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GM 2 stroke diesel

TravellingTec

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Have problems with old 871 in a piece of paving equipment. Diesel fuel is leaking into bottom end. (Crank case). Wonder if anyone can steer me in the right direction. The guys who worked on these are getting few and far between. Any help or advice would be appreciated
 

td25c

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Pop the valve covers off late at night in the dark . Then use a flashlight & hold a piece of notebook paper at each base of the cross over lines . The diesel will flow visibly over the paper in the dark with the engine running .


You got a line or a fitting leaking under the valve cover .
 

willie59

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I agree with TD, you have a line or a fitting leaking under the valve cover, that's the only place where fuel is being moved inside that engine, through the lines that feed or return fuel for the injectors. And I've preached it here before and will do it again at this thread, don't use 15W/40 oil in that engine, use only SAE 40 Delo 100 oil in that engine.
 

RZucker

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More than likely its an injector feed tube cracked at the flared end. that will be patently visible with the engine running. Normally there will be oil puddled on top of the flare nut around the tube, if its leaking fuel it will be clean on top. Also check around the fuel connectors that screw into the head. They use a special seal washer that should never be re-used, and torqued to 40 lb ft. I use a little blue Loctite to help seal them when I install them. I'm betting a fuel tube on an older engine. Oh, 12 lb ft on the fuel tube nuts, no more, no less.
 

willie59

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Not long ago at my former job my boss purchased a Deere scraper. It came in on a lowboy, no one wanted to off load it. Me, hell yeah! Much to my delight it had a 6-71. Oh yeah, after tossing it from the trailer I indulged in numerous laps around the yard at full governor while swapping gears. Prolly my last trip in a 6-71. Of that I shall sorely miss.
 

thepumpguysc

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Don't forget about the seal in the supply pump fellas..
BUT.. your probably right.. injector feed line leaking..{MOST COMMON}
Best way to find is, as stated, remove v. cover & LOOK.. OR.. ya might be able to shoot it w/ a temp gun & find the "cold" cylinder.??
 

RZucker

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Don't forget about the seal in the supply pump fellas..
BUT.. your probably right.. injector feed line leaking..{MOST COMMON}
Best way to find is, as stated, remove v. cover & LOOK.. OR.. ya might be able to shoot it w/ a temp gun & find the "cold" cylinder.??
The supply pump has a weep hole between the fuel side seal and the oil side seal, a leak will make a huge external mess.
Unless an injector feed line is completely broken off, a heat gun check wont show a cold cylinder, but that would fill the oil pan pretty fast.
 

Vetech63

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Got my b*****d child 6V92T done yesterday. Im sick of Detroits right now. What everyone else said X100 ^
 

td25c

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indiana
Not long ago at my former job my boss purchased a Deere scraper. It came in on a lowboy, no one wanted to off load it. Me, hell yeah! Much to my delight it had a 6-71. Oh yeah, after tossing it from the trailer I indulged in numerous laps around the yard at full governor while swapping gears. Prolly my last trip in a 6-71. Of that I shall sorely miss.

That JD scraper was a real sweetheart of a machine !
 

kshansen

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The supply pump has a weep hole between the fuel side seal and the oil side seal, a leak will make a huge external mess.
Unless an injector feed line is completely broken off, a heat gun check wont show a cold cylinder, but that would fill the oil pan pretty fast.
There is always the chance someone saw those threaded holes and decided it needed a plug!:p
Also some rare cases they had a drain line hooked to one of the holes in the supply pump and that got plugged.

But I'd agree that 98% chance it is a loose or cracked line under a valve cover with a slight chance it is a bad injector.
 

TravellingTec

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Ontario, Canada
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Heavy Equipment Mechanic
Thanks for all the good advice. Took valve covers off and can certainly see the potential for leakage at those tubes. However cannot see leakage around any of these tubes. Used brake clean to dry area up. Ran it both hot and cold. Could not see any leakage. Used heat gun on manifold. No noticeable difference on any of the cylinders and seems to run fine. On face of injector there is a frost plug and below that the throttling rod. Can it leak around this rod? Rod so very close to the bottom of the injector housing and very difficult to see if any of them are leaking there. Thanks
 

Birken Vogt

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Has anybody used UV dye in a diesel tank? It would be the cat's meow for one of these I should think, but not sure how many gallons of dye you would have to dump in to make it strong enough in the diesel fuel.
 

Nige

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Has anybody used UV dye in a diesel tank? It would be the cat's meow for one of these I should think, but not sure how many gallons of dye you would have to dump in to make it strong enough in the diesel fuel.
What we do for a dye test is run the engine from a small fuel tank (5 gallons or so) so that it doesn't take a gazillion gallons of UV dye to get a concentration that will show up under a black light.
 
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