2017 F50 6C1E 390 Fuel Issue

Problem with the VST running out of fuel and starving the motor. The motor has had this intermittent problem since new but it's much more frequent now. No codes and the dealer can't replicate the problem at the shop.

To me, is appears that the VST isn't venting properly and building high enough pressure that the needle valve can't open to refill the VST. When the motor stalls, I release the pressure at the schrader valve and sometimes it's like letting the air out of a tire. Lots of pressure. Use the primer bulb to refill the VST and the motor starts and runs without issue.

I've run the motor with the vent lines from the VST disconnected so it vents into the atmosphere and no issues.

The venting solenoid is pulsating very fast and seems to be preventing sufficient vapour from escaping the VST.

The dealer has never seen or heard of this problem.

I'm thinking that this solenoid should be either on or off, not pulsating. Don't know, but I'm sure the problem is excessive pressure in the VST.

When the motor is running the solenoid is getting between 3 and 2.6 VDC. I see in the manual that the test for the solenoid valve uses battery voltage.

If anyone has access to a wiring diagram so I can trace the wires or if anyone has seen this problem before I'd really appreciate hearing from you.

Thanks

The wiring diagram is in the back of your Yamaha service manual.

When you use the term "venting solenoid" are you talking about the VST vapor shut off valve?

Thanks for your reply.

Yes I'm talking about the vapor shut off valve.

I have an online manual that doesn't include the wiring diagram. I spoke to the dealer and he sent me a wiring schematic. What I have is the G/B wire goes to pin 11 on the ECU. The R/Y goes to pin 9 on the Joint Connector 2. I haven't located that connector.

Seeing as the problem has been progressive and the voltage at the value at the valve fluctuates, I'm hoping it's a bad connection.

Can you tell me if the power comes from ECU or the Joint Connector and if the voltage should be 12 VDC.

Anything you could offer would be appreciated.

I am at a complete loss as to why and how folks try and do trouble shooting, particularly with respect to electrical systems, without a Yamaha service manual.

Anyhow, R/Y is the colour for key on battery power from the main relay.

Connector 2 is just a shared bus for certain R/Y wire colours. It also includes a number of black wires that share their common buss.

All of the R/Y wires should have the same voltage.

Thank you very much. Big help

Problem solved. It was a bad VST venting solenoid. It's tested OK but was faulty.