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  #1  
Old 02-26-2010, 06:48 PM
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pop pressure om615

I recently had 2 injectors plug up so i got new monark nozzles and built a pop tester. After cleaning and lapping the injectors onto the poptester they go.

lowest pressure was ~112 bar, next was ~114bar and the last two were ~124bar. The #'s on the injector housings are

112bar -> KCA30SD27/4 130 115atu
114bar -> KCA30SD27/4 423 115at
124bar -> KCA30SD27/4 130 115atu
124bar -> KCA30SD27/4 226 115at

The two injectors at ~124bar need to be brought down ~ 9bar to get to 115 bar, if i understand this correctly i will need to get the shim down ~.15mm. should i get a shim kit or try and reduce the thickness of the shim itself?

If its to hard to reduce the thickness of the shim does anybody know of a place in the Portland, Or. metro area to get shims for these injectors.

Hopefully with the injectors all clean and popping at ~ the same pressure maybe i won't look like I'm going down the road fogging/spraying/smoking for mosquitos

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Old 02-26-2010, 08:39 PM
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Any Bosch certified Fuel Injection Shop would have the Shims. Besides Mercedes the same Shims are used on a bunch of other Bosch Injectors.

The Problem with changing the shims is each Injector is an individual.

Let us say .15 mm will change the Opening/Pop Pressure higher by 50psi. On the next injector with the same thickness of Shim you might only raise the pressure 25psi.
This means you use a thinner or thicker Shim; but you measure it before you put it in and you measure the shim that came out.

You Pop the Injector again and see what the Pop Pressure has changed to. You now have a little math formula because you have the difference between the measurements of the Old and New Shim and you now know how much Pop Pressure change you got from that difference.
Now if you need to change the Pop Pressure again you will know how much thicker or thinner of Shim you need.
On the next Injector you start over again.

The bugger is that you have worked out your formula and you know what thickness you need but you find out they do not make a Shim that is the size you need.

Some people would say no but you can hand sand the Shims thinner; but, it is time consuming.
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Old 02-26-2010, 08:43 PM
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Quote:
Originally Posted by holdthewind View Post
should i get a shim kit or try and reduce the thickness of the shim itself?
With only two injectors to adjust, it would be easier to trim down the two shims. The shims are pretty hard, but some time with a file and whet stone will do it. You can bring the low pressures up by lapping the spacers and upper injector bodies.
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Old 02-27-2010, 05:47 PM
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So I was lapping down the shim of one of the injectors at 124 bar and making good progress using 600 grit wet/dry paper. I took down the shim bye .0762mm and the pop pressure went down to 117 bar. So I decided to take the shim down another .0254mm. A few minutes of lapping I got to my desired thickness and reassembled the injector. The pop pressure increased to 131 bar what the heck? How can reducing the size of the shim increase the pressure? So apart comes the injector to see what in the heavens happened.

The end of the pintel, that the thrust pin sits against, sheared off right where the pintel increases in size. The metal at the shear point is wavy looking.

Of course the place that I purchased the nozzles is closed on Saturdays so my car will be down for another week at the minimum.

Has anybody have a similar experience with the pintle breaking at the same spot? I wonder if this nozzle was made 5-minutes to quitting time before a long weekend or if there was a whole batch of inferior metal and or some kind of error in the manufacturing process when this nozzle was made?

More than likely I did something wrong, I can't figure out what I did wrong. The whole process is pretty straight forward and simple.

Anybody got a single new monark nozzle for a om615/616 lying around?
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  #5  
Old 02-28-2010, 02:21 AM
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I posted some comments in your other thread.
http://www.peachparts.com/shopforum/diesel-discussion/272351-pintle-new-monarch-nozzle-broke.html?posted=1#post2415166

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