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Thread: 941 not cranking with glow plugs update

  1. #1
    Join Date
    Mar 2014
    Location
    TN
    Posts
    131

    Default 941 not cranking with glow plugs update

    i got the new breaker put in and it isnt tripping no more but it still wont crank when 50 outside or below after being heated 2mins. it tries to but wont quite do it. when its about 60 or hotter about 30secs of glow plug and it will crank right up. i took all the battery connections from battery to starter and all the grounds off and cleaned them up but didnt seem to make no difference. it sounds like the engine is spinning fast enough.
    any ideas why it might not be cranking like it should?

  2. #2
    Join Date
    Nov 2016
    Location
    Western States
    Posts
    25

    Default Clean Water Free Fuel Flow, Check

    Check for water in your diesel fuel, cleaned your fuel screen, check for free flow of diesel from the tank and changed your main fuel filters. I have had algae cause a problem very similar to what you are describing. It just was not getting enough fuel to start after sitting over the course of just one winter. When you do change your filters try dumping out the fuel from the fuel filters into a clean bucket and see if the fuel is discolored or smells different than fresh diesel.

    Also sometimes if it is really cold I have had luck with cranking the diesel with the fuel in the off position for about 10 seconds. Then wait about 30 seconds, then apply the glow plugs for same duration as you would normally for the conditions, then give it a little bit of fuel, not too much and then crank it. You have effectively heated the engine a little and it can make a big difference in starting in the cold. Also if you give it too much fuel when trying to start it can make it much harder to start form a few tractors I have had. Keep us posted. Have you checked to see if all of your glow plugs are working?

  3. #3
    Join Date
    Nov 2006
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    Corralitos, Ca.
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    15,407

    Default

    What's the status and specification of the batteries you are using?

  4. #4
    Join Date
    Mar 2014
    Location
    TN
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    Default

    just going from memory here old magnet but i think the specs below are correct for the batteries i put in it about 2yrs ago. and it was checking somewhere around 24.8volts to the starter.



    Battery Electrolyte Composition:Acid
    Battery End Type:Top Post
    Battery Purpose:Starting Lighting Instrumentation
    BCI Group Size:27
    CA at 32 degrees F:1035
    CCA at 0 degrees F:840
    Freight Class:65
    Polarity:Left Positive
    Reserve Capacity:140
    Terminal TypeIN
    Volts:12

  5. #5
    Join Date
    Jan 2009
    Location
    Colorado Springs and Waitsburg WA
    Posts
    957

    Default

    Even though you have the trip fixed, are you sure the glow plugs are not burned out?
    John Liebermann
    2 9U's, 5J, IHC544, Ford860, (All working farm tractors)
    cojhl2@gmail.com

  6. #6
    Join Date
    Mar 2014
    Location
    TN
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    131

    Default

    all 4 plugs are working

  7. #7
    Join Date
    Nov 2006
    Location
    Bakersfield, California
    Posts
    2,548

    Default I'm no expert . . .

    but if all four glow plugs are working for sure, you have good batteries and the voltage you describe, it sure seems that you just need more heat to get that thing started when its cold. Two minutes at the temperatures you describe is way more time on the glow plugs than I'd expect. That time to me would be more expected at freezing or below.

    i'm afraid you may be seeing the effects of a worn engine. If the compression is low because of worn rings or valves not sealing well, it won't make anywhere near as much heat upon cranking. I don't remember you posting any information about blowby. If there is enough wear to cause this starting difficulty, I'd expect you to see a fair amount of blowby when it is running.

    If the blowby isn't bad, I'm confused. When you are cranking with it below 50 degrees and the fuel on, are you getting a lot of white smoke? I think in your other thread we pretty much ruled out a fuel supply problem.

    catdozer876's suggestion to crank it a bit with the fuel off would really help build some heat, even if internal wear is part of the problem.

    You mention that you have 24.8 volts at the starter, but you might want to measure volts at the glow plugs with them energized. Even though you cleaned all the connections, maybe you've got a voltage drop somewhere which means your glow plugs aren't making the heat they should.

    Pete.

  8. #8
    Join Date
    Nov 2006
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    Corralitos, Ca.
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    15,407

    Default

    Those batteries should be adequate if they are in good condition. I'd note your voltage reading. Batteries in good shape should produce 2.2v per cell = 26.4v for the two 12v batteries.

  9. #9
    Join Date
    Mar 2014
    Location
    TN
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    Default

    Quote Originally Posted by Garlic Pete View Post
    but if all four glow plugs are working for sure, you have good batteries and the voltage you describe, it sure seems that you just need more heat to get that thing started when its cold. Two minutes at the temperatures you describe is way more time on the glow plugs than I'd expect. That time to me would be more expected at freezing or below.

    i'm afraid you may be seeing the effects of a worn engine. If the compression is low because of worn rings or valves not sealing well, it won't make anywhere near as much heat upon cranking. I don't remember you posting any information about blowby. If there is enough wear to cause this starting difficulty, I'd expect you to see a fair amount of blowby when it is running.

    If the blowby isn't bad, I'm confused. When you are cranking with it below 50 degrees and the fuel on, are you getting a lot of white smoke? I think in your other thread we pretty much ruled out a fuel supply problem.

    catdozer876's suggestion to crank it a bit with the fuel off would really help build some heat, even if internal wear is part of the problem.

    You mention that you have 24.8 volts at the starter, but you might want to measure volts at the glow plugs with them energized. Even though you cleaned all the connections, maybe you've got a voltage drop somewhere which means your glow plugs aren't making the heat they should.

    Pete.
    the engine only has about 50hrs on it since i rebuilt it, but i didnt do any head work and am wondering if that is my problem,although they seemed to be sealing good when i inspected them when rebuilding the engine.

  10. #10
    Join Date
    Aug 2013
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    Rita Island north Queensland Australia
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    1,485

    Default

    Quote Originally Posted by Old Magnet View Post
    Those batteries should be adequate if they are in good condition. I'd note your voltage reading. Batteries in good shape should produce 2.2v per cell = 26.4v for the two 12v batteries.
    Old Magnet maybe onto something here as the cranking speed when the motor is cold is critical as it generates the heat and faster it cranks the more heat
    Even in my mild climate and our very mild winter motors can wind over at what appears normal speed but still not fire straight up and the problem is its just not making the speed to make the heat
    So maybe it is as simple as Old Magnets suggestion

    Paul

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