1967 won't run after 30 minutes

[Edward J.]

Re: 1967 won't run after 30 minutes

Lee, it appears your missing battery voltage to the coil, the pink wire should be battery voltage on start up, and when the key is released to run the voltage will drop about 1.5 volts as the ballast will kick in. have you checked the coil + side for voltage with key on? a test light will work, but a volt meter is better.

[Lee B.]

Re: 1967 won't run after 30 minutes

I just checked it and it is a little under 7 volts with key on and close to 10 volts with the car running.

[Edward J.]

Re: 1967 won't run after 30 minutes

Lee, you do not have the correct voltage, if the battery shows 12.6 volts that's what you should see at the ballast res. with key on, I believe the pink wire on the bottom of ballast comes from ignition switch. the top wire will show less. by about a 1 to 1.5 volts

[Lee B.]

Re: 1967 won't run after 30 minutes

I hooked the voltage meter from the neg battery terminal to the pos coil terminal like you said in the post and that is what it read. If I understand you correctly, I need to check at the ballast not the coil?

[Edward J.]

Re: 1967 won't run after 30 minutes

I hooked the voltage meter from the neg battery terminal to the pos coil terminal like you said in the post and that is what it read. If I understand you correctly, I need to check at the ballast not the coil?

Lee, with the ignition on, not in start position, you should see battery voltage to ballast as this is the first place when it leaves the ig. switch.

[Edward J.]

Re: 1967 won't run after 30 minutes

Next would be to check the positive side of coil with key on, as the voltage goes through the ballast to the positive side of coil. voltage will be slightly lower as it passes through the ballast.

[Lee B.]

Re: 1967 won't run after 30 minutes

At the input for the ballast, I see 13.5-14 volts and on the output it is 9.5-10 volts with the car running. At the coil, I am seeing 7 volts with key on and 10 volts with it running.

[Edward J.]

Re: 1967 won't run after 30 minutes

Lee, I have a 66 at my shop and will take some voltage measurements later and post them. something does not seem right 7 volts at coil does not seem right with key on.

[Lee B.]

Re: 1967 won't run after 30 minutes

Joe, the jumper between the battery and coil fixed the problem. Is there another test I could try to narrow the problem down further? It is a new coil and ballast. Thanks. Lee

[Duke W.]

Re: 1967 won't run after 30 minutes

Get out your '67 CSM, go to the chassis wiring schematic and trace from the + coil terminal back as far as you can. Then inspect every component and connection in that path.

A common cause of intermittent ignition failure is the bulkhead connector into the fusebox from the engine compartment. Dirty or corroded terminals have been reported several times as the source of this problem, and a good cleaning is the cure.

Inspect pins and receptacles with a magnifying glass and use an Xacto knife or dental curette to clean off any exfoliation corrosion, then clean with electrical contact cleaner. When that is dry, give them a shot of WD-40.

Don't use "dielectric grease" on these connectors. "Dielectric" means insulator, and it should only be used on high voltage connections like plug wire boots. The WD-40 will provide plenty of moisture protection for a car that spends most of its life in a garage.

Duke

[Lee B.]

Re: 1967 won't run after 30 minutes

Duke,
Thanks for the reply, I will certainly check this out, but this same issue occurred the day I picked the car up from the guy who was helping me restore it. In other words, the problem has been there the whole time even when the wiring harness was new. Will let you know what I find out.
Lee

[Joe C.]

Re: 1967 won't run after 30 minutes

Joe, the jumper between the battery and coil fixed the problem. Is there another test I could try to narrow the problem down further? It is a new coil and ballast. Thanks. Lee

Low voltage at the pos coil terminal means that you have a weak connection somewhere, or a partially broken wire. Resistance increases with temperature, and your symptoms are classic for a bad connection or broken wire. At a high resistance point, heat is generated and that section of wire and/or connection gets hot, increasing the chance for a fire. You may also have the wrong ballast resistor. Since your wiring harness is new, there is a possibility that it was defective right out of the box and the same goes for your ignition switch, so you should proceed as follows:

Put a jumper across the ballast resistor. Are you buying the proper replacement ballast(s)?
If that doesn't work then check/clean/lube the ppl wire connector from the ballast on the firewall.
If that doesn't work then disconnect, clean, and lubricate the bulkhead connectors with dielectric grease.
If that doesn't work then check the connector socket behind the ignition switch.
If that doesn't work then check the contacts within your ignition switch.
If that doesn't work then back trace the wire from the ballast resistor and jumper it.
If that doesn't work then jumper the "run" wire from the ign switch to the firewall connector.

It's a long process of elimination and we start easy and gradually get more difficult.

[Lee B.]

Re: 1967 won't run after 30 minutes

Will start this weekend. I will post the results when I have something to share. Thank you for the response.

[Duke W.]

Re: 1967 won't run after 30 minutes

Duke,
Thanks for the reply, I will certainly check this out, but this same issue occurred the day I picked the car up from the guy who was helping me restore it. In other words, the problem has been there the whole time even when the wiring harness was new. Will let you know what I find out.
Lee

A new wiring harness doesn't mean it's not hiding a gremlin. Case in point: 1976 Cosworth Vega, brand new owned by a friend. It suddenly started quitting about once a week, then started back up after a few minutes. In multiple trips to the dealer they changed virtually every component on the EFI system including the ECU, which I "salvaged" from the parts department for my spares inventory for my CV.

Finally, GM sent a tech who was properly trained, knowledgeable , and experienced troubleshooting the EFI system, I think an instructor from the training center that was up in the San Fernando Valley at the time.

Part of the circuit includes a wire from the ignition switch to the ECU. When the ignition switch is turned on this circuit energizes two micro-relays inside the ECU that provide power to the ECU and fuel pumps circuit. Without this circuit closed the system has no power to either the ECU or fuel pumps. They are completely dead even though everything else works.

The tech found a poor terminal crimp on this wire. The fix was merely to re-crimp the terminal to the wire properly to ensure good electrical contact.

Duke

[Joe C.]

Re: 1967 won't run after 30 minutes

A new wiring harness doesn't mean it's not hiding a gremlin. Case in point: 1976 Cosworth Vega, brand new owned by a friend. It suddenly started quitting about once a week, then started back up after a few minutes. In multiple trips to the dealer they changed virtually every component on the EFI system including the ECU, which I "salvaged" from the parts department for my spares inventory for my CV.

Finally, GM sent a tech who was properly trained, knowledgeable , and experienced troubleshooting the EFI system, I think an instructor from the training center that was up in the San Fernando Valley at the time.

Part of the circuit includes a wire from the ignition switch to the ECU. When the ignition switch is turned on this circuit energizes two micro-relays inside the ECU that provide power to the ECU and fuel pumps circuit. Without this circuit closed the system has no power to either the ECU or fuel pumps. They are completely dead even though everything else works.

The tech found a poor terminal crimp on this wire. The fix was merely to re-crimp the terminal to the wire properly to ensure good electrical contact.

Duke

I addressed that already in my last post. You would be wise to read it.