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  #1  
Old 02-15-2021, 08:35 PM
rwd4evr's Avatar
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Clogged heatshields

First time I've had injectors out of a om617.
Got this car free (300d NA)and it was idleing terrible and needed constant block heater for mornings, then after a couple days it was dropping power very badly. I thought lt lost a cylinder. Cracked injector lines and one barely made a difference in idle. Pulled it and found this. This was after poking it with a pic. So it was essential completely shut other than a tiny hole. All 5 were similar. Runs great again even though it's got bad blow by, which is why I thought it cracked a ring or something. I stabbed it all out with a pic and tiny vac hose sucking the chunks out. Not sure if any stayed in there but it's running great. It's running on black diesel I make with mineral spirits and WMO. First na motor I've run on it but no power loss like this one on the turbos. Wondering if it was built up and me beating on it with new fuel just finished it off. Have to pull one and check it shortly.

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  #2  
Old 02-15-2021, 10:43 PM
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It would be interesting to see if compression increases or blowby reduces after running it hard for a while.

Good luck!!!
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Old 02-16-2021, 02:54 AM
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Yeah we'll see. I'm doing door dash when I have spare time on my hands instead of staring at you tube nonsense. So it's foot through the floor all night while I'm out. It just needs to live while I finish up my 4 speed and engine swap in my 300sd. Just a little more fab work on the clutch pedal and then I'm yanking the rod knocker and slush box. Hopefully in the next day or two. Once in I have to relocate the center bearing mount. I found the 280slc rear driveshaft I have is the right length but different bearing support area. At least the tape measure tells me that

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  #4  
Old 02-16-2021, 10:05 AM
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The 615, 616 & 617 seemed to run better when driven often and briskly. Just stay reasonable with the rev's for extended durations...not redline all day long and it will be happy.

Good luck with the project, it sounds interesting!
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Old 02-19-2021, 11:10 PM
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I enlarged one of your pics to try to get a good look at the heat shield. At one time what we call heat shields were reusable plates and to the best that I can see that is what you have.
Those plates were replaced by the one time use heat shields used on later models.

Thought I had some pics of the plates but I cannot find them. If the problem continues comes back later it could be the plates have reached the end of their life and they can be replaced with the one time use heat shields if the ends of the Injector Nozzles are not eroded away in the area where the heat shield seals.
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Old 02-21-2021, 06:11 AM
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Ahhh! Now that makes sense. They look different than the one time seels I've seen and that were in the 300d parts car I pulled an injector out of. It seems like they have began plugging up again already like 600 miles later. Losing power and some missfire. Could it be from them being worn out?

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  #7  
Old 02-21-2021, 10:52 AM
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Run it on the cleanest-burning fuel with the highest detergents you can find, get some synthetic oil in it - maybe 10w30, to "rinse" the motor out - and run it under load, at speed, as much as possible. Chances are that engine is filthy, in the fuel system and inside the motor. Blow-by may just be a result of clogged up rings and will probably reduce if you clean it up inside and get it tuned up right.
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  #8  
Old 02-22-2021, 02:57 AM
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Well I run it on black diesel I make so that's what it gets. I'm sure it needs an oil change. I wonder if that old style heat shield plate deal runs hotter than the newer heat shield and the fuel is coking on it. I'm not familiar with what is going on just inside the injector hole in the pre cup. I need to replace the hestshilds(maybe the old ones are just giving the carbon a good place to latch onto?).I was thinking about really cleaning the hole in the precup. If I get a little wire brush on my Dremel to clean/polish that hole am I going to wreck anything? I run a vacuum hose in there but it's possible some chunks and or a wire could get in there. If I turn the motor to open intake valve on that cylinder and plug an air hose or shop vac on blow in the intake it would kick everything out.

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Last edited by rwd4evr; 02-22-2021 at 10:03 PM.
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  #9  
Old 03-12-2021, 09:20 PM
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Quote:
Originally Posted by rwd4evr View Post
Ahhh! Now that makes sense. They look different than the one time seels I've seen and that were in the 300d parts car I pulled an injector out of. It seems like they have began plugging up again already like 600 miles later. Losing power and some missfire. Could it be from them being worn out?

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I have none on my own vehicle and have not read much about them. The disposable heat shields don't cost too much but only if you buy the online.

Maybe someone would be willing to part with a single new disposable heat shied so that you can see if there is an improvement if you use one.

Except of course for the protruding needle/pintel the nozzle face is supposed to be flat. Any erosion of the flat surface indicates an issue issue with the injector or something like late timing or poor compression.
If the Nozzle is eroded in the sealing area of even a disposable heat shield it is not going to seal as it should.

See the attached pic in post #2. That burned out area is supposed to be flat.
300D Surging Idle

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