Really need help been stick for months now

[jeepcj7304]

I am stuck in a very confusing situation. I have a 85 CJ7 with a 360. I recently installed a new 360,EZ-EFI fuel injection and an electric fan. I am having charging issues since getting it running not sure if its related but it would seem. I thought it was a bad alternator so i swapped it worked fine for a day or so then no voltage. took it to a shop (which i hate to do) and they said the alternator need to be a high output due to needing more amps for the injection and fan. They charged me 300 dollars and installed a NAPA 120 amp alt. Worked great for a few days again and then no voltage. I have pulled the fuse for the electric fan and it didnt seem to change. The alternator is the AC Delco one wire style. It has 8-12 volts on the white wire (Excite) and the case seems to be grounded since I am getting continuity between it and the battery with a multimeter. I tried the old wire jiggle to no avail. I pulled the alternator and swapped in the old autozone one that was on before and it worked fine for me for the first 2-3 starts and then first test drive. I parked it for 10 minutes and started it back up and now no voltage other then battery voltage. I had the Napa alt tested and it tested good 14.8 volts so any ideas on the problem? It seems that i have excite going in to the alt, ground and the wire coming off is new, not that it matters since testing at the alt output shows no voltage. Im stumped and dont know where to go from here.

[Mudrat]

Don't know dude, but will be watching this CLOSE since I'm still in the process of finishing an 85 rebuild with a built 360 and electric fans. Dont have the FI side, but will be watching. Good luck and keep posting progress!!

'Rat

[jeepcj7304]

I don't think it is the fan causing it because it is unhooked and still am having the issue

[msalaba]

More information is required:

1)Are you the one who installed the 360?

1a)If so, what mods did you make to the factory harness?

2)Did you do the electrical for the EFI?

2a)If so, what further mods were made to the harness?

3)Did you wire this system from scratch?

4)Where do you ground the (-) lug on the battery? (very important)

There are a few factory circuits that loop back on themselves (can't remember which ones) so if you are tapped into a factory harness, I can look them up.

When I bought my Jeep, the harness was bad in many places. So, I rewired the entire thing. The only "factory" circuit I have is for exterior lighting and that came out of a waggy.

The GM 3-wire alt is a very simple system yet subject to many old wives tales. IMHO 1-wire = CRAP, they are made for hobbyists that do not understand electrical systems.

The GM 3-wire have 3 connections:

1) Stud = Charging output to bat.
2) Spade (a) usually small brown wire (color may vary) = excite wire. must go through a light bulb (dummy light) or equivelent ohm resistor to switched +12VDC (ign switch) do not use a LED. This is the most important or else your alt will not charge.
3) Spade (b) large red or yellow wire = load sense input. This tells the alt how much load is present in the electrical system and modifies the output accordingly. Racers run this to +12vdc @ the coil or MSD box. You might want to run this to your fan as that would be the greatest load.

I may have spade a & b reversed as I'm writing this from memory. Google "12si GM alt" You shold be able to find a schematic.

A word of advice on electric fans- make sure you run a heavy enough guage wire for the load. I have seen a few of my friends rigs burn due to inadequate wiring. again, Google "wire guage load" and you should be able to find a chart.

After writing all this the simple explanation has hit me. Is your idiot light burnt out? When you turn your key past "run" before the starter engages, all the idiot lights should light up. Make sure you see the one for alt/batt/or =

If you need more help, post back. I'm pretty good at vehicle electronics.

[jeepcj7304]

1. yes I installed the 360
1a. The harness is a new Centech harness no mods were needed and the jeep had a 360 in it with this harness previously the motor blew and i just put in a new one.
2. The EFI is an aftermarket unit that comes complete with a stand alone harness only thing i hooked in was power and ground direct from battery and a 12v switched from the fuse panel.
3. I believe the previous answered this.
4. Battery gets grounded to the motor mount bolt and then up to the intake with another wire.


It is a AC Delco 12SI alternator. I have the power lug on the back running to the battery and a small wire spliced in that jumps to the plastic clip and into the alternator. Then there is a white wire that I believe is the excite wire it has voltage with the key on. There is no dummy light in my jeep for this that i know of but i will double check and im unsure of any resistor on this wire. It seemed to work previously with the old motor. but something could have got switched i guess. I dont think it has anything to due with the fan since i pulled it as soon as i got the alternator working and pulled the fuse from the main power for the fan weeks ago.

[jeepcj7304]

OK went out and screwed with the jeep it seemed to have voltage 12.15 at the battery with the key off and 12.00 with the key on. I started it up and it idled at 12.20 and built to 13.56 after 1 minute and 14.14 after 1 1/2 minutes. I turned on the lights and it dropped to 12.70 right away and stayed at 12.70. This was at 800 rpm idle. I reved the engine up to 2000 rpm and held it there for 30 seconds and it drops steadily and reached 12.11. I couldnt continue to test because the engine was begining to run hot. but when i let it go to idle it seemed to start building slowly again. This should be the opposite correct??? At higher RPM it should build more voltage. Also this is without my electric fan which would pull even more current.

[msalaba]

It is a AC Delco 12SI alternator. I have the power lug on the back running to the battery and a small wire spliced in that jumps to the plastic clip and into the alternator. Then there is a white wire that I believe is the excite wire it has voltage with the key on. There is no dummy light in my jeep for this that i know of but i will double check and im unsure of any resistor on this wire. It seemed to work previously with the old motor. but something could have got switched i guess. I dont think it has anything to due with the fan since i pulled it as soon as i got the alternator working and pulled the fuse from the main power for the fan weeks ago.

This could be your issue. There needs to be a resistance in the excite wire. This is usually provided by the battery indicator lamp in the dash. The alternator will not charge otherwise. In one wire alternators, this wiring is performed internally and no other connections are required other than the charge wire to the battery.

The spade terminals on the alternator are labeled (1) and (2). #2 is on the left if looking at the rear of the alternator.

In most some applications the load sense wire (#2) is looped to the charge output as yours is. This works fine if your battery is very close to the alt. This works fine in modern OEM applications as most high loads originate near the battery +12vdc terminal. If you have a fan relay mouted close and fed from teh battery this will be fine for you.

As peak loads move farther from the battery, it takes more of a draw to tell the alternator to turn up the juice. I have a rear mounted battery. I have a +12vdc stud under the dash (fed from the bat) that feeds all my electrical needs. So this is where I routed the load sense wire. I have the charge output from the alt directly to the battery. This really only becomes a concern when you stray to far from factory specs.

I feel your problem is in the excite wiring.

There are some simple tests you can do.

#1) Start your engine. Remove the +12VDC connector from your battery. If the engine dies, there is an alternator problem.

#2) Rig up some wire with a female spade connector on one end. Put a 12v light bulb in the middle (an old marker light works well) Make sure the wire is long enough to reach your battery. Put an alligator clip on the other end.

Connect the spade connector to #1 on the alt. Connect the other end to the +12V at the battery. The light should be on.

(If not on your battery is dead, the bulb is burnt or the volt regulator in the alt is junk)

Start the engine. Light should go out. If not, rev the engine a little then it should go out. If the light is out, your alt should be charging. If the light stays on, you have alternator problems.

And if you really must know.... Go here

http://www.rowand.net/Shop/Tech/Alte...onversions.htm

for more information on alternators than you will ever WANT to know.

[msalaba]

Seems i forgot obout one of my previous posts. Dang CRS

For even more than you'll ever want to know go here -> http://oljeep.com/gw/alt/edge_Alternator_Theory.html

There is a troubleshooting section down the page after a bunch of links.