Click on image for the lowdown. 
====
| | | Forums66 Topics128,022 Posts1,055,382 Members48,422 | | Most Online14,466
Apr 26th, 2026 | | AD Chevy Trucks  Over 6,000 pictures Brad Allen has an awesome collection of Chevrolet factory pictures that he has set up from film strips. Check them out!
Lots of work on Brad's part ... pure enjoyment (and references) for you!
| | THANKS!
For helping keep this great
old truck web site
on the Internet for over 30 years! and not clogged down
with Ads!  Again, thanks!
| | | | Joined: Jun 2015 Posts: 59 Wrench Fetcher | | Wrench Fetcher Joined: Jun 2015 Posts: 59 | I was wondering what the coil supply voltage should be,key in the run position engine off. My engine quit on me yesterday , this is a 1962 261 in a gmc, I wasn't getting any spark, and I measured 5.8 v at the coil key on not running, I installed a wire direct from battery to coil and it fired right up. After getting home I pulled the by-pass and it restarted on the normal truck wiring.again I measured the voltage at the coil and it was around 5 v engine off, but it was 9.6 v engine running . What's going on? This engine is 1 year on rebuild all new ignition parts at rebuild.
1962 GMC 920 step side 261 4 spd
| | | | | Joined: Jan 2013 Posts: 2,232 Moderator: Interiors, Texas Bolters, Name that Part | | Moderator: Interiors, Texas Bolters, Name that Part Joined: Jan 2013 Posts: 2,232 | GMC,
I just found out the hard way that I need a resistor on the positive coming into the coil. (OPS!) My truck also stopped while I was driving it down the road due to a extremely hot coil. Once it cooled down, she started right back up and I was able to limp her home. I am dealing with all the gremlins involved with mine.
I am thinking out loud after learning from my MANY learning opportunities over the past month.
Did your coil get hot or just warm? (I assume warm due to the Voltage change, but not hot)
How long did you wait before you ran the wire directly?
Do you have a bad battery (if you ran wires directly then you may have bypassed other things that would create a draw)
Do you have a bad ground or bad/loose wiring? Have you changed/alter anything recently that might caused this issue?
Good luck and keep us all posted. I am sure that many others may have this same issue and will read this.
Chris | | | | | Joined: Feb 2004 Posts: 29,746 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,746 | 9-10 volts with the engine running at the coil (+) terminal is about right. Don't be surprised if the next time you measure voltage "key on engine off" if you get full battery voltage. That happens if the engine stops with the points open. Resistors only reduce voltage if they're flowing current at the time the measurement is made. You need to rig a bypass wire to the coil input while the starter is turning. If you're using a stomp starter, install the stomp switch intended for 55-62 engines with the small bypass terminal on the side.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Jan 2013 Posts: 2,232 Moderator: Interiors, Texas Bolters, Name that Part | | Moderator: Interiors, Texas Bolters, Name that Part Joined: Jan 2013 Posts: 2,232 | Jerry, is that the stomp switch you were referring me to over the phone last night? | | | | | Joined: Mar 2010 Posts: 10,270 Renaissance Man | | Renaissance Man Joined: Mar 2010 Posts: 10,270 | On a 6 volt system without a ballast resister, what are we trying to "bypass" with the '55-'62 bypass starter switch?
Based on my interpretation of the OP's descriptions, I would suspect that he has an issue with his ignition switch or associated wires, preventing full battery voltage (or very close to it) to the coil.
Carl
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
| | | | | Joined: Feb 2004 Posts: 29,746 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,746 | If he's getting 9.6 volts at the coil on a 6V system with the engine running, he's got some serious charging system problems as well as ignition trouble. I'm betting a 62 GMC has a 12 volt electrical system.
Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Feb 2004 Posts: 29,746 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,746 | Jerry, is that the stomp switch you were referring me to over the phone last night? Yep, same one. Try one of the online parts places like Rock Auto and search for a starter switch (not ignition) for a 1960 Chevy pickup with a 235 engine. AC Delco D928A Copy/Paste this link for a photo: http://www.rockauto.com/info/301/D982A_Primary__ra_p.jpgJerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!
| | | | | Joined: Mar 2010 Posts: 10,270 Renaissance Man | | Renaissance Man Joined: Mar 2010 Posts: 10,270 | If he's getting 9.6 volts at the coil on a 6V system with the engine running, he's got some serious charging system problems as well as ignition trouble. I'm betting a 62 GMC has a 12 volt electrical system.
Jerry Missed that crucial tidbit. I got the 2 "kids" mixed up (one of them has a '51 truck).
1952 5-window - return to "as built" condition | 1950 3100 with a 235 and a T-5 transmission
| | | | | Joined: Jan 2013 Posts: 2,232 Moderator: Interiors, Texas Bolters, Name that Part | | Moderator: Interiors, Texas Bolters, Name that Part Joined: Jan 2013 Posts: 2,232 | sorry for confusing you dad! | | |
|
|
