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Sanity Check: Fuel pump relay bypass?

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  • #1

    Sanity Check: Fuel pump relay bypass?

    Still working on bringing my 2nd Hawk back to life. Ignition switch contacts cleaned, Carbs rebuilt, valve clearances adjusted, Nuetral switch replaced, fluids, etc. It now starts & runs but only on the rear cylinder. No spark to front cylinder.

    I've been troubleshooting forwards and back and finally took a look at the fuel pump relay. Its been removed & bypassed by a PO. However, it looks to me like its done incorrectly. In my understanding, connect the black & black/blue wires together and that's it. Attached pic shows the blue/yellow wire from the coil also attached to the two aforementioned wires.

    I'm going to disconnect it and see if that fixes the issue, but wanted to do a quick sanity check with the pros here first.

    Thanks in advance!
    Attached Files
    Tags: None
    • #2
      No idea why somebody would do that. Just BLK to BLK/BLU. You can put it on a quality toggle too.
      "I couldn't afford NOT to buy it!"

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        • #3
          THANK YOU!! Will report back progress later. Hopefully that fixes it.

            Comment

            • #4
              Well, unfortunately I did not win the easy fix of the day award. Same results, no spark on front cylinder.

              At the CDI, pulse generator resistances all within spec

              Coil resistances, measured from the CDI 6-pin connector, within spec, measured at front coil, in spec

              With the switch on:
              The black/white & blue/yellow measure 10.7V to green (supposed to be battery voltage??)

              Here's what's really weird:

              The Yellow/blue to green measures 1.4V to green - this is for the rear coil, the one that is actually firing.

              I have a EE background and normally good with electrical issues, but this ignition stuff is black magic voodoo to me sometimes.

              Confirmed I have good continuity to chassis ground/battery via the reservoir ground strap, even took that connection all apart, wire brushed it, etc & confirmed w/ meter afterwards.

              The Yellow/blue wire also goes to the tach, so I disconnected that within the headlight and no difference.

              Any thoughts on what I'm missing?

              TIA

                Comment

                • #5
                  why look at a fuel problem when you have no spark ?

                  pump relay bypass needs a BLACK wire connected to the BLUE/BLACK in your photo, so look for it.
                  Last edited by squirrelman; 03-28-2023, 06:13 PM.
                  "It's only getting worse."


                  MY rides: '97 VFR750, '90 Red Hawk, '88 Blue/Black Hawk, '86 RWB VFR700 (3), '86 Yamaha Radian, '90 VTR250, '89 VTR250 (2), '73 CB125, '66 Yamaha YL-1

                  Sold: '86 FJ1200, '92 ZX-7, '90 Radian, '73 CB750, '89 all-white Hawk, '88 blue Hawk, '86 FZ600, '86 Yam Fazer 700 , '89 VTR250, '87 VFR700F2, '86 VFR700F.

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                    • #6
                      Originally Posted by squirrelman
                      pump relay bypass needs a BLUE wire connected to the BLUE/BLACK in your photo, so look for it.
                      SM, I just looked at my Hawk, it's BLK to BLK/BLU. BLU/YEL is the unused wire on a bypass.
                      "I couldn't afford NOT to buy it!"

                        Comment

                        • #7
                          Originally Posted by squirrelman
                          why look at a fuel problem when you have no spark ?

                          pump relay bypass needs a BLUE wire connected to the BLUE/BLACK in your photo, so look for it.
                          'cuz the blue/yellow wire from the CDI to coil also went to the relay, so wasn't really looking at a fuel problem, per se

                            Comment

                            • #8
                              sorry for my error
                              "It's only getting worse."


                              MY rides: '97 VFR750, '90 Red Hawk, '88 Blue/Black Hawk, '86 RWB VFR700 (3), '86 Yamaha Radian, '90 VTR250, '89 VTR250 (2), '73 CB125, '66 Yamaha YL-1

                              Sold: '86 FJ1200, '92 ZX-7, '90 Radian, '73 CB750, '89 all-white Hawk, '88 blue Hawk, '86 FZ600, '86 Yam Fazer 700 , '89 VTR250, '87 VFR700F2, '86 VFR700F.
                                👍 1

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                                • #9
                                  Well, after checking & double checking every connector, tracing voltages, etc, trying to figure out what's going on & why I'm not getting spark on front, I did some reading up on how CDI's work.

                                  Got just enough knowledge to be dangerous and concluded my CDI was bad. Ordered a used replacement off ebay, which magically showed up in 2 days!

                                  Bingo! Voltages at the CDI are all now @ battery level, as they should be, bike fires right up and runs like a champ! In retrospect, it seems like it should have been more obvious from the get go, but hey, that's called learning.

                                  Picture of inside of CDI attached for anyone else who is curious, like I was. I expected to see larger caps in there. Surprised how clean it is as it is not hermetically sealed.
                                  Attached Files
                                    👍 1

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                                    • #10
                                      Glad to hear! Just in time for Spring!
                                      "I couldn't afford NOT to buy it!"

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                                        • #11
                                          i usta think that if a cdi failed there would be no sparks anywhere, but i was so f'in wrong. on one of my eighty-six vfr's, the cdi failed to spark just one cylinder.

                                          Picture1-12-2020_808.jpg.42029ba045a49d740a064f10a23f6400.jpg
                                          "It's only getting worse."


                                          MY rides: '97 VFR750, '90 Red Hawk, '88 Blue/Black Hawk, '86 RWB VFR700 (3), '86 Yamaha Radian, '90 VTR250, '89 VTR250 (2), '73 CB125, '66 Yamaha YL-1

                                          Sold: '86 FJ1200, '92 ZX-7, '90 Radian, '73 CB750, '89 all-white Hawk, '88 blue Hawk, '86 FZ600, '86 Yam Fazer 700 , '89 VTR250, '87 VFR700F2, '86 VFR700F.

                                            Comment

                                            • #12
                                              Originally Posted by squirrelman
                                              i usta think that if a cdi failed there would be no sparks anywhere, but i was so f'in wrong. on one of my eighty-six vfr's, the cdi failed to spark just one cylinder.
                                              Now you tell me!

                                                Comment

                                                • #13
                                                  Well done that man for sorting what looks like a really tricky problem. A great feeling to finally get there
                                                    👍 1

                                                    Comment

                                                    • #14
                                                      Awesome you got it running right!

                                                      Just in time. M
                                                      Don't spend money and buy, spend time and learn.
                                                        👍 1

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