Electric fuel pump wiring

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Rmoore

Rmoore

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I have always wired my electric fuel pump and ignition on the same switch . Flip on ignition switch to on and fuel pump comes on. Turn ignition off fuel pump goes off. Seems to me these to go hand and hand. 1) for safety. 2) there is no need to have one without the other. So my question is why do people and professional builders wire the fuel pump on a different switch from the ignition . I would say most of the race cars I see down here in texas are all mostly like this. Maybe there is a good reason to do it that way. I just don't know what it would be. Someone please tell me why ??
 
Fuse each circuit. Also there may be a time where you want fuel pressure without ignition like priming a carb, setting fuel height or to kill fuel pump with ignition on to drain the carb prior to storage or transport. plus it gives the driver 2 more aircraft switches to throw prior to starting...fuel, ignition, start! (could also pump, start, THEN ignition to prime oil pressure prior to starting).
 
pishta said:
Fuse each circuit. Also there may be a time where you want fuel pressure without ignition like priming a carb, setting fuel height or to kill fuel pump with ignition on to drain the carb prior to storage or transport. plus it gives the driver 2 more aircraft switches to throw prior to starting...fuel, ignition, start! (could also pump, start, THEN ignition to prime oil pressure prior to starting).
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Starter motor still turns the motor over. Ignition nor fuel pump needs to be on if all you want to do in spin the engine over. I can spin the engine over till I burn the starter up or battery dies. My car has a lot of compression. I would spin the engine over then flip the ignition and fuel on and she fires right up. You can spin the engine over to get oil pressure. Getting oil pressure doesn't require ignition or fuel. So we are still without any reason to have a seperate fuel pump switch. Please understand im all about safety here. So im wanting real life facts why anyone would wire their fuel pump separate from the ignition. And most evryone does. I'm not sure what NHRA/ IHRA says about it. I think its worth a phone call tho.
 
Then wire it like you want to. I would want it separate from the ignition. And funny thing is, I cannot tell you why. I would just wire it on its own circuit.
 
RustyRatRod said:
Then wire it like you want to. I would want it separate from the ignition. And funny thing is, I cannot tell you why. I would just wire it on its own circuit.
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Now that's a factual answer Sir. Just cause you want to. Ok. But you do see my point. Hey from what I see just about everyone does. Not just you .
 
Rmoore said:
Now that's a factual answer Sir. Just cause you want to. Ok. But you do see my point. Hey from what I see just about everyone does. Not just you .
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Well here's the thing. I know some people have wired their electric fan in with the ignition. That never works because when you cut the ignition off the fan becomes a generator and keeps charging the system and the engine runs on......but poorly.

So......it just makes sense from THAT perspective to leave the ignition all on its own. But that's just my opinion. WTF do I know? lol
 
RustyRatRod said:
Well here's the thing. I know some people have wired their electric fan in with the ignition. That never works because when you cut the ignition off the fan becomes a generator and keeps charging the system and the engine runs on......but poorly.

So......it just makes sense from THAT perspective to leave the ignition all on its own. But that's just my opinion. WTF do I know? lol
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Totally agree. My electric fan is on a different circuit also. Ignition and fuel pump is together tho. Don't mean to sound harsh to anyone. But I have yet had anyone I have ask that could give me a real reason. Mostly cause that's the way I wanted to do it. I did have a guy at our local track changed his. After I brought it up to him. My deal is in case of a wreck all I would have to deal with ignition and fuel is one switch . not two. Could make a difference. Maybe not. I'm just wondering that's all. Just makes sense to me. But not to most.
 
I always relay my electric pumps, so that's my #1.
I also get my engine cranking before I flick my ignition switch on my dart, but I'm locked at 40 degrees.

Also allows me to crank w/o full fuel flow if say...it flooded. Or...run the pump to set floats or adjust fuel pressure.

If it was a 318 on pump gas with a little holley red....there is no harm in doing it your way.
 
Rmoore said:
Totally agree. My electric fan is on a different circuit also. Ignition and fuel pump is together tho. Don't mean to sound harsh to anyone. But I have yet had anyone I have ask that could give me a real reason. Mostly cause that's the way I wanted to do it. I did have a guy at our local track changed his. After I brought it up to him. My deal is in case of a wreck all I would have to deal with ignition and fuel is one switch . not two. Could make a difference. Maybe not. I'm just wondering that's all. Just makes sense to me. But not to most.
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I totally understand. I cannot answer it myself.......unless maybe it's NHRA mandated or some such. But, for "my" personal preference, I will wire them separately. I agree with a relay though.
 
Johnny Mac said:
I always relay my electric pumps, so that's my #1.
I also get my engine cranking before I flick my ignition switch on my dart, but I'm locked at 40 degrees.

Also allows me to crank w/o full fuel flow if say...it flooded. Or...run the pump to set floats or adjust fuel pressure.

If it was a 318 on pump gas with a little holley red....there is no harm in doing it your way.
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I do the same thing with mine. I also run a lot of timing. So I get the engine spinning then a hit the ign/ fuel switch and she fires right up . if the engine is flooded put the accl pedal on the floor and she will fire up . there are situations where turning the fuel pump maybe needed. But everything I have heard about that is like . fix your car dude !!! I'm just thinking out loud.
 
RustyRatRod said:
I totally understand. I cannot answer it myself.......unless maybe it's NHRA mandated or some such. But, for "my" personal preference, I will wire them separately. I agree with a relay though.
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You can put a relay on ignition/ fuel pump circuit . By all means. That's even more safety conscious
 
Rmoore said:
You can put a relay on ignition/ fuel pump circuit . By all means. That's even more safety conscious
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That's how the factories do it. Now, I don't think the ignition and fuel pump are on the same circuit in modern vehicles, BUT they are certainly energized together.
 
RustyRatRod said:
That's how the factories do it. Now, I don't think the ignition and fuel pump are on the same circuit in modern vehicles, BUT they are certainly energized together.
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Yes Sir. These new vehicle have modules running modules. Well what's inside these modules. Relays and circuitry .
 
Rmoore said:
Yes Sir. These new vehicle have modules running modules. Well what's inside these modules. Relays and circuitry .
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Yeah, it's all a bunch of bull **** if you ask me.
 
RustyRatRod said:
Yeah, it's all a bunch of bull **** if you ask me.
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Yeah I get it. I like it really. I think we have better vehicles in todays times than we have ever had. Some pretty neat stuff. But you have to be an electrical engineer to work on them tho. I have worked for the same Ford Dealership for the past 30 yrs. I have seen just plain bad engineering . and I've seen brilliants .... Would love to have a 9 sec Demon tho. Off the showroom floor.
 
jimjimjimmy said:
if your about safety you forgot the most important part the inertia switch .
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They are mandated by Law on all fuel Injected vehicles !! The reason why is fuel injected vehicles run such high fuel pressure . Thank you Sir. We are starting to have lots of FI hot rods these days. The factory cars already turn off with the ignition .
 
Rmoore said:
They are mandated by Law on all fuel Injected vehicles !! The reason why is fuel injected vehicles run such high fuel pressure . Thank you Sir. We are starting to have lots of FI hot rods these days. The factory cars already turn off with the ignition .
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No that is not the reason why. It's because an EFI car can run as good when you are hanging upside down after a wreck as it can when driving down the road/ track. Even a low pressure system with a broken tube/ hose can pump a huge amount of fuel and fuel a fire in a short time
 
67Dart273 said:
No that is not the reason why. It's because an EFI car can run as good when you are hanging upside down after a wreck as it can when driving down the road/ track. Even a low pressure system with a broken tube/ hose can pump a huge amount of fuel and fuel a fire in a short time
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No Sir !! High fuel pressure is the exact reason why injected vehicles run inertia switches. Running efi pressure on most vehicles are 40 to 60 psi. Some higher. None efi 4 to 6 psi ! None efi vehicles that have mechanical pumps works off the ignition switch by default. When the motor is not running the mechanical fuel pumps do not work !!
 
Rmoore said:
No Sir !! High fuel pressure is the exact reason why injected vehicles run inertia switches. Running efi pressure on most vehicles are 40 to 60 psi. Some higher. None efi 4 to 6 psi ! None efi vehicles that have mechanical pumps works off the ignition switch by default. When the motor is not running the mechanical fuel pumps do not work !!
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If its a big deal to you, why not wire it up to the ignition, and have a manual cut off switch too ??
 
Rmoore said:
Starter motor still turns the motor over. Ignition nor fuel pump needs to be on if all you want to do in spin the engine over. I can spin the engine over till I burn the starter up or battery dies. My car has a lot of compression. I would spin the engine over then flip the ignition and fuel on and she fires right up.
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electric pump: What if the bowls are dry? You could turn motor over a few hundred times with separate ignition ON before the bowls fill. Dunno. Maybe its a safety thing with a electric fuel pump, lose Magneto control (switch fuses) and all you got left to kill the motor is lack of fuel? When you ask NHRA, tell us the answer. EFI kills the pump when it loses cam or crank sensor, it thinks the car is not running, and it'll also strand you if either sensor goes.
 
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In my cars case (not a race car) the fuel pump is on a relay that energizes when the ignition switch is turned to the run position.
If I want the ignition on or to crank the motor without the fuel pump running I just unplug the relay on the inner fender.
Turn the ignition on to fill the carb bowls and a second or two later turn it to start.
Turn the key off and it kills the ignition and fuel both.

For a daily driver this way made sense to me, and I'm not into throwing multiple switches to start or shut off the car.
 
pishta said:
electric pump: What if the bowls are dry? You could turn motor over a few hundred times with separate ignition ON before the bowls fill. Dunno. Maybe its a safety thing with a electric fuel pump, lose Magneto control (switch fuses) and all you got left to kill the motor is lack of fuel? When you ask NHRA, tell us the answer. EFI kills the pump when it loses cam or crank sensor, it thinks the car is not running, and it'll also strand you if either sensor goes.
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Lol !! Sir you do not have to turn the motor over to fill up the carburetor bowels with an electric fuel pump . Turn your fuel pump on. Wait 10 to 15 seconds if that long . Then turn start your engine. Now a mechanical pump you would have to turn the engine over and over and over to feel the bowels up. But there is no electricity on mechamical pump. That's why its called mechanical !! And if your magneto goes out you don't have to worry about killing the fuel. Motor will not be running..
 
I run through a relay and a low oil pressure switch, so the pump only runs when the engine has oil pressure. I look at it as a safety feature if the engine explodes on the track or dies. I have a priming button under the dash. If the car sits for a couple of weeks I hit the priming button to fill the bowls before I try to start it. If it sits for a long time, I can also turn it over without fuel pressure to get the oil moving.
 
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