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Carter P4070/Relay/Oil Pressure Safety Switch Wiring

ObscureMachine

Seatbelt Orifice Officer
Joined
Sep 28, 2006
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Does this help? http://static.summitracing.com/global/images/instructions/hly-199r9680.pdf

I used a wiring harness for this and didn't use the NO (normally open), so my pressure has to get up before the pump starts. I'll probably go back and hook up the NO to fix this, but it works fine now.

Also, I ran the ground into the cab, put in a switch (hidden) then ran a wire from the other side of the switch to ground. The switch opens the ground circuit and boom, instant kill switch (for security).
 
OP
OP
Patrick.M

Patrick.M

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Messages
148
Loc.
Greenville, SC
So it looks like there's a wire going from each terminal on the op safety switch to a terminal on the starter solenoid.
 

ObscureMachine

Seatbelt Orifice Officer
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The OP sensor has 3 terminals. One is marked NC, one is NO, and one is C.

(NO) goes to the hot side of the starter solenoid . (NC) goes to an ignition switch source that is only hot when the ign. is on . And (C) (fused) goes to the pump itself

Only the one marked NO (normally open) goes to the Starter Solenoid.
 
OP
OP
Patrick.M

Patrick.M

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Jan 11, 2011
Messages
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Loc.
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Ok, I ended up replacing the whole harness over the past 6 months and I'm now I'm back to wiring up this fuel pump. I am using a 30A bosch relay and an oil pressure safety switch, referencing these two diagrams:

http://www.supermotors.net/registry/media/870469_1

and

http://www.how-to-build-hotrods.com/images/elecpump04.jpg

I've run pin 30 of the relay through a 20A fuse and back to the starter solenoid and have run pin 87 back to the fuel pump.

So, a couple questions:

1. What goes to pin 87a on the relay?
2. Where exactly do the I and S terminals of the oil pressure safety switch get wired to?

Thanks,
Patrick
 

Broncobowsher

Total hack
Joined
Jun 4, 2002
Messages
34,821
S = Start, goes to the normally open (NO) on the oil pressure switch.
I = Ignition, it boosts voltage to the ignition during crank (bypass the ballast resistor). Never add anything to the "I" terminal. It will add extra load to the ballast resistor which will reduce the voltage to the ignition system. Less ignition system voltage lowers power and economy. Anytime you see wires attached to the "I" terminal of the starter solenoid it is a garanteed sign that whoever did the wiring doesn't know how the ignition system works.

For a full power switched (run position) power go to the voltage regulator. The "I" is a full power, run position only power source (turns on the voltage regulator).
 
OP
OP
Patrick.M

Patrick.M

Jr. Member
Joined
Jan 11, 2011
Messages
148
Loc.
Greenville, SC
Ok so I should run the s terminal on the op safety switch over to the s terminal (violet wire on my harness) on the solenoid and run the I terminal on the opss over to the regulator? I've got a 4g alternator, would that be to the green/red wire?

Thanks for your help
 
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