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’83 533i, Does anyone know the function of Item 13, p/n 13311713470 (connection piece)? One is located before the fuel pressure regulator and the other near the firewall.

http://www.realoem.com/bmw/enUS/showpar ... Id=13_1092


Both of mine have same markings of BMW and Bishoff 1.284.337.3





BavAuto shows something completely different:
https://www.bavauto.com/bmw-fuel-line-13311713470

They are fuel dampers. Many folks 86 them, when replacing fuel lines.

Thanks! Once you gave me the name of them, I was able to find prior posts. Looks like not needed.

heinek077 wrote: Looks like not needed.

That is based on experience, not the engineering that BMW did. But BMW doesn't reinstall them so maybe not having them available is a clue that their experience is the same. I'm sure the engineers would state a case for reuse if they do not leak which was a common failure on these.

heinek077 wrote: Jan 29, 2019 7:08 PM ’83 533i, Does anyone know the function of Item 13, p/n 13311713470 (connection piece)? One is located before the fuel pressure regulator and the other near the firewall.

I use the picture of first post but it is the same in my car. Question is where it is supposed to this fuel connector goes???....according realoem drawings it goes into the fuel inlet hose to the injectors bar, but in the picture (and my engine and others I saw) it was installed into the fuel return hose.....what is the right position???....and its function????

Aldo525 wrote: Aug 06, 2024 6:41 PM Question is where it is supposed to this fuel connector goes???

The OP pics are telling. The first photo shows the one on the fuel return line after the fuel pressure regulator. The second photo shows the one on the way to the fuel rail. The car has two from the factory.

Blue Shadow wrote: Aug 06, 2024 10:19 PM

Aldo525 wrote: Aug 06, 2024 6:41 PM Question is where it is supposed to this fuel connector goes???

The OP pics are telling. The first photo shows the one on the fuel return line after the fuel pressure regulator. The second photo shows the one on the way to the fuel rail. The car has two from the factory.

Hi, your are right about the two units in OP pictures, didn't see that ....but realoem shows just one is used in all the M30 engine models....533i, 535i, 525i, 635csi, etc....and it goes only in the fuel inlet hose.

Aldo525 wrote: Aug 07, 2024 7:39 AM Hi, your are right about the two units in OP pictures, didn't see that ....but realoem shows just one is used in all the M30 engine models....533i, 535i, 525i, 635csi, etc....and it goes only in the fuel inlet hose.

Just to add to the confusion, your 525i probably came with the return line piece as per this photo:



Maybe you can find marks showing something was mounted there.
My 528i has that and nothing on the inlet side; they probably used the big loop of hose between the pump & filter as a damper.

The realoem ETK is much newer. Look at one from a couple decades ago and it probably shows two.

Federico wrote: Aug 07, 2024 9:43 AM

Aldo525 wrote: Aug 07, 2024 7:39 AM Hi, your are right about the two units in OP pictures, didn't see that ....but realoem shows just one is used in all the M30 engine models....533i, 535i, 525i, 635csi, etc....and it goes only in the fuel inlet hose.

Just to add to the confusion, your 525i probably came with the return line piece as per this photo:



Maybe you can find marks showing something was mounted there.
My 528i has that and nothing on the inlet side; they probably used the big loop of hose between the pump & filter as a damper.

Hola Federico,

Nop...that piece or marks there are not present in my 525i. In fact, the car has not any of that dampers...so the question is Are those dampers important for the injection in any way???.....What should be the original intention on BMW engineers???

In my 525i you can feel how the inlet hose pulsates following what appears to be each injector opening, so maybe these damper are intended to avoid that pulsations (at least inlet hose)???....ideas???....In the end I would just like to know if it is a crime not to have these pieces or it doesn't matter at all.

Many people have driven around without those dampers in place, so no worries there.
They are supposed to keep the fuel pressure more steady, preventing the idle from drifting up/down. They may also reduce noise.

Below is the most decent explanation I found online, at https://jetronic.org/en/d-jetronic/66-introduction

Every car has one or more dampers in its fuel line. Very early versions had a ring pressure damper sitting in both suction and pressure line of fuel pump with a diaphragm in between. The problem with that solution is that a torn diaphragm will also short cut the fuel pressure. Later cars only have a pressure damper behind pressure regulator and some an additional in suction line. Dampers have the task to reduce noise and dampen fuel pressure peaks. Why some also have a screw for adjusting it like we have it on pressure regulators is a miracle that I cannot explain.
Your Dr-DJet (Volker)

Federico wrote: Aug 08, 2024 10:05 AM Many people have driven around without those dampers in place, so no worries there.
They are supposed to keep the fuel pressure more steady, preventing the idle from drifting up/down. They may also reduce noise.

Below is the most decent explanation I found online, at https://jetronic.org/en/d-jetronic/66-introduction

Every car has one or more dampers in its fuel line. Very early versions had a ring pressure damper sitting in both suction and pressure line of fuel pump with a diaphragm in between. The problem with that solution is that a torn diaphragm will also short cut the fuel pressure. Later cars only have a pressure damper behind pressure regulator and some an additional in suction line. Dampers have the task to reduce noise and dampen fuel pressure peaks. Why some also have a screw for adjusting it like we have it on pressure regulators is a miracle that I cannot explain.
Your Dr-DJet (Volker)

Gracias Federico!!!....Good explanation and clarifies things. In fact, the replacement for that round damper is now what appears to be a simple tube, I don't know if it has anything internally, but it appears to be just a plastic tube. Maybe here somebody knows that new plastic tube.

That's just a simple connector. That and also molded hoses have been issued as supercession parts on E30's as well:
https://www.bimmerforums.com/forum/show ... -this-part

Threw them out of all my cars, literally no changes ever

Maybe if you drive in -30°C weather and fuel is much more viscous it makes a difference.. I don't