return line. I am currently running the inlet at 16 psi. I have a gage on each line.
            Mickey

            Comment


            • #7
              You just answered my other post!
              [CENTER]1994 Buick RoadMaSSter Estate Wagon LT1/4L60E. White and Woodgrain Sleeper...PCM 16188051 With SS/V4P/Custom Tune! WOT 12.9 AFR!

              1990 Chevy Suburban Silverado 5.7L 2wd ECM 1227747 HiWay Lean Cruise 18.5 MPG and 12.5 to 1 AFR at WOT!

              1972 IH 1210 Isky Cammed Balenced 345 4 speed PCM 16197427 Project!

              [SIZE=3][B][URL="http://www.gearhead-efi.com/"]GearHead-EFI.com[/URL] EFI Conversions and Chip Tuners![/B][/SIZE]
              [B]May be all you need to know about EFI![/B]

              and I still help local JustIH members (for fun) free! :cool: [/CENTER]

              Comment


              • #8
                Thanks for all your info, guys. I went ahead & got the stuff to run a new return line back to the 1/2 " overflow on the filler tube. I was gone this weekend, so I don't know if my buddy that's installing this for me got to run the line yesterday, so I don't know how it works for me yet.

                WheeledScout, when I used the cannister line I bypassed the cannister, but the line was restricted anyway, back at the tank.

                As I'm using the original feed line the bring fuel to the TBI, Is your feeling that the line will be too small? If I get the proper pressure to The TBI it shouldn't matter, right?

                Thanks again for any imput, advise, concerns, ect.

                Mike

                Comment


                • #9
                  The original feed line is 5/16.
                  Both Holley and GM require a 3/8 fuel feed line. It may work but I think it would put undo pressure on the pump shortening it's lifespan.
                  Also the original line and fittings are designed to be a feed to the mechanical fuel pump which causes a vacuum (sucks) to get the fuel to it. "No Pressure" Now you are thinking of using it for a high pressure fuel feed after 25 or so years.
                  My advise would be to back up and think safety.
                  Just think how much fuel that pump could feed a fire?
                  Could cost you your truck? Your life?
                  My new fuel lines on the fuel feed side are 3/8 300 psi efi lines. Cost of new lines, clamps, fittings and proper hangers $35.
                  Hope that helps!
                  [CENTER]1994 Buick RoadMaSSter Estate Wagon LT1/4L60E. White and Woodgrain Sleeper...PCM 16188051 With SS/V4P/Custom Tune! WOT 12.9 AFR!

                  1990 Chevy Suburban Silverado 5.7L 2wd ECM 1227747 HiWay Lean Cruise 18.5 MPG and 12.5 to 1 AFR at WOT!

                  1972 IH 1210 Isky Cammed Balenced 345 4 speed PCM 16197427 Project!

                  [SIZE=3][B][URL="http://www.gearhead-efi.com/"]GearHead-EFI.com[/URL] EFI Conversions and Chip Tuners![/B][/SIZE]
                  [B]May be all you need to know about EFI![/B]

                  and I still help local JustIH members (for fun) free! :cool: [/CENTER]

                  Comment


                  • #10
                    Makes sense to me. I have no aversion at all to doing things right. I just for there to be a good reason, & yours is a good one. Right now it's hooked up to the original & we ran the return to the overflow. They took it for a test run last night(I'd had to leave for a moment & my mechanic buddy & his father in law couldn't wait), and the report was, this thing is scary fast now. Said it doesn't even feel like the same rig.

                    So I'll run new fuel line, & then we'll start fine tuning it & see how it reacts. I gotta tell ya, I'm pretty excited about so far.

                    Mike

                    Comment


                    • #11
                      All this talk about fuel line size has added another thing to my EFI conversion to do list. My poor little 800 has maybe 1/4 fuel line at best and no return. Now a question, since i have dual tanks does the electric fuel tank switching units like on a chevy have the proper plumbing for a return to both tanks as I want to install one in the future? Or am I going to put all the return fuel into one tank as that will be a pain. I see lots of tank mods coming up!!!!

                      Thanks all!!!
                      My "Disasterpiece"
                      1970 800A 4X4,HFI'd,304,B/W,27,44,3:73,28's.
                      The rest are in my 25 year plan!

                      My "Ruedh"
                      FREE 1972 1110 4x4,V8(?)727,205,44 drum/60/3.54's,small cheap tires.
                      LOOOOADS-O-RUST!! Donor body located. Not!! JY owner played the "crusher value" card. : angry:
                      NON-working rear window. Need info!!!

                      www.northtexasbinders.com

                      Comment


                      • #12
                        I wonder what the Chevy truck do with dual tanks?
                        Do they have a pump in each tank?
                        Never thought about it, maybe just run one till you find a donor with all the right stuff?
                        [CENTER]1994 Buick RoadMaSSter Estate Wagon LT1/4L60E. White and Woodgrain Sleeper...PCM 16188051 With SS/V4P/Custom Tune! WOT 12.9 AFR!

                        1990 Chevy Suburban Silverado 5.7L 2wd ECM 1227747 HiWay Lean Cruise 18.5 MPG and 12.5 to 1 AFR at WOT!

                        1972 IH 1210 Isky Cammed Balenced 345 4 speed PCM 16197427 Project!

                        [SIZE=3][B][URL="http://www.gearhead-efi.com/"]GearHead-EFI.com[/URL] EFI Conversions and Chip Tuners![/B][/SIZE]
                        [B]May be all you need to know about EFI![/B]

                        and I still help local JustIH members (for fun) free! :cool: [/CENTER]

                        Comment


                        • #13
                          Yes they (Chevs) run a pump in each tank, so I guess you answered my question with yours. Will have to go dig through the parts book at my local Carquest and see what is offered in way of tank selector valves. Just one more hurdle to jump I guess. May run on the one tank for now until I get it up and running then work on the dual tank setup. But only having ten gallons of gas is not real good. I might need my siphoning hose under the seat just in case! Like you say ALMOST fuel injected. Well mine should look like Aaaaaaaaaaaaaaaaaalmost fuel injected. Thanks!!!
                          My "Disasterpiece"
                          1970 800A 4X4,HFI'd,304,B/W,27,44,3:73,28's.
                          The rest are in my 25 year plan!

                          My "Ruedh"
                          FREE 1972 1110 4x4,V8(?)727,205,44 drum/60/3.54's,small cheap tires.
                          LOOOOADS-O-RUST!! Donor body located. Not!! JY owner played the "crusher value" card. : angry:
                          NON-working rear window. Need info!!!

                          www.northtexasbinders.com

                          Comment


                          • #14
                            Check JC whitney. It is $80 I think, and will switch the fuel feed and the return for both tanks. It might be iffy, but you may try 1 pump right before the motor. Keep it at the same hieght as the bottom of the tank for a little siphoning help.

                            or....
                            Do like i do on my test(street scout) and use the stock mech pump to feed the elec pump!!!! Then the pump won't have to work so hard.

                            Just a thought.
                            Bill USN-1

                            COMMITED TO TEACHING PEOPLE THE "PROPER" WAY TO EFI
                            HAMILTON FUEL INJECTION
                            May be the answer to all your fuel injection needs!
                            Learn to do it right.

                            Comment

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