CIS Primary Fuel Pressure Regulator Assembly

[blg5035]

Over the weekend I installed a new FD system fuel pressure regulator, and I wanted to be sure I installed the proper o-rings that came in the kit, 928-110-920-01.

I forgot to take a picture of the regulator/plunger while I had it out, so I am going to use others' pictures.

The kit I bought came with 2 o-rings, other than the large green one in this picture. I found the two different ID o-rings slipped around the two steps on the needle. See the red and blue arrows in the below picture.



The ID of the "red" o-ring seemed too small to fit on the plunger, so I put the "blue" o-ring on it.

Next is where I'm not sure I did the correct thing. After slipping the large spring over the regulator, I put the "red" o-ring back on the tip of the needle. Was this correct or should the "red" o-ring not be used at all? I am thinking I should not have used the "red" o-ring based on searching the forums, although I was not able to explicitly answer my question. I also had to add an extra copper sealing ring to lower the system pressure. There was only one shim on the old regulator when I removed it. System pressure was a healthy 4.9 bar with the old regulator and one medium thickness shim.

(Pic copied from another thread, although mine was missing the o-ring on the plunger as well)


I will be traveling the next few days, so I might be slow on the response, but thank you for your input

[T77911S]

in the bottom pic you need the one that is missing on the end of the plunger. that seals the input to the PR when the pump is off.
there is another ring in the threaded housing on the right,. that one seals the return from the WUR when the pump is turned off. this helps to raise the residual pressure.

if you added a copper washer to the OUTSIDE of the PPR, that is a DRASTIC change.
look inside the FD, I bet the old oring from the plunger is still in there, especially if the pressure was good before you removed it.

there is no Oring on the tip

[blg5035]

Thanks for the response, T77911S. I'll remove the o-ring on the tip and check for the old o-ring.

Unfortunately the car got hit while I was out of town, so it might be a while before I can do the work

[blg5035]

I finally got around to working on this. I removed the extra o-ring from the tip of the regulator, please confirm that I got it right this time



I did not see remnants of an old o-ring from the plunger, but I think you are right about something causing the control pressure to rise significantly, that extra o-ring! With the extra o-ring and a single copper washer, the system pressure was something >5.5 bar. Adding a second copper washer brought the pressure down to ~5 bar. After removing the extra o-ring and using a single copper washer, the system pressure was 4.5 bar.

[blg5035]

I looked at boyt911sc's post on the pressure regulator and I did wrong again lol. The o-ring needs to be pushed down some more...try #3
Residual fuel pressure loss.............

[boyt911sc]

Originally Posted by blg5035

I finally got around to working on this. I removed the extra o-ring from the tip of the regulator, please confirm that I got it right this time



I did not see remnants of an old o-ring from the plunger, but I think you are right about something causing the control pressure to rise significantly, that extra o-ring! With the extra o-ring and a single copper washer, the system pressure was something >5.5 bar. Adding a second copper washer brought the pressure down to ~5 bar. After removing the extra o-ring and using a single copper washer, the system pressure was 4.5 bar.

Ben,

Could you post the Bosch ID number of your distributor? Do you have a -031 or a -077 or a -097 FD? Hard to see the detail of the primary valve tip in your picture and that's the reason for my request. Thanks.

Tony

[blg5035]

Hi Tony, thanks for chiming in. My FD appears to be -031



This is a better view of the plunger:



Is 1 or 2 correct?

[jimbeaux911]

having just gone thru all of this myself for the first time, two looks much better than 1!

I bought a new primary pressure valve for mine, and it did not quite match up with the old one, so I wound up reusing the old plunger, and replaced the orings. Best of luck!

[blg5035]

Originally Posted by jimbeaux911

having just gone thru all of this myself for the first time, two looks much better than 1!

I bought a new primary pressure valve for mine, and it did not quite match up with the old one, so I wound up reusing the old plunger, and replaced the orings. Best of luck!

Thanks! This solved my hot start issue. Hooray!