Activating a pump via an oil pressure switch.

So I'm up to the wiring part of the lift pump install. I want to run the pump via an oil pressure switch, around 10lbs, so it only comes on when the motor is actually running. Not just via the ignition power. I dont want override switches etc etc if it can be done without.
Therses a spare port on the LHS of the block I could use to access oil pressure, a big PITA to get to, but it might be doable. I first thought the switch would be just a two wire jobbie, so power runs through the switch from one terminal to the other. Not so. The two wire switches are actual for a gauge, so its a sender in fact. The switches are only a single wire.
So my question is.
How can I implement a single wire oil pressure switch in to turn on the pump?
Or is there a wire in the ignition side of the cars loom thats only powered when the engine is running? Not just with the ignition on.

In my conversion, I used the single wire TB45 oil pressure switch.

For my lift pump, I use a feature of the TB45E ECU that runs my pump for 5 seconds then stops. When I get oil pressure, the pump runs continuously.
This means that if the engine stalls, the lift pump stops.

Here's how I wired it. The fuel pump relay is the original relay for the EFI pump that's no longer there.
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Originally Posted by jff45

In my conversion, I used the single wire TB45 oil pressure switch.

For my lift pump, I use a feature of the TB45E ECU that runs my pump for 5 seconds then stops. When I get oil pressure, the pump runs continuously.
This means that if the engine stalls, the lift pump stops.

Here's how I wired it. The fuel pump relay is the original relay for the EFI pump that's no longer there.
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Righto! O.k I might have to look at your diagram a few times. I have no relay but thought I will need one. So you added in the oil pressure switch? Plus the single wire on the switch is just an earth isn't it? And I would need a normally open switch I assume? As the OEM switch is opposite to what i need, I think.

How is your car running anyway? I've been meaning to swing you an email and ask.

Mine runs beautifully with the auto. Doesn't have the power level of yours but it's a much nicer car to drive now than with the TB45 engine.
It just pulls away effortlessly. Auto shift changes under boost is really nice.

If you remove the TB45 ECU from the diagram, all you need is 2 relays side by side.
Both relays powered from the same ignition source. Earth for the pump relay transits through the NC contacts of the 2nd relay so the pump relay will have no earth while there's no oil pressure because the oil pressure switch is holding relay 2 open.
Once there's oil pressure, relay 2 releases and the earth for the fuel pump relay is established via 87a.

Quote:

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Originally Posted by jff45

Mine runs beautifully with the auto. Doesn't have the power level of yours but it's a much nicer car to drive now than with the TB45 engine.
It just pulls away effortlessly. Auto shift changes under boost is really nice.

If you remove the TB45 ECU from the diagram, all you need is 2 relays side by side.
Both relays powered from the same ignition source. Earth for the pump relay transits through the NC contacts of the 2nd relay so the pump relay will have no earth while there's no oil pressure because the oil pressure switch is holding relay 2 open.
Once there's oil pressure, relay 2 releases and the earth for the fuel pump relay is established via 87a.

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Err ok. Ill need to sit down and figure this out with two relays.
Im wondering if i have a wire in the loom somewhere thats only powered when the engine is running. Then i could use this to switch the relay on.

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Originally Posted by mudski

Err ok. Ill need to sit down and figure this out with two relays.
Im wondering if i have a wire in the loom somewhere thats only powered when the engine is running. Then i could use this to switch the relay on.

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No need for such a wire. The pump can't run until the oil pressure cuts the earth of the 2nd relay.

Let's discuss it via email..

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Originally Posted by mudski

Im wondering if i have a wire in the loom somewhere thats only powered when the engine is running. Then i could use this to switch the relay on.

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There is. You could use alternator return signal to charge lamp (it goes 12V+ when alternator is charging) this feature is commonly used to run "alternator charge relay" in heavy vehicles. You could also include oil switch in to that circuit and that way you would have best of both worlds. ..... Indeed that's how subtank fuel transfer pump module is controlled/operated.

Also it would benefit everyone if you keep the line of communication on this public aka in this thread, I'm sure there are many who'd like to know how this can be done.

Cheers

Yes, point taken.

Mine is wired as shown in the diagram I posted.
I think Mark did the same but without the 5 second connection through the ECU that's only an option with the TB45.

I'm sure he'll post when it's up and running.

I have borrowed the idea with oil pressure switch as well as without. Here is my effort, I can't see any obvious issues. I had a second look at how subtank module is wired and it seems that strangely Nissan just uses the alternator charge lamp signal as earth/ground control/signal to subtank module which is weird.

Attachment 63318 Attachment 63319

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.

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Originally Posted by jff45

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.

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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

Attachment 63320 Attachment 63322

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.

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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.

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 :)

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Originally Posted by 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 :)

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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:

Attachment 63325 Attachment 63326

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. :(

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Originally Posted by Rumcajs

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:

Attachment 63325 Attachment 63326

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

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Originally Posted by 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. :(

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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.

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.

Quote:

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Originally Posted by 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.

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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...

The 2 different power sources are just the way it has been drawn. You can use the fused power source going to 30 which will power your pump and simply bridge it across to 85.

Thanks to you both. I want to get this done right now but its 33c in my garage so all I'll get done is drinking beer. Lol might have a go tonight when its a bit cooler and thats one for thing ticked off my list.

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Originally Posted by jff45

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

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Its really simple, you can use MS® Windows Paint to run lines and use your favorite PDF reader to copy symbols, connections whatever from actual Nissan diagram then pasting them to "Paint".

I use GNU/Linux version called KolourPaint cause it is really simple to use. I tried in Photoshop, Gimp and CAD software but thats just too complicated. "KISS" principle is the best.

I'm considering rewiring my fuel pump circuit (currently hooked to overide switch only) to include inertia switch (to cut off fuel pump feed in case of accident) and your 5s timer given me an idea to include little timer relay as well.

Another thought, if you are using TB45 ECU shouldn't that one be able to keep your pump running as well when engine is running? I'm guessing the ECU sees no engine running......

If one was to get hands on TB42S electric fuel pump module then everything will be taken care of....

Regards

The TB45E ECU waits for a 120 degree signal from the distributor to tell it the engine is running so that's not going to happen now. The only signal coming from the TD42T is the tacho and the ECU can't use that.
It's the same for the A/C so those wires had to be bridged.

I was using a free programme called TinyCAD where I could copy images and store them into a user library.
I'll try it with a collection of pics from the PDFs.