Porsche 911 SC - Varm Control Pressure to high, how to lower?

[PorscheCollecto]

Hi all,

I recently had to change my heating element in my WUR. It was in this thread.
WUR - 0 438 140 045 - bimetalic resistor broken - how to fix?

Wanted to create a new thread, since I got further and did want to mix the two up. I fixed the WUR, exchanged the heating element with an original resistor I sourced, so that's all good.

Now reinstalled the WUR again and wanted to ensure all fuel pressures is fine, so did a full pressure test. And the conclusion seems to reveal that the Warm Control Pressure (WCP) is too high.
So I'm asking for help on how to decrease it?
I've understood from other threads that to increase the WCP you have to "knock" on the DISC on the WUR.
So how to do the oppersite? do you have the dissembled WUR and "Knock" the DISC from the inside out or?


Here's my results from the Fuel Pressure test (done at 22 degrees):



My car is Porsche 911 SC from 1978 (actually one of the first one done in late '77)
The WUR is: Bosch 0 438 140 045

I can see from Bentley graph, that the Cold Control Pressure is ok, just inside the range:




But according to the table, the WCP is too high, max is 3.6 bar, where mine is 4.2 bar max.


Thanks for help in advance.

[Mark Salvetti]

You can make the WUR adjustable. Check out these two threads:

https://nineelevenheaven.wordpress.com/adjusting-the-warm-up-regulator/
Made an Adjustable WUR- Step by step, got Pics!

Mark

[SiliconSurfer]

I recently rebuilt my WUR and I learned a lot about how they work and how to adjust. There is a rebuild guide you can download at k-jet.biz which is very helpful.

There are actually several adjustments that have to be set correctly. The level of the pin which holds the bimetallic plate and controls the cold enrichment (reduced control pressure) is only one of them. There is also the warm pressure which isn’t controlled by the bimetallic plate and there is the vacuum control which increases pressure with high manifold vacuum.

The hot pressure is set by a brass cap on the bottom of the regulator that gets tapped in to increase it. In your case that probably means you need to open the regulator to tap it further out to reduce the pressure and slowly tap it back in until you get the right setting.

Download the rebuild guide for dual diaphragm WUR for more details. Note that it talks about setting hot pressures without power, because during reassembly after rebuilding you leave the pin for the bimetallic plate high so it doesn’t affect the pressure, then lower it after setting the hot pressures. In your case the cold setting is done so you’d need power to adjust the hot setting.

Good luck, it’s a fiddly job that takes a lot of adjusting and testing to get everything right.