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.

 

[MIDNIGHT RIDER]

I can't understand why you want a fuel pump controlled by an oil-pressure switch unless it is to kill the fuel-pump when the engine is not running.

I would definitely want a bypass toggle-switch to allow me to run the pump when the engine was not.

On any self-respecting diesel engine, if the fuel-pump runs when the engine isn't, it just cycles the pumped fuel through the return line and back to whichever tank is chosen.

Anyway, as for anything that taps into an oil-pressure orifice --- this is what I do:

Most oil-pressure access ports on an engine are 1/8"NPT.

Plain old grease-gun hoses are 1/8"NPT Male at both ends and very capable of handling anything engine oil-pressure is going to throw at them.

They are available anywhere from six-inches to longer than you are tall.

If you look, you can probably even find them in braided stainless.

I find where the original oil-pressure sending unit is screwed in and replace it with my grease-gun hose.

If I want to re-orient the direction the hose is pointing and to prevent kinks, plain old 1/8"NPT street-elbows can be employed.

If the engine port happens to be something larger than the grease-gun hose's 1/8NPT, a reducer bushing can be used.

With the engine end of my grease-gun hose firmly attached, I orient the hose to somewhere convenient to access and where I can add all my oil-pressure switches and their associated wiring.

This is accomplished by adding TEE fittings with the end of the last one plugged so more TEEs can be added ass necessary.

With my grease-gun hose arrangement, there is only one connection down there on the engine to worry about.

All my switches and gauge senders are well away from the engine's heat and vibration; plus, I don't have a host of wires against a hot engine.

As for my line of TEE fittings, they do make many-ported manifold fittings that can be used instead; I just found one in my swap meet bargains stuff that is bristling with hose barbs of every size imaginable and wondered to myself "what would I ever use that for";and, while typing this, it came to me that it would be ideal to use instead of a string of TEE fittings.

Now, for any oil-pressure line that connects to my grease-gun hose oil-pressure access manifold, such as the line to a mechanical gauge, I install a 1/8NPT Ball-Cut-Off Valve first in line and then screw the gauge line into that; thus, in an emergency event, such as oil spraying all inside the cab, I can close that valve and drive on.


I have a big continuous-duty solenoid that ties the Leece-Neville and Starting Batteries to the solenoid-isolated accessory battery once 2-psi oil-pressure is achieved; thus, the accessory battery gets charged when the engine is running and gets switched out of the circuit when the engine is not running with no further thought nor input from me.

The only things connected to the starting batteries are the starter and the twin solenoids that control it; all other circuits are connected to the accessory battery.

I can leave everything electrical ON and drain that accessory battery to the nub and still have two very-hot Group-31s batteries just itching to sling the rods out of the engine.

The switch that controls all this wonderfulness is a tiny ON-at-2-psi/OFF-below oil-pressure switch that gets it's oil-pressure from my grease-gun hose arrangement.

 

[MIDNIGHT RIDER]

Okay, now you have your big Carter electric fuel pump up and running; let's make it useful for other purposes as well.

TEE into the pressure side of the fuel line, downstream of the pump, and route this fuel line to somewhere really convenient that you can access standing on your hind legs.

In that corner near the brake master-cylinder is a good place.

To the end of this line, connect a 1/4"NPT Ball-Cut-Off Valve.

In the other end of this Ball-Cut-Off Valve, connect a good non-leaking Female Air-line Quick-Coupler.

When not in use, keep the valve closed.

Make yourself a fuel hose with a Male quick-coupler plug on one end.

You can get as fancy with the other end as you wish or just leave it raw.

You are now able to easily access the fuel in your truck and pump some in the 4320 John Deere, or the Bobcat Loader, or in a syrup bucket, or whatever.

If your little fuel hose happens not to be long enough to reach the tank of the guy stranded on the Ice Road who has ran out of fuel, couple on your fifty-foot air-hose first and then your little made-up hose to that and it will probably reach.

Even if you never ever have reason to use this feature, it is just really cool to know that you are that smart to have it and to show others just how smart and well prepared you are.

 

[raydav]

I can't understand why you want a fuel pump controlled by an oil-pressure switch unless it is to kill the fuel-pump when the engine is not running.

A crash will typically stall the engine. The oil pressure switch avoids a fuel puddle under the vehicle.

I find where the original oil-pressure sending unit is screwed in and replace it with my grease-gun hose.

I have a 2001 PSD where I have an aftermarket, electronic oil pressure gauge monitoring fuel supply pressure. When mounted hard to the chassis, the pressure transducer could now handle road vibration, so it is on a hose.

The only things connected to the starting batteries are the starter and the twin solenoids that control it; all other circuits are connected to the accessory battery.

I have two batteries for the engine and four for accessories. There is a rather small relay for charging the accessory batteries, and a larger relay for using the accessory batteries to jump start the engine.

The engine batteries operate everything related to the engine. Only things not essential to the engine are on the accessory batteries because one of the things is a refrigerator which often drags the accessory batteries down.

 

[raydav]

Okay, now you have your big Carter electric fuel pump up and running; let's make it useful for other purposes as well.

In my was 460 now IDI van, I have had a "faucet" on the frame and a hose under the seat for a few decades. I have used it to provide gasoline to someones car. I have not had the opportunity to rescue anyone with a diesel.