CAS or ECU Faulty

[AjWit]

Vehicle: 90 Laser 2.0 NT, Manual trans.

Problem: The car does NOT start sometimes and will rarely but possibly start and then run for about 10 seconds perfectly fine, then die and will not fire back up. Most of the time the car starts fine and drives great with good power and good engine rpms, noise, etc. Other times, no start, just cranks. I took it into my schools auto diagnostic class and they said the injectors are NOT firing. Fuel pressure is good, spark is good, compression is good. Ive researched this and im finding that the ECU or the CAS is typically the culprit.

Question: Does anyone know of a way that i can check to determine which one it is?

Thank you.

 

[gofer]

Your CAS has four wires going to it, a 12v signal and ground the other two are signal wires for the TDC and CAM inputs to the ECU. To test them you'll have to pull the CAS off the head and turn it by hand, this will allow you to test the signals with a multimeter as you spin it. Both the CAM and TDC signal wires should read up to 5v as you spin the CAS, the CAM signal wire pulses 4 times per revolution and the TDC pulses 2 times.

Heres a pin out of the CAS connector going to the ECU so you can check continuity of the wires and know which wires to test for the CAM & TDC pulses.

ECU Pins to CAS connector Pins -

• CAM Signal wire (BRN/YEL): Pin 21 at the ECU to Pin 3 at the CAS (4 pulses per revolution)
• TDC signal wire (BLK/BLU): Pin 22 at the ECU to Pin 4 at the CAS (2 pulses per revolution)

When you pull the CAS off to test it you need to make sure you don't have it spun 180* out or else your motor won't start at all, heres what it SHOULD look like.

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[AjWit]

Thank you. That was very helpful. Being that my car normally runs great (i just drove it all day with no problems and about 4 different starts), wouldnt I have to get the car into another no start situation to test the CAS? Being that it obviously is going to test WORKING if the car is running properly?