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  1. #1
    Member
    Join Date
    Nov 2020
    Location
    Charleston, SC
    Posts
    2

    250 HPDI - no VST fuel pressure

    Good morning BBC boards- so after reading many helpful threads on here I decided to tackle the project of changing out all of my fuel filters due to some rough running/surging and abrupt RPM loss at WOT. I changed all 10 of the mystery filters, the low pressure canister filter, both low pressure fuel pumps, the fuel water separator, the high pressure “can filter”, and cleaned/blew out all the injectors. After all this the boat ran flawlessly...for about 4 hours. After the boat sat for an hour or so while fishing I went to restart and had some trouble starting. Eventually got the motor started but couldn’t get over 1000 rpm without major surging and choking out. When I got home I still couldn’t start the motor. I noticed that when I cycled the key I normally hear the fuel pump motor cut on to pressurize the VST- This was not happening. I checked the Schrader and there is no pressure. After that I took apart the VST and bench tested the fuel pump motor… Everything checked out and the motor works fine. I checked the power supply to the pump motor while cycling the key- No voltage at all. I have checked the fuses on the starboard side of the motor as well as the Killswitch. For the life of me I cannot find out why I am not getting voltage. Am I missing something? Maybe ignition switch assembly fault, bad connection, or pinch in the wiring harness. Today I put in another key switch...still no luck and no power to the fuel pump motor in the VST. My last thought might be damage or short to the ECU?

  2. Born on th Llano Estacado Tx Champ's Avatar
    Join Date
    Jun 2004
    Location
    Abilene, TX
    Posts
    20,809
    #2
    If you pulled the covers off the rear of the engine, there was a relay you had to unplug. That relay is what powers the VST pump. Make sure you got it plugged back in good. Same thing happened to me when I changed my pressure relief valve. I apparently didn't get the connector latched and it worked its way apart after an hour or so of run time.