Dismiss Notice

Welcome To CK5!

Registering is free and easy! Hope to see you on the forums soon.

Score a FREE t-shirt and membership sticker when you sign up for a Premium Membership and choose the recurring plan.

Run on...

Discussion in '1982-Present GM Diesel' started by BigBluOx, May 5, 2003.

  1. BigBluOx

    BigBluOx 1/2 ton status

    Joined:
    Aug 30, 2001
    Posts:
    301
    Likes Received:
    0
    Location:
    Auburn, WA, USA
    I have an issue with run on in my 'Burb. It seems that occasionally, when I shut the key off, the truck keeps running for a second or two before shutting down (more-so than it used to). Anyone have any ideas where I should look?

    Thanks

    Jon /forums/images/graemlins/burb.gif
     
  2. NewK5Guy

    NewK5Guy 1/2 ton status

    Joined:
    Mar 2, 2001
    Posts:
    556
    Likes Received:
    0
    Location:
    Alexandria, VA
    Usually means the diodes in the alternater are bad. The diesel engine runs by shear physics alone. There's no electrical system that keeps it running, just pure mechanical goodness. A +12v signal to a valve keeps the valve open allowing fuel to enter the pump and be used. That's the only thing keeping the ol'6.2 alive. Pull that +12v, and the motor dies from lack of fuel. When diodes in the alt burn out or go bad, alternater feedback usually filtered by the diodes runs rampant thorugh the electrical system and backfeeds to the fuel solonoid(fat pink wire on injection pump) and can supply it with just enough voltage to hold the valve open even when the key is off. That's where I'd check first.
     
  3. Oblin Goblin

    Oblin Goblin 1/2 ton status

    Joined:
    Apr 30, 2000
    Posts:
    205
    Likes Received:
    0
    Location:
    Davis, CA
    Or the shut off solenoid is just sticking. My truck used to run on quite a bit, sometimes I would have to kill it by holding the brake and letting out the clutch. It would stop running on if I ran stanadyne in the fuel, but start running on again if I forgot the stanadyne when I filled up. I ran a quart of oil through the fuel system a while ago, and it doesn't seem to run on anymore, even if I forget to add stanadyne to the fuel when I fill up.
    I would just try pouring a quart of oil in the tank the next time you fill up and see if that works.
     
  4. BigBluOx

    BigBluOx 1/2 ton status

    Joined:
    Aug 30, 2001
    Posts:
    301
    Likes Received:
    0
    Location:
    Auburn, WA, USA
    [ QUOTE ]
    Usually means the diodes in the alternater are bad. When diodes in the alt burn out or go bad, alternater feedback usually filtered by the diodes runs rampant thorugh the electrical system and backfeeds to the fuel solonoid(fat pink wire on injection pump) and can supply it with just enough voltage to hold the valve open even when the key is off. That's where I'd check first.

    [/ QUOTE ]

    What's the best (or in my case, the cheapest) way to determine if the diodes are bad? Can this be determined by a VOM on either the AC o DC setting?

    Thanks,
    Jon /forums/images/graemlins/burb.gif
     
  5. BigBluOx

    BigBluOx 1/2 ton status

    Joined:
    Aug 30, 2001
    Posts:
    301
    Likes Received:
    0
    Location:
    Auburn, WA, USA
    [ QUOTE ]
    Or the shut off solenoid is just sticking.

    [/ QUOTE ]

    If this is the case, can this be opened and cleaned by me (I'm pretty mechanical and electrical savvy), or should this be done in a shop under controlled conditions (I don't want to hose-up my injection pump - too d*mn expensive to replace).

    Thanks,
    Jon /forums/images/graemlins/burb.gif
     
  6. Tybee

    Tybee 1/2 ton status

    Joined:
    Mar 25, 2001
    Posts:
    1,565
    Likes Received:
    0
    Location:
    Centennial, CO
    It sits on top of the pump two wires going to it.
     
  7. BigBluOx

    BigBluOx 1/2 ton status

    Joined:
    Aug 30, 2001
    Posts:
    301
    Likes Received:
    0
    Location:
    Auburn, WA, USA
    [ QUOTE ]
    It sits on top of the pump two wires going to it.

    [/ QUOTE ]

    Yep, knew that, I just haven't ever taken it apart. /forums/images/graemlins/grin.gif But thanks for the info. I suppose I could just pull the pink wire to see if it's sticking and causing run-on... If it isn't, I can concentrate on the alt. diodes...

    Jon /forums/images/graemlins/burb.gif
     
  8. arveetek

    arveetek 1/2 ton status

    Joined:
    Mar 1, 2002
    Posts:
    722
    Likes Received:
    0
    Location:
    Granby, MIssouri, USA
    Yep, you've got it. Next time it keeps running, just pop the hood and pull the pink wire. If it shuts down immediately, then you have an electrical problem keeping power to the pink wire. If it keeps running, then it's the fuel cut-off solenoid itself.

    Casey
     

Share This Page