Damaged the Fuel Pressure regulator O-Ring - Mercedes-Benz Forum
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post #1 of 12 (permalink) Old Yesterday, 09:40 PM Thread Starter
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Damaged the Fuel Pressure regulator O-Ring

Hi Guys,

Was checking out my fuel pressure regulator, took out the components, all was well... but, when trying to re assemble, I couldn't get the o-ring to fit. I took the spring out and managed to get it in easily but with the spring on it was really difficult.

Long story short I ended up pressing the screw in and engaging the 1st thread of the screw by hand in the fuel distributor and started to screw it in gently with a spanner. To my surprise, shortly I saw a shred of rubber and bye bye o-ring .

So questions are:

1) Does anyone know the dimensions of this O-Ring, so I can source it locally?

2) Is there any trick to install this? How do I keep the pressure on the spring and manage to get the o-ring in without pinching it?

3) What would happen if I start the car (not run it) without this o-ring. System pressure goes low?


Part in question is #8 or the green one on the pic.


Any advice is welcome!

Thanks
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post #2 of 12 (permalink) Old Yesterday, 11:21 PM
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I'd go to dealeship and get an o-ring kit or all the o-rings there.

Fuel pressure adjustment will be required after o-ring replacement

next time make them fuel wet or coat with engine oil before assembling.
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post #3 of 12 (permalink) Old Today, 01:03 AM
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Install with silicon grease to help it center on the valve .
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post #4 of 12 (permalink) Old Today, 07:33 AM
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Correct: the greater the distance the regulator is out the higher the pressure so the gasket would act minimally in the manner a ship does IF it keeps the regulator out of the dist further.
djenka018 is correct.

However- if you're just hoping to find the gasket I have a regulator out and can measure the gasket with a micrometer.

Note: the working condition of the spring is essential! On most of these cars it could stand to be replaced!
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post #5 of 12 (permalink) Old Today, 08:21 AM Thread Starter
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Thanks for the feedback the o-ring was in fact fuel wet, and without the spring installed it went in easily.

Problem is actually knowing if the force you are feeling is being exerted by the spring or the o-ring not wanting to get in.

So if I get this right the correct procedure should be:

1- Oil the o-ring a bit.
2- Press the whole unit until it feels like the o-ring has slipped in and the thread has made contact.
3- Should be able to easily screw by hand?
4- Torque

Another question that comes to mind, how come only changing 1 o-ring will mess up the tolerances so much as to vary the system pressure if I'm not messing with the shims?
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post #6 of 12 (permalink) Old Today, 10:07 AM
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Originally Posted by Kpeters View Post
Thanks for the feedback the o-ring was in fact fuel wet, and without the spring installed it went in easily.

Problem is actually knowing if the force you are feeling is being exerted by the spring or the o-ring not wanting to get in.

So if I get this right the correct procedure should be:

1- Oil the o-ring a bit.
2- Press the whole unit until it feels like the o-ring has slipped in and the thread has made contact.
3- Should be able to easily screw by hand?
4- Torque

Another question that comes to mind, how come only changing 1 o-ring will mess up the tolerances so much as to vary the system pressure if I'm not .messing with the shims?
It shouldn't but the pressure regulator is stupid sensitive. You may want to consider replacing the whole regulator with the rebuild Bosch kit since you wanted to see the shims so badly 😉
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post #7 of 12 (permalink) Old Today, 10:35 AM Thread Starter
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Originally Posted by okyoureabeast View Post
It shouldn't but the pressure regulator is stupid sensitive. You may want to consider replacing the whole regulator with the rebuild Bosch kit since you wanted to see the shims so badly 😉
I see... well the car was having pressure problems hence why I wanted to see if someone had made something stupid at the regulator. Turns out I was the one who ended up doing something stupid haha. Go figure...
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post #8 of 12 (permalink) Old Today, 12:42 PM
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I see... well the car was having pressure problems hence why I wanted to see if someone had made something stupid at the regulator. Turns out I was the one who ended up doing something stupid haha. Go figure...
Hehe, why not just get the rebuilt pressure regulator kit?

It looks like this:
Primary-pressure regulator, K-Jetronic

Pro-tip: don't use all of the included shims.
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post #9 of 12 (permalink) Old Today, 01:27 PM Thread Starter
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Originally Posted by okyoureabeast View Post
Hehe, why not just get the rebuilt pressure regulator kit?

It looks like this:
Primary-pressure regulator, K-Jetronic

Pro-tip: don't use all of the included shims.
Yeah I should do that but I'm reluctant to do it without having the gauges myself, may be time to take it to the shop. Don't want to be fiddleing with it to much.

Using all the shims gives you more horsepowers right? hahaha.
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post #10 of 12 (permalink) Old Today, 02:22 PM
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Yeah I should do that but I'm reluctant to do it without having the gauges myself, may be time to take it to the shop. Don't want to be fiddleing with it to much.

Using all the shims gives you more horsepowers right? hahaha.
Since you're in costa rica I can't help you on the gauges.

But you might be able to make one using off the shelf parts, some high pressure rubber fuel hoses, and metric connector bits for cheaper than what you'll find online.

I don't recall what it is, but I think more shims equals less fuel. Low pressure equals rich, high pressure equals lean.
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