HPDI VST Motor

[tdillon@voselectric.com]

I have a 2003 250 hp Yamaha HPDI. The motor in the VST is not getting a neatral. With the key switch turned on (not cranked) the vst motor does not cut on and build up presure. I can take a jumper to the negative wire and the motor in the vst comes on and builds up presure. so the vst motor is good. I have changed the VST filter & high presure filter allong with the primary fuel filter with the water seperator. When I crank the engine it does the same thing the engine will only run for a few seconds bulb goes limp and fuel in the primary filter installed on engine drops down about an inch.

[Sparkieboat]

I am no professional like Rodbolt, so anything I say is just a guess. but my guess would be to follow that ground wire and find the short/break..if it goes into the ECU you may have a bad day. not sure if you can bypass it or not...better wait on Rod to chime in.

[tdillon@voselectric.com]

Thanks. I swaped ECU with the Port motor and it does the same thing. The Blue wire (-) goes to the fuel pump relay. thier is a Yellow wire from ECU to relay, a Black wire going to ground on relay and a 12v red/y wire to fuse panel.
It apears as if a saftey on one of the sensors has trigerd off and the ECU is not sending the (-) signal from the ecu to the relay via yellow wire.

Does any one know what Alarm conditions shut off the vst fuel pump motor?

[jb123]

a friend has a similar issue on an ox66, he was told to check grounds @ ecu

[Sparkieboat]

if you have a way to find out what problem codes are in the ECU..maybe try clearing them and see if ground returns. then see if the trouble code happens again..and fix problem

[rodbolt17]

no alarms shut off the fuel pump.
anytime the key is on the main relay feeds 12V via the red/yellow wire to the pump.ANY red/yellow wires have this voltage applied any time the key is on.

the ECU completes the ground path for 3-5 seconds at key on.

at cranking the brown wire on the start relay sends a signal to the ECU that its cranking and the ECU completes the ground path via the blue wire.
once running the pulser coil input gives it a run signal so the ECU maintains the pump ground path.
the blue wire from the pump DOES NOT go to the relay.
pin 15 or 16 is going to be the fuel pump blue to ECU.
one is for the return path of the VST electric oil pump the other is the fuel pump ECU return.
the pin 1-20 connector is the far left one on the ECU.
and yes the wiring diagram is rather poor and rather difficult to interpet.

[Sparkieboat]

so is he looking at having to buy a new ECU????