Hi all, short time lurker and first time poster. Thanks in advance for any responses
I recently acquired a 1990 K75 that I am trying to resolve an electrical issue with. The previous owner said the bike started to stall intermittently, but eventually would restart after a short time. Eventually the bike would crank but would not run. The PO replaced the fuel pump, but a new fuel pump didn't resolve his issue. This is the state I received the bike in.
I began troubleshooting by verifying the new fuel pump's operation. I supplied B+ and B- to the pump and it buzzed to life. The fuel pump fuse has voltage on both sides. I tested the tank fuel pump connecter and got the following results:
Key off test:
gr/wht wire- B+
yellow wire- B- (with some variance)
Brown- B-
White- B-
Key on test:
Gr/wht- B+
yellow- B- (with some variance)
Brown- B-
White- 1.0 volt
when cranking:
gr/wht: 0 volts (12 volts drops to 0)
Brown- B-
When back probing the green/white wire, while cranking, the pump buzzed to life. I was able to duplicate this by wiggling the probe. I then attempted to start the bike, and it purred to life. However, it would then slowly die, sort of like it was running out of fuel. I started it again and probed for voltage. As soon as the bike starts running the voltage drops to 0. As soon as it dies, the 12 volts return, and I can hear the pump buzzing. At this point I bypassed the connector and tested for 12 volts again while the bike ran. The voltage dropped to 0 when running and returned when it stalled.
So here are my questions:
Is the voltage drop on the green/white wire while running correct? or should I see 12 volts?
Am I correct in understanding the fuel pump should only receive voltage when the ECU sees a signal from the crank position sensor?
Am I going the wrong direction here?