Air bubbles in Davco 382 - hard starting series 60

Discussion in 'Trucks [ Eighteen Wheelers ]' started by allan5oh, Nov 2, 2013.

  1. allan5oh

    allan5oh Road Train Member

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    Been having a hard starting issue for a few months with my detroit series 60. I've done a lot of work to it including a rebuild, bullgear, new head, new injectors(which have been pop and leak tested), all new fuel lines, Rebel 127 programming the ECM, new TRS/SRS about a year ago, new return line check valve. The 382 has a new bowl, new lower plate, new fittings, new o-rings, new check valve, everything is brand spanking new except the body. I have 3 clear fuel lines, one on the inlet, one on the outlet, and one on the return (the return fuel heats the incoming fuel controlled by a thermostat). The inlet is crystal clear, the other two are filled with air, lots of small bubbles, but nothing big. According to Davco it is not vapor because the return has bubbles as well, if the return was clear it would be vapor. You can also see a lot of bubbles creeping up the davco clear bowl.

    The starting issue is white smoke (it is raw diesel) when the engine is cold. Sometimes it will do it hot, but it's quite random hot. If it sits for 6-8 hours it will start very hard. It seems as though if I run the espar engine heater it really helps. While cranking it is sputtering, and if I feather the throttle back and forth a bit it really helps. After firing, rev it to 1500 and hit the high idle. If I let it drop it will start missing again.

    It did this before I did the bullgear/rebuild. It was the reason I did the bullgear as I've heard it's a common symptom and I'm paranoid about this stuff. If I pull the fuses it will NOT smoke, so to me that eliminates coolant leaks and the injectors at least partially (no leakdown).

    Tomorrow I'm going to do the TRS/SRS again and I bought a newer style davco just to see what happens. The only thing not changed in the fuel system is the pickup tubes, but with the inlet hose being completely clear I don't see an issue there. If the problem persists I'm going to have to look elsewhere and consider the amount of air in the fuel as "normal" even though it just doesn't feel right.

    Also to be clear the Davco is the only fuel filter in the system so I have to run 7 micron filters. The engine itself runs great, good power(36 psi at 1600 rpm) and fuel mileage (7.5 lately pulling heavy). Could be smoother, but I'm used to a volvo. Maybe if there was no air it would be smoother, also one of the injector codes has to be changed from 28 to 26. Oil samples are very very clean, and I last did an oil change about 19,000 miles ago and it's just now getting close to the fill mark.
     
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  3. little cat 500

    little cat 500 Road Train Member

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    i have a 60 series with a very simular problem to and i do have a davco but i have a two filter set up ive changed every thing from the tanks forward runs better as the motor gets hotter be interesting to see what you find maybe i have the same problem mine a 2005 14liter
     
  4. Heavyd

    Heavyd Road Train Member

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    Run a test line from your Davco inlet straight into the fuel tank and see of the bubbles go away. Then you will know it is pick up tubes or something like that.
     
  5. DL550CAT

    DL550CAT Road Train Member

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    To me it sounds like your davco is letting air in since you have clean fuel inbound and bubles outbound. Could be one of your new o rings is twisted or split. You say your replacing it? My guess that fixes your problem/s.
     
  6. allan5oh

    allan5oh Road Train Member

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    The inlet line is clear and shows no bubbles.

    The o-rings have been replaced multiple times. Didn't have a chance to put the new unit on. Should be able to get to it later today.
     
  7. boneebone

    boneebone Road Train Member

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    Does the Davco you have on the lower plate have a threaded plug that looks like a big thin hex nut, if you do there's a O-Ring under there that will suck air if it's bad?
     
  8. Gear head

    Gear head Medium Load Member

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    Put a small amount of air in the fuel system with the vent hose and a air blower. Suction side never sees pressure if there is a leak in suction side the pressure will find it. Be carefull doing this do not over do it and to get rid of pressure you can open drain on davco. I have made pressure fuel caps by drilling different fuel caps and putting in tire valve stem.
     
  9. allan5oh

    allan5oh Road Train Member

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    Yes it's tight. I also tried tightening/loosening it while the truck was running and it made no difference.

    Suction side is fine, it seems as though the davco itself makes air. Literally everything in the fuel system has been changed and is tight. Except for the pickup tubes, but the clear line on the inlet of the davco indicates zero bubbles.

    I put the new unit on and there didn't seem to be a significant change in the amount of air. Everything is tight. In the Davco literature it says a small amount of air is fine. There's very very little at idle (600 rpm) maybe 2-3 very small bubbles per second. Rev it up to 1500 and there's quite a lot. I should make a video.

    I also changed the SRS/TRS sensors. We'll see if that helps in the morning. If it starts like crap again I'll take it in for a idle cutout test. After that I think it's time to call up Rebel127 and get him to send me a test ECM.
     
  10. allan5oh

    allan5oh Road Train Member

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    Still starts like crap. Moving on to ECM. Also started doing a valve set, although I just did one 20,000 miles ago. Mostly looking for anything out of the ordinary, nothing should need adjusting.
     
  11. Gear head

    Gear head Medium Load Member

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    Put sight glass in suction line upstream of the davco see if you see any bubbles. Return line has lots of turbulence and will fool you.
     
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