LUVTruck.com

Hi,

I'm currently searching but thought I'd post just in case. I had an oil leak and was pressure washing in around the motor with degreaser and my gen light started coming on and then the truck would shut off. I can turn it back on but then it shuts off 15 seconds later. Gen light on the whole time. I swapped out a spare alternator I had laying around and it seemed to fix the problem. I left town for a week and now that I'm back, the truck is doing the gen light shut off every 15 seconds again. I'm thinking regulator now. Any ideas?

Thanks!

_________________

1979 4wd Mikado. G200, Gemini 250 Turbo, Clive Cam, Offenhouser Intake, JE Pistons, maXspeeding Forged Rods, Blow Thru Weber, Trooper 5spd, Intercooled

Oh and I have. Fixed mount digital volt meter that shows 12.0-12.2 while the truck is running with the gen light on and it usually shows 13+ when driving. I'm getting 12.4 off the alternator post at idle with the gen light on.

_________________

1979 4wd Mikado. G200, Gemini 250 Turbo, Clive Cam, Offenhouser Intake, JE Pistons, maXspeeding Forged Rods, Blow Thru Weber, Trooper 5spd, Intercooled

Have you done the fuse box fix? One of the symptoms of a problem there is the gen light on. If not, and there are electrical gremlins, do that first.

I have not done the fuse box fix. My regulator looks pretty new. I bought the truck from another member who had done a lot of restoration on the truck. Can't tell if the fuse box was done or not.

After some thought, it seems that the regulator is shutting off my fuel pump. When the truck dies, I can start it up by using the starter, which as I understand activates the fuel pump. If I try to compression start it, I can't get it running. So I'm still not sure if it's a bad regulator or bad wiring to/from the regulator.

I will do the fuse box fix tomorrow.

_________________

1979 4wd Mikado. G200, Gemini 250 Turbo, Clive Cam, Offenhouser Intake, JE Pistons, maXspeeding Forged Rods, Blow Thru Weber, Trooper 5spd, Intercooled

Ok I cleaned the fuse box and all the connectors to the fuel pump and regulator. The gen light is gone now but the batt terminals still don't show the alt charging. The alt post does show 14v though. The truck still shuts off after a few seconds.
Thanks

Mike

_________________

1979 4wd Mikado. G200, Gemini 250 Turbo, Clive Cam, Offenhouser Intake, JE Pistons, maXspeeding Forged Rods, Blow Thru Weber, Trooper 5spd, Intercooled

Ok a new regulator doesn't fix anything. Any ideas? I think this wiring is kinda shot.

_________________

1979 4wd Mikado. G200, Gemini 250 Turbo, Clive Cam, Offenhouser Intake, JE Pistons, maXspeeding Forged Rods, Blow Thru Weber, Trooper 5spd, Intercooled

I had some issues with my 73 a few years ago that were a little similar, my (+) cable to my starter motor had rubbed through the insulation behind the engine. Occasionally engine vibrations would move it against the firewall at the back of the block and it would short out and the engine would stall (no power to make a spark) it took me months to find it but i did eventually. My truck had a G161z in it with starter driver side (your passenger side) and the battery passenger side (your driver side) so im not sure if this is the same as yours with a G180 but food for thought anyway.

I also removed the externally regulated alternator and replaced it with an 80A internally regulated alternator as I was barely charging the battery with thermos fans running and electronic ignition controller and stereo constantly on.

I'm pretty confident now there is an issue with the fuel pump not getting fuel. The longer I crank the truck, the longer it stays running. If I bump the starter and it starts, it runs for just a second.

I'm thinking I either need to pull apart the wiring looms, run a couple new wires, or get a one wire alternator.

Does anyone have a part number for a one wire alt that fits?

Thanks!

_________________

1979 4wd Mikado. G200, Gemini 250 Turbo, Clive Cam, Offenhouser Intake, JE Pistons, maXspeeding Forged Rods, Blow Thru Weber, Trooper 5spd, Intercooled

Ok I think I figggered it out.

download/file.php?id=5607&mode=view

According to this, the A post on the alt, which is 14V should go straight to the battery, which in my case it does not, because my battery only shows 12.0 when running. I think if I run a new wire to the battery, everything should work.

Any objections?

_________________

1979 4wd Mikado. G200, Gemini 250 Turbo, Clive Cam, Offenhouser Intake, JE Pistons, maXspeeding Forged Rods, Blow Thru Weber, Trooper 5spd, Intercooled

Have you checked the voltage to the fuel pump when the engine is running?

The fuel pump doesn't have any voltage. I have to jumper the connector to keep the truck running.

I cleaned more connections and now the GEN light is back on. I now have no voltage on the excite terminal of the alternator.

_________________

1979 4wd Mikado. G200, Gemini 250 Turbo, Clive Cam, Offenhouser Intake, JE Pistons, maXspeeding Forged Rods, Blow Thru Weber, Trooper 5spd, Intercooled

When you turn the key to the start position, the fuel pump draws power from the battery. After the engine is running, it draws power from the alternator. There are 2 terminals on the alternator. One post recieves power when the key is on, this "activates" the alternator. This prevents the alternator from draining the battery when the key is off.

The other terminal puts out voltage and runs the fuel pump and ignition and maybe some other things. The reason for this is in case you get in a wreck and the motor goes dead, it will shut the fuel pump off.

My guess is a poor connection to one of the terminals. Have someone start the truck and watch the voltage to the fuel pump. If it drops after the key is in the run position while the truck is running, you know where to look.

The 2 wires on the alternator could be connected to the wrong terminals, but I think this is less likely.

Voltage is supplied to the "excite" terminal when the key is on. The alternator doesn't put voltage out on this terminal.

Now it does sound as if the wires are crossed on the alternator... The wire that gets hot when the key is on goes to the excite terminal. The other terminal won't put voltage out unless the excite terminal has power going to it and the alternator is spinning.

At this point I've checked lots of stuff and the terminal I thought was the excite wire is the ground. It has an E next to it. I thought it was insulated somehow from the alt frame but it's just a ground. So my excite wire does have power and I'm not getting power from the alt when it's spinning so I ordered another alt. picking it up in a bit. I broke one alternator washing it so much due to the oil leak and the spare I had laying around broke an hour after I installed it. Just my luck.

_________________

1979 4wd Mikado. G200, Gemini 250 Turbo, Clive Cam, Offenhouser Intake, JE Pistons, maXspeeding Forged Rods, Blow Thru Weber, Trooper 5spd, Intercooled

Yep that fixed it. I had two bad alternators in a row.

_________________

1979 4wd Mikado. G200, Gemini 250 Turbo, Clive Cam, Offenhouser Intake, JE Pistons, maXspeeding Forged Rods, Blow Thru Weber, Trooper 5spd, Intercooled

Ok the truck is eating alternators.

It must have eaten all three because now I have a brand new one and my gen light comes on and my voltage drops to 12.2. I noticed just before it stopped working it was putting out 14.8 max. It ran all day at 14.0 which I thought was odd at 3000 rpm but then the voltage went higher and shortly after it died completely. It ran about 70 miles before killing the alt. that's probably how much my last alt lasted. I ordered a new fuse block and I have a new regulator just in case but the reg didn't help last time. I'm thinking the wiring/fuse block is messing up the alternators.

_________________

1979 4wd Mikado. G200, Gemini 250 Turbo, Clive Cam, Offenhouser Intake, JE Pistons, maXspeeding Forged Rods, Blow Thru Weber, Trooper 5spd, Intercooled

The excite terminal recieves 12v when the ignition is on. It's not supposed to be grounded. The other terminal powers the coil and fuel pump (through their respective relays)

The alternator will not charge if power is not supplied to the excite terminal. There is no ground wire.

Edit. I may stand corrected. I'm doing this from memory and don't remember a ground wire. I've been told that there is one though. I sure don't remember one though. If there is one it'd be the 4th wire though.

I doubt your alternator is bad. I believe you either have poor quality voltage regulators or bad wiring to the regulator from maybe the crumy fuse box thing. Alternator should be able to charge 14-15 volts all day long. Normal is 13-14 volts depending on the charge in the battery. 14.8 is on the high side though.
The excite terminal noted is the field (f) terminal. It gets 12 volts from the regulator by when the key is on to start the charging process. As the voltage is regulated this voltage drops as the battery charges up and the load lessens.
Disconnect this two wire plug (F & N) and the charging stops. Jumping 12 volts to the F terminal and the alternator charges max. This is how you test the alternator. Hope this helps.

I'm pretty sure this alternator is dead. I ran a wire to my coil for the excite terminal and it still won't charge on either the fuel pump terminal nor the main battery cable. I made a separate ground to the battery. I think I've cut ou the regulator completely and the alt still doesn't charge. Maybe it fried from having a bad lead to the battery or a bad ground.

What is the thing that looks like a condenser that goes on the blue wire of the regulator. Perhaps I need a new one of those.

_________________

1979 4wd Mikado. G200, Gemini 250 Turbo, Clive Cam, Offenhouser Intake, JE Pistons, maXspeeding Forged Rods, Blow Thru Weber, Trooper 5spd, Intercooled