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testing injector pump ?? won't start??

Discussion in '1982-Present GM Diesel' started by Big Truck, Sep 13, 2005.

  1. Big Truck

    Big Truck 1/2 ton status

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    Long time listener, first time caller. I got an 86 2wd, 3/4, 6.2 diesel for a good price (non running), it died on the previous owner while she was driving and has been sitting for about 8 months. It has a good amount of fuel coming out of the outlet of the filter while cranking but maybe a couple of drops coming out of the line that goes to the injector while cranking. The pink wire to the injector pump is getting power and enough to keep the solenoid open during cranking. With the top off the injector pump it is really clean in there and full of fuel. No smoke comes from the exhaust while cranking. Is there any way to test the injector pump with it in the vehicle, is there anything else I should check. Any assistance would be appreciated. Thanks.
     
  2. dallassnowman

    dallassnowman 1/2 ton status

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    weird when purging fuel from changing fuel pump I get smoke out of pipes just from cranking it.
     
  3. Big Truck

    Big Truck 1/2 ton status

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    It has dual exhaust and I feel a back pressure coming out of each pipe while cranking. I've also tried using wd-40 and nothing not even a hint of starting. looking in the top of the injector pump with the engine spinning, cover off it spins internally, should there be alot of pressure at the injector on start up.
     
  4. 6.2 man

    6.2 man 1/2 ton status Premium Member

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    Did you crack the injecter lines while cranking to see if you have fuel ? Also sounds like maybe the glow plugs aren't working .You won't see smoke unless they come on . To check the pugs unpug the connecter put the clip on the positve side of the battery and touch the spade of the glow pug and it should light up.
     
  5. Big Truck

    Big Truck 1/2 ton status

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    I unpluged the glow plug wires and one of them had the isulation melted away and on the exhaust I'll fix that in the am. I cranked it with injector lines cracked and it only seemed like a small amount of fuel was coming out or leaking. Would it also be a good idea to plug in the block heater when starting or prior. Also does anyone know the best way to check if your return lines are clear or plugged. thanks.
     
  6. 6.2 man

    6.2 man 1/2 ton status Premium Member

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    Did you check the glow plug itself ? Return lines really only work when it's running
     
  7. 6.2 man

    6.2 man 1/2 ton status Premium Member

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    I know one time I started mine up shut it off and it wouldn't start again . I checked the glow plugs and all 8 were dead . I had been having trouble starting it and figured I must have only had a couple that worked
     
  8. jerrod710

    jerrod710 Newbie

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    6.2 not starting

    those old chevy 6.2's and 6.5's are bad about leaking fuel lines such as the ones that go from the pump to the injector. My advice to the return lines is don't plan on removing those old return lines that go from injector to injector unless you plan to replace them. You can buy one of those kits for about 20 dollars, but make sure you cut the new return lines to almost the exact size as the one you took off and I mean as close as you possibly can to the same size don't just wing it. Those old chevy diesels as well as the old ford diesels they do not have alot of fuel pressure. The mechanical fuel pump (not injector pump) it is also called a lift pump only pumps out about 2 to 3 psi of pressure so there isn't going to be alot of fuel coming out when you crack an injector. Check for fuel leaks anywhere on the injection pump. It could be a number of different things to why it won't start which obviously probably has to do with why it died to begin with. The old 6.2 really isn't worth keeping in there or putting a bunch of money into. It would be alot cheaper to just drop a 2,000 dollar crate 350 in it in the long run. I have had 2 K5's with the 6.2 and I just sold the recent one I had and it had 210,000 miles on it and still ran decent, though I turned the fuel at the pump up for a little extra horsepower and had some performance injectors in it. Believe me, if you get that 6.2 to run where it is dependable (dependable isn't a word to describe the 6.2 by the way) you would have had enough money spent to drop that crate 350 in it. But it could be a number of things that caused the problem you are having. Could go as far as it possibly has a cylinder down in it. Means engine overhaul. And if that is the case with all the machine work and parts for the overhaul doing it yourself and doing everything the right way and not being cheap about it you will spend a bare minimum of three grand. Well thats my opinion, take it for what it's worth to ya.
     
  9. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Hmmm, nice contradiction. The majority of us here would beg to differ with your opinion though. Aside from general maintenance items the 6.2 is as reliable as a small block but without the tuning headaches.

    Rene
     
  10. 6.2 man

    6.2 man 1/2 ton status Premium Member

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    Couldn't have said it better !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! :D Thank you !!!!!
     
  11. jarheadk5

    jarheadk5 1/2 ton status

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    So, spending (maybe) a couple hundred on some fuel lines, glowplugs, and wire... is expensive compared to dropping $2k or more on a crate 350 that is less fuel-efficient and less durable? Whatever...



    Anyhoo, back to the issue at hand:
    Have you checked your glowplugs for operation? You may find they're not working...
    Have you bled the fuel system, especially after having the IP apart?
    Have you replaced the fuel filter recently? If you can't remember, I'd highly recommend doing it (but BEFORE you bleed the fuel system!).
    Are your batteries fully charged, with good cables and clean terminal ends?
     
  12. jerrod710

    jerrod710 Newbie

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    Obviously you didn't read my full reply. I said it could cost a minimum of a couple grand maybe three. I never said it would. It was just a possibility. And if you read his reply I remember him saying he used some sort of starting aid not starting fluid but something inferior, bad glowplugs or not it would have fired up with right starting aid such as starting fluid. Come on and understand what you are reading before you reply with a remark like that.
     
  13. Big Truck

    Big Truck 1/2 ton status

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    Yep the batteries have been charged about three times, had the glow plugs out twice to prime the fuel system. the glowplugs still get red when hooked up to the battery.
     
  14. Big Truck

    Big Truck 1/2 ton status

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    So when I am cranking with an injector line open I should have the pressure of the lift pump at the injector. ?
     
  15. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I've never seen one of those lines leak. More common is for the injector itself to leak usually indicating it's time to have them rebuilt (which is cheap BTW)



    lift pump doesn't generate a lot of psi because it's only a supply for the IP. The IP can generate 1500 psi, which it needs to do to 'crack' the injector so it sprays fuel. Loosening the injector line at the injector removes the restriction the injector provides, so you only get to see the volume which would be a small drip. It's a high pressure/low volume deal as any diesel would be.


    A lot cheaper in what respect? Even if he needs all 8 injectors and the IP rebuilt he is looking at about $400 max. The sbc you'd have him drop in will cost him more than the purchase price to install and will pull down an astonishing 10 mpg if he is lucky. So, a crate engine would cost more than repairing the 6.2 and because it's the gift that keeps on raping your wallet it'll cost him double for fuel as long as he has it.

    So, could you please define what your understanding of cheaper is?


    Unless the 6.2 needs to be rebuilt this is just untrue.

    In this regard the 6.2 is more expensive initially, but it will outlast a small block by 50% commonly, as well as help pay for itself in fuel saved.

    Rene
     
  16. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    No, the lift pump is just a fuel supply for the injection pump. The injection pump sends a small volume/high pressure spike to each injector. This 'cracks' the injector and the injector then sprays this small volume of fuel in a very fine mist into each cylinder.

    When you crack the line all you'll see is the volume of fuel dripping out, and the volume is small...hence dripping.

    I'd probably get a compression check done on that motor. Unless your cranking speed is too low it should run according to what you've said so far.

    When you turn the key how long do the glow plugs cycle? I would consider manual glow plugs personally. They may work, but if they aren't cycling long enough or have cooled too much while you're cranking you'll have trouble starting it.

    There is a small blue wire going from the Glow plug relay on the fender to the glow plug controller at the back of the motor. I cut that blue wire about 6" from the controller on the motor, and re-routed it into the cab under the dash. A simple push button switch that grounds the blue wire is all it takes. As long as I push the button my glow plugs will stay on. So, in colder temps I keep them on a bit longer...and if the truck is even somewhat warm I don't use them at all.

    Cranking speed is crucial. You may have fully charged batts but a somewhat poor starter...

    Poor cranking speed made my 6.2 very hard to start when I first got it swapped in. I needed the glow plugs even when the truck was warm. I eventually replaced the starter with a Bosch reman'd 28MT gear reduction starter and was awed at the difference. Cold starting was way easier and when warm it spun fast enough to start without glow plugs in one or two turns.

    The air inside the cylinders must be compressed quickly enough to generate a lot of heat. The faster the crank speed the hotter the air being compressed gets...the easier it'll start.

    Any diesel can give you fits trying to get it running, but it's worth it. Once you have it fixed and running it'll be a lot easier to maintain it. They're actually quite easy to work on once you get your head wrapped around them.

    Rene
     

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