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tommyw-5088

injectors stuck in 8v71

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my old 4200 wont do anything but idle ,i have about determined the injectors are stuck.

the rack will not move .

with a book could i tear the injectors apart ?.

any other ways to unstick ,while in engine?

thanks

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my old 4200 wont do anything but idle ,i have about determined the injectors are stuck.

the rack will not move .

with a book could i tear the injectors apart ?.

any other ways to unstick ,while in engine?

thanks

Try penetrating oil sprayed into the rack on both ends and into the fuel in and out ports. Let sit for a day and repeat a few times over a few days. If that doesn't work try carb cleaner. Carb cleaner WILL work but I am unaware if it will cause damage to any o-rings or seals in the injectors. You could also try running some ATF fluid through the fuel system. Maybe start it up on a kerosene/ATF cocktail and let sit for a day and repeat a few times. What ever you do don't try giving it throttle while running. Well, maybe if it's in road gear and you can dump the clutch. It's what I had to do when I set my rack to the wrong side on my little 2-71. Good thing I was smart enough to put it in road gear before I started it up!

Mark

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thanks ,ill give that a try .

dont you have the 2-71 in a M ?

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thanks ,ill give that a try .

dont you have the 2-71 in a M ?

Yea. Super M actually.

Mark

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my old 4200 wont do anything but idle ,i have about determined the injectors are stuck.

the rack will not move .

with a book could i tear the injectors apart ?.

any other ways to unstick ,while in engine?

thanks

You are very lucky, normally the injector/rack sticks wide open and at startup it runs away!!!!!

If you are using the new style with individual spring loaded arms you can determine the stuck injector by simply pushing on the controll arm of the injector. The old solid rack will require removing the control shaft to work an individual injector.

I think you will find that (there is actually nothing about the rack to stick after you verify the linkage) you have an injector seized internally and the only cure will be replacement.

They are less than $100. exchange at a detroit diesel dealer.

I have attempted to free-up mine (removed from engine) by soaking for a week in penetrating oil, and oven baking at 350F in hydraulic oil, nothing worked.

The injector can be disassembled but the very thin sleeve that is used for fuel metering is probably rusted the shaft it rides on.

Water ruins a 71 injector very quickly.

I have tried the cheap fix by buying injectors off ebay; every one I got was either stuck or the wrong one.

By the way I have a N65 reliabilt injector that is good you can for the price of shipping.

I bought it off ebay its good but my old 2 valve engine uses HV injectors and the N is shaped differently.

Nothing like a 71 blowing smoke on a cold morning.

My experience is current, maintaining a 3-71 boat motor for the past 3 years.

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my old 4200 wont do anything but idle ,i have about determined the injectors are stuck.

the rack will not move .

with a book could i tear the injectors apart ?.

any other ways to unstick ,while in engine?

thanks

You are very lucky, normally the injector/rack sticks wide open and at startup it runs away!!!!!

If you are using the new style with individual spring loaded arms you can determine the stuck injector by simply pushing on the controll arm of the injector. The old solid rack will require removing the control shaft to work an individual injector.

I think you will find that (there is actually nothing about the rack to stick after you verify the linkage) you have an injector seized internally and the only cure will be replacement.

They are less than $100. exchange at a detroit diesel dealer.

I have attempted to free-up mine (removed from engine) by soaking for a week in penetrating oil, and oven baking at 350F in hydraulic oil, nothing worked.

The injector can be disassembled but the very thin sleeve that is used for fuel metering is probably rusted the shaft it rides on.

Water ruins a 71 injector very quickly.

I have tried the cheap fix by buying injectors off ebay; every one I got was either stuck or the wrong one.

By the way I have a N65 reliabilt injector that is good you can for the price of shipping.

I bought it off ebay its good but my old 2 valve engine uses HV injectors and the N is shaped differently.

Nothing like a 71 blowing smoke on a cold morning.

My experience is current, maintaining a 3-71 boat motor for the past 3 years.

You can put the new offset style injectors in the old two valve heads with a bit of work. I just changed my 2-71 over a couple of months ago. Slightly modify the rack, get the new style clamps and modify the shape of one of the fuel tubes is all you have to do. It really opens up the options of injectors you can then use.

Mark

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my old 4200 wont do anything but idle ,i have about determined the injectors are stuck.

the rack will not move .

with a book could i tear the injectors apart ?.

any other ways to unstick ,while in engine?

thanks

You are very lucky, normally the injector/rack sticks wide open and at startup it runs away!!!!!

If you are using the new style with individual spring loaded arms you can determine the stuck injector by simply pushing on the controll arm of the injector. The old solid rack will require removing the control shaft to work an individual injector.

I think you will find that (there is actually nothing about the rack to stick after you verify the linkage) you have an injector seized internally and the only cure will be replacement.

They are less than $100. exchange at a detroit diesel dealer.

I have attempted to free-up mine (removed from engine) by soaking for a week in penetrating oil, and oven baking at 350F in hydraulic oil, nothing worked.

The injector can be disassembled but the very thin sleeve that is used for fuel metering is probably rusted the shaft it rides on.

Water ruins a 71 injector very quickly.

I have tried the cheap fix by buying injectors off ebay; every one I got was either stuck or the wrong one.

By the way I have a N65 reliabilt injector that is good you can for the price of shipping.

I bought it off ebay its good but my old 2 valve engine uses HV injectors and the N is shaped differently.

Nothing like a 71 blowing smoke on a cold morning.

My experience is current, maintaining a 3-71 boat motor for the past 3 years.

You can put the new offset style injectors in the old two valve heads with a bit of work. I just changed my 2-71 over a couple of months ago. Slightly modify the rack, get the new style clamps and modify the shape of one of the fuel tubes is all you have to do. It really opens up the options of injectors you can then use.

Mark

I will keep this in mind because I want to switch to the spring loaded rack for startup safety.

At that time I will switch to N injectors.

According to the book, the N's are higher pressure and cleaner running.

I will probably never go to a 4-valve head unless the 2-valve develops a problem.

Mine is a General Motors Diesel around 1955 issue.

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SEA FOAM in the filters start her up The stuff works wonders

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Just a heads-up on the two valve injectors. You can replace them with HN injectors. They are "N" type with the "HV" top. I have HN55 in my 671 20,000# and 10.5 mpg. The Detriot dealer was clueless. The parts "BOY" didn't know a thing about them, or didn't want to. They are available from rebuilders. Norm

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Just a heads-up on the two valve injectors. You can replace them with HN injectors. They are "N" type with the "HV" top. I have HN55 in my 671 20,000# and 10.5 mpg. The Detriot dealer was clueless. The parts "BOY" didn't know a thing about them, or didn't want to. They are available from rebuilders. Norm

That's true. I initially had some 70's built that way too. The same company that built them said that they couldn't build 90's that way for some reason so I decided to convert over to the offset ones and be done with it. The company really turned out to be pretty flaky though so I'm not sure if they truly can't make them in anything larger than a size 70 or just didn't want to bother.

Mark

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