starting or not

turn engine over but will not fire up but when I let the key go it fires. what do you all think ?

 

I think you need to provide a better description before we fix what ever you have.

 

Your vehicle doesn't have a resistor bypass wire from the starter solenoid to the coil.

A simple solution might be a push button on or under the dash connected to a hot all the time pin on the fuse block and to the side of the coil that the wire from the ignition switch connects to. Push the button when you turn the key to crank it and let off the button as soon as it fires.

Or if the solenoid has a stud for a resistor bypass wire to connect to hook the bypass wire to that and then to the coil.

I didn't check to see what you are working on but that would help for us to give a solution.

 

From key switch output make sure you have correct resister and coil if 12 volts.You may have 2 resisters losing power when cranking.

 

It sounds like your losing voltage to the coil while cranking, it could be a simple voltage drop, or it could be a bad ignition switch...

 

If you have a Ford type starter solenoid it will have two small posts. One is I for ignition and the other is for S start. Got em backwards maybe?

 

Your ignition switch is probably bad...I had the same problem with my '56 Cadillac...after using the car/switch a few times it was less fussy...but you can tell that if you jiggle the key that the contact is bad..

 

Its a 350 chevy with hei dizzy If I hot wire the dizzy from a separate battery that would prove if it was low voltage would'nt it

 

The problem is you are not getting voltage to the coil in start position or cranking.
Probably at least 20 things it could be..

 

Where does the + wire come from on the HEI? Is it from the ignition switch or the starter?

 

I think the wire comes from the starter but I'll start working on it tomorrow

 

I think the starter only supplies current when cranking. Connect to the "on" connection of your ignition switch and it should work.

 

On your Chevy engine, the I terminal on the starter is used to deliver 12 volts only while cranking.
Depends on how your car is wired & determines whether or not you need it.
Some ignition switches drop all voltage except for starter while cranking. There also is a 9 volt run 12 volt start required for points and that's probably how the car was originally wired.
Can't say for sure since the harness is being kept a secret.

 

Weak battery will cause the ign not to fire till starter load lets 12v flow. A weak battery cranking can have 10-11 volts left.

My MSD would not fire till I let go either when old battery was in it.

 

checked the wiring the + feed to the HEI comes from the ignition s/w and I found a bad connection on the spades that pushes on the HEI termnial crimped it a little a she fires first time now Thanks all