QuestionQUESTION: The following is an explanation of what we have done. A/C was not working. Installed belt A/C worked. Belt broke.Replaced A/C compressor clutch with bearing and belt. A/C working, low pressure side low. Turned off A/C, restarted A/C and had loud squealing noise. Turned off vehicle, restarted vehicle, squealing still present. Turned off A/C squealing stopped. Checked belt. It is tight. A/C clutch no longer engaging. Direct power to clutch and it works, appears to be bad ground. Checked grounds and fuses still won't engage now the key won't start the vehicle. Direct power to starter and the vehicle starts. Recheck grounds, fuses and relays still no go. Now direct power to starter, vehicle cranks but won't fire, no fuel, no spark. All other vehicle electrical appear to be working normally, code reader has no dtc error codes, code reader does read iso# for vehicle. Did not test automatic reset relays under dash. What have I missed that the vehicle will not start?
ANSWER: I am unclear as to the status of starting. You said that you can get it to start if you jump the starter motor. Now you say it won't start that way. What did you do in the interim other than check ground, fuses, relays?
Are you checking the fuses with a voltmeter or just visually. A fuse wire can be cracked but not appear damaged.
You could have crank or cam sensor that is beginning to fail, but not so badly as to set a code. You can measure the pulsing of the sensor when you turn it over by hand with the key in the run position. Let me know if you have a volt meter.
By 'check grounds' do you mean all the wires that are connected to the -post clamp have been followed to where they ground?
Roland
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QUESTION: My explanation was a sequence of events. The vehicle originally started with direct power, but now with direct power the vehicle cranks but will not fire. All that was done was remove the fuse box under the hood to check the grounds related to that fuse box. The fuses were all tested with the voltmeter. All of the true grounds were disconnected, cleaned and reconnected. We did seem to have a problem with connection from the fuse panel under the hood to the fuse panel under the dash on the a/c and starter relay circuits, and have been unable to find a wiring diagram that shows the connection between the two. These would be the circuits going to the automatic reset relays under the dash. Is there a circuit with a reset button (that normally is activated in an accident and shuts off fuel and spark) present in this vehicle, and is it possible to trip this without the vehicle being in an accident?
AnswerHi Ron,
The relay you are thinking about is the autoshutdown relay located at the very rear of the box under the hood. It will close so as to power the spark coil/fuel pump/injectors only for about 1 second when you turn the key to the run position (listen for the pump). Then when you start cranking it closes again IF you have pulsing from the cam and crank sensors as indication that the engine is rotating, otherwise it won't close. So you could listen for pump in the tank while cranking or check the dark green/orange wire at the spark coil which are powered by that ASD relay. If you don't have output from the ASD then either fuse 17 in the box is blown, or the pulsing of either the cam or crank sensor is missing. The sensor wires to check for 5 to 0.3V pulse are black/light blue (sensor ground at sensors or pcm 43) and gray/black (crank signal,at sensor or pcm pin 32) and tan/yellow(cam sensor, at sensor or pcm pin 33) doing these measurements with the key 'on' and turning the engine over by hand via the crank pulley. The voltage pulses should occur several times per revolution. You might have a weak sensor without setting a fault code.
If you want to by-pass the asd (not safe if driving around, ok for trouble shoot) simply jump between the two in-board pins of its socket (30 to 87).
Let me know if you find what is wrong or something else of interest. Also, tell me which engine, just in case.
Roland
