What in the world did I do to deserve that kind of attitude. I DO like to eat and sleep every few days. In this case, I just had a three week old hard drive crash a few minutes after I posted my reply. This is the seventh laptop crash in four computers since the first of the year. I can't keep spending hundreds of dollars every month to help ungrateful people. I hooked up a ten-year-old tank that has never failed me, then headed right back to the computer to see if you replied. Do you still want help? If so, I promise I won't leave to go to the bathroom or search for a service manual on your behalf.
You didn't give any preliminary test information. That's why I asked you to measure the two voltages as a starting point. I don't know what you expected, but this is a real simple circuit that can be broken down into two parts.
Now, thank you for providing the readings. Had you taken those first, you would have known neither the Engine Computer nor the alternator would solve the problem. Do I dare ask you to confirm the engine was running when you took the readings? At the risk of getting chewed out further, you WILL have 0 volts on those wires with the engine stopped.
Yes, it does make a difference if it's a diesel; not in the circuit, but in the symptoms. The alternator field gets it voltage from the automatic shutdown relay, but that relay also feeds the injectors and coil(s) on gas engines so they can be used for diagnosis too. A dead ASD circuit would result in a no-start condition. For the diesel engine, I don't see any reference to anything else getting voltage from the ASD relay, so that would be the best guess at this point. Swap the ASD relay with a different similar one to see if you get battery voltage to the field terminals with the engine running. If you still don't have voltage, we have to determine if that relay is turning on. Since we don't have working ignition coils to prove the ASD relay is turning on, you can pop the cover off the relay and watch the movable contact, or poke a wire into the terminal and use it as a test point. I'll describe which terminal if you want to pursue that approach.
If a known good relay is turning on, that leaves only the wire from the relay to the alternator. There is one 6-pin connector in the middle of that wire. It is on the right side of the intake manifold. The 12 volt feed wire from that connector to the alternator is dark blue. Up to the connector, the wire is dark green with an orange tracer.
You can also check for voltage at all times on one pin of the ASD relay. There is a fusible link wire in that circuit but it also feeds the ignition switch and Engine Computer, so chances are that circuit is ok.
Thursday, July 22nd, 2010 AT 10:08 PM