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Discussion Starter · #1 ·
I bought a 2006 Majesty with the idea it needed a fuel pump. The fuel system fuse would blow instantly. After doing a little tracing of wires thanks to a wiring diagram I found that the wire leaving the fuse block feeds the ecu, then off to the fuel pump relay and then to the pump and injector. The bad news is that the short disappears when the ecu is unplugged. Anyone ever experience this? I have a feeling that the scooter was jump started or the battery was hooked up with polarity backwards. Thoughts? Thanks
 

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The ecu sends power down line to the various components. With the ECU test all the others for continuity, if you haven't done so already. That may show where there is a problem. Check the wires themselves for integrity. Electrical gremlins can be tough to track, I hate it!I would make sure of the integrity of every thing else the ECU controls, an ECU is not a cheap item.
 

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Discussion Starter · #3 ·
The ecu sends power down line to the various components. With the ECU test all the others for continuity, if you haven't done so already. That may show where there is a problem. Check the wires themselves for integrity. Electrical gremlins can be tough to track, I hate it!I would make sure of the integrity of every thing else the ECU controls, an ECU is not a cheap item.
I removed the plug from the ecu and checked all the conductors going out to the bike with a Fluke meter. None had any shorts or grounds on them. I did get some conductors with measurable resistance but I assume they would be sensors. The short to ground is internal to the ecu unfortunately.
 

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Before replacing the ECU I'd pull the R/L wire Pin coming from the secondary side of the Fuel Injection Relay at the ECU connector and key on (connector still connected to ECU). If the fuse doesn't blow it's the ECU, if it does look elsewhere. Easy way to confirm your diagnosis.
 

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Discussion Starter · #5 ·
Before replacing the ECU I'd pull the R/L wire Pin coming from the secondary side of the Fuel Injection Relay at the ECU connector and key on (connector still connected to ECU). If the fuse doesn't blow it's the ECU, if it does look elsewhere. Easy way to confirm your diagnosis.
Thanks Itinifi for the response. With the fuel pump plugged in the R/L wire has a direct short to ground. Unplugged it is clear. I have a fuel pump on order to correct that. But also with the ecu disconnected, the pins that provide power to the unit are also a dead short. Im not sure which problem came first but a used ecu is in order also. And the fuel pump relay shows a diode in parallel across the coil. That diode fails the test with my multimeter. Electrical wiring Circuit component Gas Technology Audio equipment
 

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This may or may not apply. 2005 YP400. A little over 5K miles when purchased in 2018. 8K miles now. Fuel pump was losing power within a month of ownership. You never knew when it was going to completely stall. Verified with a test tapped into the fuel pump power wire AT the fuel pump. This was a randomly occurring intermittent open somewhere between the fuel pump relay connector and the fuel pump connector. These two connectors tested good continuity so the issue was in the wiring harness. I believe I did see where wiring harnesses were replaced for this issue. If you've seen this harness in the parts diagram you would see that it would be a nightmare to replace. Since this was the only fault (no other functions or devices affected) my solution was to route a wire bypassing the harness instead of digging through the taped up wiring harness/connectors to find a problem that may or may not be there during the search. I left the original fuel pump harness wire intact. Yes I replaced a perfectly good fuel pump. What else could it have possibly been. HA!

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