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  #1  
Old 09-23-2009, 10:54 AM
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Injector shim sizing

Does anyone know of a chart or list where the size of the shim and the amount(roughly) of psi change it will cause might be found?

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  #2  
Old 09-23-2009, 03:47 PM
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Used Injector springs will exhibit a variation in spring tension to the point that you cannot count on a x sized shim to change the Pop/Opening Pressure the same on all of the Injectors.

You test an Injector; write down that Pop/Opening Pressure. You use the FSM recommendation to guess the size shim you might need. You put that Shim in and you test again. If the Pop/Opening Pressure is not correct you take the difference between the original Pop Pressure and the Pop Pressure with the new shim and see how much shim thickness it took to cause a change in Pop Pressure.

Now you have a little formula for your individual Injector and go off with your Micrometer or Vernier Caliper to find the next thickness of shim based on your formula.

And, you do that with each Injector. It is easier to do than to write about.

Added:
This is from the Factor Service Manual concerning changing the Spacer (Shim): "Increasing the preload by 0.05mm increases the Injection Pressure by about 3.0 bar positive"
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Last edited by Diesel911; 09-23-2009 at 04:00 PM.
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  #3  
Old 09-23-2009, 04:04 PM
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Quote:
Originally Posted by Diesel911 View Post
Used Injector springs will exhibit a variation in spring tension to the point that you cannot count on a x sized shim to change the Pop/Opening Pressure the same on all of the Injectors.

You test an Injector; write down that Pop/Opening Pressure. You use the FSM recommendation to guess the size shim you might need. You put that Shim in and you test again. If the Pop/Opening Pressure is not correct you take the difference between the original Pop Pressure and the Pop Pressure with the new shim and see how much shim thickness it took to cause a change in Pop Pressure.

Now you have a little formula for your individual Injector and go off with your Micrometer or Vernier Caliper to find the next thickness of shim based on your formula.

And, you do that with each Injector. It is easier to do than to write about.

Added:
This is from the Factor Service Manual concerning changing the Spacer (Shim): "Increasing the preload by 0.05mm increases the Injection Pressure by about 3.0 bar positive"
just as i was hoping was not the case...lol...oh well off to the bench for a while to test,test, test.Thanks for the info, much appreciated.
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  #4  
Old 09-23-2009, 09:45 PM
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If you intend to balance your injectors well you really need an assortment of shims to pick from.
Even, with an assortment of shims there often is one Injector that can not be balanced as close as the others.
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  #5  
Old 09-24-2009, 11:36 PM
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When installing new injectors, is balancing a necessary step?
Any idea how much it should cost, at a shop?

thanks,
Bri
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  #6  
Old 09-25-2009, 12:41 AM
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Quote:
Originally Posted by brihawaii View Post
When installing new injectors, is balancing a necessary step?
Any idea how much it should cost, at a shop?

thanks,
Bri
Not my words but from post #5 in the thread at the bottom
"Bosch OEM... I'll put it this way... this week I had a client without funds to purchase genuine MB injectors, so they opted for Bosch OEMs at lesser cost to them. The initial order of five injectors yielded two that were within specification. One of them exhibited no chatter and simply streamed its fuel. This is unacceptable, but is and has been the norm for a number of years. I would not install any Bosch OEM injector without testing it first. They can not be trusted without testing, in my opinion. These are typically rebuilt in third world countries, hence the decreased cost and poor quality control.

Local rebuilder? If you have a local outfit that is skilled with these injectors and is using a quality nozzle, there should be no problem withe them. However, you want to know the pop pressures and to witness the spray patterns first hand. I would not trust someone's word on the matter. Fact is, it takes some time to dial in an injector for optimal performance. It is quite easy to throw one together and to get mediocre performance."
est injectors for a 617.952 engine

Back to me. I believe Rebuilt Injectors that are grabbed randomly from a parts bin will most likely not be balanced. Due to the allowable range of pressure of 1958-2074 psi that they can be rebuilt to.
As that guy said in post #5 of that other thread a local shop will try to balance them much closere that the max allowable 5 bar (72.5 psi).
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  #7  
Old 09-25-2009, 12:44 AM
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Quote:
Originally Posted by brihawaii View Post
When installing new injectors, is balancing a necessary step?
Any idea how much it should cost, at a shop?

thanks,
Bri
Even though I live in the LA area I have no idea what the labor charge would be to rebuild Injectors.
There is not as many Fuel Injection shops as there used to be so there will not be many listed in the Phone book.
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  #8  
Old 09-25-2009, 01:37 AM
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thanks,
I was just gonna ask if you knew a shop around here.

I think it'll take months if I do it myself.

I'll see what I can find.
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  #9  
Old 09-25-2009, 02:38 AM
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************** on eBay sells kits that come with many different sized injector shims, and they even make an inexpensive pop tester for the DIY'er!
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  #10  
Old 09-25-2009, 12:31 PM
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Originally Posted by brihawaii View Post
thanks,
I was just gonna ask if you knew a shop around here.

I think it'll take months if I do it myself.

I'll see what I can find.
My fuel injection experience is from 1975-1980 with some temp work in fuel injection around 1988.
The Shops I knew of back in the day are all gone.
The last place Iworked for in 88; Fuel Injection Sales and Service, in El Monte is still around ad they are a big Company.
They are a good quality shop; but I do not know their prices as I worked only on Fuel Injection Pumps when I was there and even if I knew that price could have changed since 1988.
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  #11  
Old 09-26-2009, 10:21 PM
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I'm thinking about getting the pop tester and nozzle kit
from mercedes source.
$300 for the tester, monarch nozzles w/heat shields, 30 pc shim kit,
manual and gloves.
wondering if anyone on here has experience with their tester.
seems like an alright deal,
since I plan to do the nozzles on the other car soon as well.

unless someone else on here is doing rebuilds?

also wondering, what would be cause to replace entire injector,
as opposed to just changing nozzle?

obvious mechanical failure?
pitting, or...?
I don't know what happens to them.

or just the assumption that they would already be balanced?

thanks,
Bri
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  #12  
Old 09-26-2009, 11:27 PM
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I remember a while back, there were a few members on here that were doing injector rebuilding/balancing for a fee...is anyone still doing that?
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  #13  
Old 09-27-2009, 12:43 AM
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BGKAST was doing them, to a search on his name and PM him, he`s a real
nice guy and takes pride in his work.

Do a search on pop testers, there have been a few different one`s made from a bottle jack or other type small jack.

Charlie
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  #14  
Old 09-27-2009, 01:14 AM
Diesel911's Avatar
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Quote:
Originally Posted by brihawaii View Post
I'm thinking about getting the pop tester and nozzle kit
from mercedes source.
$300 for the tester, monarch nozzles w/heat shields, 30 pc shim kit,
manual and gloves.
wondering if anyone on here has experience with their tester.
seems like an alright deal,
since I plan to do the nozzles on the other car soon as well.

unless someone else on here is doing rebuilds?

also wondering, what would be cause to replace entire injector,
as opposed to just changing nozzle?

obvious mechanical failure?
pitting, or...?
I don't know what happens to them.

or just the assumption that they would already be balanced?

thanks,
Bri
Like you said "obvious Mechanical Failure".
Leaking Fuel Return Nipples, Broken Springs, Cracked Injector Nut. Less ofter there is a plate inside of the Injector that can some times have problems.
But, most of the above can be solved with anothe Injector from the J Yard.
The main problem is the Expense of the Pop/Nozzle Tester.

There is at least 2 Members that have bought the M Source modified Hydraulic Jack Pop Tester. It would be nice if they would comment on it.

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