Activating a pump via an oil pressure switch.

[Rumcajs]

I like the way you draw it to match the factory diagrams.

Personally, I don't think both alternator charge and oil pressure need to be combined.
My reasoning for preferring the oil pressure model is that there's historically more risk of losing the alternator charge than losing oil pressure.
Of course, with a bypass on the lift pump you don't really risk being stranded but it's nice to have everything running as it's meant to.

Good info about the sub tank pump. I didn't know that.

What I'm unsure is if the alternator can support any load on the charge lamp signal cause as I dig deeper it makes no sense why Nissan ignores the obvious. I have re-done the diagram to keep up with the Nissan theme basically energizing relay via alternator field exciter circuit when engine is not running which seems like Nissan does the things e.g. subtank module, A/T temp warning light etc...
I also added variant with just oil pressure switch control.
Regards

Fuel_pump_circuit_with_alternator_Nissan_style_control.jpeg Fuel_pump_circuit_with_oil_pressure_switch_control.jpeg

[mudski]

Ok. Ive wired it up using two relays as per Johns advice. I havent plumbed up or wired the pump in yet. A bit too hot the last few days to do anymore... but i pre wired it and it worked. I then got in the car to go to a job and noticed the oil pressure light coming very dim.
I have the ignition wire fused and i had pulled the fuse out so the system would be inactive while the pump is not in. This might had caused it, not sure. The earth for both pump and relay is just to the body of the car. Maybe the earth for the relay needs to be on the motor. Again. Not sure. Ill work it out tomorrow hopefully.

Thanks again John for your help. Im ok with wiring in relays for lights etc but doing something like this was beyond my knowledge.

Sent from my SM-P600 using Tapatalk

[jff45]

I prefer this circuit which deactivates the relay when it charges.
The relay will only be around 150 milliamps and I would assume the exciter circuit could handle that.

[jff45]

You just need to open the NC contacts on the relay in the diagram when it's shown with no oil pressure so it doesn't confuse some

[Rumcajs]

You just need to open the NC contacts on the relay in the diagram when it's shown with no oil pressure so it doesn't confuse some

Yeah, I suppose but diagrams are meant to be drawn with everything at rest/off. So NO(normally open contact is pin 87) and NC(normally closed contact is pin 87a) on the 5 pin relay which I can't really find in Nissan diagrams.

Regards

Edit: OK I made my own:

Fuel_pump_circuit_with_alternator_Nissan_style_control_5_pin_realy.jpeg Fuel_pump_circuit_with_oil_pressure_switch_control_5_pin_relay.jpeg

[jff45]

Mark, What Alan is showing is that you could have done your lift pump with the oil pressure switch and only used a single relay.
My diagram is based on using my original fuel pump relay and wiring and that relay only has NO contacts. I also needed a 2nd relay for my alternative earth after the ECU ran the pump initially.
I didn't think it through enough to realise the ZD30 had no original fuel pump relay.

[jff45]

Yeah, I suppose but diagrams are meant to be drawn with everything at rest/off. So NO(normally open contact is pin 87) and NC(normally closed contact is pin 87a) on the 5 pin relay which I can't really find in Nissan diagrams.

Regards

Edit: OK I made my own:

Fuel_pump_circuit_with_alternator_Nissan_style_control_5_pin_realy.jpeg Fuel_pump_circuit_with_oil_pressure_switch_control_5_pin_relay.jpeg

What programme are you using to draw those diagrams? I really like the "factory" look

[mudski]

Mark, What Alan is showing is that you could have done your lift pump with the oil pressure switch and only used a single relay.
My diagram is based on using my original fuel pump relay and wiring and that relay only has NO contacts. I also needed a 2nd relay for my alternative earth after the ECU ran the pump initially.
I didn't think it through enough to realise the ZD30 had no original fuel pump relay.

Yep. SO I can wire up using the second pic as I have already tapped into the oil pressure switch wire, I just need to put a blocking diode in, and remove the second relay. I'll have a go tonight or over the weekend. Just so I dont stuff this up. On the Diode it has a silver line at one end. This goes toward the oil pressure switch? The Diode I have here is a 3A 400V one...

Thanks.

[jff45]

Personally, I'd try it without the diode.
The oil pressure light won't find an earth through the relay coil.
I have no diode on my setup.

[mudski]

Personally, I'd try it without the diode.
The oil pressure light won't find an earth through the relay coil.
I have no diode on my setup.

Ok. Now Just looking at the second pic that Alan has done. Which is the way I would be doing it. Pin 85 and 30 each go to a different ignition power source. Why is that? I have just tapped into an ignition power source from one of the other relays in the engine bay. Can I just run both 85 and 30 to this? I'm trying to limit the amount of wires I'm running into the cab. My custom 1inch ID wire feed tube I made up that runs from the engine bay and into the cab is kinda getting full...

I finally understood your way of using two relays, now I'm back to the start.... Not that it matters, I like doing this stuff. I even thought about somehow running the two a/c thermos and the IC thermo on a timer or something, so after I turn the car off they continue to run for a bit. Dunno why, and if it would help in any way. Or even run an over ride switch to manually run the a/c thermos if i ever need too. Again. Dunno why. Lol.

So back to my first question...