PT1850 Alternator Conversion

[Charlie_Iliff]

It appears that you are feeding the plus side of the fuel solenoid with 12 volts, when running. You just might have to rewire the fuel solenoid with a separate switch.

I think JJ's right, and it is a function of the single wire alternator. As I understand it, the initial field voltage to the alternator before starting is supplied by the "ignition" post of the starter switch. Once running, the regulator keeps that field voltage at its set level, no longer needing the battery connection. (Do we have an alternator guru lurking?)
A kill switch in the fuel solenoid line solves the problem. It may also work to wire it to the accessory circuit rather than the ignition circuit. The accessory circuit should still shut down when the key is turned off.

 

[J_J]

We finished hooking it up.

The voltage meter reads a steady 14 volts, the way it used to. So it seems to have fixed it.

But theres a strange side affect. With the new alt. unhooked, the fuel solenoid shuts off by the switch as it should; but with the alt. hooked and running, the fuel shut off doesn;t cut off, and the keys off alll electrical cuts off, except the fuel solenoid...so I have to manually shut off th fuel to stop it.

I think its some kind of ground loop. But at least its running good now.

Does anyone have a wiring diagram of the electrical system for that model PT? If I had one, I could do a little more research. How ever, if you are satisfied that the battery is being charged, then a separate fuel shut off switch is a good thing, for this reason. If your ign switch goes bad , and will not shut off the engine, then the fuel cutoff switch is like an emergency shutoff.

 

[AltavistaLawn]

Thanks,
Its still charging good.

I talked with Terry at the plant today, he said the number 7 terminal in the main engine plug (the one we unhook to zew it to bleed the hydros) was hot, key-on. After this job, I'll try to rewire it and post back.

Also he mentioned a diode which keeps voltage from going one way (?) ; we didn't use the gm harness, but the GM harness has a diode jumper between the two wires on top.

 

[Bob999]

Thanks,
Its still charging good.

I talked with Terry at the plant today, he said the number 7 terminal in the main engine plug (the one we unhook to zew it to bleed the hydros) was hot, key-on. After this job, I'll try to rewire it and post back.

Also he mentioned a diode which keeps voltage from going one way (?) ; we didn't use the gm harness, but the GM harness has a diode jumper between the two wires on top.

John Coxon (Sedgewood) has posted some wiring diagrams at his website that may be of assistance:

http://www.coxontool.com/documents/powertrac/diagrams/wiring/wiringlogicfromptdwgs.gif
http://www.coxontool.com/documents/powertrac/diagrams/wiring/wiringlogicdiagramafterrebuild.gif

 

[AltavistaLawn]

Thanks for those, I'll print them out.

 

[cqaigy2]

Thanks,
Its still charging good.

I talked with Terry at the plant today, he said the number 7 terminal in the main engine plug (the one we unhook to zew it to bleed the hydros) was hot, key-on. After this job, I'll try to rewire it and post back.

Also he mentioned a diode which keeps voltage from going one way (?) ; we didn't use the gm harness, but the GM harness has a diode jumper between the two wires on top.

Years ago I had a motorcycle that wouldn't start no matter how hard i kicked it over. I dug through the wiring harness and tracked the trouble down to an open diode. I wired around the diode and it started rightup, no problem. But one time i started it up, revved the engine while letting out the clutch and away i went....backward?? So the second time it happened i thought, Ok that's gotta be hard on the engine so i bought a diode from a tv repair guy, wired it in and it never went backward again.

 

[AltavistaLawn]

Thanks,
Its still charging good.

I talked with Terry at the plant today, he said the number 7 terminal in the main engine plug (the one we unhook to zew it to bleed the hydros) was hot, key-on. After this job, I'll try to rewire it and post back.

Also he mentioned a diode which keeps voltage from going one way (?) ; we didn't use the gm harness, but the GM harness has a diode jumper between the two wires on top.

Oops.
I think I popped something, I miswired the Alt., trying to use the GM plug and now my #7 (green) wire doesn't have juice...and the PT won't start.

I tried to jump a wire to the fuel solenoid, and th esolenoid kicks in; but it still not getting any fuel. I cracked the injector line and it s dry.

I printed out the wiring diagrams above..they should help. Thanks a bunch for that.

 

[J_J]

Oops.
I think I popped something, I miswired the Alt., trying to use the GM plug and now my #7 (green) wire doesn't have juice...and the PT won't start.

I tried to jump a wire to the fuel solenoid, and th esolenoid kicks in; but it still not getting any fuel. I cracked the injector line and it s dry.

I printed out the wiring diagrams above..they should help. Thanks a bunch for that.

Check 20a fuse, if good, check ign switch for 12 volts coming in, Turn ign switch on, and check 12v at accessory. When the switch is turned to start, check 12 v at the start terminal. If all that checks out, trace it down line to fuel solenoid. Is the fuel solenoid a shut off device, or is this the fuel pump?

Did you wire the alternator directly to the battery?

 

[AltavistaLawn]

Check 20a fuse, if good, check ign switch for 12 volts coming in, Turn ign switch on, and check 12v at accessory. When the switch is turned to start, check 12 v at the start terminal. If all that checks out, trace it down line to fuel solenoid. Is the fuel solenoid a shut off device, or is this the fuel pump?

Did you wire the alternator directly to the battery?

I didn't realize it had any fuses until I saw the wiring diagram, I'll have to track 'em down.

The fuel solenoid shuts off the fuel, the fuel pump is mechanical, and seems to be pumping OK.

I bet its a fuse somewhere, that happened to my old John Deere F620, and I replaced the ignition switch before figuring it out.

 

[AltavistaLawn]

And the alternator was wired to the side of th esolenoid where the batt.'s hot wire is. I unhooked the alternator for now.