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is this rough start problem a result of my gp controller

Discussion in '1982-Present GM Diesel' started by colbystephens, Apr 5, 2006.

  1. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    ok, so i got my 6.2 up and running. on first start up after the engine has cooled for quite some time, it has a really rough idle while i wait for the engine to warm up. i misses intermittently, and is just rough. when i hit the glow plugs tho, it smoothes out until i let go of the button (manual set up). now, my gp controller doesn't click on and stay on and then click off, but rather when i depress the button it buzzes as if it is switching on and off extremely quickly. could it be that my gp's aren't getting hot enough b/c of this? also, for what it's worth, i didn't replace the copper washer/gasket deals on the injector lines when i reinstalled it - don't know if that's causing a loss of compression which would affect this (but keep in mind i only have this problem on cold start ups.) Thanks guys.
     
  2. 86dieselburb

    86dieselburb 1/2 ton status

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    Yeah it's normal for them to run rough untill they get warm. The GP controller should cycle the GP's on and off untill it gets warm enough to idle.
     
  3. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    how long should that take? instead of my manual button, i'm thinking of doing a switch so i don't have to hold the button for 5 minutes. it's crazy.
     
  4. imiceman44

    imiceman44 1 ton status

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    YOU DO NOT HOLD IT FOR 5 MINUTES.

    Basically after a few seconds you start it and then maybe every minute or so you give it a few seconds too until you feel it smoothed out.
    A better way I found is to start it and wait 30 seconds or a minute max then drive it just off idle for about a mile, that will warm it up faster and is safer for the engine.
    It's something I learned from engine rebuilders, they say that will get you the most mileage out of an engine because idling it until it warms up is too long with no load and it wears out the rings faster the more you idle it.
     
  5. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    yeah, 5 minutes seems pretty d@mn long - but i don't think it's good for me to drive it while it misses. interesting tho about the engine rebuilders. my buddy has an old tired 6.2 which he has a little harder time starting, but he doesn't have the rough idle problem. is there something i'm missing? what do you make of my wierd gp cycle?
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    If you have the Kennedy quick heats you should only be glowing them for about 5-6 seconds, then start it up. It really shouldn't run rough when cold, unless you have a dead GP somewhere. I have 6 working GP's (:crazy: ) and they're AC 60G's...so starting mine i let em glow for 10 seconds, give it a little throttle and fire it up. I get a bit of smoke and rough idle for about 20 seconds, but I raise the idle to about 1000 rpm to get it to smooth out a little quicker. It doesn't take long for the two cylinders that have dead GP's to start firing.

    If all the gp's work, and you have a rough idle it could be something else like a bad injector or two not misting the charge properly.

    When my IP and injectors needed rebuilding my 6.2 smoked like a train, ran rough and a few injectors had leaks...

    Rene
     
  7. colbystephens

    colbystephens 1 ton status GMOTM Winner

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    i'm trying to be real gentle on the engine right now - it's not abusive in any way to idle it up while cold to get rid of the rough idle? i tried that today and it was helpful. funny too, b/c i smoked up real bad initially and these two old women walked by and asked, "can you turn off your truck??" i said "no." and they got all pissed off. :D how funny is that? who asks that question? they chose to stand there in the smoke for 10 seconds longer than the 2 seconds they needed to walk thru it. wierd.
     
  8. maynardogle

    maynardogle 1/2 ton status

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    I wouldn't worry about the rough idel for first ten minutes until I had run a couple tanks fuel through the whole system If this problem persists after that, suspect the injectors for those cylinders.
     
  9. diesel4me

    diesel4me 1 ton status Premium Member

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    Mine does it too...

    My 6.2 has had a "skip" at idle after starting cold,since I got it too..it sounds kind of like a gas motor thats over choked and loading up,or misfiring....goes away if you idle it up faster manually...

    I blamed my one "dead" glow plug I couldn't get out,and the wire terminal snapped off,so that cylinder has NO heat until it runs awhile..it could have dirty or bad injectors,ect, too..but it runs fine once its warm,just an ocaisonal "misfire" once in a while..

    I pulled the plug off the glow plug controller on my truck when I put the manual glow plug switch in,so there would be no possibility of them coming on by themselves..my fast idle cold advance switch probably does not work either,I've never heard it have a "fast idle" when cold..its always started up for me though,even in extreme cold with no block heater..

    I added an electric fuel pump in addition to the stock lift pump,to help prime the fuel system faster when changing fuel filters-
    (or if I ever run out of diesel:doah: )..it seems to idle smoother and a hair faster with the electric pump turned on for some reason..

    I just start my truck by holding the button for the glow plugs on for the same amount of time it takes for my seat belt buzzer to shut off (about 8-10 seconds)...it usually fires right up,and I then give it some throttle,until its running about 1200-1500 rpms,and hold it there for a minute or two..then drive off right away..a lot of diesel mechanics have always told me this..

    "There are 2 things you dont do to a diesel...never let it idle cold,or race it up high when its cold."...so I try to follow their advice!..

    I always have fears of my crank snapping in two when I start it in 20 degree weather,and I didn't have the block heater plugged in..GOD that thing sounds horrible under those conditions!..sounds like all 8 pistons are gonna jump right out!!.:eek1:
     

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