different brand, 73 Datsun pickup issue
 

Since this is the main site I mess with regarding cars I've got a question on a 73 Datsun that I have in the shop. Truck starts, drives and runs out good but shuts off whenever it is put in 4th gear. Unfortunately the wiring harness looks pretty rough. I'm considering running a wire to the coil to put 12 volt to it through a dash mounted toggle switch. I have not done any troubleshooting and this is if I find that that is where I'm losing it. It is exactly like someone turns the car off when it happens and it will not start if clutch is in in 4th gear. Any thoughts on where to start looking? tia

Is physical movement of the shift lever creating some form of electrical short? Is there any wiring in proximity to the shift linkage? Can the vehicle run if shifted into fourth but keeping the clutch pedal down?

neutral switch?

Do you need to depress the clutch to start? Or does it have to be in neutral? If the latter, I would agree with Tom a neutral safety switch issue, possibly internal linkage slop is not allowing 4th to clear the neutral detente.

NSS was issue. Seems tranny shift linkage has so much slop in it 4th was allowing the NSS to drop out, shutting it down. The wiring is quite boogered up in this vehicle. Prior to jumping out NSS you could crank this vehicle in any gear (except 4th) without the clutch mashed in. Now it will start on any gear without clutch mashed in. It runs and drives out good.

Tell the owner that the '74 models are out now...

LOL - owner is good friend and neighbor. It was his grand daddies truck or something like that. Anyway he said parts are near impossible to find for it. Personally I wish I could go out and purchase a brand new one exactly like it today. The closest I was able to find to it was a Kubota diesel side by side but it is not street legal.

I'd be happy to buy many of my former vehicles new again today.

Those who have forgotten the rugged durability of Seventie's Japanese sheet metal in Northern climates may want to refresh their recollection by watching an Alka-Seltzer tablet after being dropped in water...

A feature from that era that will drive you mad is the seat belt interlock. I don't think there is a single one left that is original with them being so easy to wire around.

I would have never thought to look for a NSS on a manual transmission.

On Chevy trucks from the early 50s the starter button was on the floor. And if you hit it the started engaged and if you were in gear you could creep the car or truck along at about ten mpg.

Think of it as an early example of an EV.

LOL, there was not really anything else that could have been causing it. Seems tranny is pretty worn and whatever linkage inside the tranny moves into position to indicate neutral is now at 4th gear position.

I will say this truck will start/run without putting it in neutral or holding the clutch in like the early ones did. Just think, if the engine dies you can then run it on electric;) by engaging the starter (for a little while).

I remember when a relative of mine bought a new 1974 Dodge Coronet, and was annoyed by the seat belt/ignition interlock. He asked me if I knew how to defeat it. I went to his car, peered under the seat, found one wire running from the floor to the seat, and unplugged it. Done.

During that time several people told this same story....

They were the type to get in the car, start it, and then put on their seat belt. This was their habit.

So they would get in the car and it would not start. Much time and sometimes money was wasted before they understood what was going on.

But a quirk was while the starter might not engage you could put the key in run, roll the car down a hill, and jump start it. Because the only thing locked out was the starter.

One guy said he borrowed a car from a friend and it would not start. So for the few days he had the car he was always careful to park on a hill.

1973 Datsun PL620
 

Glad you were able to sort it out .

The manual transmission versions of this fine old truck had a dual points distributor that the second set of points didn't work until you were in fourth gear so I was imagining a wiring or switch issue .

The seat belt starter interlock was the 1974 U.S.A. models only .

I didn't mind it too much as they were required to have a "logic relay" that would allow you to re start the car within a few minutes, those relays were typically the gremlins .

I sometimes miss my Datsun 620 pickup, I had the long bed and my 32" legs were sometimes cramped .

IIRC I sold it on to someone here .