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@mordantly - We don't know whether that relay is still being triggered by the ECU. It was before the short because his fuel pump ran then. I'd manually trigger the relay as confirmation. (green wire) Troubleshooting a circuit on a different vehicle, had a case where the ECU was throwing ground to trigger the relay, but the connection between the ECU and that relay was weak. The dumbaxx mechanic didn't figure that out and loaded up another circuit instead. So a circuit that was engineered to run one fan, was instead running two... which naturally started to melt the wires... potentially expensive and hard to locate damage if I hadn't noticed the hijinks in its early stages. When wires inside of a harness are overloaded, they melt through their insulation and begin to short against other wires in that harness.

Walt, not sure what to make of: "In between the fuel injectors and the Starting Circuit Cut-Off relay: 2.3 (pictures of these are in previous post)" But in the context of "Should the red/blue wires in between the fuel injectors and the Starting Circuit Cut-Off relay have 14 volts running through them?", I'm thinking that 2.3 is a voltage drop reading.

But yes, under normal operation the wires see as much as 14.8v. Voltage isn't typically what damages wires though; it's amperage.

Are you saying there's a 2.3 volt loss between the fuel injectors and the starting circuit cut-off module? If so, and you're still on the same wire, without the fuel pump, injectors or anything else drawing from it, at 14v that is a 16.4% loss in power; which would be indicative of a serious problem with that harness. It's possible to isolate the fualt and repair a harness, but without 100% clear communications, don't know that you have that.
 

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Discussion Starter #22
Hi Intuit,

I'm saying that the voltage reading at these red/blue wires is 2.3 volts (please see picture). They seem to lead to the injectors, but the reading at the injectors is 14 volts. How can that be?

So there are 14 volts at the red/blue wires leaving the Starting Circuit Cut-Off relay, 2.3 volts at these red/blue wires in the picture, and 14 volts at the red/blue wires at the fuel injectors.

How do I locate the exact place that the voltage loss is occurring?

375745


Also, how do you manually trigger a relay?

And what does it mean when the ECU was throwing ground to trigger the relay?

Best,
Walt
 

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The ecu grounds the black with yellow stripe to activate the relay. With the harness unplugged put a plain bulb type test light ($3-5 US everywhere) clipped on pos terminal battery and probe the black yellow. The light will come on when ecu wants to prime pump then probably go off until cranking.
 

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Discussion Starter #24
Dear Mordantly,

I don't have a plain bulb type test light, but I did test the voltage at the wire coming from the ECU at each of the fuel injectors, and I get 14 volts. So the ECU is definitely throwing some voltage at the fuel injectors.

On Monday the new housing for the Starting Circuit Cut-Off relay is arriving. I'll let you know if that makes any difference. At least the fuel pump should go back to working.

Best,
Walt
 

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Discussion Starter #25
Hi Guys,

My replacement Starting Circuit Cut-Off relay arrived yesterday, so now my fuel pump works again, and I'm back to where I started, with fuel injectors that do not fire. But I did confirm in the meantime that both the wires going into the fuel injectors have battery voltage (13 volts), so it is possible for them to fire. They just are not getting the signal to fire.

So my current question is: What part of the fuel injection system is responsible for telling the fuel injectors to fire? Is it the ECU? Could the ECU have failed, while sitting in my garage for years, never being used?

Best,
Walt
 

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Speaking in general, past vehicle designs of the day, fired them according to a camshaft sensor. Plugs were fired according to crank sensor. Motorcycles have a lot more safety built in though. Kill, sidestand and clutch switches prevent crank but I'm not sure whether the other safeties like the lean-angle prevent a crank. Check all of your safety gear then look at the crank and cam signals. Check your manual to see what items are covered by Diagnostic Mode.

20 Crank Signal
21 Intake Air Temp
22 Coolant Temp
23 Throttle Position
24 Intake Air Pressure (MAP)
25 Atmospheric Pressure (Engine Side)
26 Cylinder ID (Cam Sensor)
27 Speed Signal
28 Lean Angle Sense

375768
 

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Discussion Starter #27
Hi Intuit,

I checked all the connectors that are visible to me. One of the wires seemed loose, and I completely disconnected it in the process of messing with it, but I think I managed to put it back the way it was.

One thing I did not mention is that this is a race bike built by a former pro racer (Jamie James), who apparently just disconnected a lot of the street-related connections (for lights, perhaps). So there are quite a few connectors not connected to anything. I wonder if they could be causing a problem.

I did confirm that the ECU is sending a signal to the fuel injectors when I turn on the ignition. Each of the injectors gets battery voltage (13 volts) for about 4 seconds when I turn on the ignition. Further evidence that the fuel relay is intact.

Finally, when I cranked the engine today it tried to turn over, which I was not hearing before, but then it died.

I'm running out of ideas. Maybe it's time to take it somewhere?

Best,
Walt
 

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Discussion Starter #28
Hi Intuit,

One last try: can you tell me approximately where those connectors (20-28) are? Are they by the fuel injectors? I don't see them.

Best,
Walt
 
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