73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Electrical => Topic started by: lax4life93 on November 01, 2014, 10:35:04 pm
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Hey guys, first post so go easy on me.
I have a '79 c10 that I received in reasonable running order I.e. I didn't have this problem before.
Then I tore out the stock 350 engine and trans, rebuilt, put it back in and went with an MSD box.
The emissions were torn off and most of the electrical simplified as much as possible.
Problem: no matter what the key position is there is always power.
Key is off and brake like is lit.
When I start the truck it runs and fires, when I turn the key off to shut it down, the truck keeps running.
The only way to shut it down is to disconnect the battery.
Does anyone have any ideas where to start? I'm assuming something from the factory harness wasn't reconnected ? Because nothing was changed with the column.
Appreciate the help.
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Welcome to the Forum.
No worries! We're easy on everybody! 8)
Battery is directly powering the ignition circuit, bypassing the ignition switch. Perform/answer the following...
- Which MSD box are you using? Does the ignition circuit power up correctly using the ignition switch if you disconnect the B+ feed to the MSD box?
- When you posted, "...most of the electrical [was] simplified as much as possible," what exactly did you change?
- When you posted the brake light is lit up with the ignition off, I assume you are referring to the warning light in the dash. Is everything that's normally controlled by the ignition switch "on" all the time? Does the ignition switch seem to exercise any control over what's on or off?
- Once you disconnect then reconnect the battery, does the ignition remain "off" until you cycle the key? Or, does ignition come on as soon as you reconnect the battery cable?
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bd, Thanks for the reply.
This has been an on again off again project, so I will answer what I can, and check anything I cant answer in a day or two when I can work on it again.
1) I will double check my MSD part number (i believe it is a 6A or 6AL maybe?), and will try disconnecting the B+. Off hand, which color/input is this on the box?
2) The only wiring I believe we left was, battery to starter, engine to ground, alternator to negative, power to MSD, ignition to dist/msd, and electronic choke to carb. I will double check this aswell.
3) There seems to be no control over anything from the ignition other than the starter. Everything is on from the second the battery is connected
4) once the battery is connected everything is on, the only thing that doesn't happen is the truck doesn't start. Dash lights, warning lights are all hot though.
Thanks again for the response bd, appreciate the help.
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The B+ to the MSD box is the 10-gauge red wire running direct from the battery positive post.
I'm sorry to report, if "the only wiring [you] left was, battery to starter, engine to ground, alternator to negative, power to MSD, ignition to dist/msd, and electronic choke to carb," you're in a world of hurt! - lol Where did you source power into the cab - off the starter, as originally designed or ___________? Did you retain or install the appropriate fusible links? The alternator requires ground (typically achieved through the alternator mounting to the engine), battery positive (via the 12-gauge or larger charge lead) and regulator connections (unless the alternator is set up for single-wire service). Did you remove the various ground wires in and around the engine compartment (cab-to-engine, battery-to-frame, battery-to-radiator support)? Such connections are fundamental and necessary to proper function.
"Once the battery is connected everything is on, the only thing that doesn't happen is the truck doesn't start. Dash lights, warning lights are all hot though." So, the only function presently controlled by the ignition switch is the starter. When you posted, "Dash lights, warning lights are all hot," by 'dash lights,' do you mean the instrument cluster backlighting or just all the warning lights? Did you rewire under the dash?
Begin with the B+ feed to the MSD ignition box, and we'll proceed from there as necessary.
Tip: When you alter wiring, it's useful to pencil your changes on a wiring diagram for future reference. It's virtually impossible to accurately remember wiring details indefinitely.
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I will document all connections over the next day or so, but thanks for the initial "heads up list"
Unfortunately I am just picking up other people's pieces on this project, trying to fix their haste. When they pulled the engine, they cut out a good portion of the factory harness, so I am trying to track down what is missing.
The majority of the fusible links that are around the engine and bay are still intact, other than the cab to engine that I know of, But I will find out.
Cluster lighting function is unknown, I will check.
No rewiring was done under the dash.... only things cut out from the engine bay harness, nothing added only deleted or not hooked up lol.
Thanks again bd, you are definitely pointing me in the right direction. I also found the wiring diagrams posted on the forum and will utilize that to see what is going on.
Cheers
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FYI - Wiring diagrams are located in the Technical Pages in two discrete folders.
Year-specific factory wiring diagrams and manuals (preferred) are here (http://forum.73-87chevytrucks.com/smforum/index.php?topic=25639.0).
Generalized wiring diagrams are here (http://forum.73-87chevytrucks.com/smforum/index.php?topic=11766.0).