User Tag List

Thanks Thanks:  0
Likes Likes:  0
Results 1 to 11 of 11
  1. #1
    Join Date
    Jun 2007
    Posts
    14
    Thanks (Given)
    0
    Thanks (Received)
    0
    Likes (Given)
    0
    Likes (Received)
    0
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

    99 Merc 200 EFI VST Fuel Pump

    I am re-activating the subject motor after it was garaged for 13 years. VST pump was grimey/gooey but I soaked it and cleaned it for weeks and got it running. I get fuel to the VST but injectors are not firing (injectors were just @ Brucatos and are good). Motor fires right up when pre mix is squirted into EFI manifold. VST pump runs when tested in place per Merc shop manual procedure. When performing voltage check on VST pump by turning on key voltage never goes to zero as it should for 30 sec. When key is turned on voyage oscillates between 13.5 and about 12 volts at about 5-10 cycles per second. Any ideas? I don't have a fuel pressure gauge to check the VST pump pressure ($450 from mercury).

  2. #2
    Join Date
    Dec 2011
    Location
    Sunny Oregon
    Posts
    1,770
    Thanks (Given)
    0
    Thanks (Received)
    1
    Likes (Given)
    1
    Likes (Received)
    11
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)

  3. #3
    Join Date
    Apr 2001
    Location
    Michigan
    Posts
    13,220
    Thanks (Given)
    79
    Thanks (Received)
    224
    Likes (Given)
    3548
    Likes (Received)
    2005
    Mentioned
    0 Post(s)
    Tagged
    1 Thread(s)
    The fuel pump always has voltage. It's ground side triggered.

  4. #4
    Join Date
    Mar 2011
    Location
    Carrollton VA
    Posts
    1,759
    Thanks (Given)
    13
    Thanks (Received)
    37
    Likes (Given)
    56
    Likes (Received)
    120
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    So,the pump is running but no fuel is being delivered to the injectors? Did you clean the pump inlet filter/screen in the VST? You should check fuel rail pressure (gage hose and schrader valve fitting are cheap) to try and determine if you have a blockage or maybe the regulator is FUBAR.

  5. #5
    Join Date
    Jun 2007
    Posts
    14
    Thanks (Given)
    0
    Thanks (Received)
    0
    Likes (Given)
    0
    Likes (Received)
    0
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Yes my pump has the correct voltage when checked without key on (13.5), the voltage does not go to zero for 30 seconds when the key is turned on. I have disassembled and cleaned VST tank and pump and replaced blue strainer screen on VST pump. I cleaned and rebuilt pulse pump. I replaced water separator/filter. I disassembled and cleaned EFI manifold and removed injectors. Injectors were sent to Brucato and cleaned/tested/replaced as required. I have not checked the fuel pressure regulator. I think I am down to 3 possible items - ECU or wiring, VST pump, or pressure regulator.

  6. #6
    Join Date
    Jan 2013
    Location
    indiana
    Posts
    4
    Thanks (Given)
    0
    Thanks (Received)
    0
    Likes (Given)
    0
    Likes (Received)
    0
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Why are you wanting the voltage to go out when the key is on???

  7. #7
    Join Date
    Sep 2005
    Location
    South Jersey Shore
    Posts
    1,026
    Thanks (Given)
    0
    Thanks (Received)
    1
    Likes (Given)
    0
    Likes (Received)
    4
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    These maybe obvious but I will say them... Replace Fuel Pump Diaphram, maybe rotted out. Check general flow to the fuel rail with some tubing and container. Lastly, check the fuel rail is clear. It's gotta be a block from A to B some how...
    Boats love hundred dollar bills.

  8. #8
    Join Date
    Aug 2007
    Location
    Hopedale, IL
    Posts
    2,556
    Thanks (Given)
    1
    Thanks (Received)
    1
    Likes (Given)
    7
    Likes (Received)
    5
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Check the injector harness. My ProMax had a few injector wires that were exposed b/c the insulation cracked off due too much bend in harness.
    Sunsation 288 - 496 HO

    Nothing runs like a Deere when a CAT's on it's ASS!

  9. #9
    Join Date
    Sep 2005
    Location
    South Jersey Shore
    Posts
    1,026
    Thanks (Given)
    0
    Thanks (Received)
    1
    Likes (Given)
    0
    Likes (Received)
    4
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by njj502 View Post
    Check the injector harness. My ProMax had a few injector wires that were exposed b/c the insulation cracked off due too much bend in harness.
    I second this advice... A good friend with a 300x wound up getting a new harness because of this problem, same symptoms.
    Boats love hundred dollar bills.

  10. #10
    Join Date
    Jun 2007
    Posts
    14
    Thanks (Given)
    0
    Thanks (Received)
    0
    Likes (Given)
    0
    Likes (Received)
    0
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    I got it running now. VST pump was bad. Now i have a fuel leak like this:Click image for larger version. 

Name:	Merc 200 Fuel Leak.jpg 
Views:	47 
Size:	50.4 KB 
ID:	294003Is there supposed to be a hole in the back of the brass 90?

  11. #11
    Join Date
    Dec 2011
    Location
    Sunny Oregon
    Posts
    1,770
    Thanks (Given)
    0
    Thanks (Received)
    1
    Likes (Given)
    1
    Likes (Received)
    11
    Mentioned
    0 Post(s)
    Tagged
    0 Thread(s)
    Quote Originally Posted by roberwb View Post
    I got it running now. VST pump was bad. Now i have a fuel leak like this:Click image for larger version. 

Name:	Merc 200 Fuel Leak.jpg 
Views:	47 
Size:	50.4 KB 
ID:	294003Is there supposed to be a hole in the back of the brass 90?
    Yes. Shove a wire through there to clear it out. The way it's designed is to pull air through the tube at idle with air coming through the hole aspirating the fuel that makes it into the plenum. If its plugged on the other side it will blow gas out.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Aeromarine Research