# Fuel Injection, No lower O ring and cap on injector.



## jtgraham (Sep 17, 2010)

I had a PL 1.8 16v in my race car that had bad compression in it so I got a 9A 2.0 16V to go in it. I had to swap the intake and when I pulled out the fuel injectors from the 1.8 it only had the upper large O ring on it and no smaller one and still ran great like this. What is the importance of the lower O ring and cap that goes over the injector? Do I need to get some?


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## ziddey (Apr 16, 2006)

You're talking about the small gray one that fits in the hat at the tip of the injector? That's for the air shrouding. It keeps a seal for the vacuum run to the head. The idea is to prevent vapor lock from hot injectors, I believe. May also help with a smoother idle.


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## Heitjan (Nov 22, 2010)

I discovered almost the same problem with my rocco, except the whole cap is missing on the number one cyl and both o-rings are melted on #2! tomorrow i go digging for the cap!


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## Glegor (Mar 31, 2008)

if someone didnt remove the air shroud, then the engine ate it. most likely trapped in front of the catalytic converter if you still have one..

you will probably never find that air shroud that dropped off the injector..


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## WaterWheels (Aug 14, 2005)

jtgraham said:


> What is the importance of the lower O ring and cap that goes over the injector? Do I need to get some?


Importance? I would not say it had any real importance but rather maybe an attempt by VW to meet US emission standards. It could possibly make a street engine run a tiny bit better due to the atomization (is that a word) improvement of the fuel (the intended reason plus to cool the injector I guess), but just how much has never been documented that I have seen. If it were a street engine I would say buy the 0-rings and make it right as designed, but being a race engine I don't see the real need to put them on if you don't want to.



> I discovered almost the same problem with my rocco, except the whole cap is missing on the number one cyl and both o-rings are melted on #2!


Melted? I would have to see that for myself as melting them would be a real good trick. The material used does not melt easy and even if you had some severe backfiring through the intake it would be very hard to melt them (the upper real real hard). I doubt the end piece just fell off and into the engine. I guess it would be possible for it to sneak past the intake valve, the lift is enough I believe but the path and speed of the valve would make it tough, engine off maybe, just maybe. If it did find it's way into the combustion chamber that is as far is it would get. The combustion or movement of the piston is not going to discharge it into the exhaust, again a tough path also. It would bounce around doing what ever damage it could, only the aluminum in this case, until it formed itself into a little ball. That is the lucky part as it could also become lodged between the piston and the cylinder wall scratching it with ever movement of the piston. It is stainless steel and is not going to melt even with the combustion temperatures. I hope for your sake, and believe, that the injector was just installed without it by someone before you got the car. If you have had it the entire time from new then either it is in there doing whatever damage it can or was a screw-up at the factory.


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