Author Topic: Air Shrouded Fuel Injector  (Read 259 times)

TNNBENZ

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Air Shrouded Fuel Injector
« on: 01 October 2021, 12:52 PM »
 I cannot find anything on an Air- Shrouded Injector. I read they are a good upgrade, but can not find what they look like or where to buy them............!!!
Any thoughts.  Of course I find this information after I buy new non shrouded injectors..........
« Last Edit: 04 October 2021, 10:26 AM by TNNBENZ »
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TNNBENZ

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Re: Air Shrouded Injector
« Reply #1 on: 02 October 2021, 06:30 PM »
 After some thought , I think I am inquiring about shrouded fuel injectors for a K-jet fuel system.  I read about this upgrade in a Bosch manual..........
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ptashek

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Re: Shrouded Fuel Injector
« Reply #2 on: 03 October 2021, 03:46 AM »
Did you mean air-shrouded fuel injectors? They're the same as standard Bosch CIS injectors, what's different is the mount they use, from what I remember when reading about this a few years back.

In some CIS cars the injectors are mounted in brass holders, without any isolation from the head as such, which transfers all the engine heat into the nozzle, affecting spray pattern and atomisation. Some used a holder that had air circulation around the nozzle to cool it.

MB injectors, at least on the M116 and M117, are mounted in a plastic cup which acts as a heat isolator. This helps the injector run cooler, which is supposed to improve fuel atomisation in the cylinder and by extension a more complete burn.
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TNNBENZ

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Re: Shrouded Fuel Injector
« Reply #3 on: 04 October 2021, 10:24 AM »
Yes ptashek, air shrouded fuel injectors. I confused myself by overthinking because I had not received a reply.  I edited the post from air shrouded to just shrouded to see if that would help me get a response.
 Thank-you so much for the answer.  I read that there are special heads for the air shrouded injectors.  I am skeptical that this true !!! Your explanation seems more logical.  I did read that injectors from different years & models can be swapped around by just installing with or without the holders. This appears to be similar to your information. I think hotter fuel would burn better/quicker, just more susceptible to detonation if running rich.........???  Oh, I think it is the air that improves burning hence "air shrouded" not the heat insulated.  Now I wonder if the injector is shrouded or the holder.  I say this ptashek because you did say it has been some time since you read that.  I have asked several sourses and noone seems to know for sure. ptashek has given me the BEST response. I even contacted Bosh. Matter of fact I found another number & gonna call them again now.......
I have read  several times,  not replace the plastic holders unless absolute necessary because they are usually stuck & brittle, most always fall apart and go into the engine. Then you really have a mess !!! 
I am NOT a professional mechanic . Also have zero experience with Mercs. I am just learning as fast as I can so if anyone disagrees  don't condemn me............ ::)
I
« Last Edit: 04 October 2021, 10:36 AM by TNNBENZ »
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UTn_boy

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Re: Air Shrouded Fuel Injector
« Reply #4 on: 04 October 2021, 11:38 AM »
Don't forget that the early D-Jetronic models had no plastic cup.  The injectors literally sat on the rubber injector seal.  That was the only isolation it had from the cylinder head. 
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ptashek

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Re: Air Shrouded Fuel Injector
« Reply #5 on: 04 October 2021, 11:40 AM »
The holders can be replaced, and removal is not that hard. Yes, these do get brittle, but if pulled straight up with a steady force instead of being yanked at, they come out in one piece. I've pulled 16 across two engines without issue.

The injectors used on the small V8s were used across many other K-Jetronic powered cars. Porsche, Audi, VW etc. There's nothing special about them.

I've never seen another set-up, aside from D-Jetronic which is a completely different system, used on the W116.
1993 "Pearl Blue" W124 280TE
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TNNBENZ

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Re: Air Shrouded Fuel Injector
« Reply #6 on: 04 October 2021, 12:02 PM »
 Bosch guy told me #62274 is only injector for a 1977 450SEL. It is air shourded !!! 
ptashek  you are the man..........well your the man after I replace my holders without any breaking !!!  ::)
 I believe I bought the right #62274 injectors many moons ago & they are Air shrouded  :)  :)  :) Yes, also got them @ $14.00 which I think is a bargain...........now they r $21 which is much lower than I thought they were lately. I got mine on special sale.........
UTn_boy & you have helped me more than you realize...... :)  I have been having severe undeserved problems in my life resulting in mucho stress.  Stress has hindered my mechanicing on my increasingly beloved Merc.  My life has gotten much better & you 2's help is a big reason..........Thank-U very much ~~~ 
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TNNBENZ

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Re: Air Shrouded Fuel Injector
« Reply #7 on: 04 October 2021, 12:12 PM »
So I guess air shrouded heads are not needed. I think I heard that on a U tube video about a Porsche K-jet or somewhere.  Just need a plastic air shrouded plastic holder & right gaskets.  I AM SO STOKED ABOUT THE NEWS ABOUT 16 REMOVALS AND NO BREAKS.  I was really bummed thinking I got new injectors but afraid to change the holders.  I want as close to a new fuel system as I can afford and almost have all the parts and kits. It has been a fun challenge (most of the time) so far just hope it pays off.........This forum is such a help...........Thankx 2 ALL
« Last Edit: 04 October 2021, 12:22 PM by TNNBENZ »
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TNNBENZ

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Re: Air Shrouded Fuel Injector
« Reply #8 on: 04 October 2021, 12:19 PM »
The holders can be replaced, and removal is not that hard. Yes, these do get brittle, but if pulled straight up with a steady force instead of being yanked at, they come out in one piece. I've pulled 16 across two engines without issue.

The injectors used on the small V8s were used across many other K-Jetronic powered cars. Porsche, Audi, VW etc. There's nothing special about them.

I've never seen another set-up, aside from D-Jetronic which is a completely different system, used on the W116.
My car has been setting for many, many, many moons before I got it so I pray the holders are not stuck.......I am hoping maybe the holders will come out with the injectors. Another member suggested an injector puller from Uncle Bill or some Cuz Joesph guy ha........I may try it.  Thankx again.........
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ptashek

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Re: Air Shrouded Fuel Injector
« Reply #9 on: 04 October 2021, 01:17 PM »
You have to pull the injectors before you pull the holders.
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rumb

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Re: Air Shrouded Fuel Injector
« Reply #10 on: 04 October 2021, 05:40 PM »
"Uncle" Kent is what we call Kent Bergsma from https://mercedessource.com/

He has lots of interesting tools and tips for keeping old Mercedes running.

The injector cleaner he sells is : https://mercedessource.com/store/cis-gas-fuel-injector-spray-pattern-tester-and-nozzle-cleaner.  Not a "puller".

'68 250S, '77 6.9 euro, '91 300SE, '98 SL500 '14 CLS550

TNNBENZ

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Re: Air Shrouded Fuel Injector
« Reply #11 on: 20 October 2021, 12:20 PM »
"Uncle" Kent is what we call Kent Bergsma from https://mercedessource.com/

He has lots of interesting tools and tips for keeping old Mercedes running.

The injector cleaner he sells is : https://mercedessource.com/store/cis-gas-fuel-injector-spray-pattern-tester-and-nozzle-cleaner.  Not a "puller".
Yes. I totally agree  ;)
I have watched & learned a lot from his youtube videos  8)
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Jan S

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Re: Air Shrouded Fuel Injector
« Reply #12 on: 20 October 2021, 12:29 PM »
I'm renting a similar tester this weekend, will test both the old and the new ones (for a 6.9).

The standard k-jet injectors shall open at approx > 3.5 bar, right?

Will be interesting to see the condition of the old ones.
1975-mod W116 450 SE with 6.9 engine

TNNBENZ

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Re: Air Shrouded Fuel Injector
« Reply #13 on: 20 October 2021, 12:56 PM »
   I saw a video of a man pulling the injectors & turning on pump & watching spray pattern for partial trash in injector !!!
He had injectors in jars to observe their spray patterns...
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TNNBENZ

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Re: Shrouded Fuel Injector
« Reply #14 on: 20 October 2021, 01:05 PM »
Yes ptashek, air shrouded fuel injectors. I confused myself by overthinking because I had not received a reply.  I edited the post from air shrouded to just shrouded to see if that would help me get a response.
 Thank-you so much for the answer.  I read that there are special heads for the air shrouded injectors.  I am skeptical that this true !!! Your explanation seems more logical.  I did read that injectors from different years & models can be swapped around by just installing with or without the holders. This appears to be similar to your information. I think hotter fuel would burn better/quicker, just more susceptible to detonation if running rich.........???  Oh, I think it is the air that improves burning hence "air shrouded" not the heat insulated.  Now I wonder if the injector is shrouded or the holder.  I say this ptashek because you did say it has been some time since you read that.  I have asked several sourses and noone seems to know for sure. ptashek has given me the BEST response. I even contacted Bosh. Matter of fact I found another number & gonna call them again now.......
I have read  several times,  not replace the plastic holders unless absolute necessary because they are usually stuck & brittle, most always fall apart and go into the engine. Then you really have a mess !!! 
I am NOT a professional mechanic . Also have zero experience with Mercs. I am just learning as fast as I can so if anyone disagrees  don't condemn me............ ::)
I
Just clarify :  The Bosch manual I refereed to as air shourded injectors being a recommended upgrade evidently was published before the current injectors were being made !
Hey, I read all I can...........makes me an educated FOOL somtimes... :o  ???  :o
Neglected ~ Rescued ~ 1977 450SEL 4.5L 
Project of Compassion
Silver Green/Metallic
Left Hand Drive ~ Retractable Roof