Quote:
Originally Posted by 47silver
The main cylinder injectors should NOT operate when the air sensor is at rest. When you lift the sensor you can hear them operate, that is how they should operate not until the sensor is raised.
On my car the fuel pump starts when the key is on. My injectors do not spray (i adjusted them as detailed in the Haynes manual). The manual says to pull an injector and put it in a container. then activate the fuel pump. adjust the fuel mixture 3mm ccw 2 turns. then adjust the mixture screw until an injector just barely starts to operate then turn it ccw 1/2 turn so it is off.
Since the injectors dont add fuel when the car is starting the designers added a cold start valve and the cold start valve only operates when you energize the starter. If you see the wiring diagram on here you will note that it gets power from the yellow wire off of the starter.
On a 75 the power is sent through a switch on the throttle body. When the switch is made the power flows to the CSV. The ground side of the valve is sent to the thermal time switch. On my 75 this ground wire is red/black. The red/black wire on the TTS is open to ground if the engine temp or the electric heater element is above a certain temperature. If the temp is below setpoint then the ground is made and the valve can work. The other contact on the TTS has 12VDC when the key is on...
I tested my CSV by pulling off the throttle body, and I put 12vdc across the valve. I turned my key to ON which starts the fuel pump and I heard a faint click and saw the spray in the air box from the CSV. I knew it worked with direct power so I was able to trace my problem to a bad contact in the connector at the CSV.
Some CIS cars have a switch located on the air sensor. This switch starts the fuel pump when the sensor is raised. Since My 75 fuel pump starts when the key is on the pressure is always high. If yours has the switch on the air sensor then
jumper the fuel pump to on and then test the valve again. If you have spray then your cold start valve is ok.
If you dont have spray then I would guess that the check valve that is located on the fuel pump is bad because it will not keep the pressure in your supply line high enough to let the cold start valve injector work.
With gauges you can test the leakage of this pressure.
The CSV is necessary to get initial fuel to the system as the cylinder injectors are designed not to work when the air sensor is at rest. The main reason I believe that the cylinder injectors dont work until the engine is running is to prevent hydrolock.
So here is sequence:
1. turn key to start.
2. power flows to throttle switch to cold start valve to ground at tts.
3. Cold start valve sprays fuel.
4. then the engine starts.
5. when the engine starts the air sensor raises.
6. then the fuel pump starts.
7. then then injectors operate.
I just replaced an air box, so i reviewed a million pieces of info to find out how this stuff works. you need gauges, a good vom and wiring diagrams and you can figure out most problems.
After replacing the air box i am an advocate of removing the CIS system for maintenance to replace any seals, hoses, gaskets and suspect fuel lines. it is easier than you think.
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Gary,
I'm impressed with your CIS diagnostic but I tend to
disagree with your theory about the injectors (6) not adding fuel during the start phase. If that's the case, how do you explain when the engine is warm/hot? The
CSV is inactive when the engine temperature is around 60°F or higher. Once you crank the engine during a START phase, it sucks air and displaces the AFS plate causing the injectors to squirt fuel. I'm no CIS expert and would be much obliged to be educated and informed about your findings. Thanks.
Tony