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Discussion Starter #1
My fuel pump prime cuts out intermittently. The bike wont start.
What it's doing: When I turn the key on, I hear and feel the relay clicking.
What I've done: 1st, swapped in my known good headlight relay. Same thing.
2nd, unplugged the relay from the socket and inspected the wiring - seems to look sound. (I've previously treated it with dielectric grease)
The wiring is burried in the rear harness, until it emerges as a 3P black connector. I inspected that connection as well. followed the wiring to the underside of the tank and it seems to check out visually as well.

I'm refering to the manual now to figure out what to do next.
It appears I'm not getting reliable power up to the solonoid to get it to throw power to prime the pump.
This only happens when trying to start. Of the threee times now it's happened, I cycle the key a couple times and then she primes. Doesn't cut out once the engine is running. Yet.

Anyone have any advice what to test next?
 

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My fuel pump prime cuts out intermittently. The bike wont start.
What it's doing: When I turn the key on, I hear and feel the relay clicking.
What I've done: 1st, swapped in my known good headlight relay. Same thing.
2nd, unplugged the relay from the socket and inspected the wiring - seems to look sound. (I've previously treated it with dielectric grease)
The wiring is burried in the rear harness, until it emerges as a 3P black connector. I inspected that connection as well. followed the wiring to the underside of the tank and it seems to check out visually as well.

I'm refering to the manual now to figure out what to do next.
It appears I'm not getting reliable power up to the solonoid to get it to throw power to prime the pump.
This only happens when trying to start. Of the threee times now it's happened, I cycle the key a couple times and then she primes. Doesn't cut out once the engine is running. Yet.

Anyone have any advice what to test next?
Are you reliably getting voltage to the 3p Connector attached to the fuel pump? should only get if for a few seconds after ignition switched on
 

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Discussion Starter #3
Are you reliably getting voltage to the 3p Connector attached to the fuel pump? should only get if for a few seconds after ignition switched on
I didn't check there. since the relay itself is buzzing, even when I swap in a known good one, I figure the problem is before that.

So I tested the brn/blk wire with the relay unplugged. According to the manual, that wire leads to pin 8 on the ECM. It provides that momentary power to prime the pump. Key on, no power at all. So that's a problem.
Next looked at the wiring diagram again, and saw the Bank Angle relay shares the blk/wht wire. Wondering if this is a common ground, it runs to pin 2 on the ECM.
Then I wondered if swapping the bank angle relay for a known good one would do the trick.
So I did, and PrestoWellahhhh! _PumpPrime_ every time I cycle the key. both relays (fuel cut-bank angle) click good and strong when I turn the key on.

So does this make sense, or is it coincidence and my problem may come back?
 

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The Bl/W wire is not a ground. It's a +

If you remove the 30A fuse on the Battery, with the solo red wire, you'll see that it will die.

As you describe it, sounds like a faulty relay. I don't think it'll happen any time soon.

Even if it does, you'll know where to look first.

The Black/White wire is the power source for ECU, fuel injectors, air duct solenoid valve and the spark converter unit box. And all that is ON and OFF through the Bank Angle Sensor relay.
So if you lean the bike, everything shuts down.
 

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Discussion Starter #5
Thanks Makis, I saw how that Bl/W wire went to all the components you listed.
Yes, I agree, I seem to have had a bad bank angle relay.
That wasn't exactly my first line of reasoning, but I know both of them are integral to the pump priming before startup, so it was kind of a lucky find.
 

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This site is awesome . Sorry to hear of your problem Jon, but you and Makis , Weeg ,sure have helped others here , who may encounter your problem with their own bike at some point . Good diagnostics . Glad you got her running :)
 

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This site is awesome . Sorry to hear of your problem Jon, but you and Makis , Weeg ,sure have helped others here , who may encounter your problem with their own bike at some point . Good diagnostics . Glad you got her running :)
My good friend, I can seriously tell you that there are a lot of time that I see things I can say a word, but working out my technical english and lay them down to a web page is so difficult that I prefer just not to participate......and I am sorry about that....seriously!

I have been a vehicle's electrician/ electronic (that's my degree's title actually) since 1997.
Never said I know everything, especially the newer bikes which I can't follow anymore since I've left the workshop business and working as a driver.

But I love my job so I try to follow up the technology as much as I can.

Of course I am wrong many times......it isn't that easy to diagnose a problem through a screen and a keyboard.

I am lucky that I have found this beautiful company of RC51 fans and i am really sorry that I can't offer more.....I really am :)
 
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