Electric fuel pump wiring

[JDHJR]

I am replacing the manual pump with an electric fuel pump on my 89. I want to wire it correctly with a relay and a safety cutoff on the oil pressure switch. I have searched and not been able to find a wiring diagram to help me and I can not get my head wrapped around how this needs to be wired. If anyone has any advice and/or a diagram they would share with me or can point me to a diagram it would be greatly appreciated.

 

[DaveBen]

Your proposed safety cutoff switch can cause "no starts" as you will not have any oil pressure when you try to start it. You will need to temporally bypass the oil pressure switch when you start it. I don't know how this is done, but others here do.

 

[ihc1470]

This site should give you the information you need. https://www.wiringtoday.com/12-volt-relay-wiring-diagrams/
The diagram for the cooling fan will work for your fuel pump. Just ignore terminal 87 you will not need it.

You will need a oil pressure switch to control the relay, not a sensor. Then you will need to wire in a momentary normally open switch that you will need to activate when starting. It would tie into the same number 85 terminal as the oil ps.

 

[Kdo58]

You dont need a relay. Just tap into the fuse box.

 

[divemaster5734]

Your oil sensor has an analog output that the gauge will interpret based on voltage to indicate the oil psi.
You would need a normally open pressure switch that just closes at the minimum running pressure.
This would complicate operation as the oil pressure doesn't build until a few moments of running and could cause your fuel pump to never start.

 

[chickenpot]

i ran my electric pump off a relay and it's triggered by key-on power at the glow plug solenoid. if you want an oil pressure cutout, what i would do is get an AC low pressure cutout switch and tee it into the oil system on back of block. these switches are adjustable so you can set them really low in the -5-10 range so you wont bave to crank forever waiting for it to build oil pressure.

 

[franklin2]

Why re-invent the wheel? Ford has this exact setup on the 460's with the hot fuel handling and electric pumps in the tanks (early trucks with carbs).

Ford had a pressure switch that activated the relay. Just order a switch for a 1985 F250 or 350 with a 460.

To run the pump before the oil pressure built up, they simply went back to the starter relays on the fender that had 4 terminals, the two large terminals and 2 small terminals. One small terminal is the "s" or start terminal and is for cranking. The other small terminal is the "i" or ignition terminal.

In the old days this "i" terminal sent a full 12v to the ignition coil for a hotter spark during cranking. For awhile they got rid of this terminal and only used a relay with one small terminal. But when the carbed 460's came back with the electric pumps in the tanks, they brought it back and used the "i" terminal to send voltage to the pumps directly during cranking only.

 

[franklin2]

Here is how Ford did it, this is a 1986 with a 460 and a single tank. "Hot in start fuse link T" is hooked to the "i" terminal of the starter relay.

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[raydav]

I control fuel pumps with a three position - on-off-on - toggle switch. I can run the pump only when there is oil pressure, whenever I want - good for maintenance - or never - also good for maintenance.

There is an oil pressure switch that has the usual close-to-ground when there is NOT oil pressure. That runs the idiot light. There is also a pair of free contacts that close when there IS oil pressure.

I have banks of relays, that insures there is full voltage to the devices, and allows me to control everything from the drivers seat with just mini-toggle switches - very small, easy to group together.

I typically control a relay by grounding one side of the coil while the other side is connected to 12V.

On the three position switch, the center terminal is connected to the to-be-grounded side of the relay coil.

One switch terminal is connected to ground - that allows you to run the pump whenever you want - maintenance, prime before start,,,,.

The other switch terminal is connected to one terminal on the previously mentioned oil pressure switch. The other terminal of that switch is connected to ground.

You now have fuel pressure when there is oil pressure, whenever you want, or never.