Flow path for CIS 3-way Pressure Tester-Can someone explain
 

We are going to fabricate a CIS pressure tester based on the photo from the factory manual with available shop fittings and valves. The workshop manual references the 3-way valve. We are trying to understand the flow path in each valve position.

In Position 3, does the gage read only the pressure from that direction and the flow path is from 3 to the gage with the line at position 1 being isolated?

In position 1, does the gage read only the pressure from that direction with the line from position 3 being isolated?

What happens when valve is in position 2? Does the gage read anything? In that position does the flow path go straight through the valve and the gage reads nothing or is it open to read the pressure of the flow from 3 to 1?

Sorry for what might be a dumb inquiry, but we want to get this right.

Thanks

Jeff

http://forums.pelicanparts.com/uploa...1306198852.jpg

Can't see the valving in the Porsche tool.

However, you can see the valving in what you build so I will walk through the flows and you can back into what you need.

Hook position 1 hose to the fuel distributor. Hook position 3 hose to the warm up regulator. Fuel flows from Distributor to the WUR.

Flow paths/Tests:

1. Fuel can flow from hose #1 to hose #3 to test control pressure and entire system residual/rest pressure.

2. Hose #3 is cut off from the test for testing system pressure and partial (upstream) rest pressure

3. Hose #1 is cut off to test partial (downstream) rest pressure.

Someone will confirm or challenge what I have typed here so wait for some more input to be sure.

this may be of some help later



http://forums.pelicanparts.com/porsche-911-technical-forum/118631-cis-fuel-test-pressure-question-77-2-7-a.html

http://forums.pelicanparts.com/porsche-911-technical-forum/132936-cis-test-questions.html

As Bob has posted, since you are making your own tester you don't need to decipher the internals of the photo.

First, there is a bit of confusion in your post. The valve only moves to two positions, not three--it rotates 90 degrees. Using the photo as a reference, create the following flow pattern for your set-up: When the valve arm is in line with the hoses (hoses next to the #1 and #3 in your post), fuel should flow directly through them, and also into the gauge--that orifice should always be open.

Turn the valve handle 90 degrees so it is perpendicular to the above mentioned flow-through hoses, and shut off one side--that's the side you will eventually connect to the WUR. As the hose connecting the gauge is not valved, it will read your pressure.

In short, you are creating a two position valve that blocks off a through-flow but always allows a flow into the gauge hose.

Thanks to all for the replies. I think we understand the flow. It is pretty straight forward, but the 3-position valve the workshop manual references is a bit confusing.

Anyhow looks like we need an open/close valve on the hoses going from 1 and 3 and in between them a tee with the gage attached (position 2).

In fact if I understand Ossiblue's post I really only need one valve.

Thanks,

Jeff

You will have a T with one inlet and two outlets. The valve in my tester is a three way valve (they go by various nomenclature; diverter valve, bypass valve mixing valve).

Essentially you take fuel from the fuel head (the port going to the WUR aka the control pressure regulator), and send it to either the gauge (blocking the WUR). In this position it reads your dead head pressure from the pump. Moved to the other position, it allows fuel to go to the WUR and the gauge, reading control pressure.

If you build one with two straight thru valves, they simply need to direct the fuel through those two paths.