74 cis Fuel mixture troubles
 

just finished assembly of a 74 cis - 911/93. Mechanically the motor is now in great shape with most of the credit going to Wayne ad his two most helpful books. The motor started without any trouble but is running too rich. The exhaust is black as but still manages to idle although it is laboring. After trying unsuccsefully to change the mixture on the fuel control unit it looks like some advanced info may be necessary.
I purchsed the car with the motor out and partially disassembled, so I never got a chance to see where all of the cis fuel and vaccum lines were connected. here's a few questions that you experienced guys will probally find amusing but could help solve my problem.

1. When should the WUR be receiving 12 volts?


2. Where does the motor temp that the cis uses for reference temp to control mixture originate?

Any links to pics that show the cis system would be most appreciated.

Thanks in advance

Kent

1 To my knowledge (and on my '75/77), the WUR will receive 12V as long as the car is running. This is to keep a stable "hot" control pressure. The engine itself may or may not heat the WUR adequately, so the internal element is designed so that it always runs.

2 The WUR controls the hot and cold control pressures during normal operation. The Thermo Valve also causes the 7th injector to fire, but that's only for the first few seconds after starting.

There is a modification to the WUR that allows you to adjust the baseline cold pressure, but it does not affect warm pressure. If you are out of spec during warm running, and the WUR is getting power, you may have a bad WUR, fuel pump, fuel filter, etc. Small system pressure changes can be made (<3-4 psi) to pressure by adjusting the shims in the fuel distributor, but that won't fix a real problem like a bad WUR.

Send me an email adddress to fintstone@aol.com and I will send you a link to some pictures. I can't get the link to work by posting it here.

If your cold start valve//7th injector on the back of your throttle body is not closing after the car starts, you will run very rich. Also, if the o-ring sealk is left off when it is installed, it will leave an air leak which will cause you problerms adjusting mixture. the injector is vey easy to test, but difficult to remove/install enough to test with the engine installed.