SteveJ

I thought it was a shining analogy.

You can get a new Aisin WPN-013 water pump. I have no idea whether or not GMB was an OEM supplier, but Aisin is a Japanese based company that is a parts supplier for that country's automotive industry.

I'm not sure of the location on the 70/71. I think for 72, the body ground moved to frame rail. I'm pretty sure it's on the frame rail for the 73.

Just for completeness, the Nissan part number is 48750-E7705.

Also to replace the back of the module, you do NOT need to remove the ignition switch. You can unplug the harnesses for the combo switch and ignition, remove the 4 bolts from the steering column bracket and lower the steering column enough to get to the screws.

If the solenoid works fine, the likely problems are the module on the back of the ignition switch (2 screw modules may still be available from Nissan) or corrosion in the wiring.

Find a weather resistant maxi fuse (or ANL fuse) holder if you are planning to mount the fuse holder where the current fusible link holders reside. I also suggest using ferrules on the wire ends to improve clamping force on the wires. You will need to find a ferrule crimper that can handle the wire sizes (relatively easy to find on Amazon). Here is an example of a marine ANL fuse holder: https://www.crutchfield.com/p_867FUSEDIS/Wet-Sounds-WWX-FUSE.html

The click you hear is normal. That is the accessory relay. Move on from that. You need to verify voltage to ground (or negative) at the starter solenoid when the key is in START. That is the black/yellow wire. Suggested actions: Pull the black/yellow wire off the starter solenoid. Put the positive voltmeter lead on the black/yellow wire and the negative lead on the battery negative. Have your assistant turn the key to the START position. Measure the voltage (and report it here). If you have around battery voltage at the black/yellow wire, then here is the next test. Keep the black/yellow wire removed. Ensure the car is in neutral. Get a screwdriver. Touch the screwdriver to the positive cable on the starter and the spade terminal where the black/yellow wire was. You don't have to hold it there for long. If it doesn't engage the solenoid immediately, try a couple of more times. Red arrow - Spade for black/yellow wire Orange arrow - Positive cable from the battery. If the solenoid immediately engages, then your starter solenoid is probably in good shape. Report your results.

Also: https://www.vredestein.com/classic-tires/products/990-SPRINT-CLASSIC/ Tire Rack link for the above tires: https://www.tirerack.com/tires/tires.jsp?tireMake=Vredestein&tireModel=Sprint+Classic&sidewall=Blackwall&partnum=7HR4SC&tab=Sizes

Look here: https://cokertire.com/amfinder/index/index?finder_id=33511382

https://www.zzxdatsun.com/

@Mike, I think osinpowe may be some kind of bot or spammer.

I just semi-permanently installed the electric fuel pressure gauge in my car. My job (and helping the parts cannon crowd) has conditioned me to have more diagnostic info readily available.

The redneck way is to use a long piece of hose. I took a different direction. I went a 0-30 from this brand: https://www.glowshiftdirect.com/elite-10-color-100-psi-fuel-pressure-gauge/ If you want a cheaper alternative: (Wrong part removed) https://www.ebay.com/itm/176895594944?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D20200818143230%26meid%3D5a579eb1d3964f638fde15fc3eb8a2e0%26pid%3D101224%26rk%3D4%26rkt%3D5%26sd%3D176367258697%26itm%3D176895594944%26pmt%3D1%26noa%3D1%26pg%3D2332490%26algv%3DDefaultOrganicWebV9BertRefreshRankerWithCassiniEmbRecall&_trksid=p2332490.c101224.m-1 I can't vouch for the quality, though.

The fuel pressure gauge should go between the fuel filter and the fuel rail.

That would indicate a failed diode to me. Wouldn't you agree, @Captain Obvious ?

The two ways a diode can fail: Open or Closed. Open: Detection - You will see infinite resistance (OL) no matter what orientation you use with your meter leads. (Always try both directions.) Result - The alternator won't charge. Closed: Detection - You will see zero (0) resistance no matter what orientation you use with your meter leads. (Always try both directions.) Result - The alternator will charge, and the car will probably try to keep running with the key off since this will backfeed the ignition circuit.

Try swapping the leads around where you got the open line. Diodes will block a resistance reading on a meter if you have the leads reversed.

I have seen the diode fail open in that design before. That would keep the car from charging. Also, if the ignition fuse in the fuse box is blown, it won't charge. The test I asked @Zedyone_kenobi to perform would help to identify those problems.

The problem is that I don't see the results of the tests I suggested you do.

There is no lamp on a 71. On the original 71 alternator, it would be a field wire and alternator neutral on the T plug going to the external VR. Since the car is modified, the field wire is jumpered to the ignition wire, and the neutral wire is jumpered to the battery wire.

The signal wire should have battery voltage. The ignition wire should have no voltage with the key in OFF, and it should have battery voltage with the key in ON.

12.3 volts while running tells me that there is a problem. However, diagnosis is not complete. Have you verified the signals for the sense and ignition inputs? Those are the two wires going to the T plug on the back of the alternator.

There are times to be pedantic. This isn't one.