620 relay issue?

[machowgn]

hey all. I hope someone can help me out here, I have a 74 620 pickup, l-18

engine. the truck only has 67k on it. today I drove the truck home, and when

I pulled into the drive way, I noticed smoke from under the hood, I shut off

the motor, and raised the hood, On the passenger side fenderwell I found a

relay with a wire going to the voltage regulator, or resistor. One wire was

completely burned up. The relay has 4 wires. I tried to start the truck, but

right when it begins to fire it dies. I checked for gas, spark, starter. Both

Datsun service books I have don't even show this relay in the electrical,or

charging, or starting systems of the truck? Can anyone tell me about this relay? what is it's function, where can I get one? My local parts store doesn't even list it? thanks, machowgn.

[ggzilla]

Sounds like the electric choke relay. It goes from the N terminal of voltage regular to choke, also hot and ground wires. If you disconnect it, the engine will still start.

 

Perhaps the main IGN wire is damaged, or the ballast resistor is now burnt? Check it with a voltmeter, you should get 6 or 9 volts at the coil + when the closed, and 12 at the coil + when the points are open. If you get no voltage at coil + (except when key is at Start), that explains "it starts to catch, then dies", in other words is it dying when you release the key from Start back to On?