No power to electric fuel pump

[fisherpeakhippie]

I have a 2005 Yamaha F90 TLRD that is not getting power to the electric pump in the vst tank. I have replaced the pump and it is working but I can't seem to get power to it. The fuses are good and I have power to turn the starter. I can't see any damage to the wiring but I have not dissected them and don't want to. I'm leaning toward the ecu but don't know. Any suggestions would be greatly appreciated. Thanks

 

[99yam40]

I believe the pump gets power at key on, but the ecu tells it when to rim by completing the negative side.
so, are you getting 12V + at key on?

 

[fisherpeakhippie]

No, used a test light on the connector and got nothing when I turned the key on. Used a battery and jump wires to know the pump is working.

 

[boscoe99]

The ECU does not provide battery power to the electric fuel pump. Battery power is from the fuel pump relay.

 

[Jeff J]

What tells the pump to pump? It should cycle when the key is turned on and I would assume constantly while the engine is running but I don’t know what controls it. I can’t remember if I can turn it on with the YDS.

 

[boscoe99]

The ECU applies the ground to the pump to cause it to run.

Turn the key to the on position and the relay closes. Battery power to the pump motor. Turn the key to the start position and the ECU applies the ground. Motor starts the ground continues to be applied. Motor dies then the ECU disconnects the ground.

 

[fisherpeakhippie]

So it can't be the ECU, right? Then it must be in the wiring harness or relay. Getting closer. Man I didn't want to dissect the wiring. I guess I don't have a choice.

 

[Jeff J]

There is power only for a moment when first turning on the key. If the connector at the VST is dead when the key is turned on then I would backtrack that until I found power.

It could also be a bad ground.

 

[99yam40]

There is power only for a moment when first turning on the key. If the connector at the VST is dead when the key is turned on then I would backtrack that until I found power.

It could also be a bad ground.

why do you think he has only for a moment when first turning on the key?
he never wrote that

 

[99yam40]

why do you think he has only for a moment when first turning on the key?
he never wrote that

that was suppose to be why do you think he has power only for a moment when first turning on the key?
he never wrote that.

 

[boscoe99]

There is power only for a moment when first turning on the key. If the connector at the VST is dead when the key is turned on then I would backtrack that until I found power.

It could also be a bad ground.

How can a bad ground effect battery positive voltage to the pump?

 

[boscoe99]

So it can't be the ECU, right? Then it must be in the wiring harness or relay. Getting closer. Man I didn't want to dissect the wiring. I guess I don't have a choice.

If you do not have battery power to the pump then inspect for battery power from the relay.

Only if there is battery power from the relay but not at the pump would I suspect a wiring fault.

 

[Jeff J]

that was suppose to be why do you think he has power only for a moment when first turning on the key?
he never wrote that.

Pumps only run that long when you turn on the key. No power no run. Also, we don’t know where he is grounding his test light. No ground no light no matter how much power there is. The VST is mounted on isolators so that isn’t likely going to give him a ground. Any painted surface would be questionable. If he is trying to ground the light through the connector and the ECM controls the ground then either the ECM must be bad or a connection must be bad.

 

[99yam40]

Pumps only run that long when you turn on the key. No power no run. Also, we don’t know where he is grounding his test light. No ground no light no matter how much power there is. The VST is mounted on isolators so that isn’t likely going to give him a ground. Any painted surface would be questionable. If he is trying to ground the light through the connector and the ECM controls the ground then either the ECM must be bad or a connection must be bad.

there should be 12v+ to the pump as long as the key is in the on position.
He needs to figure out how to test to make sure he does or does not have it at the pump at key on, before he goes any other direction