CIS cold start enrichment circuit/relay

[ssinparadise]

I have been trouble shooting my cold start system in my 73 1/2 t (cis). There is a relay (typical round, used in the 914 for f.i., headlights,etc. as well as in the 911 horn circuit) that controls the enrichment circuit, according to Haynes. I have a CIS trouble shooting guide that does not mention this relay. Anyone know something about this?

Scott S.
74 914 2.0
73 911t cis

[Early_S_Man]

Scott,

I believe the relay and Thermo-Time switch were added later, perhaps for '74 or '75, because the '73 CIS circuit diagram below only shows the #12 cold-start solenoid and #14 airflow microswitch in the circuit ... besides the power from the Yellow #2 starter solenoid lead. You may want to check for a good ground at the microswitch, and +12 Volts at the Yellow wire from the solenoid during cranking. All of the circuits are in the lower left corner of the diagram:

[Jim Sims]

Adding to Warren's information: The '73 CIS cold start circuit only works while the starter is cranking and if the hand throttle is pulled up enough to engage the micro-switch on the side of the throttle housing. After the engine starts and the starter is no longer running the WUR is what controls the system during warm up. However, the hand throttle if it is pulled, helps by holding the throttle open and causing a higher idle. Check to see that your hand throttle is causing the throttle linkage to move and engage the microswitch on the side of the throttle body (driver's side). If not, the attachment fitting from the hand throttle to the throttle linkage rod in the tunnel between the seats may have loosened or broken. I think you may be able to access it by reaching forward through the hole that grants access to the shifter coupling (under cover behind the seats). Jim

[Sunroof]

I have a 73.5 CIS and god knows how much trouble I have encountered with this system. .......their is no thermotime switch. The only electrical connection to any of the system delivery components is the warm up regulator and cold start valve. The WUR was always the culprit because high and low side pressures require the proper adjustment and the WUR in this system, is antiquated compared to the newer revised units. The original units can be adjusted. The hand throttle is no doubt another critical part of the cold start system. If it is not working then the "claw" where the hand break sits is broken from getting brittle over the years. It takes removing the seats and small hands to get to it, but replacement is not a tough task.

Buy yourself the CIS enrichment adjustment tool (3mm) and keep it handy. Once the car is warmed up you can fiddle with the mixture setting to get any surging out. It takes tweaking to get these set right despite the factory spec. of ......%CO everyone suggests to follow.

Good luck

Bob
73.5T

[ssinparadise]

Thanks for your replies. What can I say about your efforts? Truley amazing.

The hand throttle is working, actually too well. The micro switch actuates and has been adjusted per Bosch specs. Thanks Warren, again, for your help. The hand throttle is very basic. Unless I am missing something, it merely acts a foot. It holds the throttle open, thus actuating the microswitch and doing what every throttle does.

Interesting that I have a relay for a circuit that is not actually used until the later (74 or 75) models however. I guess I don't have a thermotime switch (the cis troubleshooting guide makes no mention of this). So the starter must fire the cold start circuit.

It has got to be my WUR. ?

What is the story on the different year WURs. I have a later model WUR. Can I use it to troubleshoot.?

Thanks again guys

[zioo]

What is the Porsche or Bosch Part # for the airflow microswitch? -- Zio (1974)

[boyt911sc]

Originally Posted by zioo

What is the Porsche or Bosch Part # for the airflow microswitch? -- Zio (1974)

Zioo,

1974 CIS engines do not have airflow switch in them!!!!! What year is your car? Post a separate thread and you'll get a better response. HTH.

Tony