Starter Direct Short- Battery fuse?

[OX1]

A hair off topic, as this was on my Capri I just spent a year doing eng upgrades and making engine comp show ready..

http://luxjo.supermotors.net/CAPRI/MOTOR FRESHEN/INSTALLED/IMG_1632.JPG

So I'm finally ready to do the part throttle section of the tuning, get
it about 7 feet away from the lift and it stalls twice (new grabby clutch
too). 3rd try to start it, it cranks for 1/2 second and stops. I then see
smoke pour out from under the hood.

Best I can figure is starter became direct short, solenoid then welded
itself stuck in the start position.

***Luckily***, I had a smaller 16 ga wire running from neg term to body,
and the insulation on that smoked like crazy. Otherwise, I would not
have known anything was even up until battery exploded, or the
whole thing went up in flames (and may have taken the whole pole
barn with it).

So in 30+ years of messing with cars/trucks, I never really gave
it a second thought that the battery itself is not fused, but I started
digging around. I stumbled on this marine stuff, an ANL fuse holder
and 500 amp fuse. I'm guessing 500 amps should be plenty to start
a 9:1ish 302, but never gave true starting amperage that
much thought either.

I'm seriously considering adding these to all my broncs also, as one
has dual batts and batt size cables for the plow, another has dual 3G's
and winch wiring, etc.... Only about 100 places those things could short
out, although even if a cable sheathing was cut, could it transmit over
500 amps, probably not.

 

[RustBeltRefugee]

Nice looking engine compartment on your Capri. I had a nose cone break on a starter which caused an excessive high current draw. I might have gotten lucky that I didn't melt any wires or weld my starter solenoid when it happened. I am kind of wondering if your starter broke in a similar way.

 

[ntsqd]

While you're lucky that the small wire got hot and started smoking, I think that you've got a grounding problem too. Starting current should not have been going thru that wire.

Ford has been using that starting relay design for, what, 50+ years? Pretty rare that one sticks. I am going to guess that it is not an original Motorcraft part. If it was a recent (meaning in the last ~5 years) purchase than I'll guess it's a chinese part. And there's the problem.

 

[brianstrange]

I've seen both new aftermarket, and original Ford ones stick, but fewer Ford ones for sure. If you're running the fuse, It might be a wise idea to bring a jumper along just in case. I ran ANL fuses back in the early 90's for high current car audio (200 AMP) and they worked very well.

 

[ransil]

I have burned thru starter cables by having them touch the headers before, first start is ok it the second start that get shorted after the header heat melts the insulation.

 

[Jdgephar]

I thought most batteries for larger v8's are somewhere around 800 cranking amps.

 

[welndmn]

Most Broncos are only wired with 4 gauge cable, even if you changed it out to 2 or 0 gauge, those are only rated for 250-300 amps.
I put one of these beakers on the last car I wired.
300 Amp 12v Dc Circuit Breaker Replace Fuse 300a 12vdc https://www.amazon.com/dp/B007AUPY6I/ref=cm_sw_r_cp_awd_tak2wb62P2FVA

 

[OX1]

While you're lucky that the small wire got hot and started smoking, I think that you've got a grounding problem too. Starting current should not have been going thru that wire.

Ford has been using that starting relay design for, what, 50+ years? Pretty rare that one sticks. I am going to guess that it is not an original Motorcraft part. If it was a recent (meaning in the last ~5 years) purchase than I'll guess it's a chinese part. And there's the problem.

I agree that current should not have been going through that wire, but I checked ground going to block, ground strap on engine to firewall and pos cables to and from solenoid. They all check out good. It may have been trying to create another loop through that small wire and than back to engine block through firewall ground strap. The pos wire right at battery was bright red from heat by the time I got pos wire off battery.

That starter was original and I kept it, as it seemed to be working and I figured an original would be better than most put out today. It did start upwards of 25 times after re-assembly with no problems.

That solenoid is original also (car only has 86k original miles) and I bought that car new. I did grab the current motorcraft replacement for it, not sure of quality or where it is made.

 

[OX1]

Most Broncos are only wired with 4 gauge cable, even if you changed it out to 2 or 0 gauge, those are only rated for 250-300 amps.
I put one of these beakers on the last car I wired.
300 Amp 12v Dc Circuit Breaker Replace Fuse 300a 12vdc https://www.amazon.com/dp/B007AUPY6I/ref=cm_sw_r_cp_awd_tak2wb62P2FVA

I should prob back down on that fuse and use the 500's on one of my broncs with dual 1000 ampers, where I would guess I could get closer to 500 amps with a real bad direct short. The batt in this car is just your average size 58 with 550 CCA.

 

[ntsqd]

Most later model starters have a kW listing. Assuming that there's a listing that works in your car I'd assume a worst case of 10.5 volts and back out how many amps that is. Should give you a rough idea of amperage anyway. Keep in mind that if the later model unit is a gear redux starter that it's kW's will probably be lower than an older, direct-drive type starter.

 

[OX1]

Most later model starters have a kW listing. Assuming that there's a listing that works in your car I'd assume a worst case of 10.5 volts and back out how many amps that is. Should give you a rough idea of amperage anyway. Keep in mind that if the later model unit is a gear redux starter that it's kW's will probably be lower than an older, direct-drive type starter.

I did not go for gear reduction starter, did not feel like re-wiring and this thing starts fine with stock starter. In perfect world, it looks like 1100 watts/10ish volts = 110 amps. not sure if that is a startup amp rating or just running. Suspect running, so what is startup?

The real question in this situation is what will battery supply with a direct short? I've tested batts like this with load tester to 300ish amps, so I know they will at least do that for short periods.........

http://www.oreillyauto.com/site/c/d...ck=Search_01920_1133851_-1&pt=01920&ppt=C0330

 

[ntsqd]

Typical lead-acid battery can go well over 1000 amps in a dead short. Won't do it for very long, but it will do it.

Looked up the gear redux starter that I bought for the Bronco. Listed at 1.4kW for the std trans and 1.7kW for the auto trans. So a hand-wavy guess is a direct drive type is in the low 2kW range. 2000W/10.5V = 190.5A Being that it's an electric motor it will have an in-rush current that exceeds the constant use current, so a 250A or 300A fuse or breaker is about what I'd look at.

 

[brianstrange]

I thought most batteries for larger v8's are somewhere around 800 cranking amps.

The CCA battery ratings are based on what they can produce at 32 degrees for 30 seconds. The fuse is there to protect the circuit from overload or short. They really don't have much to do with each other, but when fusing a starter, you need to consider the amperage increase as the voltage drops during start. It's really not an issue, until the car has a starting issue creating long engine turnover cycles. If fusing a starter, I would lean to maxing out the fuse based on wire size and wire length.