Quote:
Originally Posted by psalt
Most starter problems are really battery problems, first check out your battery or substitute a known good battery. I have had the same symptoms and if you charged the battery for a minute before attempting to start, it disappeared. My experience is BOSCH starters die with intermittent starting, sometimes the solenoid, sometimes not, which is why BOSCH rebuilds sometimes are short lived. The rebuild process often does not touch the real problem. The cores are now all over 20 years old. I always recommend the gear reduction starters for this reason.
First I would wire up a volt meter from the yellow solenoid terminal to see what is actually happening when you turn the key and nothing happens. Are you getting 12 volts to the solenoid ?
The proper way to wire a push button is with a relay at the starter, then one wire up to the dash, and a push button to ground the relay coil. Cost about $20 and very easy to fit. Since the 911 starter is so hard to get at when in the middle of the road, I installed a remote button near the oil tank. Nice to have for valve adjustment/distributor removal/etc. You do however have to remember not to hit the button with the car in gear when there is no one in the car.
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Diagnosing electrical circuits requires specific diagnosis rather than relying on common/historical solutions - much like replacing parts instead of pinpointing the real source of a malfunction.
Measuring available source voltage at the load (light bulb, motor, etc.) is a basic troubleshooting technique, and it works for most circuits. However, the no. 50 yellow wire from the ignition switch is only used when cranking the engine.
When measuring cranking voltage at the battery, one notices it drops as the engine cranks (e.g. 12V > 9 or 10V), and thus the same voltage found at the starter solenoid during cranking, >9 volts, but never 12V due to the voltage drop as a result of the starter motor cranking the engine.
A relay mounted near the solenoid reduces the existing current path (by about 6'). This minimizes voltage drop (while maximizing source voltage) to adequately energize the starter solenoid. As I mentioned in my earlier post, the added relay also increases ignition switch life by minimizing current through the normal "cranking" contacts of the switch.
Sorry for any redundancy.
Sherwood