Try reading through this Dwane.... https://axleaddict.com/auto-repair/The-Datsun-and-Nissan-Pickup-Fue... ...
My factory manual has a chart of what turns it on and hold it on...and it didn't make much sense to me.
I take it that the relay is somewhat like a room lamp timer. Turn the key to ON and the timer starts. If you don't start the engine it times out and the pump stops, if you engage the starter it keeps the pump going. Once the starter stops it starts the timer again.
Once started, two thinks keep it on. The alternator output, 12 volts, and the oil pressure light OFF. These are two indications that the engine in running or not. You definitely don't want the engine running for long if there is no oil pressure. It may be that you have to have both as you certainly could drive with a non charging alternator.
Tapping it to keep it going sounds like a loose solder connection.
THANKY!! Mike. Good article. Bookmarked it. Haynes manuals are REAL good IF you don't REALLY need a manual
The way I tell if it's working is by turning(holding) the key switch just past IGN but between(before) START. I can hear pump if everything's working.
I'll get my Harbor Freight special super duper magnifying visor down and look at the solder joints and the business side too.
You could wire it so it's on whenever the key is on, or learn how to do this in case it should quit in the future.
It's a safety device in case of an accident and you are unable to turn the ignition off. You don't want to be trapped in a vehicle on it's side or upside down with the pump going trying to empty the tank into the engine bay, let alone a fire.
Hey Datsun Mike. This is zman. I was watching the output info on Dwayne's fuel pump issue. I also will have to investigate this same issue with my 720. No problems at all, just suspicious of mine running in the accesorie position. Been that way since I bought it. Doesn't make since.
Mine just kinda got steady worse, sure don't wanna hotwire it. Already marked the plug in case I HAVE to though. LOVED the old mechanical pumps. They quit when the engine did.
Sounds like somebody hotwired yours zman.
Hey Dwayne. Thks 4 the reply. Yeah hoping 2 have time 2 chk that out soon. I've got a sweet truck,got it from the original owner,but being that said they'res a long story that's cool as hell behind that it'll blow your mind. I only have cell internet and it don't like more than 200 hndrd chartrs.
LOL, I just hate typing, have no "smart" phone, don't text.
I'm 731 584 6591. Call and tell me sometime.
Resoldered, reinstalled, so far so good!