Is this an ignition switch problem?

[Regulatori]

My 73 240Z will start for a second and then die. If I hold the key in the forward position when starting and don't release the key when it starts (keeping pressure on the key so it stays in the forward/start position), it will continue to run. But soon as I release the key, it instantly dies.

 

And if it is an ignition switch, is this something that I can do myself? (I'm somewhat mechanically inclined..I can do alternators, water pumps, suspension, etc..)

[HowlerMonkey]

I would say more ignition switch than most anything else.

 

On your car you should be able to unscrew the two philips head screws that hold the switch to the locking assembly.

 

These are on the opposite side of where the key is put in.

 

There are a bunch of different ones concerning amount of pins and how far they turn which varies from year to year so you have to be careful if you are swapping them.

 

Another possibility is that you have a ballast resistor that has blown open passing no voltage.

 

It is there to keep lower the voltage that the points see to extend life and is usually bypassed when the key is in the start position.

 

Since your car does start, I would disconnect the connector going to the starter solenoid and have somebody hold the key turned so you can figure out which wire going to the distributor has the +12volts and trace it back to where you should find the ballast resistor (if it is still there).

 

It is white and is the size of a 1x1 piece of wood about 4 inches in length with a connector on each end.

 

Once you find it, you should be able to use a test light and a have a friend turn the key so you can check whether the light lights up on both sides of the resistor.

 

If it only lights on one side when the car is in the run position, then it is blown.

 

It it only lights in the start position (both sides) then the switch is bad.

 

My bet is the switch, though.

[HLS30RACER]

I experienced the same symptoms a while back, it turned out to be the ballast resistor (mine was mounted on the coil itself). it is much easier to test the resistor so I would start there.