Positive Ground Electrical System

[Wolfy]

All:
I believe that my GMC may have a + ground Electrical System. How do I tell for sure. It is supposedly converted over to a 12V system. However, I just purchased this truck, and have no clue what they have done to it. I have had it running, while pouring fuel into the top of the carb. Now, I cant even get it to turn over. I will be purchasing a new starter in soon.

How do i connect the battery? Do I connect the + to the frame? And the - to the starter switch? Please provide any info that you can.

My truck is a 3/4 ton 1952 GMC.
See link http://www.oldgmctrucks.com/page0375.html
See detail #9 for positive ground.

I may have messed something up. When I was trying to start it, I hooked up jumper cables, the normal way that you would. Did I possibly mess up something? How would you hook up jumper cables for a + ground set up?

Is it worth converting to a - ground set up. Any other advice would be helpful.

Thanks
BDW

[EdsClassics]

If it was converted to 12volt you would think they would have also changed any bulbs, gauges, generator to alternator etc. to 12v neg ground. Check a light bulb to see if it is a 6 or 12 volt bulb. Does it still have the generator or has a alternator been installed for the 12volt?

On a pos ground setup the positive post on your battery would go to the ground on the motor. Negative post would go to starter/solenoid. To jump a pos ground system you would still put the pos to pos and neg to neg jumpers wires to each battery. That does not swap over. It would be like arching your pos and neg posts with a screwdriver, not good.

Does it still have the starter with the solenoid on top and has to be started by foot? If so it sounds like it still has the original 6volt setup.
One way to tell if your power is hooked up backwards is to run the motor and look at the charge on the volt gauge. If it shows that it is discharging instead of charging the battery your power is hooked up backwards.

What does the coil say, 6 or 12volt? If pos ground then those wires are reversed too.

[Mr_Mac]

On a pos ground setup the positive post on your battery would go to the ground on the motor. Negative post would go to starter/solenoid.

Agreed. Follow the wires and see where they lead. As for the voltage, get a DC volt meter and measure the battery voltage or, if your battery is old enough, count the cells (each cell is good for two volts).

Mac

[Wolfy]

Thanks for the fast responses. The truck has an alternator, which to me says its been converted to a 12V neg ground. It has a foot start starter, looks to be original. The whole thing that started this mess, is the starter. It did crank over for about a week, when i has trying to start the truck, bad fuel pump. I hooked it up to jumper cables, and it cranked over for a while as well, now I have nothing. I will pick up a new 12V starter here in a few days, and will let you know how that works. Meanwhile, I will try to pull out some bulbs, and see what they say. the battery that came with the truck is a 12 V battery, only about 2 yrs old. I had it tested and its fine.

Also when I got the truck, the the Neg was connected to ground, and the positive was connected to the starter. I just don't know what others have done to it. My goal now is to put the new fuel pump in, and get the new starter in. I have already replaced all the battery cables, and regrounded the starter and the neg cable on the frame.

Thanks again for the help!!! I will keep you posted
bdw

[EdsClassics]

What did the coil have on it? 6 or 12 volt?

[Wolfy]

Not sure what it has on it currently, I will check tonight. the new coil that I purchased is a 12V coil

[Wolfy]

Got the new starter installed! I went ahead, and replaced all the battery cables, and regrounded, everything. Did a complete tune-up, and now I am waiting on my fuel pump. I did try and crank it over, and it worked great! Now I just will be buying a new master cylinder, and brake lines. I will hopefully start on that soon.

[Rich-Md]

Great progress your your truck. One thing I have learned is that when you are able to drive your truck the project moves along a lot faster because your interest is held.

[Mr_Mac]

Good job! My only problem is, I can't see what you're saying! Are you creating a photo journal for us to look at? ;)

Mac

[Wolfy]

I will try to get some pictures uploaded soon. I have been so busy lately, so when i do get free time, i just work on the truck and don't take any pictures. I will try to get some pictures soon!!!

[Wolfy]

here is an updated link to what I have been up to lately... enjoy
http://talk.classicparts.com/showthread.php?t=9213
http://talk.classicparts.com/showthread.php?t=8752

[Rich-Md]

Whats the status on your truck? Did you get the issues resolved and get it fired up?

[Wolfy]

Yeah I finally got it fired up and actually drove it around the block... without a passenger door. But to update I have replaced the starter, rewired that and the ignition system, did a complete tune up. Replaced all the brake lines, rebuilt the wheel cylinders, replaced master cylinder. Rebuilt the carb, and all the interior gauges. Now I have to button up some wiring of tail lights and such, and take it to a body guy to get the door back on and seals replaced. its been a lot of fun. Can't wait to drive it regularly. :D