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  • Fuel pump PSI

    my 99 TLR is riding a bit funny since i bought it in june. around 4k rpms and below it has the worst throttle response. sometimes its ok sometimes it is jumpy. so i checked the fuel pump pressure and it is only putting out 32 or so psi. so i pinched the return line to see if it could reach 41 psi, and it didn't move. looking back i think that the person told me to pinch the in line to the tank....not sure.. what next?

  • #2
    Re: Fuel pump PSI

    Originally posted by motofreak87 View Post
    my 99 TLR is riding a bit funny since i bought it in june. around 4k rpms and below it has the worst throttle response. sometimes its ok sometimes it is jumpy. so i checked the fuel pump pressure and it is only putting out 32 or so psi. so i pinched the return line to see if it could reach 41 psi, and it didn't move. looking back i think that the person told me to pinch the in line to the tank....not sure.. what next?
    If i remember correctly, the secondary fuel injectors kick in at about 4k rpm. Might have a look at them.

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    • #3
      Re: Fuel pump PSI

      Other things could be causing your "throttle response" issues, but concerning your fuel pressue, you should be able to reach the 41psi by pinching the return line. If it won't go up to 41psi then you either have a weak pump, or a clogged filter, or something really smothering the pickup screen.

      Once you get the fuel pressure up to where it should be, you can chase the throttle response problem, if it still exists.
      Last edited by Six5; 10-25-2010, 01:15 PM.
      January 2012 - BBOTM & TLOTM

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      • #4
        Re: Fuel pump PSI

        Problems with the filter or pickup screen affect volume, but shouldn't really affect the pressure with the line pinched unless it's completely clogged.
        It's about control skill; this is a motorized dance for joy and not Russian roulette.

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        • #5
          Re: Fuel pump PSI

          The fuel rail regulator keeps the rail pressure 41psi above TB pressure not atmospheric pressure. (Although pinchin the return line should cause te pressure to rise).

          Check that fuel pump pressure during prime when the throttle body pressure (vacuum) = atmospheric. Or bypass everything and run the pump manually and check the pressure.

          If you check the ouput pressure of the pump when it's not connected to the fuel rail it should be between 69-99psi IIRC

          (You might have a split line in the tank too).
          "I spent most of my money on Scotch, women and cigarettes. The rest I just wasted"

          Comment


          • #6
            Re: Fuel pump PSI

            what do you mean the pump pressure during prime?? are you talking about when you turn the bike on and the pump comes on for a few seconds? when i turn it on it goes up to 20psi and that's it. and the fuel regulator keeps the rail pressure 41psi above TB pressure and not atmospheric pressure? im not sure what you mean by that.

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            • #7
              Re: Fuel pump PSI

              Originally posted by motofreak87 View Post
              what do you mean the pump pressure during prime?? are you talking about when you turn the bike on and the pump comes on for a few seconds? when i turn it on it goes up to 20psi and that's it. and the fuel regulator keeps the rail pressure 41psi above TB pressure and not atmospheric pressure? im not sure what you mean by that.
              throttlebody pressure is relative to throttle position. At closed throttle it is under vacuum so the fuel pressure will be lower. At open throttle the vacuum disapears so it goes to a higher fuel pressure.

              Also it could be a clogged filter, but the filter would be pretty clogged. But I would start there. Change the filter, and clean the pickup screen. Then check. Make sure you use a new gasket and not silicon.
              Mike Rock
              NESBA #506 '98 TLR
              American cycle performance MRP motorsports

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              • #8
                Re: Fuel pump PSI

                i already took the fuel pump out and checked the screen, isn't that the same as the filter? or are you talking about the in line filter. i thought that was just an aftermarket thing that the prior owner had put on there. the screen is a little dirty so i sprayed it out with choke carb cleaner. and i did the same with the in line filter a while ago when i thought that was the problem. i unbderstand what you mean with the pressure. when i hooked up the gauge to the line it read the same psi from closed throttle to full open.

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                • #9
                  Re: Fuel pump PSI

                  Originally posted by motofreak87 View Post
                  i already took the fuel pump out and checked the screen, isn't that the same as the filter? or are you talking about the in line filter. i thought that was just an aftermarket thing that the prior owner had put on there. the screen is a little dirty so i sprayed it out with choke carb cleaner. and i did the same with the in line filter a while ago when i thought that was the problem. i unbderstand what you mean with the pressure. when i hooked up the gauge to the line it read the same psi from closed throttle to full open.
                  You cannot clean that filter. No amount of spraying will dislodge all of the gunk inside. But it sounds a lot like you have a weak fuel pump or leaking injectors. Do what was posted above and put the gauge directly on the fuel pump by taking it out of the fuel system. If you get less then ~50 psi I would put a pump in it. There have been people that have used a caravan pump and had good results.
                  Mike Rock
                  NESBA #506 '98 TLR
                  American cycle performance MRP motorsports

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                  • #10
                    Re: Fuel pump PSI

                    i found the post to send off the pump and get one back for $100. so im thinking i might do that depending on how the next test goes. so is the "filter" the in line filter or did i miss something inside the tank?

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                    • #11
                      Re: Fuel pump PSI

                      It is kinda inline factory but it is inside of the fuel pump assembly. Some people remove it and put a filter inline between the fuel tank and the fuel rail.
                      Mike Rock
                      NESBA #506 '98 TLR
                      American cycle performance MRP motorsports

                      Comment


                      • #12
                        Re: Fuel pump PSI

                        is there anyway you or anyone can post a pic of this in tank filter? i think that mine may have been removed. that's just for curiosity sake. i think that i may just send mine off and see if that fixes everything. the other problem is that it doesn't start.. i can get it to start but i have to use starter fluid. could that be the same problem causing that? once i start it with starter fluid it will start up on its own for a while after it is warmed up. could something be wrong with the regulator? how can i check it if there might be?

                        Comment


                        • #13
                          Re: Fuel pump PSI

                          Originally posted by motofreak87 View Post
                          is there anyway you or anyone can post a pic of this in tank filter? i think that mine may have been removed. that's just for curiosity sake. i think that i may just send mine off and see if that fixes everything. the other problem is that it doesn't start.. i can get it to start but i have to use starter fluid. could that be the same problem causing that? once i start it with starter fluid it will start up on its own for a while after it is warmed up. could something be wrong with the regulator? how can i check it if there might be?
                          I will see if i can get a pic. But first thing to check Is the pump itself. Check to see if you get the pressure Steve posted. If that is good, then you check the regulator.
                          Mike Rock
                          NESBA #506 '98 TLR
                          American cycle performance MRP motorsports

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                          • #14
                            Re: Fuel pump PSI

                            No luck with a search for a pic. Maybe Steve or les will have one to post. I didnt take any pics when i had mine apart. And there might be pictures along with a troubleshooting guide in the manual.
                            Mike Rock
                            NESBA #506 '98 TLR
                            American cycle performance MRP motorsports

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                            • #15
                              Re: Fuel pump PSI

                              ill check that and get back with results

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