short on startup

Bri7man

Bri7man

"Yeah! Take the lemons.."
Jul 17, 2009
580
0
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36
Torrance, CA
So there's a short that happens on startup but I can't locate the wire shorting for the life of me.

It happens on startup when the motor is just about to start and then after it will just crank forever.

I see the smoke shoot out behind the alternator in the loom sitting on top the lower IM but can't locate it.

The problem is once the short happens I can't get it to short again for a bout a couple hours to a day which is making it really hard to locate.

I'm about to pull my upper IM to get in there but I don't want to until I can get a visual on exactly which wire is smoking.

Anyways my purpose of posting this is to find out why it won't short again after it does it once.
 
8

89supra7mgte

New Member
Sep 20, 2009
797
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colorado
I would start unhooking the wires and pull the loom off and see which wire is toasted. It is not a ground wire unless shorted to power which would mean in the loom somewhere two wires are cracked or exposed, one pos and one ground.

I would not worry about trying to get it to short again until having all the wires visible. doing so might cause serious failure where it could have been prevented.

As far as only shorting out every once in a while, sounds like a circuit breaker or fusible link, both of which are not located in that section of the loom. The only other possibility is that it is the alt itself coming from the bottom portion rising too appear that it is the wires in the loom.

Recommendation:

Pull loom the visually inspect wires
Remove alt belt.

If no wires look burnt and no smoke with alt belt removed than your issue lies inside the alt.
 
Bri7man

Bri7man

"Yeah! Take the lemons.."
Jul 17, 2009
580
0
0
36
Torrance, CA
89supra7mgte;1459817 said:
I would start unhooking the wires and pull the loom off and see which wire is toasted. It is not a ground wire unless shorted to power which would mean in the loom somewhere two wires are cracked or exposed, one pos and one ground.

I would not worry about trying to get it to short again until having all the wires visible. doing so might cause serious failure where it could have been prevented.

As far as only shorting out every once in a while, sounds like a circuit breaker or fusible link, both of which are not located in that section of the loom. The only other possibility is that it is the alt itself coming from the bottom portion rising too appear that it is the wires in the loom.

Recommendation:

Pull loom the visually inspect wires
Remove alt belt.

If no wires look burnt and no smoke with alt belt removed than your issue lies inside the alt.
Click to expand...

Yeah I'm in the process of removing my upper IM atm to check the loom for burnt wires.

The alt itself could be the problem because the smoke was a strong upward stream at first meaning there had to motion from the part that short...
 
8

89supra7mgte

New Member
Sep 20, 2009
797
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0
colorado
sometimes the diodes in the alt will short out there is rotating mass inside that when cranking can be shorting out, but then going away. this for some reason could be backfeeding through the positive cable or connector cause ecu malfunction creating no crank no start.
 
Bri7man

Bri7man

"Yeah! Take the lemons.."
Jul 17, 2009
580
0
0
36
Torrance, CA
I took my alt off and the plate in the back along with what looks like the heatsync to see inside and it does look pretty black.

I'll snap a pic for reference in a bit

The harness looks great all wires that split out of the loom like injector wires, knock sensors, vsv's are not burnt and not really even brittle and insulated well. Should I still cut into the main loom??

Edit: Here's the pics.
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Bri7man

Bri7man

"Yeah! Take the lemons.."
Jul 17, 2009
580
0
0
36
Torrance, CA
jetjock;1459913 said:
Got news for you Sparky: carbon dust usually is black. And I'm curious to see how long it's gonna take you to figure out the secret of putting that brush holder back on...
Click to expand...

It's 10:44 clock starts now gatto go will post when its back together!
 
Bri7man

Bri7man

"Yeah! Take the lemons.."
Jul 17, 2009
580
0
0
36
Torrance, CA
Twas the alternator!!!!! I had the alternator out and so I wrapped the b+ wire in lacquer thinner gloves(thanks to Zumtizzle's advice) and she started up!!!

Thanks for the help 89supra7mgte you were spot on!!

Now to acquire a good alternator.
 
Bri7man

Bri7man

"Yeah! Take the lemons.."
Jul 17, 2009
580
0
0
36
Torrance, CA
jetjock;1459913 said:
Got news for you Sparky: carbon dust usually is black. And I'm curious to see how long it's gonna take you to figure out the secret of putting that brush holder back on...
Click to expand...

Just curious what was the secret? I really wanna know.
 
8

89supra7mgte

New Member
Sep 20, 2009
797
0
0
colorado
On most alts when you remove the brush housing there is a that goes through the assemble that sets just in front of the brushes when they are completely moved against the spring. A tooth pick or small sturdy piece of wire works well to hold them in place. Not sure is this alt is the same but gm and fords are like that.

As for finding an alt, there are alot that will work but not the correct replacement. i found that checker has a new brand, Ultima instead of autolite, we use them at work with no failures, yet. But you can get the lifetime warranty. I also did some cross referencing on there website. One of the celica alts i believe 92 or 93 has the exact same ULTIMA part number as an 89 7mgte, but costs about 30 less.
 
Bri7man

Bri7man

"Yeah! Take the lemons.."
Jul 17, 2009
580
0
0
36
Torrance, CA
supraguy@aol;1460159 said:
I think it's a noise filter?
Not sure though.
Click to expand...

Yeah I think you're right. I heard the same from someone else. What does that mean though?

Some don't have it.
 
8

89supra7mgte

New Member
Sep 20, 2009
797
0
0
colorado
Very true on the alts, i was actually doing a little more research asking questions to my buddy that works at csk and has his own little honda tuner (600whp on e85) He is knowledgeable and said to stay away from ultima, on imports. They are good for american cars and thats about it.

That is a noise filter. I am not sure of the purpose of it myself.
 
8

89supra7mgte

New Member
Sep 20, 2009
797
0
0
colorado
Well atleast you got a good life out of it. I am sorry but electrical is not my strong side neither are these cars, but i am becoming more familiar with them because of this site.
 
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