No ignition voltage when cranking

[James W.]

[Richard M.]

Re: No ignition voltage when cranking

James, When you say it "starts", do you mean it tries to start, but does not start?

I had similar results in the past. It would try to start just when ignition key went from START to RUN. At first I though bad IGN switch. Not so. After diagnosis it was found to be a bad distributor pickup coil. Intermittent internal cold solder joint.

I'd check this first.....
Disconnect the 2 terminal plug at the distributor base from the TI harness and attach a ohm meter to the 2 terminals of the mating plug wiring of the distributor pickup coil. You should read 500 to 700 ohms. While the meter is connected, wiggle the 2-pair wiring up near the underside of the distributor and see if the meter readings change.

A common issue is the PU coil wiring can short or open internally from constant wear due to rotation of the baseplate. If you do not read 500 to 700 ohms it's either a short(0 ohms) or open(infinite ohms) or a bad PU coil. It is also possible it's a simple connection problem at the distributor 2 terminal mating plugs. Make sure those 4 terminals are clean.

Also......
The TI ignition system has a Solenoid R wire but it goes to the TI Amp and PU coil. This retains a higher voltage during crank for the TI system, much like it does for the Ignition Coil for a Points system, which uses a Ballast resistor. TI uses Resistor Wire built into the TI harness for the Ignition Coil.

During RUN or START, 12v is supplied to the IGN terminal internally to the ignition switch. This supplies power to the TI AMP and PU coil, but the Solenoid R terminal is activated simultaneously during START, thus supplying a higher crank voltage(from battery directly) to the TI AMP and PU coil. When keyed back to RUN, the R terminal is deactivated, and the TI system is supplied power via the switch IGN(RUN) terminal only.

The only other possibility I'm thinking of for your type of fault is that BOTH a defective Ignition Switch(no IGN voltage during START) AND a faulty Solenoid R terminal circuit. Both faults would have to be present for the condition you're seeing. During START, the engine would crank with no IGN voltage from either source, then when keyed to RUN, it may give a slight burst to try to start as the engine is winding down and seeing IGN power for a very short time.

Rich
PS Attached is the 64-65 TI Troubleshooting sheet and 64-65 TI Wiring Diagram which may help.

[Ray K.]

Re: No ignition voltage when cranking

James,

As Richard has related I have had issues in the past with the distributor pickup coil, although some years ago. Also, double check that the connection in the harness going to the amplifier box is secure. A loose connection here will yield a no start similar to your situation.

Ray

[Carl N.]

Re: No ignition voltage when cranking

Make sure the amp is not grounding at mounting points, should have rubber insulators on attaching bolts/screws. Also make sure coil wires are not arcing to top shield on distributor surround

[Richard M.]

Re: No ignition voltage when cranking

James,

As Richard has related I have had issues in the past with the distributor pickup coil, although some years ago. Also, double check that the connection in the harness going to the amplifier box is secure. A loose connection here will yield a no start similar to your situation.

Ray

Yes good idea to check the mating harness plug at the TI Amp. Sometimes the terminals inside the plug can move or could be corroded.

Make sure the amp is not grounding at mounting points, should have rubber insulators on attaching bolts/screws. Also make sure coil wires are not arcing to top shield on distributor surround

Carl, Yes good point about the coil wires hitting the BB shielding.

The TI AMP case must be grounded for proper operation as the internal circuit board uses its mounting screws to connect ground to the case. The TI Amp case is mounted to the radiator support with sheet metal screws. The radiator support is grounded via the Horn Relay Black ground wire. One of the TI Amp mount screws also captures the Black ground wire in the TI harness which connects through a resistor wire attached to Coil- as shown below.

[Richard M.]

Re: No ignition voltage when cranking

James, Did you ever solve this problem? If so what was the fault?

I'd like to know if you did so I can add your findings to my TI fault database.

Rich

[James W.]

[Richard M.]

Re: No ignition voltage when cranking

James,

Thanks for the update. Interesting the way the starter fault affected the TI system. It appears that the solenoid R contact may have been bad also, which supplies full battery voltage to the Distributor Pickup Coil and AMP during CRANK, bypassing the resistor wire.

Rich