Ignition With Fuses?

Hello all,

I got my jeep running but now i think i am overthinking a few things. One of which is the ignition to starter wiring.

Should there be a fuse to between the batt and key switch?

Between key switch and starter?

I have a main fuse box after the key switch to power everything else, i am just wondering if i should add any in these areas too? It with the exception of the Fuel Pump there doesnt seem to be any wiring in the "running" of the motor.

 

Would you want to accept the risk of sudden total loss of power?

 

That’s what I was thinking too.

 

How much would you risk an electrical fire from an unprotected circuit?

 

Suddenly out of power or suddenly out of power and on fire... take your pick.

Might up the wire guage and fuse accordingly.

All this said I've still got the factory wire that feeds the 134 coil powering a hei distributor. I'll likely bump it to 12ga and use a breaker for the extra wtf roadside trouble shooting so the engine suddenly loses power but fires right up.

 

I would focus on protecting the wires and leave out the fuse. Sheath the unprotected wires in vacuum hose or split loom, put grommets everywhere they passes through sheet metal. Tie them down to prevent chafing. On the race cars back at Chuchua's, he would use the yellow weatherstrip cement and glue the wires down along their whole length.

If you worry about a fire, you could use a large value circuit breaker to prevent the wire from igniting, say 20 or 30 amps. You won't want to keep driving if the ignition wire wants to set the Jeep on fire. Note that any additional device introduces new liabilities of its own. Fuses break and terminals corrode, circuit breakers fail, etc.

 

Check out fusible link wire. If I recall correctly, the fusible link wire is 4 wire gauge numbers larger (which makes for a smaller link wire) for the link than the "real" wire.

Circuit breakers are also useful for this application. They make them that bolt to a suitable flat spot and have #10-32 studs for the wiring.

About the only wire I leave unprotected is the large battery cable from the battery to the big terminal on the starter or starter solenoid. That wire gets carefully routed and protected.

 

A fusible link is only useful where the protected wire is much larger in gauge than the fusible link. The ignition wire is probably 14 or 16 ga, I would guess. You would need an 18 or 20 ga fusible link if such a thing exists.

Well ok, seems you can get a 20 ga fusible link. https://www.amazon.com/Pico-5557PT-Universal-Gauge-Fusible/dp/B00030CZV4

These links are very reliable, but not serviceable in the field.

 

Aye, Ford liked/likes to use fuse links, I always made it SOP to make sure to toss extras in the glovebox, just in case.

 

So this diagram shows a fuse in the ignition circuit. So good or not good idea?

 

His diagram shows a 30 amp fuse in the charging/starting circuit ("battery" terminal of ignition switch) which also includes an amp gauge. I'd swap to a volt gauge instead of the amp gauge.
-Donny

 

x2 do away with amp gauge

 

If you get rid of the ammeter, there is no reason to have the charge current go from the alternator to the dash and back to the battery. Instead it can go direct to the battery. This is a lot safer than the ammeter setup. Then run a single wire to the dash for lights, ignition, etc.

 

Yes I have done that but was referencing the fuse. If that vjwavehihe driving no engine dies right?

 

Not seeing it.
Not good idea anyways.

 

It's labeled "main 30A fuse" next to the ignition switch.

I don't see much value in that diagram, esp. if you don't have an ammeter. What kind of charging system will you use? Delco alternator? Separate alternator and regulator? Generator and regulator? It matters. Without an ammeter, all the charging wires stay under the hood, except for a single wire to a GEN or ALT light, if you want one.

The ignition switch is powered from dash power. So is the engine ignition and lights and gauges etc. You can protect the main power feed to the dash - I'd suggest a fusible link that's sized according to the wire size (4 digits or 2 steps smaller, ie 14 ga wire gets an 18 ga fusible link). Ignition requires very little current, and starting only needs to energize the solenoid.

The way to think about this - you protect the Jeep from the battery. If you have a wreck or one of the wires is pinched, it's the battery that will make your wires burst into flame. Typically you'd have one wire that goes to the fuse panel and then branches to all the devices, including the ignition switch and engine ignition. Up to you whether you protect the wire to the ignition switch with a fuse or not. You could use a 16 ga wire to the ignition switch from the fuse panel dash power connection, and protect it with a 20 ga fusible link.

 

Great stuff thank you. Yes I’m pretty set on my wiring now that I’ve hand wire the entire jeep. I’m just trying to fine-tune some circuits in which fuses to use. This is not my drawing as it came from a post here about five years ago I think. I am using a voltmeter and it’s all connected and working.

If I was to use a circuit breaker at the battery what size amp breaker do I use? I am still thinking the fusible link route as well. I did over wire size my wires. I just thought they looked better and more durable. So their capacity is much more than what they’re connected to in most cases. Most of my wire is 12 and 10 with some 14

 

Circuit breaker - Add up your maximum load and double it, rounding up. It's not really critical, since a short is an instantaneous huge load, hundreds of amps.

For fusible links, size them to the smallest downstream wire size. For example, if you have 10 ga from the battery to the fuse panel, put a 14 ga fusible link at the battery end. The wires downstream from the fuse panel are protected by the fuses, not the fusible link, so don't include those.