So I had my 69 HO running after all new wiring, motor and all accessories rebuilt then I go to start it during tuning and it will not run. New fuel pump, new carb, checked fuel line pressure all ok.
I discovered the car runs with the key held to the start position but then dies when released.
Any ideas?

 

You don't have voltage to the coil+ when the key is in the on position. Your only getting voltage to the coil from the starter R terminal on the solenoid.

 

Could it be a fusible link gone bad?

 

You have the two small wires reversed on the starter solenoid.

 

I was thinking solenoid too. Purple wire S terminal, yellow, R terminal.

 

Ill check that tomorrow.
The odd part is that I had it running and never changed the starter wires after that. Would it start or even turn over if the wires are reversed?

 

That is what it sound like has happened. Many years ago I reversed the wires & got the same symptom as you. Maybe you have a broken wire or some other issue though? Let us know what you find.

 

Its not at the solenoid, those wires are doing what they are supposed to be doing as there is voltage to the coil when the key is in the start position. He is missing the run circuit voltage at the coil+ terminal on the coil provided through the resistance wire from the ignition switch.

 

Bad/misadjusted ignition switch.


It is mounted on top of the steering column under the dash.

 

Or a broken or disconnected resistor wire.

- Eric

 

Does the car have stock points, HEI, or other aftermarket electronic ignition conversion? As Eric correctly points out, the problem is that you are not getting voltage to the coil when the key is in the RUN position. This could be a bad ignition switch, a bad resistor wire, or a problem with the firewall connector.

 

So I jumpered the coil positive to the battery and the car runs. Where is the fusible link in the run circuit?
I changed the ignition switch and that didnt do it although the key does turn easier now.
Looks lime I have a broken wire or bad link somewhere. It was running fine before this problem.

 

There is none.


Did you test the ignition switch first? If it wasn't broken, why did you change it?


Yes it does.

Now you have to systematically troubleshoot it until you find the problem.

Just go one step at a time - start at the battery and test every step along the way.

- Eric

 

The switch was sticking and had a small crack in the plastic. It looked to be o.e. so it was worth replacement for the 20 bucks. Unfortunately not the problem.
Tomorrow ill start checking the wires from the battery to the switch and out to the coil and starter.

 

First question: is this a stock points distibutor or an electronic conversion (and if so, which)?

Second, when the engine fires in START but immediately dies in RUN, the problem is nearly ALWAYS the resistor wire to the coil. Keep in mind that there are TWO wires from the ignition switch to the coil on point-style distributors. The wire that is powered with the key in the START position is normal copper and provides full battery voltage to the coil for easier starting. When the key is released to the RUN position, this copper wire is disconnected and instead a resistor wire is powered. The resistor (which is built into the wire on stock GM harnesses) drops battery voltage down to about 9 V at the coil to let the points live longer.

Since you have replaced the ignition switch and presumably adjusted it properly, the problem HAS to be this resistor wire. Note that the problem could be between the switch and the firewall connector, between the firewall connector and the coil, or a bad terminal in the firewall connector itself.

 

But note that the actual resistor (nichrome) wire runs only from the firewall connector to the coil - the wire between the ignition switch and the firewall connector (Pink) is copper.

- Eric

 

How's this:

"The problem HAS to be the wire that INCLUDES the resistor..."

 

Just didn't want to send him looking under the dash for a resistor wire he wasn't going to find...

- Eric