Oil pressure safety switch wiring help

[hath]

Today I tried my hand at installing a fuel pump relay and oil pressure safety switch, but didn't quite get the result I'm looking for. The fuel pump isn't supposed to run until the oil pressure sensor hits 5 psi, but right now the pump turns the second I hook the ground cable up on the battery (key off), so obviously I've got my constant wrong, but not sure how to make it all work together. This is how I have it right now:

From the relay:

30 - to battery +
85 - to ground
87 - to fuel pump
86 - to "C" on oil pressure switch

From the oil pressure switch:

NC - to starter solenoid
NO - to ignition wire

Any ideas would be great. Thanks.

 

[Spoon]

Draw out the circuit of how you have wired it and post it up. So that we get a better idea.
What is this for?

 

[hath]

See attached for my current set up.

 

[Richard Burns]

Are the ignition and starter solenoid for the fuel pump or are they for the engine, if for the engine then why are you trying to use the switch for the fuel pump.
If they are for the fuel pump what is the connection you show to the fuel pump?
Does the oil pressure switch operate at 5 psi at the moment and is it designed for the operating the fuel pump?
Is this a personal project for you or is this for a customer, because we cannot advise on a safety system for a customer.
Generally you would want the oil pressure switch to connect, on operation (C to NO), power to the relay coil (85-86) and have the pump connected as you show at the moment, positive to 30 and positive out to the fuel pump from 87.

 

[Deleted member 26818]

Why do you want to wait until oil pressure reaches 5psi before allowing the fuel pump to operate?
Generally the fuel pump either operates before the engine attempts to start, or whilst it is cranking over.

 

[hath]

This is the oil switch i'm running: JEGS 11200: Oil Pressure Safety Switch 1/8" NPT | JEGS - https://www.jegs.com/i/JEGS/555/11200/10002/-1

This is the fuel pump relay i'm running: JEGS 10564: Single Fuel Pump Harness and Relay Kit 30 Amp | JEGS - https://www.jegs.com/i/JEGS/555/10564/10002/-1

This is a personal project.

This is a safety setup to where if the engine oil pressure drops below 5 psi, the fuel pump will shut off. Before starting, a primer button will be used to avoid a lean condition.

 

[ruston]

Usually the the low pressure fuel pump runs momentarily to prime the high pressure pump( for a simplistic description) when the ignition is turned on , then it stops . Then as Spin says it will not run again till cranking. When started the ecu will take over and supply the high pressure pump which is driven from the engine.
This is not model specific , it is the Bosch system on early Audi cars .
You can not play about with modern fuel flow and timing unless you have the appropriate equipment.
You have to be more specific as to what you are trying to achieve.

Sorry I was typing as your post come in , and I have not read it yet.

 

[Deleted member 26818]

I take it that this is a Diesel engine.
What you need is a live to the ‘c’ or common terminal on the oil pressure switch.
From the normally open terminal to terminal 85 or 86 on the relay. The other terminal to earth.
Connect the fuel pump across terminal 30 and 87.
Connecting the starter solenoid to the oil pressure switch would mean the starter stops turning when oil pressure reaches 5 psi.

Something you should also be aware of, is that the live from the ignition switch to the starter solenoid will cut out once the key is released.

 

[hath]

It's an ls1 and I'm running a walbro 255 fuel pump. Just one fuel pump on vehicle.

 

[hath]

Ok so I did some resistance testing, results were as follows:

NC to NO = 1
C to NC = 000
C to NO = 1
Switch housing to frame = 001

I also did some other testing:

With ignition wire (86)(yellow) disconnected from C on the oil switch, there is no power to the purple (87) or yellow (86) wires at the relay. Not even when cranking. Nor is the fuel pump kicking on.

When I attach 86 to C the pump turns on, and 87 and 86 get power at the relay.

When 86 is disconnected from the oil switch NC and C have power when the key is off.

When the key is on, all three terminals on the switch have power, C, NC, and NO.

All this said, it didn't lead me to any conclusions, but I'm no electrician either. Does this lead anyone to a conclusions?

 

[Deleted member 26818]

With 86 disconnected there should be no power at either 85 or 87. There should only be power at 30.
You need to take power from the ignition switch (position II) to the ‘c’ terminal on the oil pressure switch.
Then from the ‘no’ terminal to 86.
Do not connect anything to the ‘nc’ terminal.
Take power from the ignition switch (position III) direct to the starter solenoid.

 

[Flash]

your fuel pump would need to earth through the oil pressure switch to work how you would like as at present 30 - 87 is straight through on this type of relay and only energises the coil that is 86-85.