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Discussion Starter · #1 ·
My 88 GT has an electrical short on the EGI sircuit, i have cheacked to see if the injectors where causing it but they are not. There is a slow drain that will kill the battery in about 4 to 5 hours if not less, i put a volt meter on the battery and was plugging and unplugging things to see if i could see a change in voltage, when i pull the EGI Fuse the volts jump up a few tenths and when it is re-installed they drop a few tenths and then continue to drop every 30 secs or so by a thenth. I was also told it could be the fuel pump....is there a fuel pump relay that i could disconnect or a fuse? Also what in the EGI circuit says hot when the igntion is turned off, there would have to be voltage in the circuit with the key off to cause a drain right? Does the whole circuit stay hot or just parts, i would think only parts b/c of the EGI relays under the hood, i tryed un plugging them but no change...I need help....any one know where to get wire diagrams.
 

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Observing the voltage at the battery when unplugging various things is not the correct method. You need to observe the current draw from the battery with the multimeter. You do this by putting the meter in series with the battery. (Disconnect negative battery cable, connect one lead of meter to battery, other lead to disconnected terminal; set meter to measure current in amps)

Try this method and it will work better. To be honest, my 90-92 wiring diagrams probably won't help as there are differences with respect to the 88-89. I'll look at the diagrams a bit more and see if I come up with anything.
 

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Ok, so I looked at my schematics some more, and it appears that this fuse is used for less things than I thought. Try unplugging the following and see if the current drops:

1. Alternator two-pin harness connector. (used for voltage regulator)
2. Main relay (far left of the group on the firewall under the hood - used to supply power to the injectors)

My guess is that it's probably a bad alternator.
 

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Discussion Starter · #4 ·
yeah, I wanted to used current draw but the meter was not really reading it....i tried differnt settings but i will try the alternator, it was replaced already. I found some diagrams and by looking at them, all i could figure out was that one of the 30A fuses in there control the injectors almost exclusivly and the other 30A fuse is for the circuit with many sensors for the Fuel Injectors, such as the Knock sensor, the IAT, the AFM etc etc. This car is a project for my girlfriend and I, it runs strong but needs tlc, like it has oil leaks and and needs some body work and this damned electrical problem, I would love it if I could just get this electrical problem solved that way I don't have to pull that top 30A fuse everytime the car is parked(it is not in use as of yet). But i guess that the previouse owner replaced the alternator already does not mean it is functional in every way...hell, it is for all intents and purposes, soaked in oil. All and any help would be apreciated.
 

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Discussion Starter · #5 ·
well the diagrams was half right and half wrong, from looking it, i thought both main EGI relays operated on different circuits, it was wrong, both are on the top, but they switch on and off just fine, so i started to trace the circuit from the fuse box to the relays and come across another circuit coming from that same fuse, it has the white wire with a green stripe and i think an orange dots along it, the same that ran to one the relays, so i was like i bet the short is over there, the likly hood of a short being between the relays and the box is small because there are no connections, so i unplugged it and using my voltage testing method from above it showed that the short was on that circuit....i left it un plugged and yet, no drop in voltage. The wire is the two plug one, with the white/green/orange and a bigger black with red stripe on it, i could not follow it because i was getting cold, so can anyone tell me where this wire goes and what stems off of it.
:confused:
 

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Did you try unplugging the two pin connector on the alternator? I think that might be your problem. The 30A EGI fuse only powers two things on the 90-92's: that alternator terminal and the main relay on the firewall (marked "I"). Not sure if 88-89 is different.

Also, the black with a red stripe wire near the fuse box goes to the starter solenoid. Could try unplugging that as well.

I'm also not sure why you say you can't measure the current draw from the battery. This is the only effective way to do this. To measure current, as I said before, you cannot just switch the meter to current and put the leads across the battery. You need to switch the meter to current, plug one of the multimeter leads into the amperage terminal on the multimeter and the other on the ground(common) terminal. Then disconnect the neg battery cable, and put one lead to the battery and the other to the disconnected battery terminal.
 

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Discussion Starter · #7 ·
I tried that, i did not work, i hooked one lead to the negative on the battery and the other lead to the cable. Something must be wrong with the meter. But anyway, the battery stopped droping when i unplugged the two pin connector by the fuse box. The problem lies there, and i think it is where ever that white and green wires goes...i would have unplugged the wire at the alternator but it was dark, cold and i am wroking in a barn that is not all the way closed in with a dirt floor. So I called it a night. I will try to jack it up and get under it to unplug the alternator. I really appricate your help.
 

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No problem. You should't need to jack it up to unplug the alternator...you can reach your hand in there and unplug it without tools. Unplugging the black/red wire from the starter might require jacking the car up though. As I said over on probetalk, check to see if you're getting any voltage at the starter solenoid (black/red wire) with the ignition off. If you are, the ignition switch is malfunctioning as there should only be voltage there with the key turned to "START".

Are you sure your meter was set to measure current and that you had the positive multimeter lead plugged into the "A" terminal on the meter?
 

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magik8 said:
You need to switch the meter to current, plug one of the multimeter leads into the amperage terminal on the multimeter and the other on the ground(common) terminal. Then disconnect the neg battery cable, and put one lead to the battery and the other to the disconnected battery terminal.
I'm thinking it would amount to the same thing, electrically, if IROC just removed the 30amp fuse from the offending circuit and stuck leads from his multimeter into the fuse contacts.

Either way, his meter is in series with the load.

Lazy folk (like me!) do it this way to avoid losing them radio presets and clock time when battery is disconnected.
 

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Good call, SleepCounter. That would work as well. The main point I was getting at is that you have to have the leads plugged into the ground and amperage terminals on the multimeter, not the same high-impedance terminals as the voltage measurement uses.. Not doing this and not putting the meter in series with the load are common mistakes for the electrical novice.
 

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Also the fuse in the multimeter itself could be poped. I have done this on accident when testing amps and then forgetting to move the leads back to high impedence and trying test a voltage...

~Chris
 
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