any thoughts on whether 16ga wire is sufficient? bigger? pump is the rotary from cb.

k

I'd say 16 is marginal, but that is what the bug pack pumps have coming off of them. I use 14 just to be safe, and if it frys, it's not my fault

For a carb pump, 18g should be plenty, let alone 16g. A carb pump shouldn't draw more than 2-3 amps, but there should be some indication on the box for the Carter pump on exactly how much it draws.

Here's a chart showing capacities of various wire gauges, both "in air" and "enclosed" (i.e., bundled up with other wires).

Wire Gauges

There are some wire gauge standards out there that are several times more conservative than the above measure. I've seen some sources insist you shouldn't use anything smaller than 14g for anything on a car at all, which is clearly overkill.

I agree... its kind of surprising how small of a gauge you can get away with.

each component (pump) has indications of what you should use..

also the distance or length plays a role.

there are tables about length of wire and size of wire.

when we wired the race car we used all aircraft wire (lighter weight) and calculated the necessary gauge for every single wire.

Its amazing how small you can get away with.
Even looking at the factory looms they are running pretty small gauge for the length of the car on many things.

brant

thanks guys. the wires that feed a stock fi pump aren't very stout either. i will err on the side of caution.

k

Length only seems to matter when you're dealing with very high currents, or very small currents, or very long lengths. In a car, the typical longest length is going to be roughly 20 ft. For an 18g wire, you only has a resistance of 7.7 ohms over 1000ft. So, over the 20ft lengths seen in a car, that's 0.15ohms, or a voltage drop of 0.05v for a 3amp current. Hardly enough to worry about. For a 50 amp current, you'd see a whopping 7.7v drop over the same length through the same wire, which is why the cables that connect the alternator to the battery or the battery to the starter are so big. A starter motor can draw 60-80amps, depending on the motor, so you really need to 2-4g wiring you often see on them.

the splice in is going to be a whooping 12" or so from the pump to the stock pump wires. i'm a week out from wanting/needing to finish this project. whole new approach for me. usually i wait until the day before.

k

if you are talking about the wire to make the fuel pump relay kick on, it is only grounding out the relay control, and therefore is only carring the coil wattage. so any size wire will work

QUOTE (scott thacher @ Aug 19 2005, 11:59 AM)

if you are talking about the wire to make the fuel pump relay kick on, it is only grounding out the relay control, and therefore is only carring the coil wattage. so any size wire will work

done. andy's method was really slick. found rolls of red and black 14ga in a drawer and went with that. made up a little harness with some shrink tubing and the pump ran with the first turn of the key. i had been experiencing a little "fuse" problem with the pump power being pulled off of the fuse panel. i'm at 99% that with the pump utilizing the proper relay, that "problem" will disappear. danke!!

k