How do you prime a Carrier ComfortPro APU

Discussion in 'Trucks [ Eighteen Wheelers ]' started by 88 Alpha, Sep 1, 2015.

  1. 88 Alpha

    88 Alpha Trucker Forum STAFF Staff Member

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    The title pretty much says it all. The APU lost its prime this morning and I'm not sure how to re-prime the system in order to get it running again.

    My guess is there is a bleeder screw somewhere near the fuel pump (figured out where that was by following the lines from the fuel filter back to the top of the engine) that needs to be loosened or removed and probably some kind of manual pump to push the fuel, but I'm not sure where that is.

    Any ideas?
     
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  3. KeithT1967

    KeithT1967 Road Train Member

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    I just held the start button down till it primed. Within reason of course. Maybe 20 seconds, stop for a minute, another 20 seconds. Etc Usually started on the 2nd or 3rd attempt. Most ever might have been 4
     
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  4. 88 Alpha

    88 Alpha Trucker Forum STAFF Staff Member

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    Sounds like that is some sort of auto-prime system. I let it try to start and it tries to crank for 5 seconds, then it stops and rests for a sec or 2 then repeats the "trying to crank" cycle and does that 5 times. Then the screen says it has reached its cranking limit.

    I will try your suggestion of holding the start button and report back.

    Thanks.

    edited to add: I tried holding down the start button on the display and it tries to crank for about 17 seconds then it stops (even with me holding the button). I remove my finger from the button and let it rest for a minute or so and tried it 4 more times, to no avail.

    It still acts like it is not getting fuel to the engine. Got to get an early start on tomorrow so I will try any other ideas when I'm done for the day tomorrow evening.
     
    Last edited: Sep 1, 2015
    Reason for edit: tried what Keith suggested.
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  5. dclerici1

    dclerici1 Medium Load Member

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    why did it lose prime in the first place? Re-trace your steps. Do you need to fill fuel filter and re-install?
     
  6. skateboardman

    skateboardman Road Train Member

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    Many apu have electric fuel pump, they go out, nothing happens.
     
  7. 88 Alpha

    88 Alpha Trucker Forum STAFF Staff Member

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    In short, I ran the APU fuel filter out of fuel. That happens when you know you are cutting it close on fuel and you loose power to the truck. Then, as you are sitting on the shoulder of the road, you attempt to crank the APU. If the APU doesn't crank, you ran the truck out of fuel. If the APU cranks, the problem is elsewhere. The APU ran for about a minute, then it too, lost power. At that point, I knew, beyond a shadow of a doubt, what I had done.

    I called one of our mechanics this afternoon to get his advice. He said the way the company has these installed, it is very difficult for a driver to re-prime one. He said you have to force air into the fuel tank to force the fuel from the tank to the APU pump. Told me the best thing to do is take it by a T/A and let them do it unless I were going by our shop so he could do it.
     
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  8. skateboardman

    skateboardman Road Train Member

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    So you ran the truck out of fuel and then trued to run the apu. Okay dokey
     
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  9. 88 Alpha

    88 Alpha Trucker Forum STAFF Staff Member

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    Yep. I prefer to call it, "verifying the truck is out of fuel". Certainly not the brightest thing(s) I have done.

    Turns out, it was not that difficult to re-prime. Open the bleeder screw, take the air hose you hook to your gladhand air lines to air up your tires, put a blower nozzle on it instead of the valve stem air chuck, put the air nozzle just inside of the fuel tank, seal off the opening of the fuel tank with a shop rag, begin applying air pressure, slowly, to the fuel tank. The pressure will force fuel to and thru the APU fuel filter to the APU fuel pump and out of the bleeder hole. When you see fuel coming from the bleeder, replace (or tighten) the bleeder screw and begin to crank the APU. It may take 2 or 3 starts, but it will soon fire up and you are back in business.

    Remind me not to try to drive 200 miles after the low fuel light comes on. 176 miles is as far as it will go.
     
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  10. KeithT1967

    KeithT1967 Road Train Member

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    Glad you got it running. Dont run out of fuel lol
     
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  11. 88 Alpha

    88 Alpha Trucker Forum STAFF Staff Member

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    Thanks @KeithT1967

    I've looked in the mirror several times over this past almost week and given that guy a lot of grief for doing that. Don't think for a minute that my fellow driving friends haven't missed an opportunity to give me some grief about it, either. I got it the old fashioned way...I earned every bit of the razzing they give me.
     
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