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Trying to get the M1008 Running...Update

Discussion in '1982-Present GM Diesel' started by jolane, Oct 29, 2005.

  1. jolane

    jolane 1/2 ton status

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    So today I spent most of the day working on the recently acquired M1008. I replaced the manifold gasket and the fuel filter. I also checked the return lines. Finally, I pulled the glow plugs out for easier spinning of the engine.

    I bled the air from the filter, and cracked all the injector lines. I also jumped the fuel cutoff solenoid and the HPCA to 12V. I ended up leaving the return line off at first, just to check that it was clear and the pump was filling with fuel.

    I then cranked the engine for 15 seconds, then let it rest a few minutes. This was repeated several times (until he batteries were dead). In reality, it was probably at least 12 times, maybe 15. It turns easily with the glowplugs out.

    The Results:
    Fuel bubbles (more like drips I guess) from the return line fitting. I assume this means the transfer pump is working. I finally saw slight moisture from about 3 of the injector lines. They were the injectors lines at the bottom of the pump. This was it. They are not spraying fuel, nor really dripping while cranking. I just notice wetness on the fitting end. Is this normal, or should they we squirting?

    This is really annoying. Maybe something is wrong with the pump. I just don't know what I am looking for when bleeding the injector lines. Also, while I am cranking, I assume that I should be stepping on the throttle pedal in the cab to open the metering valve? I did pull the top cover off, and the metering valve turns freely, and the governor linkage is moving freely. Everything seems to look good in there.

    Finally, I also received my diesel compression tester yesterday (Harbor Freight model, $150). First, the instructions say to use adapter #12 for the GM 6.2L. Wrong. According to my case, and the pictures, it is adapter #14. I tried it on two different cylinders, and am disappointed to say that it shows 0 psi (even though I cannot hold my thumb over the hole as it is blown off with compression). I tried switching gauges (I bought a separate 400 psi gauge from the welding store), and this did not help. I am not sure what is going on with this thing. There were no noticable leaks in the plumbing. I would expect it to read AT LEAST 100 psi from gut feeling. Anyone else have any problems with this POS test gauge?

    Thanks for any help,
    Joshua
     
  2. 6.2 man

    6.2 man 1/2 ton status Premium Member

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    You know I have noticed no one has mentioned is do you have a trace of smoke coming from the tailpipes ? If you do then you are getting fuel to the cylinders . If you are not then the injecters are not getting fuel .
     
  3. jarheadk5

    jarheadk5 1/2 ton status

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    Re: compression tester - silly question, but is the adapter fitting or hose to the gauge blocked? There's obviously compression if your thumb's getting popped off the head... it's just not making it to the gauge.
     
  4. 6.2 man

    6.2 man 1/2 ton status Premium Member

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    Diesels have very high compresion and need a tester . I think you may have compression just not enough ? Check your exhaust while turning it over ?
     
  5. jolane

    jolane 1/2 ton status

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    Thanks for the ideas.
    I do not have any hint of smoke from the exhaust. In fact, with the injector lines off, they did not drip one drop (a very few only seemed to get wet).

    As for the tester, I did try taking the gauge off the line, so that I could check for obstructions in the line/adapter. This worked fine, and air was coming out of the line with a force that I could not hold my thumb over either. I am sort of thinking that the problem is in the check valve. If the check valve does not work, then the air going into the gauge is being sucked back into the engine when the piston goes down. Just a guess though. The GM service manual (received it tonight) says to cover the intake before checking the compression. This does not make sense to me though. Either way, I think I am going to return the set and just make my own gauge. I really like the glow plug idea.

    What am I looking for at the exhaust when turning the engine over?

    Thanks Again,
    Joshua
     
  6. diesel4me

    diesel4me 1 ton status Premium Member

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    smoke...

    You should see smoke coming out of the exhaust if its getting fuel after cranking it awhile..not a lot,a fine mist..

    Whe I first go my truck,the dual tanks fuel lines were a jerry rigged plumbers nightmare,and Ihad some dry rotted rubber lines,that didn't leak,but I suspected they might be letting air IN,rather than sucking fuel from the tank..

    So I used a bleach bottle as a temporary "fuel tank",put a gallon of deisel in it,and ran the fuel line from the lift pump(and the electric one that came with the truck) and the return line into the bottle--THEN I was finally able to get it "primed",fuel at the injector lines...but it still took some starting fluid to actually fire it up the first time!--and I tried my best to avoid using any--it made some horrible noises while I was cranking it--but at that point I was so PO'd I didn't care if I blew it up!..

    After I got it fired up that first time,I ripped all the old rubber lines and all the jerry rigged crap off the last owner hooked up--put in some new rubber lines,hooked the electric "booster" fuel pump to the right tank only (drivers side leaked,so I said "F" it!--I never go far enough to need 2 tanks,and I'd never be able to afford to fill both anyway..its just there for the ride now!.

    You might be better off doing that too--using a smaller temporary tank--you don't know if the lines are blocked going to to fuel tank,or if the "sock" is all clogged,water could have formed in the tank and rusted the metal lines shut,fuel lines leaking air in,etc....It could be gummed up at the injector pump inlet line too--didn't you say there is a check valve there or something??

    I want to hear that sucker RUN!!..I'd try to start it first--and check the compression later--it might have more after its been run!...and I dont understand why they say to block the intake off while checking compression..makes no sense to me--if no air gets in,what is it gonna "compress"???? :screwy: :screwy:
     
  7. jolane

    jolane 1/2 ton status

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    Diesel4me,
    Thanks for the help! I had read about how you had plumbing issues in a different post somewhere. The problem I have is that I have taken the line entering the IP off, and the lift pump is sending gobs of fuel into the pump (it really does send a lot of fuel. I know that I am getting fuel into the inlet of the pump.

    After reviewing the GM manual last night though, I noticed that the IP has a inlet filter and check valve or regulator. Maybe I don't have the pressure required from the lift pump? Even though it is flowing a lot of fuel, maybe the pressure is too low. I could check this though at the filter outlet I guess, with some sot of fuel pressure gauge (guessing here, since it is diesel fuel, not gasoline).

    Maybe my IP filter screen is plugged? Maybe the check valve is barely opening? I think in the end it comes down to rebuilding the IP. This way I know it is good. I am almost ready to just pull the engine, pull the oil pan, and inspect the bottom end. Maybe just pull the engine apart completely, and inspect everything and replace anything that is measureably worn/bad/etc.

    The other option is to have the IP and injectors rebuilt, replace the lift pump, and replace the glow plug relay (and one glow plug). This should get the fuel system and the GP system ready to go. I guess it would be ~$450-$500. This is all to know whether the engine runs.

    As for checking the compression, the GM manual says to check the engine warm, and that the compression should be 380-400 psi! I think I have seen people say ~300 psi here. Maybe the difference is warm versus cold? Either way, I think I will make my own gauge (if I get that far) and return the crappy HF tester.

    Finally, after speaking with my brother, who asked his girlfriends brother (I know, I know), who is a HumVee mechanic for the airforce, he said that often they will run jet fuel in the vehicles when overseas. I don't know if the M1008's went overseas. Anyways, when they do this, I gues the IP doesn't hold up well. I really don't even know if this sounds reasonable to run jet fuel. He seemed to think that the IP was probably bad, thus the reason why the truck probably sat and was eventually sold with 48K miles.

    Again, thanks for the help. I would like this project much more if it was in my garage, and not an hour+ away (having to pack tools with me).

    Joshua
     
  8. 86Cucvbeater

    86Cucvbeater 1/2 ton status

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    When I bought my m1008 a few years back it wouldn't start.. I norrowed it down to a fuel problem, looked in the manual and read about a check valve.. I had little rubber pieces probably from the deteriorating seals in the IP and my check valve was clogged so bad I just drilled it out.. put it back in, got all the crap out of the IP and started her up.. runs great except for a small leak at the bttom of the IP. not too bad thoough, my truck still starts up every time. Might want to just try cleaning out the IP :confused:
     
  9. jolane

    jolane 1/2 ton status

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    86Cucvbeater,
    Which check valve are you referring to? Is it the valve that is immediately before the return line on the removable top cover? How did you clean the IP?

    I have had the cover off twice now, and it looks brand new inside, just spotless. If you are talking about cleaning the resevoir out, what should I use to do this? Did you do it in the truck, or was the IP out of the truck?

    Thanks,
    Joshua
     
  10. 86Cucvbeater

    86Cucvbeater 1/2 ton status

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    Yeah that should be the same one. blow through it and see if its clogged, its called the fuel return check valve i think. but if the inside of your IP cover looked brand new, your seals may not have deteriorated like mine. There was a bunch of little black pieces in mine and I just fished them out with the IP still in the truck. This was about 6 yrs ago but I dont think I really went into the IP much, I just cleaned under the cover.
     
  11. 6.2 man

    6.2 man 1/2 ton status Premium Member

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    Pull the line off your check on the IP and crank it over . You shouldn't see any fuel come out . If you do then it's bad and never will start . If all else fails pinch the line off and try to start it . If it starts then replace the valve just don't run it too long like that .
     
  12. jolane

    jolane 1/2 ton status

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    6.2 man,
    I thought that fuel was supposed to come out that line. I thought that was the return line, and it is plumbed into the injector returns, and back to the tank.

    I did take the line off while cranking. Fuel was basically dribbling out of it very slowly (almost like fuel bubbling out). I was thinking it should be coming out faster than that. So it should not be passing any fuel at all?

    Joshua
     
  13. 6.2 man

    6.2 man 1/2 ton status Premium Member

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    I believe it shouldn't until the rig is running . The purpose of it is too not let too much fuel into the IP it sends the excess back to the tank .
     
  14. dieselponyexpress

    dieselponyexpress 1/2 ton status

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    Joshua
    the military IP does have hardened internals so jet fuel shouldn't be a problem.

    IIRC there should be a decent amount of fuel out of the return line. A plugged fuel return check valve will cause a housing pressure to be too high.

    What I can't read in your postings:
    Did you loose the injector lines at the injectors?. It seems to me that you loosened the lines at the pump side.

    Loose at least 4 of them (finger loose). Crank in intervals of 15sec. Allow the starter to cool between intervals. After about 5 cycles there should be fuel at ALL loose fittings. If not, then fuel supply is your problem - either in the IP or somewhere before (fuel pump, lines, tank).

    Good luck.
     
  15. DieselDan

    DieselDan 1/2 ton status

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    Sorry, I cry BS. Although some injector pumps can be had with hardened internals; they were listed as ARTIC injector pumps for use with DF-1 (kersone). My unit has rebuilt quite a few pumps (Direct Support) and they have never ordered hardend internals (too hard to come by). Yes injector pumps wear out, especially running the Army's "one fuel" concept - JP8.
     
  16. jarheadk5

    jarheadk5 1/2 ton status

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    Maybe the check valve is backwards??? Stranger things have happened...
     
  17. jolane

    jolane 1/2 ton status

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    "What I can't read in your postings:
    Did you loose the injector lines at the injectors?. It seems to me that you loosened the lines at the pump side.

    ***No, I loosened all of them at the injectors only. I tried them first just cracked loose, then I tried them completely removed, then again only cranked. Each time I changed the fitting connection, I followed the following procedure you had listed.

    "Loose at least 4 of them (finger loose). Crank in intervals of 15sec. Allow the starter to cool between intervals. After about 5 cycles there should be fuel at ALL loose fittings. If not, then fuel supply is your problem - either in the IP or somewhere before (fuel pump, lines, tank)."

    ***This is exactly what I did each time! I spent about 3 hours just cranking and varying the line connections. Of course I let the starter rest in between cycles. I also had the glow plugs out completely for ease in turning over.

    I feel like something is wrong with the IP, or else I am doing something really dumb. Also, when I am cranking, I have tried both putting the gas pedal to the floor (yes, the cable is connecting and operating the linkage) and midway. I did also try no pedal, but it seems like you would want the metering valve fully open.

    Has anyone cleaned the screen themselves? I am getting fuel into the housing though, as evidence by fuel dribbling from the return fitting. What happens if the lift pump does not have the pressure it needs? I get a lot of fuel from the lift pump (out of the filter) with nothing connected, but don't have a way to check what happens when the lines are connected. Maybe I am being deceived by the lift pump?

    Thanks Again,
    Joshua
     
  18. 6.2 man

    6.2 man 1/2 ton status Premium Member

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    The IP goes by volume not pressure . take the chck valve off and try cranking the engine and see if fuel comes out if it does then you have enough volume .
     
  19. 3 on the tree

    3 on the tree 1/2 ton status

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    In 76-77 while overseas, we ran ALL our diesel rigs on JP-4 jet fuel. Just add oil like a 2 stroke. They seemed to make a little more power with the jet fuel.
     

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