03-19-2013, 11:00 AM
Joined: Feb 2005
Location: Alexandria, VA
Originally Posted by rdwalker
I am not 100% sure if it is a bad pump, though it is very likely. Some further troubleshooting would help.
Here are my thoughts (from being in the electronics "biz").
The fuel pump is protected by 10A fuse. If that value is still in the socket (worth checking if it is), than it should blow by about 15A. I don't know the specs on the actual relay, but that style relays are typically rated 20-30A. All this means that steady over-current by pump should not damage the relay; fuse should go first.
This is, by the way, extremely easy to measure. Plug an ammeter capable of 10A-20A into the fuse socket, see what happens. There may be some very brief inrush that is faster than fuse clearing time - indicating a bad motor.
There could be some intermittent short in fuel circuit wiring. It's worth inspecting the harness. On an R1150, the green/white wire from the relay feeds:
- the fuel pump
- plug for evaporative control valve ("carbon canister")
- fuel injectors
- O2 sensor
Lots of stuff to go bad. Connect an ammeter and jiggle the harnesses.
Finally, there could be a sparking problem. Bad fuel pump motor could cause excessive sparking when being turned off, eroding relay contacts. It's an inductive kick-back; usually there are snubbers to contain that, either the snubbers or the motor could be bad. There is no easy test for that for a home mechanic, pump replacement would be the way to go.
Fuel injectors have less inductance and are less likely to generate a damaging spike. But, maybe one is failing? Pull the sparkplugs to examine, see if there is difference between cylinders.
Good luck troubleshooting. Robert.
All also true and possible!