Definitive way to wire an electric fuel pump for a Pre EFI Bullnose

[Tarheel Blue]

The oil pressure switch will only close the contacts when the engine is running. So just turning the key to Run won't prime the carb.

And you do NOT want to bypass that permanently. When I got Big Blue the sump was FULL of gas because someone bypassed it and the PO left the key in Run. I drained 6 quarts of oil and 7 quarts of gas out.

If you want to prime it put a pushbutton switch in to temporally bypass the oil pressure switch. Turn the key to Run, push the button, let up, and crank.

Totally agree with Gary on the “why not to” and therefore the push button solution. Except I’m trying to avoid the button. Seems less user friendly, as in, other people not knowing the the secret sequence to simply go for a spin.

Something that I’ve been trying to work through in my head but don’t know enough about. I’m hoping Gary might?

Using a 4 pin relay, have the “low” 12v when key in RUN to trigger pin 87 sending the “high” 12v current on to the fuel pump. Then after a couple of seconds, driver would push in the clutch and turn the key to START which simultaneously sends “low” 12v current through the Oil Pressure Switches I pole and then on to a 4 pin relay which sends “high” 12v current on to the pump AND grounds the “low” 12v signal to the first relay, resetting it to “normally open”.

The idea of the check valve is very intriguing, I’ll look into that, thanks!

[Gary Lewis]

Totally agree with Gary on the “why not to” and therefore the push button solution. Except I’m trying to avoid the button. Seems less user friendly, as in, other people not knowing the the secret sequence to simply go for a spin.

Something that I’ve been trying to work through in my head but don’t know enough about. I’m hoping Gary might?

Using a 4 pin relay, have the “low” 12v when key in RUN to trigger pin 87 sending the “high” 12v current on to the fuel pump. Then after a couple of seconds, driver would push in the clutch and turn the key to START which simultaneously sends “low” 12v current through the Oil Pressure Switches I pole and then on to a 4 pin relay which sends “high” 12v current on to the pump AND grounds the “low” 12v signal to the first relay, resetting it to “normally open”.

The idea of the check valve is very intriguing, I’ll look into that, thanks!

The push button would be rarely needed. Very rarely. In fact, there probably aren't more then a few hundred carb'd vehicle in the world that have such a setup, and they have all been added by someone like us.

Why? Because after a carb'd vehicle sits for a long period of time the bowl will be dry from evaporation. This is more of a problem now than it used to be since our gas is more volatile given the ethanol that is in most of it. But if you have driven the vehicle in the last few days there should still be gas in the carb and it'll start right up. So priming is only helpful, not needed, when the vehicle has set for a long period of time.

As for the relay bit, I'm not following what you are suggesting. But, I do see a way of automatically priming things. A timer circuit could be set to pull the fuel pump relay in for X seconds each time the key is turned on. But leaving the key on would not keep the relay on.

So you would unknowingly be priming the carb briefly each time you turn the key on. But normally you go right through Run to Start and there's only a few milliseconds of priming, which probably wouldn't do anything. But if the truck has set for some time you could turn the key to Run, wait a couple of seconds for it to prime, and then crank it.

[Tarheel Blue]

The push button would be rarely needed. Very rarely. In fact, there probably aren't more then a few hundred carb'd vehicle in the world that have such a setup, and they have all been added by someone like us.

Why? Because after a carb'd vehicle sits for a long period of time the bowl will be dry from evaporation. This is more of a problem now than it used to be since our gas is more volatile given the ethanol that is in most of it. But if you have driven the vehicle in the last few days there should still be gas in the carb and it'll start right up. So priming is only helpful, not needed, when the vehicle has set for a long period of time.

As for the relay bit, I'm not following what you are suggesting. But, I do see a way of automatically priming things. A timer circuit could be set to pull the fuel pump relay in for X seconds each time the key is turned on. But leaving the key on would not keep the relay on.

So you would unknowingly be priming the carb briefly each time you turn the key on. But normally you go right through Run to Start and there's only a few milliseconds of priming, which probably wouldn't do anything. But if the truck has set for some time you could turn the key to Run, wait a couple of seconds for it to prime, and then crank it.

The idea of a timer sounded great so I spent some time w/ google and finally settled in on these two options.

This one, we'll call OPTION A

https://www.revolutionelectronics.com/Products/Fuel_Pump.html is more or less "plug and play"

And this one, OPTION B

https://www.amazon.com/5V-36V-Module-Trigger-Switch-Display/dp/B07H7L9W3T/ref=sr_1_1_sspa?crid=14EF5CWUFCO0I&keywords=dc+5v-36v+timer+module&qid=1638827262&sprefix=DC+5V-36V+Timer%2Caps%2C226&sr=8-1-spons&psc=1&smid=A28ZWXW3ZSVNZU&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFMQUNTMTFJOFU5U0omZW5jcnlwdGVkSWQ9QTEwMjY2MzQzVUxGV01UR1BaNldZJmVuY3J5cHRlZEFkSWQ9QTA0Nzg4MDMxTjU1MkozRFVJWTBXJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ== will take a bit more of my time and brain power.

My thoughts on OPTION A is that while most of the work has been done already, it gets three demerit points. Price, the 3 second delay (not sure if 3 seconds is long enough, probably is if that's the way they designed it) and lastly is that it "reads" from the tach and I'm prone to think that I prefer my original plan of using the oil pressure switch to cut power to the fuel pump.

OPTION B Has one pro and one con. The pro is that I can decide how low I would like the prime to be. The only con that comes to mind is the need to find somewhere behind the dash to mount it.

As always, I'm all ears to what anyone has to say about either option or any new options.

Cheers

[Gary Lewis]

The idea of a timer sounded great so I spent some time w/ google and finally settled in on these two options.

This one, we'll call OPTION A

https://www.revolutionelectronics.com/Products/Fuel_Pump.html is more or less "plug and play"

And this one, OPTION B

https://www.amazon.com/5V-36V-Module-Trigger-Switch-Display/dp/B07H7L9W3T/ref=sr_1_1_sspa?crid=14EF5CWUFCO0I&keywords=dc+5v-36v+timer+module&qid=1638827262&sprefix=DC+5V-36V+Timer%2Caps%2C226&sr=8-1-spons&psc=1&smid=A28ZWXW3ZSVNZU&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFMQUNTMTFJOFU5U0omZW5jcnlwdGVkSWQ9QTEwMjY2MzQzVUxGV01UR1BaNldZJmVuY3J5cHRlZEFkSWQ9QTA0Nzg4MDMxTjU1MkozRFVJWTBXJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ== will take a bit more of my time and brain power.

My thoughts on OPTION A is that while most of the work has been done already, it gets three demerit points. Price, the 3 second delay (not sure if 3 seconds is long enough, probably is if that's the way they designed it) and lastly is that it "reads" from the tach and I'm prone to think that I prefer my original plan of using the oil pressure switch to cut power to the fuel pump.

OPTION B Has one pro and one con. The pro is that I can decide how low I would like the prime to be. The only con that comes to mind is the need to find somewhere behind the dash to mount it.

As always, I'm all ears to what anyone has to say about either option or any new options.

Cheers

I like option A. You'd be using it for exactly what it was made for. I think 3 seconds is adequate. And it replaces everything in your circuitry.

Also, it isn't clear to me that Option B is a one-shot. In other words, I'm not sure that it wouldn't give you a high output for as long as the trigger is high. You can overcome that by using an RC circuit to filter the input, but you have to add it on. And you still need the oil pressure switch.

[FuzzFace2]

The idea of a timer sounded great so I spent some time w/ google and finally settled in on these two options.

This one, we'll call OPTION A

https://www.revolutionelectronics.com/Products/Fuel_Pump.html is more or less "plug and play"

And this one, OPTION B

https://www.amazon.com/5V-36V-Module-Trigger-Switch-Display/dp/B07H7L9W3T/ref=sr_1_1_sspa?crid=14EF5CWUFCO0I&keywords=dc+5v-36v+timer+module&qid=1638827262&sprefix=DC+5V-36V+Timer%2Caps%2C226&sr=8-1-spons&psc=1&smid=A28ZWXW3ZSVNZU&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUFMQUNTMTFJOFU5U0omZW5jcnlwdGVkSWQ9QTEwMjY2MzQzVUxGV01UR1BaNldZJmVuY3J5cHRlZEFkSWQ9QTA0Nzg4MDMxTjU1MkozRFVJWTBXJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ== will take a bit more of my time and brain power.

My thoughts on OPTION A is that while most of the work has been done already, it gets three demerit points. Price, the 3 second delay (not sure if 3 seconds is long enough, probably is if that's the way they designed it) and lastly is that it "reads" from the tach and I'm prone to think that I prefer my original plan of using the oil pressure switch to cut power to the fuel pump.

OPTION B Has one pro and one con. The pro is that I can decide how low I would like the prime to be. The only con that comes to mind is the need to find somewhere behind the dash to mount it.

As always, I'm all ears to what anyone has to say about either option or any new options.

Cheers

Kurt,

I have not looked over either of the links but what you posted the "B" sounds like the way to go.

Now for the other

On a diesel how is the glow plugs set up to run XX amount of time?

I never looked into that when I had my diesel only if the plugs were getting power.

Not that it helps you but the diesel used a temp sensor so the glow plugs would not turn on when warm / hot. So anyone know how the glow plug timer works?

As Gary said being you are starting with a carb. the only time you would need to prime / fill the bowl is if it sat for a bit, I find about 1 week in the summer / hot out that you may need to prime / fill the bowl.

What EFI system are you looking at and how do they "prime" the fuel system?

Any way to find that out?

Dave ----

[Tarheel Blue]

Kurt,

I have not looked over either of the links but what you posted the "B" sounds like the way to go.

Now for the other

On a diesel how is the glow plugs set up to run XX amount of time?

I never looked into that when I had my diesel only if the plugs were getting power.

Not that it helps you but the diesel used a temp sensor so the glow plugs would not turn on when warm / hot. So anyone know how the glow plug timer works?

As Gary said being you are starting with a carb. the only time you would need to prime / fill the bowl is if it sat for a bit, I find about 1 week in the summer / hot out that you may need to prime / fill the bowl.

What EFI system are you looking at and how do they "prime" the fuel system?

Any way to find that out?

Dave ----

To Gary,

OPTION B has many programming parameters, one of which would allow me to select between 1-999 sec as how long the the high stays on after the trigger. It also resets immediately after that time to looking for the next trigger.

Dave,

The future system will most likely be the Sniper. It has its own program that primes ahead of firing.

[Gary Lewis]

To Gary,

OPTION B has many programming parameters, one of which would allow me to select between 1-999 sec as how long the the high stays on after the trigger. It also resets immediately after that time to looking for the next trigger.

Dave,

The future system will most likely be the Sniper. It has its own program that primes ahead of firing.

If it "resets immediately after that time to looking for the next trigger" then you will have to have the RC filter on the front end. Otherwise the timer will go again, and if the key was left on but the engine was off you'd have the pump running continuously.

A resistor/capacitor circuit will cause the circuit to trigger on the rising edge of the key-on signal, but will then drop back down so the timer doesn't go again.

[Tarheel Blue]

If it "resets immediately after that time to looking for the next trigger" then you will have to have the RC filter on the front end. Otherwise the timer will go again, and if the key was left on but the engine was off you'd have the pump running continuously.

A resistor/capacitor circuit will cause the circuit to trigger on the rising edge of the key-on signal, but will then drop back down so the timer doesn't go again.

I'm pick'n up what your lay'n down.

Therefore, would selecting mode P2 accomplish the same as adding the RC?

Operating Mode:

P1: trigger signal, the relay is on "OP" time, and then disconnect; in the "OP" time, as follows:

P1.1: signal is triggered again, invalid

P1.2: signal is triggered again, the clocking is reset

P1.3: Signal is trigger again reset, relay off, and stop the clocking;

P-2: trigger signal, the relay off "CL" of time, the relay on "OP" time, and then disconnect relay after clocking;

P3.1: trigger signal, the relay is turned on after the "OP" time, the relay off "CL" time, then the operation cycles; if trigger signal again during the cycle, the relay off, stop clocking; the number of cycles times ( "LOP ") can be set.

P3.2: without triggering signal after power on, the relay is on "OP" time, the relay off "CL" time, then the operation cycles; the number of cycles times ( "LOP ") can be set.

P-4: signal holding function. If there is trigger signal, clocking is reset, the relay remains on; when the signal disappears, after clocking "OP" time, the relay is off; if another signal is triggered during clocking, clocking will be reset.

[Gary Lewis]

I'm pick'n up what your lay'n down.

Therefore, would selecting mode P2 accomplish the same as adding the RC?

Operating Mode:

P1: trigger signal, the relay is on "OP" time, and then disconnect; in the "OP" time, as follows:

P1.1: signal is triggered again, invalid

P1.2: signal is triggered again, the clocking is reset

P1.3: Signal is trigger again reset, relay off, and stop the clocking;

P-2: trigger signal, the relay off "CL" of time, the relay on "OP" time, and then disconnect relay after clocking;

P3.1: trigger signal, the relay is turned on after the "OP" time, the relay off "CL" time, then the operation cycles; if trigger signal again during the cycle, the relay off, stop clocking; the number of cycles times ( "LOP ") can be set.

P3.2: without triggering signal after power on, the relay is on "OP" time, the relay off "CL" time, then the operation cycles; the number of cycles times ( "LOP ") can be set.

P-4: signal holding function. If there is trigger signal, clocking is reset, the relay remains on; when the signal disappears, after clocking "OP" time, the relay is off; if another signal is triggered during clocking, clocking will be reset.

Yes.

[Tarheel Blue]

Yes.

Cool

One other thought that I had regarding OPTION B is that in keeping the oil pressure switch for not only pump cut off when the engine stops, would it not be a safety feature for the engine in an instance where, say, a hole is poked in the pan and oil is on the ground. It would shut off the pump then shutting down the engine via fuel starvation.

Or would that be too late to avoid catastrophic damage to bearings, etc.?