New Engine blowing main fuse (80A)
 

I installed a new engine in my truck(see signature). I got everything hooked up and applied power, immediately blew the 80a fuse in the fender fuse box.
No crank, no start, the only lights that work were headlights.
I checked every ground I can find, all tight, shiny, metal to metal.
Starter and alternator are connected correctly.
The alternator was upgraded to an 140 amp unit, connected using stock wiring.
I didn't replace any cables connecting battery to starter, although it does have a funky spade connector that the DAPO installed as a( I assume)
theft prevention measure.
I am on my way out to find a replacement fuse.
I am comfortable using a Multi meter and have the correct FSM.
I did a search and it would appear that my problem is a Short to ground?
That is why I started with the starter and alternator, thinking that I may have connected something wrong, had bad wiring, metal to metal tec, but an initial visual search did not reveal anything burnt,or melted.
So,
any thought or direction would be much appreciated. I will post some pictures this afternoon.
Thanks in advance!
John

After you replace 80Amp FL, and before you connect to battery, measure resistance between ground and the wire that goes to fuse block. That's the wire thinner than the one that screws to starter solenoid stud terminal.
Let us know what u see.

Thanks Rad,
I will get back on it in the am, let you know what I find.
The guys at 22re performance also suggested I recheck alternator connection and visually inspect where the wiring harness enters the cab.
Thanks again
Edit: That wire is cut and has the spade connector installed. I drove the truck for about 8 mos like that with no problems, but you never know.
I noticed the white wire coming out of the fuse block is a different gauge than the on it connects to.
One of the reasons I bought the truck was the lack of hacked wire.
Oh well, an opportunity to learn.

Another thing to check. Disconnect everything from stud terminal of alternator. With alternator installed normally, measure resistance of stud terminal to ground. You should get LOTS of mega-ohms (sorry forgot what mine read but, IIRC it was like 33 Meg-ohms. If you get low reading, you may have a bad rectifier diode.

Sorry... what wire? A picture paints a thousand words.

The FL that looks like a fuse is the FL AM1.
The wire between battery positive and fuse block is the MAIN Fusible in schematic. Make sure it is intact and DO NOT REPLACE WITH THICKER WIRE.

It should look like this.
https://lh3.googleusercontent.com/wK...w=w800-h600-no
https://lh3.googleusercontent.com/98...U=w800-h600-no

It is attached to a plate that screws on bottom of fuse block to the terminals of the 80-Amp FL module. Terry's87 has details how to disassemble.

If you want to fully utilize your 140-Amp alternator capacity, do as Chefyota4x4, Redeth, and I did like this , and supply all added circuits from a fused distribution block directly from the battery. This way your alternator and battery will directly work hand-in-hand, supply the higher current directly to your added circuits without passing through the stock fuses and FL's, AND stock fuse and fusible links will protect stock circuits - critical to truck operation - no matter what happens to added circuits.


https://lh3.googleusercontent.com/5m...Q=w948-h762-no

Rad,
Thanks, I will get pictures up in the morning, I realize that describing a problem on the internet is a poor
substitute for a visual representation of the problem.

You have given some great advice, which is greatly appreciated, and I will get those images up tomorrow.
I have the 80amp FL module pulled out of the fuse box after reading Terrys87 description.
Thanks,
John

https://cimg2.ibsrv.net/gimg/www.yot...d117410e90.jpg
This is the set up currently
https://cimg7.ibsrv.net/gimg/www.yot...7168cc6758.jpg
Top of FL
https://cimg9.ibsrv.net/gimg/www.yot...9e4053c82b.jpg
spade connector FL side
https://cimg3.ibsrv.net/gimg/www.yot...7c6d3864b2.jpg
spade connector starter side

Here are a couple more. Looking at this it is apparent it needs to be fixed, so I am know thinking all new ground battery cable and new starter cable with new FL.
https://cimg7.ibsrv.net/gimg/www.yot...e5e97cabb9.jpg
tape removed
https://cimg4.ibsrv.net/gimg/www.yot...a6a913ada8.jpg
gratuitous engine shot

Not able to source the fuse part that the FL screws to, so no resistance reading on that yet.
I got lots of resistance from stud terminal on ALT to ground, can rule that out.

https://cimg3.ibsrv.net/gimg/www.yot...ef047765eb.jpg
found-
https://cimg5.ibsrv.net/gimg/www.yot...8546a2b140.jpg
This has low resistance,so clean up, replace heat shrink and cut off spade and add ring terminal? Edit: This appears to be 6 ga wire?

Too short, it likely blew/burnt-out which is someone tried what you have now. Just order a new one, or replace the whole length with white fusible link wire.

Rad4Runner:::: Do you by chance know the part number of the MAIN fuseable link wire and plate unit????

Repair wire is, 82991-.....

Sorry, I've never looked for it. Would definitely be nice if someone could chime in.

This^^^

Republic77,
if you could not find OEM replacement, find out what gauge that factory white wire connected to the plate (i.e., measure diameter), find fusible link wire 4 gauges thinner, then spice to that white wire or replacement, terminate one end of FL wire with ring terminal to connect to battery connector.

I'd also replace that POS ( for positive and for you know what - LOL) battery cable. What's that silver metal thing on other end? That could short to ground.
Recommend using "Marine Battery Terminals. Robust, easily-available, versatile.

https://cimg1.ibsrv.net/gimg/www.yot...2a5a2417af.jpg
https://lh3.googleusercontent.com/S-...o=w500-h282-no

Hey Rad, I am going over to the dealer to see about a OEM replacement for the FL, I will get relevant part numbers and post.
The white wire exiting the plate on the FL is 39 strand/.4 mm copper, I had it worked out to be 6 gauge. Thoughts?
You are saying find a FL wire 4 ga. thinner (10 ga) and splice into the existing fl IF I cant find oem, right?
Yeah that cable is definitely a POS, the metal part you referenced is actually a threaded stud half way down the length I have no idea what it is for, but I am getting rid of it.
Thanks for the tip on Marine batt terminals, I will grab a couple today.

Have another look the photo he posted. I think he misspoke and I certainly did.. Note the none fusible link wire at the battery end, this is larger than the FL wire guage by one or two sizes. This wire attaches with a crimp to the FL wire, it should be a bit shorter than the battery is tall. The White FL wire (rating I think is 100-120 amps, there are some good posts that cover this) makes up the rest of the length. It crimps to the large plate at the end. This whole wire run should be covered in a noncombustable sheeth (fiberglass weave) and have the normal sheeth over this to keep it clean and dry.


Or just buy one from Toyota, 82991 (from memory) is the base part number.

Thanks CO,
I am going out the door to the stealership right now, I would prefer oem to a splice of my own making, but if it comes down to it...
In the picture, of my FL, the wire that exits the plate is*I believe* 6 gauge, I will get a 10ga FL wire to splice into the end of the existing short run I have
and solder a ring terminal to connect to battery pos (+).
Thanks for the part number,I will confirm later.
John

Update: 82991 is the number for the replacement wire. Good memory CO!
It is, unfortunately, NLA from the dealer.
So I will get some clarification on the FL wire configuration,then use my original plate and make one.
Got the marine terminals and a new run of 4 ga. wire for my (+) wire.
Thanks for the help!
Edit
Is there any reason the (-) ground wire cannot be increased in gauge?
I bought a ready made deal with the intention of lopping of the battery terminal and replacing, it is a larger diameter
than the stock wire tho. I could easily do the same with the old wire, it ohms out fine.
Thoughts?

Very good to upsize wires if feasible.
Very Not good to upsize fuses or FLs :)
Haven't tracked down if you have a dead-short to ground?

This is where I am at in the process.
After I sort out the wiring,I will have a better baseline to test. Eliminating that (+) wire with that funky metal part will
reduce possible causes by one.
Copy on that" very not good upsize" comment.

This was something I meant to mention in that last post, I guess I overlooked it or wasn't particularly clear. I was in a bit of a hurry.

The standard wire should be larger than the fusible link wire.

Ok on with the diagnostics..

You blew the main FL, did it actually break somewhere between the plate and that terminal (closer to the battery) or did you just get a bit of smoke?

Since you lost the main FL and not am1 or am2 the short should be somewhere between the fusible links. There are two circuits there (headlight, and horn/haz, these are the wires we see screwed to the plate in the above pic, check the resistance to grind on these.

https://www.toyotapartsdeal.com/oem/...991-35020.html

It let me add it to a cart so they "might" have it

Hey Fishguy,
Thanks for the link.
When I entered in my truck in the "make sure it fits" section it said it doesn't.
Interesting that the part number 82991-35020 is close but has 5 digits more at the end.
I will investigate further.

Teaching moment!

The first part of the number tells you what is is, 82991 is a fusible link (sorry lazy and not looking up the full Toyota name)

The second part of a (full) part number -35020 tells you what it fits.

Ahh very cool!
Thanks for that CO.
If I could buy a complete set of books for the truck I would in a heartbeat.
So
I have reconfigured the FL main,replaced (+) batt cable,(-) batt cable,changed to marine battery posts changed the FL80a fuse,
rechecked connections and leads, checked resistance on all that was suggested above,and
found no high resistance.
The only thing left was to connect a battery, and thanks to all that gave advice,
the issue seems to be solved. It is hard to say what exactly was wrong, but I think the pos batt cable was the culprit.
I was able to turn everything on at once, nothing blew up, no fire dept was involved and better yet I bumped the ignition
and my new motor kicked over ever so briefly.

I'm bringing this thread back as I may have found the actual FL for our trucks. Can anyone confirm this is the correct one? It sure looks right. After reading this thread I realized that someone had replaced mine years ago with nothing but a wire. I had a feeling when I saw this years ago that someone Jerry rigged this. I never even knew there was a FL.


https://www.megazip.net/zapchasti-dl...air-8299189101

I also found this website that has a diagram with part numbers....
https://www.megazip.net/zapchasti-dl...554566-4554566

Hmm, did the fusible link solve the problem for good? OP states the 80A fuse blew after installing a 140A alternator. Most high current alternators come with a kit or instructions to run an additional wire between alternator and bat, at least the one for my '85 did.

The new fusible link did indeed fix the problem.
I have about 4500 miles on the new motor and no reoccurrence of the problem.

What gauge wire did they recommend or did you install?

LC sends their kit out with an 8ga wire. They don't seem to think a fuse is required on the new wire, but I put in a maxi fuse anyway,I think 80A. To be honest the whole hi-amp alternator turned into a fiasco for me. I consistently threw belts around 4500 rpm with the smaller pulley on the hi-amp alternator, so I ended up putting a stock pulley on the hi-amp unit, making it a frankenstein with unknown characteristics. Working good for now though.
https://www.lceperformance.com/High-...-p/1080005.htm

Thanks for the follow up, Republic.

You probably didn't drop too much amperage by switching to the larger OEM pulley. I work in commercial HVAC and make sheave change calculations all the time on air handler units and motors. So if you want to know about how much I can calculate the % based on the outside diameter of the sheaves/pulleys. Or you could hook up an amp meter and just measure it across the RPM curve. With the advent of LED technology I question whether a high amp alternator is needed anymore. :dunno: Maybe if you had a 1990's system with huge amps and (10) 12" woofers. :laugh:

Wasn't necessary in the 90's. I had a heck of a system in my 85 pickup. 2-250watt amps (I think), 2-4's and tweets, 2-6's and tweets, 2-8's, & 2-12's. Had one power cap that I installed after about 6 months. I would notice a slight dimming if I had it turned up for long periods 30+ minutes. But that was around 110db to get that issue to happen, nobody want to listen to 110db in an XtrCab Toyota for 30 minutes...