gbvona
Member
Our favourite rides come equipped with a starter that has a solenoid with a separate pole to handle delivery of unadulterated 12v directly to the coil (bypassing the resistor) during start. Unfortunately, the starter for my ride (1970 3500S) is long vanished due to a series of unfortunate circumstances (car came to me with an Oldsmobile engine). I have refitted with a 3.9L 36D mill, but starters with the right configuration (solenoid below) to fit the P6 are unobtainium on these shores (Yankeeland). I ended up getting a very nifty gear reduction starter that fits nicely.
However. The gear reduction starter solenoid has only a connexion for the battery line and the starter line (through the ignition switch relay). There is no terminal for feeding the top of the ignition coil. I see two possible solutions. (1) Ignore the starter boost wire. This would mean that the coil is fed through the resistor while cranking. Does this work? Strikes me it would be ok unless the battery is iffy. Not optimal, fer sher. (2) Feed the top of the coil from the wire that drives the starter motor. This would get the unadulterated 12v to the coil while cranking, but then after cranking the feed to the top of the coil would be shunted through the starter motor, not a good idea. But wait! Block this leakage with a Schottky diode, with the anode attached to the starter motor and the cathode to the top of the coil. When the starter motor voltage is higher than the coil voltage, the diode would conduct, bringing the coil voltage up, and when the starter motor voltage is lower than the top of the coil (not cranking), it would block current flow from the top of the coil through the starter. A 10 amp Schottky diode costs about a buck and has only 0.7v forward voltage drop.
Or am I missing something? Has anyone else solved this problem?
Thanks as always for your collective advice.
gbvona
However. The gear reduction starter solenoid has only a connexion for the battery line and the starter line (through the ignition switch relay). There is no terminal for feeding the top of the ignition coil. I see two possible solutions. (1) Ignore the starter boost wire. This would mean that the coil is fed through the resistor while cranking. Does this work? Strikes me it would be ok unless the battery is iffy. Not optimal, fer sher. (2) Feed the top of the coil from the wire that drives the starter motor. This would get the unadulterated 12v to the coil while cranking, but then after cranking the feed to the top of the coil would be shunted through the starter motor, not a good idea. But wait! Block this leakage with a Schottky diode, with the anode attached to the starter motor and the cathode to the top of the coil. When the starter motor voltage is higher than the coil voltage, the diode would conduct, bringing the coil voltage up, and when the starter motor voltage is lower than the top of the coil (not cranking), it would block current flow from the top of the coil through the starter. A 10 amp Schottky diode costs about a buck and has only 0.7v forward voltage drop.
Or am I missing something? Has anyone else solved this problem?
Thanks as always for your collective advice.
gbvona
