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  1. #1

    Barely any fuel pressure at all

    Some of you are following my stuff, some not and thats ok.

    I installed a small 15psi fuel pressure gauge between the carb output and 95 restrictor-jet a few days back. Oh, and the carb return passage is drilled 1/8". Today I was finally able to give it a full test on the water.

    The engine was dreadful to start. I had to prime it a dozen times and even then I could hear air in the carbs as the primer was sucking instead of blowing. I'm using the stock disconnected accelerator pump to prime 1&3 manually. The engine barely started 3~4 times each a little better, and then finally it ran on the trailer OK enough to plop in the water. In the water leaving the dock it died within 10 feet. Cranked for another ~15 seconds twice and it started and was stable. Aftermarket RPM gauge is also a disapointment btw.

    Fuel pressure was barely anything at all at any time. The only time it jumped to ~3psi is during cranking when the engine was barely starting. Idle - 0psi. If I pump the throttle fuel psi goes up to 1.5 psi very briefly. At full throttle the pressure is also - 0psi. I'm very disappointed. Fun thing is, the ski still flies at ~65mph.

    So something is wrong. Now me and the mad scientist gotta break it all down and fix the piston rings I fried (lol). No seriously, I found this writeup on testing carbs and am going to give the suck/blow and pump test a try. I'm thinking I have the fuel pump valves in the carb pumps backwards on one/some of these carbs.


  2. #2
    OK I fixed everything. BTW I'm getting really good at taking off the stinger in 10 minutes.

    What I did was, parallel fuel lines to the carbs. What I didnt realize was - the second line from the tank I actually connected to the RETURN on the carbs! Its a good freaking thing I had a fuel pressure gauge, else I would probably have run like that for a few hours. Thankfully I only ran it for about 15 minutes and mostly 1/4 throttle on the lake (Once full throttle to ~65mph).

    The carb's pressure was instantly bleeding off to the fuel tank - unrestricted. OK so I moved the second/parallel fuel line to where it's supposed to be and now the fuel gauge should register something nice. To be continued there...

    My tach is annoying. I'm probably going to return it if I cant figure it out. It bumps and jumps all over the place but then sometimes it displays a clean reading. I think it's picking up interference. I'll try moving it around a bit and see if that helps.

    I followed the carb write-up in the link above, and it appears everything is operating normal from a pump/valve perspective. Before I put the stinger back I'll run the tests another way though just to be sure.

  3. #3
    Fuel Pump Verification

    Check fuel pump valves operation as follows:

    Connect a clean plastic tubing to the fuel inlet nipple (see Picture A) and alternately apply pressure and vacuum with the mouth. The fuel inlet valve should release with pressure and hold under vacuum.
    CAUTION: Some fuel may be present in fuel pump. Be careful not to swallow fuel when testing.

    Repeat the same procedure at the fuel outlet nipple.
    This time the outlet valve should hold with pressure and release under vacuum.

    Fuel Pump Diaphragm Leak Test
    Using a suitable pump gauge tester (like Sea Doo P/N 295000114), perform the following test as follows:
    Install pump gauge tester on the pulse fitting (see Picture A).
    Pump the tester until it reaches 28 kPa (4 PSI) on the gauge.
    The pump diaphragm must stand pressure for 10 seconds. If the pressure drops, replace the pump diaphragm.

  4. #4
    elmatta's Avatar
    Join Date
    Sep 2011
    Get a tiny tach. Works wonders.

    Also, if you havent done so, you shoud rebuild your carbs. Now that you can remove the stinger pretty fast, get used to removing the carbs and do the tests outside the hull. After everything is all said and done, you then check fuel pressure at idle and full throttle

  5. #5
    I called HardLine. They said straight up that their tachs wont work on 3-cyl waverunners. Lucky I was able to return it LOL. I'll get a TinyTach next time.

    My fuel pressure looks good now. 1.5psi at idle, and up to 6psi at wot. Starting went better than most ever today. I primed the motor 10 times per a suggestion from a coworker and it fired right up on jugs 1&3. It would probably be wise of me to get an accelerator nozzle for jug 2.

    Thank you!

  6. #6
    By request.

    To do this, you'll have to have done Onside Bill's carb mod where you drill out the returns and put a 95 jet inline on the fuel return.

    The gauge I installed was a cheap Mr Gasket gauge from AutoZone for $15. It needs some extra hardware but they all do. With 3m4200 I secured it into where the stock fuel selector normally goes. Its a perfect and tight fit. I dont really care about condensation or water as this gauge is fully mechanical. If it ever rusts out I'll get another or just take it off completely. The gauge is T'd off the fuel return line BEFORE my 95' jet.

    For fuel supply I ran dual pickup with extended drops inside the tank. Both on and reserve supply the system now. Two factory fuel filters secured to each other. Valves sourced from eBay. After on/off valve ran one line to the stock fuel input on carb #3. The second line I T'd between carb 1&2 with a brass 1/4" barbed T.

    Pics - Turn your head to the LEFT, and dont scratch the Ducati!
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