What Ampage fuse for fuel pump wiring.
Posted 13 April 2011 - 09:31 PM
Posted 14 April 2011 - 03:03 AM
That's more than what the stock alternator would put out by almost 3 times.
It would be best to know what brand and model of pump you have and use their recommendations for fuse and wire gauge.
Most electric fuel pumps will run on a 10 amp fuse. The thing to make sure of is that the fuse you are using is not a higher rating than the current capacity of the wire.
The use of a fuse is to protect the car, not the equipment it is attached to. The fuse should blow if there is a short in the wire or a malfunction of the equipment that it is attached to. This is why you will find fuses generally nearer the source of power than at or near a component. The exception is aftermarket equipment where they install a fuse in the equipment, but the purpose is the same, to protect the car, by blowing the fuse in the even that a problem occurs inside that piece of equipment.
Posted 14 April 2011 - 07:09 AM
10A is usually pretty safe.
Posted 14 April 2011 - 08:34 AM
Posted 14 April 2011 - 09:16 AM
Posted 15 April 2011 - 11:18 AM
Posted 15 April 2011 - 11:55 AM
If your losing voltage somewhere youre amps will be higher.
Posted 15 April 2011 - 01:40 PM
Posted 15 April 2011 - 07:16 PM
Posted 15 April 2011 - 08:31 PM
I am concerned it wont work for the Nationals next weekend though, its creeping up very quickly now.
Posted 15 April 2011 - 11:07 PM
If you are measuring the amperage draw on the pump, you need to set the multimeter to the AMPS setting, on the highest amperage range selectable, then place it IN LINE of the power wire (or earth wire)
Its important that all the current MUST flow through the multimeter, so not just resting the probes against two terminals, but physically disconnecting the wire and placing the multimeter between it.
Bear in mind that measuring in this way often requires some consideration of what you expect to see. No point having a multimeter thats only rated to a maximum of 20A and trying the same thing with the alternator output or starter motor, Clearly that sort of load will cause it to melt/break/explode ect.
If you have an Inductive Amperage meter, then its heaps easier, just clamp around the wire and measure, they are kinda expensive but they'll measure up to hundreds of amps....
The expected reading will be dependant on several factors, How big the pump is (how much it flows), how high the rail pressure is and often the pump is used.
Suffice to say, you should expect around 6-8 amps.
It will peak higher when it initally turns on, this is normal.
Even then, it'll only peak an amp or two over its nominal range.
Most Automotive pumps will be fine on 10-15A fuses.
Pretty much ALL the aftermarket pumps i have set up, i have used a 15A fuse.
While your doing that, it pays to ensure you have a good earth too, either measure for continuity to the chassis from the
pumps negative terminal (should be as close to 0 ohms as possible, 1-2 ohms is acceptable) Or physically remove the ground point and clean it.
Posted 08 January 2012 - 07:15 PM
Regards : Alan.
Posted 08 January 2012 - 08:03 PM
Basic electrical theory is that Power (P) = Voltage (V) x Current (I)
=> P = VI
By example, if the power of the device you are running is known (eg 90/130W head lamps), then max total power is 130 x 2 (lamps) = 260W.
So, 260 = VI
=> 260 = 12V x I
So, I = 260/12 = 21.7 Amps
So, in the case of a high beam headlamp fuse, you would run a 25A fuse minimum. I use heavy gauge wire in my installation, and use 30A fusing, which works fine, and will protect the wiring from a short.
As one of the other contributors mentioned, the fuses are there to protect the wiring, NOT the device. Shorts are caused most frequently through short circuits (eg wiring abraided and shorts to earth) OR through a device failing (eg fuel pump short circuits, effectively conducting power through the pump with no resistance in circuit). In these cases, if the fuse does not blow, the wiring will heat up and potentially cause a fire and/or damage the wiring. By blowing, the fuse protects the wiring from this outcome...the device is already stuffed, hence the fuse is not there to protect it.
Bottom line: The fuse needs to be 'big' enough to sustain the maximum current draw of the device when under load (including start up current), but small enough to blow BEFORE the wiring gets hot and fails. Hence, you need to know the power requirement of the device, and the power/current capacity of your wiring to design your fusing.
Posted 09 January 2012 - 09:53 AM
* AWG: American wiring gauge.
Posted 09 January 2012 - 01:26 PM
Just to add a little more info, according to a wiring chart I looked up (AWG) #6 wire gauge carries 37Amps / #8 24Amps /#10 15AMPS.
* AWG: American wiring gauge.
Over what length?
As the wire length gets longer, the resistance goes up, reducing potential current transfer.
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