1967 c10 no power

[dtkarst]

I’ve got a 67 c10 that’s got me stumped. It’s a 6 cylinder, 4 speed. Motor is a 75-78 250 inline. It was running and driving, everything working and the fuel pump started leaking one day. So I got a new fuel pump, changed it, didn’t mess with anything else and now it’s completely dead everywhere. No headlights, nothing. Of course it happens on the day I was gonna put it up for sale. I have 12 volts through the firewall connector and to the ignition. Changed the ignition out and still nothing. I can put a screwdriver between the posts on the starter and it turns over great but no fire. Can anyone lend a helping hand on this one, please. Thanks

[RustyPile]

Several things come to mind.. Very first thing to do is go to the ELECTRICAL forum and download the proper wiring diagram for your truck. Remove both battery cables at the battery.. Clean both cable terminals along with the battery posts.. Check to be sure there are no blown fuses also check the fuse links. There are two paths for the main power distribution wire(s). One goes to the fuse box and headlight switch for "always hot" sections. The other goes to the ignition switch. It's easy to spot this wire -- it's big and red. You say you have voltage at the ignition switch?? Have you checked for voltage on the purple wire at the switch with the switch in the START position.. Also, if the safety switches are working properly, you should have voltage on that purple wire at the starter solenoid with the ignition switch in the START position.

With the loss of power on so many "non-connected" circuits, I'm betting on either blown fuse links or corroded battery posts.

[Palf70Step]

Thing that comes to my mind is the battery ground. The one on my 81 6 banger came loose and the bolt grounding it too the block came off. The ground attaches right near the fuel pump on mine.

[dtkarst]

It’s a new battery with new battery cables, cleaned the ground on the block three times now. I’ve looked through diagrams and replaced the links with nothing changing. There’s got to be something simple I’m overlooking I’m just not sure what. Showing volts everywhere I need to when I turn the ignition to start it. I didn’t change a single thing when changing that pump and after it’s just dead in the water

[RustyPile]

I'm trying to not sound accusatory, but you HAVE missed something. I know you've been over some of this stuff, but let's do it again in an orderly manner. Don't assume anything, check each component.

Let's start with the basics.. Just because the battery cables are new doesn't mean you have good contact.. Both contact surfaces, the cable and the battery have to be clean. The same goes for the other end of the cables. Moving forward, using a voltmeter, do you have voltage on the big red wire at the ignition switch? If not, checking this circuit is a bit complex because it's at the end of the main power distribution circuit. Plus it's buried in the harness in the engine bay AND the cab. Could be a broken wire, loose connection at the firewall connector, voltage regulator, or junction connector near the battery, or any locations along the branches of this wire. Check to be sure the terminals at the ignition switch haven't overheated and caused bad connections. If all this checks out, move on to the next section. Turn on the ignition switch and check for voltage at the positive (+) terminal of the coil.. Probably won't be a full 12 volts because of the resistor wire. If voltage isn't present, work backwards and find the open circuit. Could be a bad resistor wire, bad terminal connection, or a bad ignition switch. If an HEI has been retrofitted, check for 12 volts at the "BATT" terminal on the side of the distributor cap. If all this checks out, move down to the starter solenoid. Hold the ignition switch in the "START" position and check for 12 volts on the purple wire connected to the solenoid. If you have voltage here, you have a bad solenoid. If you don't have voltage, again move backwards up the wire and find the open.. The purple wire passes through the firewall connection, to the neutral safety switch, or clutch safety switch if equipped with standard transmission.. Check either of these switches for proper adjustment. An automatic transmission has a NSW that will pass voltage only with the transmission in either park or neutral. I'm not sure when it was installed, but a manual transmission will have a clutch safety switch that passes voltage only when the clutch pedal is depressed. Follow the purple wire to locate either of these switches located under the dash.

Again, work slowly, accurately, and don't assume anything.. Especially don't assume the fuel pump had anything to do with this.. Work the job as if the fuel pump replacement never happened.

[Mid-Pack]

Nicely explained, RustyPile!

[67chevemall]

Wire from dizzy to fuse block or fuse...

[RustyPile]

Originally Posted by 67chevemall

Wire from dizzy to fuse block or fuse...

The OP is confused enough by his balky truck. Let's not confuse him more with searching for something that doesn't exist. The circuit leading to the distributor doesn't go through the fuse block. The pink wire from the ignition switch goes directly to the firewall connector where it transitions to the cloth covered resistor wire. Then straight to the starter solenoid. On the same terminal, it joins a yellow wire that goes to the POS (+) terminal of the coil. Unless one has been added, neither the pink wire nor the resistor wire in series with it is protected by a fuse..