150 HPDI surging at idle has me stumped.

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  • 150 HPDI surging at idle has me stumped.

    1. 2000 Yamaha 150 HPDI 800(ish) hours, 21’ CC, in the fall running fine 5200 WOT, 41 MPH
    2. Winterized . Fogged cylinders, drained VST, removed prop, put her to sleep.
    3. DEWinterinzed this weekend

    1. Pumped fuel bulb to fill VST
    2. Put on Muff and placed rubber tote under LU, enough to just touch anti ventilation plate. (This quiets the exhaust significantly).
    3. Started, put in gear to burn off fogging oil. (Didn’t run long in neutral)
    4. Stopped. Drained Racor replaced filter, filled with Sea foam to decarb. Ran through the decard process. Run/let soak/burn off residue. Lots of smoke. Again, ran in gear.
    5. Stopped. Drained racor, filled with fresh gas. Ran in gear until smoke clears
    6. Stopped. Changed plugs, changed Med pressure fuel canister (which was actually fine).
    7. Started boat. Idled ROUGH, surging harmonically between 600-800 RPM’s. hittinh 800 every second or so.

    Remediation steps
    1. Checked LP fuel pumps by removing bolts and pumping fuel bulb lower one was dry. Upper one was the slightest bit damp, replaced upper.
    2. Noticed some air in onboard fuel /water separator. Tightened hose clamps on filter and fuel bulb. Tightened nut on fuel cup (and verified filter was clean). AIR ISSUE FIXED.
    3. Restarted. Same issue.
    4. Started, left in neutral. Removed spark plug wires 1 at a time. All 4 cylinders that fire in neutral have an impact. Although, #1 is more noticeable.
    5. Remove engine from water tub. Surging much more pronounced. Put LU back in tub.
    6. Break out YDS (first time since buying it 2 years ago)
    a. YDS says 580 hrs on engine which is odd… but OK.
    b. 2 old faults TPS voltage, and neutral switch. Clear them out.
    c. Diagnostics all look to be normal both in and out of gear.
    d. Run cylinder drop test. I’m not exactly sure what I expect to see. Cylinder drops, and engine runs until it revs up at end of test. WHAT AM I LOOKING FOR HERE???
    i. Engine stall during one cylinder test (#4 I THINK). I repeat and it runs fine.
    e. Run fuel injector test. All injectors fire. #4 is not as loud as the other 5. But I am not sure if that means anything
    7. Surging still present. Run engine off of 2 gal tank. Step outside boat and problem SEEMS to improve. Step back In boat and notice hose is out of tank. Put hose BACK in tank. Engine MIGHT have run a bit worse, but not like at it’s worst.
    8. Reconnect hose to Racor. No change from step 7.
    9. Check VST. Looks clean, but clean it anyway.
    10. No change from Step 8.
    11. Pull of air silencer, all throttle plates moving in synch.
    12. Linkage to oil pump seems OK. Maybe a hair too much oil.

    Where I am now
    1. Engine running better than at first, but not butter smooth… But am I not remembering how it runs out of the water.
    2. Engine doesn’t SEEM to surge in gear (I know on all 6 cylinders…)
    3. I notice there is a SLIGHT sheen to the water running down by driveway. No clue if this is how it has always been as I never spend this much time running it at home.
    4. I notice a decent bit of white smoke/steam. My engine has ALWAYS had more of this than a 4 stroke especially on cold damp or excessively humid days. It was in the 40’s while
    a. Ran for a few minutes with hose off (by mistake) same amt of white “smoke” so I don’t think ant water is getting into cylinders. Plus old plugs all looked OK, no steam wash on any of them.
    1. Should I run in a barrel to account for proper backpressure?
    2. Should I change out the other LP fuel pump even though it was bone dry?
    3. What do my drop cylinder and fuel injector tests tell me?
    4. Should I check the pressure at the VST even though my pressure in the HP fuel pump is fine?
    5. Why would cylinder #1 have a bigger impact when I remove the spark plug wire than the rest? Normal?
    6. Do you think a link and synch is necessary? Did one last year.
    7. What else should/can I do before dunking her and seeing what happens? Cause I am out of ideas...

  • #2
    Seeing it's doing this at idle, I doubt it's the fuel pumps or filters. Especially since the high pressure pump is normal.

    What's your TPS voltage and throttle valve reading? For comparison mine are .62 V and 2.4 degrees at idle.

    Also, remove and clean your oxygen sensor. I did mine at about the same hours and it was gross. I believe that can cause idle problems in cars but not sure about our HPDI's. Anyway it's simple maintenance item to look at an all that Seafoam decarbing may have affected it.

    And now hopefully a real mechanic can come in and help.....


    • #3
      I'm not even going to try and answer all your questions, I'll leave that to the experts.
      I would check the LP pumps again though, the "sheen" in the water is a sure sign one is leaking although it could be residue from the work you've done already. I've had a bad time with those pumps on mine, probably due to me over tightening the mounting bolts.
      Do you have a service manual ?.


      • #4
        I agree about the sheen and LP pump. but it was BONE dry on the backside. I'll likely change the other out as I have it anyway. I'll also check the new one too, as i HEARD they can be bad out of the box... I use an online manual which has been very good to me so far.

        I'm leaning towards injector(s)...
        Last edited by JFigliuolo; 04-16-2018, 11:21 AM.


        • #5
          HPDI's can "lope" like that in neutral on muffs from no exhaust back pressure. Put it in gear, it usually stops. Put it in the water, my guess is it goes away.

          White smoke or steam is normal when the ambient temp is cold. That cooling exiting water is probably warm to the touch. We see that in our climate a lot. As long as the "steam" disappears quickly, its fine.

          I remember the very first set we installed back in 2000. Was in the rigging shop in the middle of winter, so after they were installed we ran them on muffs. A call into the RTA's at Yamaha confirmed it was normal. They actually had to go and test one on muffs to confirm. Our set must have been some of the first installed, because they(Yamaha) had no idea how they idled on muffs.

          All that being said, since then I have ran many on muffs that hardly do it at all. Go figure.
          Andrew Munao Jr
          Yamaha Sales/Tech Support, SIM Yamaha
          888-231-2392 | andyjr@shipyardisland.com | simyamaha.com


          • #6
            Well... Stuck her in a barrel for solid back pressure... not love. Better, but still surging. Ohmed out coils + plug boots. Speced fine., unfortunately it looks like I'll be pulling the injectors for cleaning which I am NOT looking forward to. Wish me Luck! Patience is NOT my strong suit

            Andy, 3 specific question:
            1. Does it make sense that pulling the wire off Plug 1 has a BIG impact (almost stalls), 5 a smaller one, then 6, then 4 while idling in neutral?
            2. Does one injector quieter than the rest have any significance?
            3. What the Heck does the drop cylinder test in YDS do/mean anyway?
            Last edited by JFigliuolo; 04-17-2018, 10:24 AM.


            • #7
              Where was the water level on the engine when it was running in the barrel? Right above the water pump or where it would be when sitting in the water? It matters.

              You can do a injector flow test(my definition) with your YDS. Doing this will tell you how well each is working. It takes some patience(lol) and some practice bouncing back and forth through the YDS screens quickly while doing this. Here is how its done.

              Start and warm up engine. Note the HPDI fuel pressure reading in the monitor screen.
              Shut engine off, but turn key back on right away so YDS software is still communicating with the engine. It won't with the key off.
              Go to the fuel injector test section
              Run injector test on #1 cylinder
              After test is run for the #1 cylinder, go directly back to the HPDI fuel pressure monitor page. Note the HPDI fuel pressure after that test.
              Now run the same exact test for all the rest of the cylinders. Remember, you need to start and run the engine to build up the HPDI fuel pressure again before retesting the next cylinder.

              When you are finished, compare the readings for all of the cylinders. They should be very close to each other. I can't recall for sure,(maybe Ole or Jethro remembers) but I think the spec is 10 psi max difference between the cylinders after the tests.

              Andrew Munao Jr
              Yamaha Sales/Tech Support, SIM Yamaha
              888-231-2392 | andyjr@shipyardisland.com | simyamaha.com


              • #8
                Andy, thanks that's awesome. I googled like heck but couldn't find that procedure over on THT. The water in the bucket was right up to where the engine would sit in the water. Thanks for all your help. When you get a spare minute I could use the part nbr for the crush washers in case I do have to pull the injectors. 2001 150 HPDI. The one with the older coils if that matters...


                • #9
                  Link to those gaskets. X 12 (unfortunately) https://www.simyamaha.com/product_p/68f-13764-00-00.htm
                  Andrew Munao Jr
                  Yamaha Sales/Tech Support, SIM Yamaha
                  888-231-2392 | andyjr@shipyardisland.com | simyamaha.com


                  • #10
                    Yeah, there's a decent spread across the injectors biggest gap was about 12 psi. Is it normal for the HP pressure to drop as soon as the key is turned off? It drops quickly to 400-500 then slowly tapers down from there. I had to start all my testr at 418 PSI as that was about where the pressure was stable enough to start all tests at the same level (although still dropping)