Good afternoon, can anyone familiar with CIS tell me where the fuel check valve is located? Does the system even use one?

Thanks

Thomas

The check valve is in the head of the fuel pump (outlet). Depending upon which one you have, it can be added or changed.

A pic of your pump would tell me more ...........

Click to view attachment

Thanks Ron.

Yup, that's the expensive little bugger (fuel pump)

See this thread on pelican, I never had to deal with the check valve, but I did have to replace a pump twice, man they are pricey.

http://forums.pelicanparts.com/porsche-911...alve-73-5t.html

Check valve is there and functioning.

What I'm dealing with is a cold start problem. I already replaced a faulty cold start valve. The check valve was my next move.

Are the control pressure regulators prone to fail?

Thx

Thomas

Cold start on CIS is a function of:

Control pressures regulated by the WUR ... cold, it drops the system pressure so the air flow plate rises more easily. Warm, it increases control pressure to lean out the mixture for hot running.

Air flow plate position ... must be centered and in the appropriate position in the funnel.

Mixture setting ... adjust one click at a time .. clockwise richer. It just adjusts the position of the metering barrel in the center of the fuel distributor.

Functional cold start valve ... don't know much about this.

The check valve in the pump is for hot starts. It maintains system pressure for about 20 mins after shutdown.

Yes, a WUR can fail both on vacuum (if yours has vacuum ports) and the heater element. The inlet port screen and outlet restrictor can plug from junk in the system .. rust, dirt, etc., If the heater element fails, car should run rich.

My 2.7L starts just fine, but I have it wired so I can turn the key on and let the pump build system pressure prior to starting. It needs to build a tad bit of heat before it will idle correctly (my cold start valve is disconnected and I have no AAR).

And the picture of the pump .... you are showing the inlet, not the discharge where the check valve is located.

The check valve is on the side of the pump, not in the end. As for cold start issues, look at a wiring diagram, make sure the wire it there from the starter, and make sure the thermotime switch is functional. That's the one in the left chain box cover.

The Cap'n

> What I'm dealing with is a cold start problem. I already replaced a faulty cold start valve. The check valve was my next move.

Check valve (and accumulator) are there to assist _hot_ starts...

What are the symptoms?

I have to crank the car 10-20 times then it stumbles to a start. Once it running, it will fire up at the first crank. Thanks for all the replies guys!!

Hand Throttle up?

Cold start issues:

1.) Cold start valve or thermotime switch faulty

2.) Fuel pump not running or incorrect fuel pressure**

3.) Air-Flow sensor plate rest position incorrect

** Problem could also be in the WUR for incorrect pressures.

And if you have a 73.5 2.4L, remember that you have an additional control pressure regulator (WUR kinda) on the throttle body.

Well I think I found the problem. There was no power to the CPR. Bad ground circuit to the relay.

Thanks for all the help everyone!