the-sleeper-z31 Posted January 10, 2010 Share Posted January 10, 2010 i have gone through the entire FSM from xenon.com i cant find anything that specifies what the computer uses ( as far as a sensor) to control injector pulse width, and activation......... stumped...... changed distributer in hopes of it being the crank sensor.... no difference, have battery voltage at all red wires on injectors when car is on. i believe the ECU controls the injectors through the ground side..... could the ECU be my problem? does anyone know which ECUs are interchangable throughout the years z31 was produced? i am a certified auto electric technician, AND IM BAFFLED.... i figured that if there is a GURU for this car he would be on here.. thanx Quote Link to comment Share on other sites More sharing options...
the-sleeper-z31 Posted January 10, 2010 Author Share Posted January 10, 2010 somebody?? anybody? Quote Link to comment Share on other sites More sharing options...
chrism Posted January 10, 2010 Share Posted January 10, 2010 ECU uses ground to pull the injectors low on one side. You can use a noid light to see if your getting a pulse. disconnect injector plug. Put light across the plug. There should be no light unitil the engine is turning over. When the engine is turning over, the light will pulse. Or you can check the voltage on the ECU side with a DVM. When the car is turning over, the voltage will drop. If not, check the ECU ground and power connections before replacing the ECU. Quote Link to comment Share on other sites More sharing options...
the-sleeper-z31 Posted January 10, 2010 Author Share Posted January 10, 2010 the noid light was the first test i did, i believe that i may have found the problem,...... the ignition signal wire to ECM is shorted out to the wiper motor wiring. i unpluged 20-pin connector at ecu and and checked the resistance in the ignition wire-s pin #3 and #5, both should show no continuity. pin #3 had 68.7 ohm on 200 ohm scale. further more i relized that the wiper motor was disconnected., pluged it in----- turned it over and wipers came on........... does ECU need ignition signal to pulse the injectors? would this shorted condition also effect spark quality? Quote Link to comment Share on other sites More sharing options...
the-sleeper-z31 Posted January 10, 2010 Author Share Posted January 10, 2010 beautiful ride by the way Quote Link to comment Share on other sites More sharing options...
chrism Posted January 10, 2010 Share Posted January 10, 2010 I'm not sure. Having it shorted to the wiper motor is not a good thing. Probably why the motor was disconnected. The ecu needs to know timing so that it can pulse the injectors at the correct time. That would be before the ignition occurred. Does sound like you found the problem. Pulse width would be determined by feedback from the air flow meter reading. Also gets feedback from o2 sensor. Quote Link to comment Share on other sites More sharing options...
the-sleeper-z31 Posted January 10, 2010 Author Share Posted January 10, 2010 disconnected wiper circuit, now have injector pulse, car is dumping to much fuel, wont start, MAF??? fuel temp sensor? pressure regulator? Quote Link to comment Share on other sites More sharing options...
chrism Posted January 10, 2010 Share Posted January 10, 2010 Could be in limp mode because one of the sensors you mentioned may not be sending a signal back to the ECU. Also, make sure the O2 is connected good. No signal from the O2 can cause rich conditions. Check fuel pressure. Should not be above 36psi for fuel Injection. If it is, could be bad regulator, return line could be clogged. I would start with making sure all sensors are connected good. Quote Link to comment Share on other sites More sharing options...
michaelp Posted January 10, 2010 Share Posted January 10, 2010 Try unplugging the fuel temp sensor, a Z31 will run fine with it unplugged but will run like crap with it plugged into a faulty fuel temp sensor Also, the MAF limp mode will not allow the car to rev over 2,000rpm. Usually difficulty starting and rich conditions are caused by a faulty Cylinder Head Temp. Sensor or CHTS sub-harness on the Z31. the MAF rarely ever goes bad, and the Z31 won't be extremely rich /w the o2 sensor unplugged (but it does stay in open loop). Quote Link to comment Share on other sites More sharing options...
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