Re: 1970 85 hp V4

[Don]

quote amuller:

Fleet, I think this is a very simple, unregulated, single-phase alternator. So it probably does have only two diodes, one on each end of the coil. The good news is that it would be easy to make a functional substitute.

The points are probably just in need of cleaning. The gap looks like about ten thou to me but haven’t gotten into them yet. The distributor rotor and stator look OK to me, no sign of any carbon tracks or cracks. So I’m expecting to have spark at the plugs when I put it together. Wow, those point sets are expensive: close to $75 new and $25-30 on ebay.

I admire the system used by West Bend on the 80 hp four: four sets of points, spaced at 90 deg, each firing it’s own coil. What could be simpler, relatively speaking?

As for the default-to-forward control logic, I can see pros and cons to it.

Yes, simple unregulated charging system….But, I think there are four diodes…Here are the simple resistance checks….
Ohm meter on high scale with rectifier leads isolated from all others and ground:
Connect one ohm meter lead to the rectifier case/ground
Now connect the other ohm meter lead to each of the two yellow leads, one at a time. You will either see an infinite reading, or some high reading less than infinity, you should see the same open or less than infinite reading on both tests.
Now, swap the ohm meter leads so the other ohm meter lead is connected to the rectifier/ground. Again, you will see either an infinite reading, or some high reading less than infinity. You should see the opposite readings than noted in the first test.
Next, you will connect one of the ohm meter leads to the red rectifier lead. Connect the other ohm meter lead to each of the rectifier yellow leads one at a time. You will see either the infinite or high reading on both leads.
Finally, swap the ohm meter leads and repeat the above test. You should see the opposite readings you saw in the previous test….
Any shorted or open diodes mean the rectifier is shot….New/used but good ones are easy to find and affordable, no need to make one up….

There are also two "shift diodes" in this system, this unit is affectionately known as the "monkey balls". I’m pretty sure there are only two diodes in this critter. This thing is here to supply current from the alternator to the shift solenoids after the key is turned off but the flywheel is still spinning. Otherwise, the engine would slam into forward gear when the key is turned off…
The resistance tests are pretty similar to the rectifier tests, just less diodes to check.
Ohm meter on high scale, shift diode leads isolated from all others and ground:
Connect one ohm meter lead to the diode purple lead, then connect the other meter lead to each of its yellow leads, one at a time….Note the readings, either infinity or a high reading, both should be the same.
Now, swap the ohm meter leads and repeat the above test. You should see the opposite readings noted in the above test.
Any shorted or open diodes mean this thing needs to be replaced. A messed up shift diode could certainly affect alternator output as well.