NEED Help Quick!!!

[dmsteele92831]

I'm wiring a killswitch to my electric fuel pump. I'm using a 10 amp switch and running 18 gauge power wire (same as original wire going to fuel pump) I have an inline 20 amp fuse. It was working for a minute but I think I keep blowing the fuse!!! IS the 20 amp too high, or my switch too low?

[72lb4x4]

Everything depends on how much current (in amps) the pump draws. Check the specs for the pump.

Check the fuse to see if its toast. If it is, you may need a larger one, or a slow-blow fuse.

The switch won't cause the fuse to blow, it'll just burn up and act like a fuse itself, or start a fire...

[dmsteele92831]

I bought the truck with the pump already on there, so I don't know the amps. Also the fuse is the cylinder type with paper around the outside so it's hard to tell if it is blown, but I replaced it once after wiring the switch wrong the first time and the switch was working. So I think I'll try a different inline fuse first. But does it matter if it only needs a 7 amp inline fuse and I use a 20 amp? I would think have a bigger fuse would be better, but I don't know much about that kind of thing.

[jojotonka]

Did you blow the fuse??

I would think your fuse is to BIG. And your wire to SMALL.
My guess is you burnt your wire somewhere.

I did the same thing last month. I ran a 7 amp inline fuse with 10 gauge wire.

NO PROBLEMS!!

[dmsteele92831]

Cool thanks!

[jojotonka]

No bigger fuse is not better. If it calls for 7 amps, and you put in a 20 amp and happen to come across a problem somewhere, it's going to look for the path of least resistance. Which could be in the wire or the switch since your fuse is to big. That's why they recommend the smaller amp fuse because you WANT that to blow first, not burn a wire.

[cdowns]

with my limited knowledge of electric fuel pumps 18ga wire seems to be very undersized all the ones i've seen and the kits i've seen run at least 12ga to power a pump//i'd think that thin wire would burnup due to very high resistance

[dmsteele92831]

Bigger wire, smaller fuse!!! Thanks for the help!

[dmsteele92831]

I don't think God wants me to have a kill switch.... OK I got the ten gauge wire and a 7.5 amp inline fuse. I stayed with my 10 amp switch. I re-ran the wire and hooked everything up and it was working perfectly... then I disconnected and reconnected the power wires into the back of the switch a couple of times; to adjust the clip for holding better and a couple times it was pulled out while I was looking for a good spot to mount the switch. Then once I found that spot, the switch no longer worked. I checked the fuse and it was fine, so did I burn up the switch by disconnecting and connecting the power wires to it while they were hot?

[dmsteele92831]

Bueller???

[dmsteele92831]

Well, I checked the fuse again (it was dark last night) and it was busted. I also switched to a 20 amp switch, and so far it is working although it has only been one drive.

[lbpd719]

Sounds like it's time to invest in, or find a buddy with a good multimeter..

I am thinking you will be chasing a ton of electrical ghosts in your truck if it's starting this early

[gator2511]

If you flashed the wires together fairly quickly and the pump was set to run you could cause a current spike that would pull enough amps to blow the fuse. Most multi meters have a 10 amp scale you could use to measure the amp draw by hooking the meter in series with the fuse. Just be sure to hook the leads up properly and be on the D.C. scale. Nothing wrong having the 20 amp switch because it is overated but will not cause any problems. Better overated on the switch than under.

[Sport/Truck]

Your fuse is nearest the power source, right?
s/t

[dmsteele92831]

So far so good, but now I think my tranny is starting to slip!!