Fuse for ignition coil power supply

[Wietse]

Hey guys,

I ran through the installation manual for my MSD ignition system looking to find how many amps fuse i should install on the 12 volt power supply.
I ran a wire direct from battery, through a relay that switches on by the original ignition wiring, to feed the coil with 12V direct from battery.
I had installed an additional fuse box near the battery to properly fuse the coil and some other things that currently have separate fuses all over the place.
But i did not find anything on how much amps the coil would be pulling.
It is a MSD Blaster SS (P/N 8207) coil, i am using a RTR distributor as well.
Any suggestions on what is the right fuse for the coil? 25 amps?

 

[coloradodave]

I've never seen an installation of an MSD that used a fuse in the 12 volt red battery wire. Not necessary.

 

[RJRENTON]

Hey guys,

I ran through the installation manual for my MSD ignition system looking to find how many amps fuse i should install on the 12 volt power supply.
I ran a wire direct from battery, through a relay that switches on by the original ignition wiring, to feed the coil with 12V direct from battery.
I had installed an additional fuse box near the battery to properly fuse the coil and some other things that currently have separate fuses all over the place.
But i did not find anything on how much amps the coil would be pulling.
It is a MSD Blaster SS (P/N 8207) coil, i am using a RTR distributor as well.
Any suggestions on what is the right fuse for the coil? 25 amps?

I've never seen or heard of an ignition system feed being fused. However, for your piece of mind, fuse the circuit ahead of the relay you noted in your write up. If you could measure the coil's primary resistance and using ohm's law, or E / R = I, where 12 volts/ resistance = Currrnt (amps). I would fuse at 130% of that calculated number with a time delay current limiting fuse to allow for any surges to pass thru yet protect against short circuit. ..... BUT....carry spares...just in case.... Just my opinion of course.
BOB RENTON

 

[Wietse]

Thx for the reply's guys.
Maybe that's why i could not find any info about it if it is not required, but i guess it would not hurt to have it to avoid any disasters like shorts and fire.

I know the relay is a 30Amp model and that has been in there for years already, so i will fuse it to 30 Amps.
It is just in case of wire damage and short to ground i guess.

BUT....carry spares...just in case....

Yes, a set of fuses and relay's is standard equipment to be kept in the glove box now days.
The fuse box installation idea came across as part of the plan on my Sniper Stealth EFI installation as i will have more fused equipment to install.