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Cat 3412e throttle problem

Discussion in 'Engines' started by Brian G, Jun 15, 2020.

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  1. Brian G

    Brian G Member

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    I'm looking for a little guidance on my 2003 Cat 3412e engines. The RPM's are jumping around a bit. My low idle is usually 550 RPM's but lately they are at 570 one day and 585 the next. What's worse is that both engines run at about 20-30 RPM's different from each other. I also get a periodic (ie. monthly) throttle position sensor error on the Cat monitor.

    A local Cat technician came out two weeks ago and hooked up his laptop and told me that I needed a new operating station. After installing a new Morse K4-a control head, I'm still having the same problem. The technician wasn't very experienced with boats so I think I might need to give him some suggestions. What should he be looking at?

    Many thanks ...
  2. rtrafford

    rtrafford Senior Member

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    I think this is a matter that needs a bit more information. Fuel pressures, clean filters. Has she been run hard of late? Might be any one of the sensors related to fuel pressure or injectors. What are your readings? Does the pressure fluctuate with the RPM? Does the RPM fluctuation follow an increase in RPM? Set them to idle at, say, 950 and watch. Push it to 1200 and watch...
  3. Pascal

    Pascal Senior Member

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    You need a different mechanic ...

    johnson used Morse controls with the 3412Es not cat controls They should have zero impact on idle RPM. I really doubt the Cat ECU would send a code showing a Morse control issue.

    this happened to me a few times over the year I ran a 70 with 3412Es. It was intermittent. Happened once and then not for another few weeks. It often happened when i d turned the keys on at the helm and not wait till the display were initialized to crank.

    This was also accompanied with a TPS error. I never did anything about it as it was pretty rare. Any decent Cat guy experienced with 3412Es should be able to fix this.
  4. Capt J

    Capt J Senior Member

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    Do you let the engines warm up to 140F at normal idle before putting them in low idle and starting to leave the dock? Allow the computers to go through their initialization between turning the key from on to start? What are are your engine batteries?
  5. Pascal

    Pascal Senior Member

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    I think the initialization of the ECUs is important but I m not a big fan of letting engines warm at idle too long. It take a while to get to 140 at idle. If his symptoms are like what I ve experienced the idle RPM is off whether in slow mode or normal, and happens as soon as it starts.

    that said I always wait till about 160 deg to go over 1000. 3412Es and C32s (and likely most modern Cats) run in a special cold mode until they reach about 150 and usually have a brief vibration and puff of smoke when coming out of cold mode.
  6. DOCKMASTER

    DOCKMASTER Senior Member

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    And is your fluctuation only when you are in low idle mode? What does it do in normal idle? What does it do when cruising and at WOT?
  7. motoryachtlover

    motoryachtlover Senior Member

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    Not sure if I am sending you in a wrong direction but are you hearing and feeling the RPM fluctuation? I had it showing up with in my tachs bouncing around but no change in engine rpm. It was the tach sender gears that were worn out throwing the tachs off.
  8. Pascal

    Pascal Senior Member

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    3412Es don’t have mechanical tachs at the helm, they have the Cat displays getting data straight out of the ECUs. ER tachs May not show a small difference in RPM

    not sure about Brian’s but when I used to have this issue the difference remained at low idle, normal idle or at cruise.
  9. NYCAP123

    NYCAP123 Senior Member

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    Lot's of possible causes, but let me give you the simplest. How are your fuel filters?
  10. Pascal

    Pascal Senior Member

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    Not enough flow at idle for filters to affect idle speed. Plus on electronic engines the computer regulates the speed.
  11. mapism

    mapism Member

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    If I should add another guess, I'd say one or more of the HEUI injectors in need of refurbishing.
    Possibly due to a bit of fuel contamination.
    But... A Cat technician not experienced with boats who needs forum suggestions? Really? o_O
  12. Brian G

    Brian G Member

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    Thank you for the excellent questions. I'll take some readings tomorrow when I take her out ...
  13. Brian G

    Brian G Member

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    Yes, I always let the engines warm up for 15-20 minutes before leaving the dock. But I might not be giving the computers enough time to go through their initialization before cranking. I usually pause for only for a split second. I'm using Interstate batteries.
  14. Brian G

    Brian G Member

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    I replaced the fuel filters on the engine last fall and replaced the Racor's this spring. I'll take look at the Racors tomorrow to see what they look like. Perhaps I got some old fuel from my marina when I filled up this spring.
  15. Brian G

    Brian G Member

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    Well, I wanted to educate myself before calling them back and complaining. This forum is giving me some ammunition to hold them accountable. It was $850 for the service call and an additional $1000 for the control head (which I installed) with no discernible results.
  16. Pascal

    Pascal Senior Member

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    $850 service call? What the hell did they do in 8 hours???? beside misdiagnosing the problem.

    Try letting the ECUs fully initialize (3 to 4 seconds) before wasting time on fuel, batteries etc. if not then
    Look into the TPS error
  17. Capt J

    Capt J Senior Member

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    THIS. But if you're getting a TPS code that probably is the issue and the TPS (Throttle Position Sensor) should be changed.
  18. rtrafford

    rtrafford Senior Member

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    Maybe I missed that point...these sensors are easily changed by the owner, perhaps $100, give or take. Far cheaper than bringing back the tech. If I hadn't seen Nashville on your tagline I would have guess Pantropic in Ft Lauderdale was your service provider....they got me so irritated once that I confronted them at the FLIBS in front of numerous bystanders and potentials.
  19. rtrafford

    rtrafford Senior Member

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    Pantropic was famous for starting my clock when the tech arrived back at the shop and began to prepare for his trip to me. Ending the clock when he returned the shop and put everything away, used the head. Once I paid for him to sit in the truck in my driveway while eating his lunch. $850 seems to me to be the standard base rate they ding you for these calls. I learned. I left Ft Lauderdale (back then), went north, and called Ring. I still paid the price, but at least the guy performed.
  20. Pascal

    Pascal Senior Member

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    Pantropic once charged me about $4k for an oil change on a pair of C32s... they call it flat fee. Never used them again. Southshore Cat Diesel Charges me half of that... about $12oo of supplies and just under a day of labor