If anybody could help me understand this behavior, I'd be grateful:

2003 R1 5PW, Fuel-injected, has an alarm/immobilizer fitted, doesn't report any fault codes:

  1. Motorcycle would occasionally (three instances in the space of two weeks) be difficult to start. It would never splutter, the motor would turn but it felt like there was just no spark. It would eventually start and run without issue.
  2. Motorcycle fails to start and will not restart
  3. I notice fuel pump isn't priming when I turn the key on
  4. I replace EFI-system relay
  5. Fuel pump now primes and bike starts
  6. Ride bike 10 miles and it starts to jerk like the kill-switch is being toggled on an off
  7. Bike stops entirely
  8. Bike will now start only for a second, before stopping
  9. Fuel pump intermittently fails to prime, even with new relay
  10. I fit old relay and fuel pump does not prime, ever
  11. I refit new relay and the pumps does prime but bike only starts for a second before stopping
  12. I notice that, when the ECU is in the priming state, both relays deliver the same voltage to the pump, but the old relay delivers a little less current
  13. I've noticed on one occasion only that when I turned the key off, the bike tail-light was still on, and indicators would still work, but dash was off. I've not been able to reproduce this.

Can anybody help me understand the best way to proceed with fault finding?

Other things I've done:

Taken fuel pump out of the tank and physically inspected the filter. There was nothing untoward there. I also ran the pump from the battery and it ran sound and strong.


  • What is the year,make and model - that would help narrow it down... – Solar Mike Sep 1 '18 at 20:49
  • Welcome to Motor Vehicle Maintenance & Repair! – Pᴀᴜʟsᴛᴇʀ2 Sep 1 '18 at 20:50

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