Keep blowing “engine” Fuse, and I'm out of ideas. Please help. (76 FJ40 - US)

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Hey everyone, first time poster(I think) long time lurker/learner. I got a '76 earlier in the year which was running at the time, and I've been fixing things as they fail.
The current problem is that the “engine” fuse keeps blowing when I try to crank. Here are the usual suspects (that I'm aware of) and their states..

Battery, starter, ignition switch, voltage regulator -> brand new (like in the last month)

alternator, coil, plugs, wires -> recently replaced

All other electrical seems to work fine, battery is reading mid 12V (can't start it so don't know what the alternator is putting out, etc)

The last issue I had was a bad ignition switch.. whenI replaced it, it cranked right up, I drove it home. Next time I went to crank, it blew the ignition fuse.

What else in the ignition chain should I be looking at? Is there anything else?? I've looked for loose or frayed wires and can't find anything.
Any help would be greatly appreciated.
Thanks
 
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65swb45

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Is it a genuine switch?
 
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I’m almost positive that I know the answer but am going to ask anyway, for thoroughness. I bought that battery to increase the cca from the newish, but cheap previous battery. Is it possible that I got a battery that’s incompatible or spiking? Is that even a thing? 12v is 12v right?
 

ToyotaMatt

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the Larger Group batter will NOT cause your issue .......

but a CHINA made key switch could and i have seen it happen new out of the cheap bag they come in ...........


you get what you pay for in your land cruiser world ........


if you wish to eliminate this possible cause ?


i can have this in the mail today .......


100% Japan Spec. TOYOTA Genuine OEM parts .....







1669721592838.png



1669721618406.png
 

Engineer8000

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When you say "Ignition fuse" do you mean "engine fuse". None of the items you listed are fused, except by the fusible link by the battery. Are you melting the fusible link?
 
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the Larger Group batter will NOT cause your issue .......

but a CHINA made key switch could and i have seen it happen new out of the cheap bag they come in ...........


you get what you pay for in your land cruiser world ........


if you wish to eliminate this possible cause ?


i can have this in the mail today .......


100% Japan Spec. TOYOTA Genuine OEM parts .....







View attachment 3180705


View attachment 3180706
Good to know, I actually looked at this one on your site last night while I couldn’t sleep. This morning I’m going to disconnect the switch and jump the wires to see how it behaves without the switch, that should tell me if it’s a problem or not. If so, you’ve got a sale!
 

ToyotaMatt

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Good to know, I actually looked at this one on your site last night while I couldn’t sleep. This morning I’m going to disconnect the switch and jump the wires to see how it behaves without the switch, that should tell me if it’s a problem or not. If so, you’ve got a sale!


how exactly do u plan to JUMP all the needed wires in the KEY START Position all at one time 🤔


you do realize u will be cheating fate with FULL-ON Battery Voltage and AMPS too .....................fyi ...


i would re-think your simply put JUMPING diagnostic approach

there are much more risk free ways to confirm and verify your fuse blowing symptoms ........fyi





1669727173806.png
 

Engineer8000

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Stuff on the engine fuse: Fuel cut solenoid, emission computer, VSV, cooling fan controller, regulator, maintenance interval detector. I would remove the engine fuse and put an ohmmeter on that circuit to ground (should see near 0 ohms) then unplug each item on the fuse to see where the short goes away.
 
Last edited:
Joined
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Messages
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Location
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www.iliketomakestuff.com
the Larger Group batter will NOT cause your issue .......

but a CHINA made key switch could and i have seen it happen new out of the cheap bag they come in ...........


you get what you pay for in your land cruiser world ........


if you wish to eliminate this possible cause ?


i can have this in the mail today .......


100% Japan Spec. TOYOTA Genuine OEM parts .....







View attachment 3180705


View attachment 3180706
ordered 👍🏼
 

roadstr6

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Check that you don't have any wiring touching the exhaust manifold, especially between the engine and the firewall. I had this happen once. Insulation burned off, hot wires shorted to ground through the manifold. Engine died on the highway at 60 mph. Cabin filled with smoke from burned insulation. Spectacular backfire blew up my muffler like a balloon. Cooked my voltage regulator and a ton of wiring. I had to call the tow truck that day. I would do a little investigation before throwing money at new parts or else you may let the smoke out of your fancy new genuine Toyota parts.
 
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Check that you don't have any wiring touching the exhaust manifold, especially between the engine and the firewall. I had this happen once. Insulation burned off, hot wires shorted to ground through the manifold. Engine died on the highway at 60 mph. Cabin filled with smoke from burned insulation. Spectacular backfire blew up my muffler like a balloon. Cooked my voltage regulator and a ton of wiring. I had to call the tow truck that day. I would do a little investigation before throwing money at new parts or else you may let the smoke out of your fancy new genuine Toyota parts.
Holy crap! That sounds like a tough day. Definitely will look into that, thanks!
 

roadstr6

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Holy crap! That sounds like a tough day. Definitely will look into that, thanks!
It was a tough month re-wiring the entire engine bay and half of the dash. Also the exploded muffler issue snowballed into a full exhaust redo.
 

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