Fuel pump relay / killswitch issues - Wrist Twisters
 
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post #1 of 10 Old 10-06-2018, 06:47 PM Thread Starter
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Fuel pump relay / killswitch issues

Hey all. Dealing with a very used 2002 919, had an accident that banged up, among other things, the throttle cables. I've done a bunch of work on the bike and I think things are back together properly, but it won't start. It cranks, battery measures fine sitting and under load, but the fuel pump doesn't turn on when I turn the key. I checked the fuel pump relay, and with power on, I can get the fuel pump to spin, or at least make noise, by grounding one of the wires. Hopefully this means it's not seized? For the 4 wires, my tester lights up for both black and white wires, spins the pump for one of the pink wires, and does nothing for the last wire.

One of the issues is that the relays don't have any exposed tabs to test, and weren't in the right places to begin with, but the bike did run fine before the accident. The killswitch/starting assembly is new from Partzilla, and with the key on, killswitch off, it'll crank but not catch. With the key on and killswitch off, doesn't crank. The lights and signals and the rest come on fine with the key on. When cranking, the FI and oil light flash, and the odometer blinks on and off.

I saw the large write-up on diagnosing FI issues, and am trying to work through it. Unfortunately, when the bike was stolen in the past, they rattle-canned the fuck out of it, even inside, so determining which wire used to be which color is a lot slower. Going to try some conductive grease on the two small contacts on the killswitch assembly, but would love any other advice y'all have.

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post #2 of 10 Old 10-07-2018, 01:11 PM
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A fuel pump troubleshooting guide.
Fuel pump problems https://www.wristtwisters.com/forums...ad.php?t=14216
Also something didn't come across right in your post. I think you meant key on, killswitch ON it will crank but not catch?
Try flicking your killswitch a few times.
I'm guessing it's your killswitch, or your relay or a bad connector somewhere.

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post #3 of 10 Old 10-08-2018, 05:31 PM Thread Starter
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Quote:
Originally Posted by Islandboy View Post
A fuel pump troubleshooting guide.
Fuel pump problems https://www.wristtwisters.com/forums...ad.php?t=14216
Also something didn't come across right in your post. I think you meant key on, killswitch ON it will crank but not catch?
Try flicking your killswitch a few times.
I'm guessing it's your killswitch, or your relay or a bad connector somewhere.
Nope, with the killswitch on, doesn't crank at all. Cranks but doesn't catch with the killswitch off. I'll work through the checklist here and see what I can find.

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post #4 of 10 Old 10-08-2018, 05:40 PM Thread Starter
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The diagnostic process suggests a killswitch problem, will start poking around in there.

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post #5 of 10 Old 10-08-2018, 05:57 PM
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Yeah somethings not right.
This is my bike. Key on, killswitch off. No fuel pump and won't crank. When the killswitch is turned on only then does the fuel pump cycle and will bike turn over.
The fact that your bike will crank with the killswitch off tells me something ain't right. Perhaps something is wired up arse about? What is your headlight doing while this is going on?

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post #6 of 10 Old 10-08-2018, 06:36 PM Thread Starter
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Oh, I think I may be using the term differently. When my killswitch is switched to Run, the bike will crank but not catch. When the killswitch is turned to Don't Run, which I think is what you meant by 'on,' no crank. Sorry for the confusion.

Checked the killswitch, in both states it puts out about battery voltage to the black and white wire running into the connector in the headlight. Nothing to the black wire in either state. Bad switch? I'm going to be a bit miffed if so, since it's brand new. Is there a way to jump around the switch to verify?

Edit to add: When the switch is turned to Run, there's more or less 12 v going to the white and black wire, and the white and green wire. When it's on Not Run, only the white and black wire. Headlight and dash lights stay on regardless.

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post #7 of 10 Old 10-08-2018, 07:50 PM Thread Starter
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Ah hell, just tried the voltage on the pink wire into the ECU, nothing. Bike thinks it's been hotwired, apparently. Any way around this?

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post #8 of 10 Old 10-09-2018, 04:15 AM
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I think this part of Robs checklist fits what you have found. I believe you replace the zener diode in the ignition switch. There is a post about here of someone having a similar problem and fixing it by replacing the diode.

1-- Turn the key on and check for voltage at the Pink wire in the 22 pin gray connector at the ECU. This is a signal from a zener diode in the ignition switch that acts as an ECU reset. It is there to prevent the ECU from initializing if the bike is hot wired.
**** +11.5 Volts (V) -- Normal. Proceed to #2
**** 0V -- Either a broken wire or a defective diode, Find out which and repair / replace the electrical part of the switch.

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post #9 of 10 Old 10-09-2018, 11:25 AM Thread Starter
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Thanks very much for your help, man. I pulled the ignition and it doesn't have the diode at all, though it does have a spot for it. I replaced it with the older ignition I had laying around, and it fired right up. Figures it would be the smallest piece on the bike that would croak. Real glad to hear her running again!

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post #10 of 10 Old 10-09-2018, 12:35 PM
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Well I'll be buggered, the diode was missing. That would explain why you had no power at the pink wire. Surely someone had removed that diode. Would have been a good moment when you pulled the ignition and realized the diode was gone.
Glad you got it figured out and bike is running again. Rob is a legend.

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