Another Electric Fuel pump wiring question.

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MileHighDart

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So doing the wiring for my electric pump on my Dart, to feed my new 5.9

I was going to follow the basic wiring diagram below that I printed off a "how to build hot rods" website. It shows wiring through a relay, and oil pressure switch, which I am doing. (but shows no breakers or fuses)

My question is more about breakers and fuses.

The diagram that came with my carter pump, shows putting an inline fuse in the 10ga line going to the pump.

My Summit fuel pump relay came with a 30amp breaker and shows putting it in the 10ga line between the battery and the relay.

So do I need to use both the breaker, and the inline fuse, or one or the other. Or neither...lol

xelecpump04_jpg_pagespeed_ic_d21eD7ngl1.jpg
 
The power (10ga) wire feeding the fuel pump you want the circuit protection to be as close to power source as you can get it. So if coming right off the battery I would install a fuse from battery to supply wire. I say fuse because if it pops an actual circuit breaker may reset and if there’s a problem I wouldn’t want that. As far as the control of the relay for the fuel pump I’d also fuse that before the control switch then to oil pressure switch then to the relay. The goal is to protect as much of the system wiring with the fuse as possible. That’s how I look at it. I’m sure someone else will be along that’s got more input.
 
You will be fine with just the breaker from the relay to the battery. Adding a fuse between the relay and the pump serves no purpose if the power feed to the relay is already fused.
 
Dubob said:
The power (10ga) wire feeding the fuel pump you want the circuit protection to be as close to power source as you can get it. So if coming right off the battery I would install a fuse from battery to supply wire. I say fuse because if it pops an actual circuit breaker may reset and if there’s a problem I wouldn’t want that. As far as the control of the relay for the fuel pump I’d also fuse that before the control switch then to oil pressure switch then to the relay. The goal is to protect as much of the system wiring with the fuse as possible. That’s how I look at it. I’m sure someone else will be along that’s got more input.
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A couple of further observations . You want to use a breaker or slow burn fuse on a fuel pump. This is because they are more tolerant of power surges where as a standard fuse will blow with the slightest surge over it intended voltage. The same is true for electric fans. Also there is no point in fusing the circuit from the relay to the pressure switch. That is a trigger wire and has very little power running in normal operation. In my opinion you don't want to insert a failure point on your trigger wires because the chance of frying them if the main circuit is fused is limited but it will most likely create an additional location for gremlins to manifest themselves down the line. Also the circuit that feeds the switch is already protected via the ignition circuit
 
Also note that unless your car is EFI that oil pressure switch is pointless.
A carbed motor will continue to run if it looses oil pressure until the carb is empty of fuel.
You will also need a manual bypass switch for the oil pressure switch so the fuel pump can run before the car starts and gets oil pressure.

In my opinion the oil pressure switch in the fuel pump circuit is a PIA.
 
I seem to be hitting all the same things planning out my own build...

I was thinking that if I end up using any kind of cut-off, it would be something like the inertia switches that only switch off if you hit something. They can be turned right back on after being triggered but it has to be a pretty substantial hit to make one go off. Around 10 g's, which would be like hitting something at 40mph.

Fuel Pump Inertia Switch
 
TrailBeast said:
Also note that unless your car is EFI that oil pressure switch is pointless.
A carbed motor will continue to run if it looses oil pressure until the carb is empty of fuel.
You will also need a manual bypass switch for the oil pressure switch so the fuel pump can run before the car starts and gets oil pressure.

In my opinion the oil pressure switch in the fuel pump circuit is a PIA.
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If he is running an electric pump the oil pressure switch will at least turn off the pump if oil pressure drops. If you get in a wreck or something the pump will still pump fuel if you don't have a pressure switch.
 
I disagree using a breaker instead of a fuse. Automotive breakers have a poor track history of protecting circuits. Even the Dodge trucks use a fuse supplying the pump. Find out what your pump draws, and fuse accordingly. Make sure the 10Ga is actually enough, and don't use "household AC" amp capacity wiring charts, use a chart for 12V. They are all over the internet

This is because, "generally" automotive cannot stand the same voltage drop as house circuits. A good example is something electornic/ sensitive, like a radio/ stereo or eFI computer
 
A 30 amp breaker for an electric fuel pump... wow!!!

Put a 10-15 amp fuse in the line from battery/alternator to relay and go with it. 10 ga wire... good god what's that pump pull for amps? Most pumps don't pull over 8 amps unless they are HUGE. 12 Ga wire is usually sufficient if the run is short from battery/alternator to pump.

I put the pressure cut off in the ignition circuit with a bypass switch when starting the car. You want to protect the engine from low oil pressure, that's how I do it. No oil pressure, no ignition!

Too bad that kit likely has a chinese relay in it. Check every single connector for proper crimping. They are bad for not being terminated correctly.
 
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yellow rose said:
If he is running an electric pump the oil pressure switch will at least turn off the pump if oil pressure drops. If you get in a wreck or something the pump will still pump fuel if you don't have a pressure switch.
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I realize why it's being done, but an inertia switch would be better for that I think.
That way you don't have to also install a manually operated bypass switch so the engine starts in the first place. (especially if the fuel has evaporated from a carb)
If a gauge for oil pressure isn't enough comfort put a buzzer on an idiot light switch.

Obviously the OP is going to do what he wants, but I thought I would offer an alternative over all the wiring and possible fail points being added into the system.
 
Ok, I'm doing this today, one way or the other. Its the last thing I need to do to have my car on the road. Been two years since I pulled the 318, and eventually decided to go 5.9

I agree that he 30amp circuit breaker is way overkill. It's just what came with the Summit relay kit.
Seems we all agree there's no need for a fuse between the relay and pump.
Think I'll go with an inline fuse, 10 or 15 amp, between the battery and the relay.
Using, or not using the oil pressure switch is kind of up in the air now.
If I skip the oil pressure switch, and just wire it like the relay kit shows, then the pump should start as soon as I turn the key on, so that should take care of filling the carb if it may have evaporated.
 
Having the switch to kill the pump isn't a bad idea as YR mentioned. Engine dies and the pump shuts off in an accident, etc. You could use the same switch to kill both ignition and pump.

My guess they matched the breaker to the rated max current of the relay. An FYI, always match the circuit protect to the expected max load plus some overhead. That way you aren't melting things that only need 5 amps and have a feed capable of 30 amps. That's bad engineering. :)
 
crackedback said:
Having the switch to kill the pump isn't a bad idea as YR mentioned. Engine dies and the pump shuts off in an accident, etc. You could use the same switch to kill both ignition and pump.

My guess they matched the breaker to the rated max current of the relay. An FYI, always match the circuit protect to the expected max load plus some overhead. That way you aren't melting things that only need 5 amps and have a feed capable of 30 amps. That's bad engineering. :)
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Oh yea, I agree it's not a bad idea, just an extra PIA to deal with.
I'd still rather do it with an inertia switch just to make everything automatic and simple instead of adding a step just to start the car.

Anyway, carry on.:D
 
crackedback said:
Having the switch to kill the pump isn't a bad idea as YR mentioned. Engine dies and the pump shuts off in an accident, etc. You could use the same switch to kill both ignition and pump.

My guess they matched the breaker to the rated max current of the relay. An FYI, always match the circuit protect to the expected max load plus some overhead. That way you aren't melting things that only need 5 amps and have a feed capable of 30 amps. That's bad engineering. :)
Click to expand...

The pump is an Airtex E8090, just a 9psi, universal, aftermarket pump. Its not a big race pump or something. But I've been all over the internet and cant find anywhere where it tells you how many amps it draws. Only thing I found is where a tech at Summit told a guy to use at least 14ga wire, and wire it to a 10amp fused circuit.
I've already got 10ga from the pump to the engine bay, and the wire coming out of the relay to the battery is 10ga, and I've got an inline fuse holder with what looks like 12ga wire coming out each side (biggest one I could find). I'll use it, with probably a 10amp fuse to start.
 
crackedback said:
Having the switch to kill the pump isn't a bad idea as YR mentioned. Engine dies and the pump shuts off in an accident, etc. You could use the same switch to kill both ignition and pump.

My guess they matched the breaker to the rated max current of the relay. An FYI, always match the circuit protect to the expected max load plus some overhead. That way you aren't melting things that only need 5 amps and have a feed capable of 30 amps. That's bad engineering. :)
Click to expand...

Agree....that was kind of my point of course make sure the wire is large enough

ALSO be careful where you mount breakers/ fuses. Engine heat DE RATES the amperage, can cause nuisance tripping
 
Ok, next question. Where do I pick up, or how do I identify my ignition wire? Any idea what color wire on a 68 dart, or which slot it comes through on the bulkhead connector?

I know, wiring is not my thing
 
^^Usual answer.....go to MyMopar, download a free service manual and the aftermarket wiring diagrams there

The ONLY source of "ignition run" in the engine bay is the IGN1 which is normally dark blue. It supplys the one side of the ballast resistor and the voltage regulator IGN terminal in 68
 
67Dart273 said:
^^Usual answer.....go to MyMopar, download a free service manual and the aftermarket wiring diagrams there

The ONLY source of "ignition run" in the engine bay is the IGN1 which is normally dark blue. It supplys the one side of the ballast resistor and the voltage regulator IGN terminal in 68
Click to expand...

Ok, I was just on mymopar and found the wiring schematics for 68. And I just about had it figured out when I saw your reply. So I can just tap into that dark blue wire anywhere, or preferably before it gets to the resistor? And I think I've got the "starter" wire I need, I believe its the yellow that goes to the starter solenoid.

Thanks
 
I realize this is an old thread...but I did this(the OP's diagram) on my 86 2wd RC(440/OD833) with killer results.....start(ignition 2 in my thinking) runs the pump and run(ignition 1....again in my thinking) runs the pump as long as there's oil pressure.

Inertia switch in conjunction with oil pressure switch is the most efficient way IMOP...but in the RC there's a an old roll over valve that one would hope it still works. I wish I would of done this with the 64 Valiant.

Some safety is better than none IMOP.

Oh...I ran a circuit breaker also.
 
You don't want to tie into IGN2 which is the ballast bypass circuit, unless the IGN1/ IGN2 have been tied for a non ballast ignition

This is because any branch on the IGN2 that can see ground will drain off the coil through the ballast when running (when key is in run), and degrade coil power
 
It actually comes from the extra terminal on my starter relay on the driver side fender...so when the yellow start wire fires the relay it does three things....one terminal does the ballast, second one does the starter & the third one runs fuel pump(to that oil pressure switch) just like in diagram from OP's post.
 
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