Hard Start after Everything...

Discussion in '6.9L IH & 7.3L IDI Diesels' started by Ratat98, Sep 16, 2018.

  1. Ratat98

    Ratat98 Registered User

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    Hello all.
    I've replaced return lines, all the glow plugs, pretty much anything fuel related from filter housing back to tank, including lift pump, and it still takes at least two 5-10 second crank tries to get started...it acts like it's still losing prime somewhere but like I said, I've replaced it all. It will start right up after it's been running for a while though. Is there a check valve or something that I've missed?? Is it time to look for a new IP??
    Thanks in advance!
     
  2. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    What rpms are you seeing while cranking?
     
  3. Ratat98

    Ratat98 Registered User

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    I havent noticed. Seems like its cranking normally but I didn't even think of that. That could be it! It does have a worn out cable
     
  4. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    I would replace the cables then, these engines need a lot of juice to spin over, and they need a lot of cranking rpms to build pressure to fire the injectors.
     
  5. franklin2

    franklin2 Full Access Member

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    It's not losing prime. If it is losing prime, it will start right up the first round of cranking, and then stop and not fire anymore until you have done a lot of cranking. This is because when you lose prime, there is still fuel in the steel lines between the injection pump and the injectors.

    If you have a heat problem in the combustion chamber, while you are cranking and cranking, you should see a lot of white stinky smoke coming out of the exhaust pipe. That is unburnt fuel.

    The previous poster is correct, cranking speed is very important to build heat in the chamber. I saw this first hand when I swapped a starter out. The starter I was using was fine, except once in awhile the bendix would make a grinding sound and it would not turn the engine over. I put another used starter I had laying around in, and while it worked fine, the cranking speed for this other starter was slower than the previous, and it would not fire at all. Something was wrong with the motor part of the starter. I ended up taking the drive part of that starter, and the old motor part of my old starter and put them together, and it starts great now. That was a lesson for me, the starter needs to whip these engines over or they are not going to start.
     
  6. Ratat98

    Ratat98 Registered User

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    Replaced the positive cable after searching for a place that had one and it starts better than it ever has since I've had it! Thanks guys!
     
    chillman88 and Thewespaul like this.
  7. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Glad that fixed it for you, I would replace the grounds as well when you get a chance, they deteriorate at the same rate as the positives do, and are arguably more important
     
  8. Ratat98

    Ratat98 Registered User

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    Ok, so I thought that I had it fixed. I was wrong. With the new cable it turns over A LOT better, but it still takes a bit to start. I'm thinking maybe glow plug controller?
     
  9. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    What’s ambient temperature when having issues starting?
     
  10. Ratat98

    Ratat98 Registered User

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    It's about 90 degrees out today and still not working good.
    On another note it does puff out grey smoke when it does finally kick over
     
  11. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    You dont need glow plugs at that temperature, something I have found to help these trucks start faster is to install a check valve at the soft hose that goes from the hardline on the frame to the lift pump on the side of the block. This prevents any drain back and holds a bit of pressure in the fuel system for a faster start up. Do you happen to have a small fuel leak coming from the connector on top of the fuel filter housing?
     
  12. Ratat98

    Ratat98 Registered User

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    Yeah I figured that about the plugs but I know they still help a little. I'll look for fuel leaks. I just went through the housing and replaced o-rings and all that not too long ago so knowing my luck I might have something sleeping still.
     
  13. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    Let us know what you find, the fuel heater on the filter housing likes to leak and are a common cause for your issue.
     
  14. Ratat98

    Ratat98 Registered User

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    Will do! I've already fixed the fuel heater o-ring once, but it could be leaking again. Any other ideas if I dont find a leak here?
     
  15. Thewespaul

    Thewespaul Supporting Vendor Supporting Member

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    There is an o ring on the back of the pump for the inlet fitting I would check as well, you will see a slow drip while idling if this is your issue. Something else you could try is installing a clear hose between the filter and pump to see if you are getting air in the lines.
     

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