Cat - 3126 Long Cranking Time Before Starting

Discussion in 'Diesel Engines/Drives/Transmissions/Props' started by Stromeister, Aug 15, 2017.

  1. Stromeister

    Stromeister Member

    118
    Oct 6, 2006
    Fallston, Maryland
    2003 410 Sundancer
    3126 CAT Diesels w/VDrives
    I have a 2003 410 Sundancer with 3126 Cats that recently had the top rack adjustment (valves and injectors) as part of the 250 hour service (currently have 300 hours on motor) and now the starboard engine is hard to start when it has been sitting longer then 20 minutes. The engine will crank for about 10 - 15 seconds before starting but once it starts, it runs fine. The port engine starts in less then 3 seconds no matter how long she sits. All primary and secondary filters have been replaced as part of the service. I had the Cat technician come back out and he wanted to start randomly replacing parts at my expense. He indicated that it sounded like the check valve(s) that is part of the transfer pump, part number 7W-7383 and I have the parts manual for the 3126 (attached photo - Item 14 points to the check valves (2 listed)) . Does anyone have pictures of the actual pump with part locations when looking at the pump? Is this easy enough to replace by a mechanically savvy person? Thanks in advance for your insight.
     

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    Last edited: Aug 15, 2017
  2. The Bill Collector

    The Bill Collector Well-Known Member SILVER Sponsor

    Jun 2, 2008
    Tacoma, WA
    450 Sundancer
    3126 Cat's
    Hi Don, I have 3126's too, this may sound way too simple, but make sure the primer valve & pump on that engine are both closed tight.
     
  3. Stromeister

    Stromeister Member

    118
    Oct 6, 2006
    Fallston, Maryland
    2003 410 Sundancer
    3126 CAT Diesels w/VDrives
    Thanks Mark. That's the first thing I did when the problem surfaced was to prime the lines and close the valve.
     
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  4. HUMPH

    HUMPH Well-Known Member

    Nov 4, 2009
    SF BAY AREA
    2003 410DA,
    2004 C14 Caribe
    CAT 3126TA's 350HP/
    50HP Honda
    Does sound like maybe air is getting in somewhere?
     
  5. fwebster

    fwebster Well-Known Member TECHNICAL Contributor PLATINUM Sponsor

    Oct 6, 2006
    Middle Tennessee ; Panama City Beach, FL
    1996 450DA
    3116 Caterpillars
    Try to rule out the governor setting first by changing your starting routine a bit. Try advancing the throttle to about 1/2 throttle then cranking the engine. It and as soon as it starts, pull the throttle back to idle. When a Caterpillar engine with the unit injection system starts, the injection pump must build enough pressure to open the governor spring. By opening the throttle, you open the governor spring for the pump and save wear and tear on the starter motor and gears.

    I said try because that approach is free and easy to try, but 10-15 seconds is pretty long for the governor spring pressure. I'm thinking your Cat guy is right on this one.

    One other thing I can tell you is that the injection pump isn't a place for a novice to be monkeying around. They are expensive, delicate and have about 8 mil little parts in them. Any part you remove to get to what you think you need to get to, may require special tools/knowledge to re-set when the parts are reinstalled. I am a better than average "shade tree mechanic", I own/run 5-6 diesel powered machines in addition to my boat and I'll tear into anything on any of them, except injection pumps and automatic transmissions.

    Good luck with it........
     
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  6. Stromeister

    Stromeister Member

    118
    Oct 6, 2006
    Fallston, Maryland
    2003 410 Sundancer
    3126 CAT Diesels w/VDrives
    Thanks for the info, Frank! I will try your recommendation later this week when I next pay a visit to the boat.

    Thanks again.
     
  7. ttmott

    ttmott Well-Known Member

    Apr 3, 2012
    Space Coast Florida
    2006 52 Sedan Bridge
    Cummins QSM11
    See this link.
    http://www.clubsearay.com/index.php?threads/cat-3116ta-fuel-system-lesson.60065/
    I find it very odd that this problem crops up after your mechanic synchronized the injectors and valve lash. However, on the front of the injector control assembly in line with that tube that goes into the cylinder head is one of the three check valves or better known as the fuel regulator. That regulator is what controls the fuel rail pressure which should be around 60 PSIG (if I remember correctly). If that is sticking open which they will end up doing eventually the rail pressure will not build up during cranking however may supply enough fuel to the rail during operational RPM's. The regulator is easy to take out and replace and they are cheap; like $35. But, as I have found out that over time these little check valves tend to gum up and will cause issues like low rail pressure or pressure fluctuations. So, if you are going to open up the fuel system change all three. This image is the regulator which is the easiest of the three to replace.
    CatFuelSystem2.jpg
     
  8. THJeff

    THJeff Member SILVER Sponsor

    250
    Jan 4, 2012
    Rochester Hills, MI/Belle Maer Harbor/Club Island
    2000 410 Sundancer
    CAT 3126 Diesels
    I recall in one of your posts a few years ago that you recommended advancing the throttles entirely and returning back to idle position before starting the engines. Is my recollection correct and if so, is this the same reason for doing it?
     
    Last edited: Aug 17, 2017
  9. fwebster

    fwebster Well-Known Member TECHNICAL Contributor PLATINUM Sponsor

    Oct 6, 2006
    Middle Tennessee ; Panama City Beach, FL
    1996 450DA
    3116 Caterpillars
    Yes, same reason. But, you don't need to open the throttle all the way.....about half way is sufficient. The idea is to reducte the cranking time, not start the engines at a high rpm, so pull the throttles back as soon as the engine fires.
     
  10. THJeff

    THJeff Member SILVER Sponsor

    250
    Jan 4, 2012
    Rochester Hills, MI/Belle Maer Harbor/Club Island
    2000 410 Sundancer
    CAT 3126 Diesels
    OK, so moving the throttles all the way open and then back to idle BEFORE starting won't help with this? The throttles need to be open about half way DURING starting in order to help reduce cranking time. I probably misunderstood your post from a few years ago then.
     
  11. Blkbird

    Blkbird Active Member

    238
    Jul 5, 2010
    Lake Lanier, GA
    1997 Sea Ray 450 Sundancer
    Twin 3126 CATS
    My Caterpillar mechanic told me to open throttles and then close prior to starting engines, and then open again maybe 1/4 throttle or less. Then hit the starter.

    Like you one engine starts immediately but the other might turn over a few times before it kicks in.
     
  12. The Bill Collector

    The Bill Collector Well-Known Member SILVER Sponsor

    Jun 2, 2008
    Tacoma, WA
    450 Sundancer
    3126 Cat's
    My PO told me to "rack" the throttles before hitting the starter button.
    1) put start switch on run (hear the buzzers going)
    2) rack the corresponding throttle (take it all the way to full then bring back to idle)
    3) engage starter
    I've been starting them this way for 10 years and they always fire off immediately...
    Your results may vary...
     
    THJeff likes this.
  13. carterchapman

    carterchapman Well-Known Member TECHNICAL Contributor SILVER Sponsor

    Mar 25, 2008
    Lake Chickamauga/Marietta, GA/Ft. Myers, FL
    2006 Sea Ray 58 DB
    MAN CRM V8-900s, Twin Disc Drives; Onan 21.5 Generator
    My 3126's had intake heaters - In addition to racking the throttles and starting with them 1/4 - 1/2 way open (pulling them back to idle immediately after start), I would turn the ignition switches on and wait 30 seconds to warm the heaters up (listening to the buzzer unfortunately). On cool days/in cool areas, this helps the starts as well
     
  14. Stromeister

    Stromeister Member

    118
    Oct 6, 2006
    Fallston, Maryland
    2003 410 Sundancer
    3126 CAT Diesels w/VDrives
    Changed my starting routine this weekend and tried some of the suggestions on this thread.
    Place the start switch to run and pushed throttle to full position and then returned to idle and proceeded to engaged the starter. Engine starts right up. Seems odd that I've never had to perform this in the past and the Port engine starts without going through this routine.
     
  15. carterchapman

    carterchapman Well-Known Member TECHNICAL Contributor SILVER Sponsor

    Mar 25, 2008
    Lake Chickamauga/Marietta, GA/Ft. Myers, FL
    2006 Sea Ray 58 DB
    MAN CRM V8-900s, Twin Disc Drives; Onan 21.5 Generator
    Good news Don.
     

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