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80amp fuse blows after about 5 seconds of cranking URGENT PLEASE HELP!!!!

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Euphoricglass

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Discussion starter · #1 ·
So the car..... is a usdm 95 240sx with an s14 sr20det swap that i did about 3 years years ago and never had this problem until now. The car sat for almost two years although i dont think that would have anything to do with it. Oh yeah and the battery has been relocated to the trunk with an 80 amp fuse in the line.

The problem.... after about five seconds of cranking the inline fuse blows.

What ive done..... ive pulled the main line out inspected it found one little puncture taped it up pulled the lower engine harness off and cut it completly apart to do a thurough examination of it... nothing touching. and ive takin the starter out and done a bench test and it works great every thing is back in and still popping the 80amps like popcorn. Its all looks like its pointing at the starter to me but im so frustrated im starting to lose my head ..... please help me, ive gotta have the car out of where it is buy tomarrow Thanks...Corey
 
#2 ·
Sounds like a current draw issue.

Dbl check grounds at battery n motor and make sure they are free of corrosion

It's possible the starter is starting to go bad, increase the fusing to 100 amps and see if the problem persist..?if so find a new starter
 
#3 ·
dont increase the amperage fuse because if its under 100 the wires on everything will literaly melt. something is touching somewhere. where out of the engine bay did u run the postive wire?


Sent from my Autoguide iPhone app
 
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#4 ·
MidnightExpress said:
dont increase the amperage fuse because if its under 100 the wires on everything will literaly melt. something is touching somewhere. where out of the engine bay did u run the postive wire?


Sent from my Autoguide iPhone app
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The 100 amp is on the battery lead from the trunk, 80amps is the bare min you should run ... Typically most people run 100-150 amp circuit breakers or anl fusing when relocating their batteries... So upping to a 100 amp circuit will not affect anything more then what's currently being affected by the 80amp circuit but it will allow the starter to pull the extra current needed to crank though.
 
#5 ·
n2hifi said:
The 100 amp is on the battery lead from the trunk, 80amps is the bare min you should run ... Typically most people run 100-150 amp circuit breakers or anl fusing when relocating their batteries... So upping to a 100 amp circuit will not affect anything more then what's currently being affected by the 80amp circuit but it will allow the starter to pull the extra current needed to crank though.
Click to expand...
Extra Amperage = Extra heat. Extra Heat = Melting. Don't use a 100amp fuse. Something in your staring circuit is drawing more current then it should be. This could be increased drag on the starter such as the bushings going bad or and armature dragging. It could also be caused by the motor having more resistance than normal.
 
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#6 ·
HuckRG said:
Extra Amperage = Extra heat. Extra Heat = Melting. Don't use a 100amp fuse. Something in your staring circuit is drawing more current then it should be. This could be increased drag on the starter such as the bushings going bad or and armature dragging. It could also be caused by the motor having more resistance than normal.
Click to expand...
You clearly haven't a clue what your talking about... You do know that on 240's that the ign circuit ALONE is 80amps NOT including anything else powering when the car is attempting to start.

Current required/drawn increases for every foot of wire between the battery and source of the current draw... Relocating the battery to the trunk with require almost a extra 40amp more fusing then what's required when the battery is located 6" from the fuse box

it's simple math, I do this shit on the daily
 
#7 ·
you realize that almost everything shuts off when the car is actually trying to start. If factory is an 80a fuse i would stick to an 80a fuse. For extra length of wire you don't go up in fuse size you go up in gage size.
 
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#9 ·
HuckRG said:
you realize that almost everything shuts off when the car is actually trying to start. If factory is an 80a fuse i would stick to an 80a fuse. For extra length of wire you don't go up in fuse size you go up in gage size.
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They don't have a factory fuse size for relocated batteries

http://www.powerstream.com/Wire_Size.htm

4g is safe for 130+ amps of fusing for stuff like battery relocations since the max current draw is typically for short periods ( ie start up ) and then after that it's just a charging lead since the car is running off the alt 90% of the time, but when doing car audio we typically don't like to put more then 100 amps of current draw on it since is typically for longer periods of time which is what generates heat and melts fuse, fuse holders and eventually cause current burn in the wire.

Also when cranking accessorys drop out but not anything powered by ign.. Ie starter, fuel pump and electric fan which if it's a correctly done sr swap means Walbro and large 30+ amp electric fans which don't help on the current draw

2 years ago his battery would have been in better shape and provided plenty of current, who is to say that the battery is older its not performing correctly cause issues also
 
#10 ·
If the 80a fuse was working fine before then there is extra drag causing the starter to pull more amperage than before. Thus blowing your fuse. if the car sat for 2 years there could be extra drag coming from the bearings, crank, even the cams. Again it could be the starter bushings. just because it passed the auto zone bench test doesn't mean its 100%. Find your cause for extra amperage draw and you'll find your problem
 
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HuckRG
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