Results 1 to 9 of 9
  1. #1

    Question Low Fuel Pressure 2008 STX 15F

    Hi all, first timer here. We bought a 2008 STX 15F late last year and it ran great, hitting around 61mph and 2 ticks past 7000 rpms. At the end of the year I fogged the engine, since I was going to change out the plugs anyway. I also put stabil marine in the fuel, but for the life of me I can't remember if I ran it for a few minutes after doing this or not.

    After getting it out this year, it ran terrible to begin with until I put new plugs in it. At this point it seems to have a mild issue idling, nothing major, just doesn't seem as smooth as last year. Acceleration is smooth, however you can tell it's missing the top-end as it won't jerk you out of the water like it did last year. Also it maxes out at around 48-50mph, barely getting over 6000 rpms. Below is what I've done so far (by reading threads and the service manual):


    • New battery (original was dead basically when I got it late last year)
    • New Iridium plugs
    • Bottle of Royal Purple fuel system cleaner and ran through a full tank of new premium fuel
    • Checked for spark on each plug
    • Checked fuel flow (around 200 mL in 3 sec)
    • Checked fuel pressure at fuel rail input (25-28 psi, can't remember exactly but it was low)
    • Checked fuel pressure at fuel pump output (28 psi)
    • Squeezed return line to see if that changed the pressure, which it didn't (thought I read that on a post somewhere)
    • Checked the fuel injectors and they shot out fuel fine (although it seemed like #2 and #3 started about 1 - 2 seconds before #1 and #4 which may be fine, didn't know so I switched #1 and #2 and it didn't make a difference)
    • Bypassed fuel filter completely to see if that made a difference in pressure, and it didn't

    So am I to the point that it could be the fuel pump, or do I need to check something else? I'm about to the limit of what I can do or have the tools available to do. I rented a fuel pressure gauge from O'Reilly, and also from AutoZone just to make sure the first one was reading correctly. I don't have a compression gauge, and the rental from O'Reilly didn't have a 10mm adapter so I haven't been able to check that, does it sound like that could be an issue too?

    So basically I'm looking for some direction. Trying to decide if it's time to take it to the shop or is there something else I can do or check. Thanks for any input.


  2. #2
    Your measured fuel pressure seems a bit low assuming your gauge is accurate.
    I've seen around 40 psi output on good running skis.
    If your fuel pressure is indeed low, then either the fump pump is going bad or the "sock" filter at the bottom of the fuel pump body is clogged up. The manual says to clean out the sock filter once a year (but I've never done on my 10-year old 15F and the ski still runs like new). But I've seen a few sock filters that were completely clogged up on other skis giving troubles.

  3. #3
    Quote Originally Posted by meangreenman View Post
    Your measured fuel pressure seems a bit low assuming your gauge is accurate.
    I've seen around 40 psi output on good running skis.
    Yeah, the gauge being accurate is definitely a question. That's why I stopped and rented another from AutoZone, and it was a brand new rental so I'm *assuming* it's ok, but who knows.

    Quote Originally Posted by meangreenman View Post
    If your fuel pressure is indeed low, then either the fump pump is going bad or the "sock" filter at the bottom of the fuel pump body is clogged up. The manual says to clean out the sock filter once a year (but I've never done on my 10-year old 15F and the ski still runs like new). But I've seen a few sock filters that were completely clogged up on other skis giving troubles.
    Thanks, I'll try and look into this tomorrow if I get a chance.

    Hypothetically, if the gauge is off and I don't have a pressure issue, does it sound at all like it could be compression? Just curious, thanks.

  4. #4

    Join Date
    May 2008
    Location
    Sweetwater
    Posts
    890
    +1
    140
    Be careful letting the injectors mist fuel over top of the motor area. I've had the engine backfire through the injector holes and make a nasty little fire. And the pressure is low, but it's easy to check what the others have said above..

  5. #5

    compression and fuel pressure

    Quote Originally Posted by GoVols View Post
    Hi all, first timer here. We bought a 2008 STX 15F late last year and it ran great, hitting around 61mph and 2 ticks past 7000 rpms. At the end of the year I fogged the engine, since I was going to change out the plugs anyway. I also put stabil marine in the fuel, but for the life of me I can't remember if I ran it for a few minutes after doing this or not.

    After getting it out this year, it ran terrible to begin with until I put new plugs in it. At this point it seems to have a mild issue idling, nothing major, just doesn't seem as smooth as last year. Acceleration is smooth, however you can tell it's missing the top-end as it won't jerk you out of the water like it did last year. Also it maxes out at around 48-50mph, barely getting over 6000 rpms. Below is what I've done so far (by reading threads and the service manual):


    • New battery (original was dead basically when I got it late last year)
    • New Iridium plugs
    • Bottle of Royal Purple fuel system cleaner and ran through a full tank of new premium fuel
    • Checked for spark on each plug
    • Checked fuel flow (around 200 mL in 3 sec)
    • Checked fuel pressure at fuel rail input (25-28 psi, can't remember exactly but it was low)
    • Checked fuel pressure at fuel pump output (28 psi)
    • Squeezed return line to see if that changed the pressure, which it didn't (thought I read that on a post somewhere)
    • Checked the fuel injectors and they shot out fuel fine (although it seemed like #2 and #3 started about 1 - 2 seconds before #1 and #4 which may be fine, didn't know so I switched #1 and #2 and it didn't make a difference)
    • Bypassed fuel filter completely to see if that made a difference in pressure, and it didn't

    So am I to the point that it could be the fuel pump, or do I need to check something else? I'm about to the limit of what I can do or have the tools available to do. I rented a fuel pressure gauge from O'Reilly, and also from AutoZone just to make sure the first one was reading correctly. I don't have a compression gauge, and the rental from O'Reilly didn't have a 10mm adapter so I haven't been able to check that, does it sound like that could be an issue too?

    So basically I'm looking for some direction. Trying to decide if it's time to take it to the shop or is there something else I can do or check. Thanks for any input.

    don't do anything else till compression is tested, buy a gauge if you have to, if compression is good you will certainly need a fuel pump cell, fuel pressure should be 43 psi.

  6. #6
    Quote Originally Posted by GoVols View Post
    does it sound at all like it could be compression?
    Don't think so based on what you described - missing top end power which sounds more like lack of fuel pressure/amount issue.
    If compression is low, lack of power would be felt all over the rpm band not just at the top end. Also, engine would be hard to start with low compression.
    However, checking compression would not hurt and it is a good idea to do on any engine mechanical diagnosing. Just like fuel gauges though, one compression gauge might give a different reading from another. So, don't sweat too much on absolute psi values but be more concerned on difference/delta between each cyl.

  7. #7
    Thanks all, I'll try and pick up a compression gauge this weekend and see what it shows.

  8. #8
    Picked up a cheap compression gauge from Harbor Freight. Reads 180 on both cylinders 1 & 2 and 210 on 3 & 4. Think I'm going to take in to and have a pro look at it at this point. Thanks for all the help.

  9. #9
    My name is Sean and I am addicted to STXs smokeysevin's Avatar
    Join Date
    May 2008
    Location
    Houston
    Posts
    4,486
    +1
    320
    read the thread in my signature and go from there, its not that hard.

    Sean

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Low Fuel Pressure 2007 STX 12F
    By vwmikey99 in forum Kawasaki PWC Performance (4-stroke)
    Replies: 6
    Last Post: 09-03-2012, 09:33 AM
  2. Chip in my Hull: 2008 STX-15F
    By sixtydashone in forum Kawasaki How To & FAQs
    Replies: 33
    Last Post: 09-05-2008, 05:39 AM
  3. 2008 STX-15F wiring harness
    By goblin in forum Kawasaki How To & FAQs
    Replies: 5
    Last Post: 08-21-2008, 08:53 PM
  4. 2008 STX - 15F Seat Cover?
    By sixtydashone in forum Kawasaki Open Discussion
    Replies: 4
    Last Post: 07-30-2008, 07:42 PM
  5. Just bought a 2008 STX-15F, Service Schedule?
    By mav7 in forum Kawasaki PWC Performance (4-stroke)
    Replies: 3
    Last Post: 06-08-2008, 12:49 AM

Posting Permissions

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