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Oil Pressure Sender wires?

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ACannell

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I am trying to re run the oil pressure sender but am having loads (:haha: - get it) of trouble. It is a three wire set-up with orange, gray and tan wires. I believe this is what they are:
Tan - Oil pressure gauge
Gray - ????
Orange - Fuel pump shut off relay

The diagrams say the gray is for the hot fuel module - what is this module? - ok so it appears I don't have one as it only exists in the BB OG set-ups.

Should the gray wire be spliced directly to the gray wire on the fuel pump relay then?
Where does the sender get it power from? Is it 12V or 5V?

I have deleted the ecu and am carbureted. I need to find out what to do with the orange wire as it won't be going back into the non-existing ecu.

Secondly - need to know what to do with the gray wire.

Can anyone help me sort this out? Thank you very much.
 
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looking on another site I found the sender is a 0-5v unit
0v-0psi
5V - 80psi

Can I use a 12V signal and install a resistor to drop the voltage without the ecu?

I'm gonna guess the gray wire is connected to fuel pump relay and is a shared ground?
 
I think there is some confusion on the wiring.

Why are you using an oil pressure switch/sender? Why not just run the relay off of 12V ignition?

You can use just the single wire on the one you have for a gauge if you like, or convert to an older single wire oil pressure sender, but they are a lot bulkier.

If you got really tricky with wiring I suppose you could use the oil pressure switch to kill the motor under 4PSI of oil pressure, but sounds like another failure point I'd prefer not to have.
 
I think there is some confusion on the wiring.

Why are you using an oil pressure switch/sender? Why not just run the relay off of 12V ignition?

I'm wanting to retain the oem oil pressure gauge without the ecu. It appears the relay doesn't use a 12v source either. The orange wire appears to be the 5v source coming from the ecu.

You can use just the single wire on the one you have for a gauge if you like, or convert to an older single wire oil pressure sender, but they are a lot bulkier.

My understanding is that the single wire won't operate my guage independently. I need the 5v coming and the gray wire for who knows what but it appears to complete the circuit.

If you got really tricky with wiring I suppose you could use the oil pressure switch to kill the motor under 4PSI of oil pressure, but sounds like another failure point I'd prefer not to have.

This actually the oem set-up but I'm not intenting on using it.

Real problem I see here is that the ecu is used to control / read the relay and sender units. I'm getting lost as to how to wire them in if I have no ecu.
 
Update:

I have no ecu - means the fuel pump relay is useless in oem config.

If I replace the fuel pump relay with an HD standard relay I only need power for the coolant temp and oil pressure senders. This means using a voltage regulator like a 7805 from radio shack. What I am trying to figure out is the total amperage required now the ecu is out of the loop. 7805's only take about 1.25A. I can piggy back two for almost 4A but is it enough?
 
it sounds like you are WAY overthinking this.. pretty sure oil pressure isn't run thru the ECM... what yr would have been helpful too...
 
The fuel pressure sender you have (assuming you used to be running TBI) keeps power to the fuel pump (bypassing the relay) when the oil pressure is above 3-5psi.

You should just be able to leave it there as I think it gets its power by backfeeding through the fuel pump relay after the engine is running.

The problem you'll have without an ecm is finding out how to energize the fuel pump relay during initial crank and while running. I'd just put a normal pressure sender on there.

Here's a wiring diagram for it. Orange is 12V power.
A71C50F8-F3A3-4137-89AC-209EAEAA45BA-7911-00000E493D999E7E_zps4eb52f2f.jpg
 
I am over thinking this hole deal. Why don't I replace the fuel pump relay with an HD standard relay that runs the pump the moment acc. is engaged? Being carbureted the float bowls will already be filled and will fire the engine. Once running the pump will remain running. I can then just put 5v to the oil sender itself and run the gauge wire to the cluster. I would then leave the gray wire unused.

How's this sound?
 
Yep. Relay that is on there will work fine. It is 12V, clearly shown on the diagram posted.

As to the oil pressure, it's a sender AND a switch. Oil pressure switch is 12V, but you don't need that. The gauge sender only uses the one wire, and does not need power.

Theoretically you don't even need the relay, as the switch will provide the power. With float bowls that don't run dry, the truck will start and run, the switch will turn the pump on, and life will be good. In that case, the fuel pump will shut off if you lose oil pressure.
 
dyeager535 said:
Yep. Relay that is on there will work fine. It is 12V, clearly shown on the diagram posted.

As to the oil pressure, it's a sender AND a switch. Oil pressure switch is 12V, but you don't need that. The gauge sender only uses the one wire, and does not need power.

Theoretically you don't even need the relay, as the switch will provide the power. With float bowls that don't run dry, the truck will start and run, the switch will turn the pump on, and life will be good. In that case, the fuel pump will shut off if you lose oil pressure.
Click to expand...

So are you thinking I should provide a 12v source to the fuel pump relay via distribution block etc, then provide a 5v source to the orange wire/s to run the switch and relay feature? I believe the diagrams show a 12v source to this orange wire but I have been told by many the senders work on 5v. I guess the ecu reduces the voltage.
 
ACannell said:
So are you thinking I should provide a 12v source to the fuel pump relay via distribution block etc, then provide a 5v source to the orange wire/s to run the switch and relay feature? I believe the diagrams show a 12v source to this orange wire but I have been told by many the senders work on 5v. I guess the ecu reduces the voltage.
Click to expand...

No, just don't connect the ECM wire on the switch to anything and you should be able to leave both the switch and relay as-is. Done. :)

Dorians alternate suggestion is to just feed 12V to the orange wire on the oil switch. Once the engine starts from the fuel in the carb bowls, the oil switch will turn on the fuel pump. This lets you disconnect/delete the relay altogether. Not a bad idea either way.
 
If you look at the diagram, you'll see that the fuel pump (through the oil pressure switch) is already wired straight to the battery...no re-wiring needed. It will turn the pump on when the motor is running as-is. With a carb, and float bowls that stay full between starts, you will never know the pump has a delay (4PSI oil pressure) in starting the pump.
 
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