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Michigan 175A, GM ?Detroit? Diesel won't run. Bleed injectors?

Discussion in 'Wheel Loaders' started by ddiiggy, Nov 20, 2013.

  1. kshansen

    kshansen Senior Member

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    Retired Mechanic in Stone Quarry
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    We have a Sterling truck with a Mercedes/Detroit engine in it that we use to water roads in a quarry. There have been many times I have threatened to rip that thing out and install the old 4-71 that is sitting in the store room. I could guarantee that old two stroke would start every time you turned the key and if it didn't I'd have it figured out in less time than you could get a laptop to boot up to try to figure out what sensor was upset on the Mercedes! Glad I only have a couple years to work before I can leave this "modern technology" to the young kids. That's assuming you can find one who can stand to get his hands dirty!
     
  2. OFF

    OFF Senior Member

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    You know, I said that same thing to someone of Thursday. "I only have 2 years left". I was talking to a Cummins tech who I waited a week for, & paid $1000 for, so he could come out to hook up his magic laptop and tell me that my serviceman had over-filled the engine's motor oil by about 2 quarts. And how that caused the crankcase pressure sensor to read an over-pressure condition and shut the engine down.

    I've always said, "a good mechanic never stops learning" but I don't know how much more of this "learning" I can take before I lose my mind. How can anyone design something so stupid?
     
  3. kshansen

    kshansen Senior Member

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    I know what you mean. These things have all this computer stuff on them with the digital readout on the dash but they don't go one small step further and have the problem the computer sees scroll across the dash in plain English, or other local language, just say "Coolant level Low". Our's was about one quart below the add line in the coolant tank and would start and run for about ten seconds.

    ddiiggy, sorry to have hi-jacked this thread! Have you had time to check that emergency shut down? That's just a large flapper plate blocks off the air to the engine when the release is operated. I would also suggest removing the valve cover and check to see if the linkage that operated the fuel injectors is working free. One thing to look for is if there is any clearance between the injector rocker arm and the top of the injector plunger if there is then the injector is stuck and I would not try starting till I had replaced them. One stuck injector can hold all the others in full fuel position and cause the engine to runaway and you will only have a few seconds to kill the engine with the emergency shut down. That is one reason why you should make 100% sure that works first of all.
     
  4. ddiiggy

    ddiiggy Well-Known Member

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    I did have the (GREEN) line loose at one point and cranked the engine and did get some fuel to come out but not as much pressure as I expected. ??
    So, the pump is at least working some...

    It sounds like I do need to take the return hose loose. I never thought about there being a return.
    That would pretty much make pressurizing the tank not really do anything. Need to find and check for a restrictor valve.


    So the fuel isn't under pressure? You almost make it sound like it is just a tank up there or something. ??


    hi-jack away. I'm sort of waiting on some warmer weather to really get back into this. It's not like it is a big hurry. It has been sitting for a while.
    I'm not really needing to USE this thing, I just want to get it moved from where it is setting.

    I did check the action of the air intake flapper. It does move. It just has a catch and then it goes the rest of the way.
    I will take off the whole cover and check the flapper and watch the blower...

    Time to figure out how rusted in the bolts are that hold the lid on so I can see inside the valve cover.
     
  5. willie59

    willie59 Super Moderator

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    The fuel leaves the fuel pump and is delivered to a port on the head. The fuel enters a hollow chamber that runs the length of the head. There is an additional hollow chamber that runs the length of the head for return fuel from injectors. There is a port on the side of the head (where fuel return line to tank is connected) that has a brass fitting where return line connects. That brass fitting "is" the restrictor valve. It's nothing more than an orifice type fitting, not a typical hose fitting. The orifice hole in the fitting restricts flow of fuel thereby creating pressure inside the fuel galleys in the head from fuel being delivered by the fuel pump.

    Along the head, inside the valve cover, are ports to deliver fuel and to return fuel for each injector (shown by arrows below), there is a steel jumper line connected to supply and return for each injector (illustrated by lines in pic below)



    Detroit 2 valve head image edited 2.jpg



    The fuel pump is a gear type pump. If it were to lose it's prime, being a gear pump, sometimes it's hard for it to pick up prime on its own and needs some assistance.



    Detroit Diesel fuel pump.jpg
     
  6. kshansen

    kshansen Senior Member

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    This restrictor valve will have a number stamped in it, something like 070, or just 70. This is the size of the hole in it. It does look like a normal brass fitting, u sally a 90ยบ Inverted flare on most engines I have seen. The line from it should head right back to the fuel tank. If It was plugged I could see this causing a problem with the engine not picking up it's prime as easy as normal. This would be due to there being no where for the air in the system to vent out.