Andy Leeds UK
Guest
Had a bit of hassle on Friday that might save somebody else a ride on the RAC van. My outfit has no sidestand (it only falls over if you really try hard!) hence the switch that kills the engine if the sidestand is down is overidden. I know a few riders also do this so they can start the bike on the stand. Take care how you do it.
The circuit looks simple. Power from the ignition switch, through the kill switch (closed= go), through the sidestand switch (closed= go) to the fuel pump relay then to the mototronic unit. Looks simple, no fuel pump at ignition on, you check the continuity. If there is a circuit, check the relay. If the relay is OK, its the pump, so call the RAC.
Not correct! The mototronic unit seems to back feed about 1.5 volts down the line to the relay when the ignition is on and the switch is open and/or as the unit shuts down. This needs to be overcome by the power coming the other way to get the relay to close and give you the fuel pump function if you close the stand switch after ignition on. If your sidestand switch or sidestand switch bypass wire is not perfect (mine had water in the connector) this is taken as sidestand down, so the bike won't run.
When checking, you need to pull the plug off the stand switch, jump the pins with thick wire then check there is zero current until the ignition is keyed. At this point when the ignition is keyed, if thats the problem the fuel pump will prime.
Three hours at the side of the road, on the truck and in the garage, all because a 2p connector let in water and Bosch have some weird features in the electronics! I think the back feed is a test signal that allows the unit to log different faults for sidestand down, side stand failed open circuit or to ground, relay open circuit or failed to ground (useful if you can read the memory).
On the up side, the RAC orange van guy seemed to know something about FI, his mate that he phoned knew BMW bikes and the recovery guy knew how to fasten it down safely. Good service IMHO.
Andy
The circuit looks simple. Power from the ignition switch, through the kill switch (closed= go), through the sidestand switch (closed= go) to the fuel pump relay then to the mototronic unit. Looks simple, no fuel pump at ignition on, you check the continuity. If there is a circuit, check the relay. If the relay is OK, its the pump, so call the RAC.
Not correct! The mototronic unit seems to back feed about 1.5 volts down the line to the relay when the ignition is on and the switch is open and/or as the unit shuts down. This needs to be overcome by the power coming the other way to get the relay to close and give you the fuel pump function if you close the stand switch after ignition on. If your sidestand switch or sidestand switch bypass wire is not perfect (mine had water in the connector) this is taken as sidestand down, so the bike won't run.
When checking, you need to pull the plug off the stand switch, jump the pins with thick wire then check there is zero current until the ignition is keyed. At this point when the ignition is keyed, if thats the problem the fuel pump will prime.
Three hours at the side of the road, on the truck and in the garage, all because a 2p connector let in water and Bosch have some weird features in the electronics! I think the back feed is a test signal that allows the unit to log different faults for sidestand down, side stand failed open circuit or to ground, relay open circuit or failed to ground (useful if you can read the memory).
On the up side, the RAC orange van guy seemed to know something about FI, his mate that he phoned knew BMW bikes and the recovery guy knew how to fasten it down safely. Good service IMHO.
Andy
