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Carrier Comfort Pro APU cranks, doesn't start

Discussion in 'Truck Talk' started by bugman, Apr 2, 2011.

  1. bugman

    bugman New Recruit

    After adding oil, my APU cranks but wont start. I drained the fuel filter,fuel was clean, hardly a trace of moisture.

    Truck is 06, not sure of year of APU, was in truck when I bought it. 6500 hours on APU and I was about to have PM done on it and truck which I will do anyway. It ran fine night before. I don't check oil on it near often enough. Was fueling, checked oil and noticed none on dipstick. I added about 2 quarts which was an over kill.

    Any ideas? I am hoping there was some sort of re-set that got tripped when oil got low even though I think it was running fine when I started up main engine that morning.

    Thanks
    Ron Johnson
     
  2. davekc

    davekc Senior Moderator Staff Member

    Probably sounds stupid, but where did the oil go that was in it?
    Might want to identify that problem before doing anything else.
     
  3. bugman

    bugman New Recruit

    Thanks for the reply. I never leaks a drop. I suspect this is just regular use for an engine with 6500 miles.
     
  4. davekc

    davekc Senior Moderator Staff Member

    Hard to tell but worth checking. If no codes are on the display, then it could be sensor, fuel switch, fuel pump, or wires/fuses at the panel. After that, I would take it to a carrier dealer if you aren't familiar with working on them and covered the items on the troubleshooting in the manual.
    Good luck.
     
  5. bugman

    bugman New Recruit

    Yes, that is my thought. I am just hoping there is a reset that needs to be tripped and that someone has had this same problem. I was a certified mechanic till my son was born in 78. I know my way around an engine, I just know nothing about this APU and don't have a manual. But I will be ordering one
     
  6. jansiemoo

    jansiemoo New Recruit

    Seperate from your oil problem, we had the same cranking-no start. Had BOTH fuel filters replaced, worked for 20mins, died, primed again, died again...long story...take up tubes were too short/placed wrong. Also the thing needed alot of priming.
     
  7. Dynamite 1

    Dynamite 1 Moderator Staff Member

    on a rigmaster, if you over fill a bunch or fill to fast the oil can over run and get in the cylinders and it will crank but not run. hope thats not the case. not a killer but a pain from what i have been told.
     
  8. LDB

    LDB Seasoned Expediter

    Yes, Rigmaster is bad about having to be filled slowly or it won't start. Eventually it all settles in and will run again but not until then. BTDT at Speedco once. Good luck.
     
  9. davekc

    davekc Senior Moderator Staff Member

    Just a FYI. I think you can go to Carrier's site and download the manual for free.
     
  10. highway star

    highway star Seasoned Expediter

    Actually, it won't crank. The oil is too thick and won't compress enough to complete the stroke. Well, that's what happened to mine, even after telling the professional oil change technician to fill it slowly.
     
  11. layoutshooter

    layoutshooter New Recruit

    My Pro Heat has hours on it similar to yours. It too uses oil. I have to keep a close eye on it. It is always a good idea to check it often anyway. I have yet to have your problem. I have had a dipstick break once.
     
  12. bugman

    bugman New Recruit

    Thanks for the reply. So you are saying the pickup tubes in the fuel tank were too short? But I still had plenty of fuel to run truck engine. Also, you mentioned priming. Is there a manual prime pump on this APU?
     
  13. highway star

    highway star Seasoned Expediter

    Your APU has its own pick up tubes. It's common in RVs to have the tubes short enough to not run the RV out of fuel, usually leaving about a 1/4 tank. I don't know if this would be the case with your truck.
     
  14. purgoose10

    purgoose10 Active Expediter

    Since it's that old and you don't check it much I would also check the water lines to see if they are collapsed. If they run hot the sensor will shut it down and won't let it crank again. When they install those things they take the shortest route with hoses and wiring. If they are laying on the frame rail or tied up they could be collapsed.
     
  15. bugman

    bugman New Recruit

    Thanks purgoose, That sounds logical. I am in line now for the PM on truck and APU. My only thought against what you are saying is that the APU is staying just as hot as if it were running, so there is enough coolant circulating for it to absorb lots of engine heat from main engine
     
  16. LDB

    LDB Seasoned Expediter

    My Onan is set up to only run with over 1/4 tank of gas in the van so that in theory I can drive somewhere to fill up rather than wait on road service. I wouldn't want it to draw down any farther.
     
  17. purgoose10

    purgoose10 Active Expediter

    Remember they have a thermostat also so if it's hot the celluloid might have shut it down. Have you checked to see if it's got fuel pressure?? If your not pumping fuel, well self explanatory. Just have to go thru one at a time and check it out.

    One other thing. Make sure the fan for the unit is working. Old unit might have a short.
     
  18. jansiemoo

    jansiemoo New Recruit

    Oh, now you're asking technical Qs? Lol ;) um, there was an accordian looking thingie that you squished together to prime. The second techs that looked at it were sure it was air in the system...I just asked the hubby, he says it was a combo of air in the system and a bad fuel pump. But the air was partly due to running it when the fuel was below the level of the pick up tubes.
     
  19. geo

    geo Active Expediter

    give bill more a call at tsi he's works wonders on gen set
    he's off of i76 north jackson oh ex 57 i think
    he also western star dealer to
     
  20. BillChaffey

    BillChaffey Active Expediter

    Since this was eight days ago it may be fixed. One if not the first thing, you need to watch the exhaust and see if anything is coming out. It can crank forever with no fuel going into the cylinders.
     

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