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My car had an electric fuel pump on it when I purchased it and it's currently wired for constant running when the switch is in the run position. I'd like to add a 3-way toggle switch under the dash and use it on an "as needed" basis but not sure if I should make it fuse protected or not. Any ideas? I haven't checked to see if it's currently straight wired in or not.

All electrical accessories should be protected by a fuse or a circuit breaker. For an electrical component in the fuel system I'd not use a circuit breaker because it would attempt to re-energize a shorted device. Install a fuse.

Agreed on the protection. It should have something and fuse would be safest. However, if you do want a circuit breaker get a type II or even better for this use, type III breaker.

Just for reference on breakers:

Type I, fully automatic reset. Avoid that type in this application.

Type II, once popped is reset by cutting the power feeding it -- for example turning the key off, waiting a bit and then back on.

Type III does not reset. You have to find and push a button on the breaker to reset it.

Napa and probably the usual others carry a few in each style. The card or packaging will specify the type -- usually located somewhere close to the value although they may call them something else such as semi automatic or manual. There are numerous online sources if the local store doesn't stock a particular value.

For this particular application I wouldn't use a circuit breaker. Problem is that circuit breakers are not fail safe because they are mechanical devices. Fuses are fail safe assuming one does not install a fuse higher rated than spec.

Also be advised NOT to buy a fuse holder that is a No-Name-Brand. I've gotten into this at least 3 times over the last 3 or 4 years. The fuse holder will melt before the fuse blows.

Bottom line: There MUST be a WELL KNOWN AND TRUSTED BRAND name on the fuse holder itself.

This is a question that begins with an 's' for either simple or stupid (or both): Which side of the switch to fuse? Supply side or equipment side? I always assumed the supply side was fused, but...

(o[]o)

I would try for the supply side just in case the switch itself decided to act up.

Howard, thanks - that's what I was thinking. Often mistaken, but never confused.

(o[]o)