no electrical power

[luna negra]

Finally buttoned up an engine and tranny swap in my '79 K5. Went to start it and it turned over fine, then quit working after about 30 seconds of total crank time. Now, I have no power anywhere - starter, lights, accessories. Thought it might be battery or cables but it has 12.7 Volts and good continuity & low resistance in both cables. Thoughts on where to look next? Didn't make any noise or smoke when it happened and I wouldn't think bad fusible links at the starter would kill the lights/accessories but maybe I'm wrong. Appreciate any insight on this, thanks.

 

[luna negra]

Should have added that I already tried a good known replacement starter that I had around.

 

[F-64]

Check the smaller wire coming off of the starter that mounts to to the big battery cable stud on the starter. That wire has a fusible link that may have blown. I have an 87 so yours may be slightly different.

That smaller wire powers most of your truck.

 

[DoubleDingo]

I was thinking fusible link as well

 

[Rickf]

First disconnect the battery, then with a multi-meter probe each side of the fusible link to check for continuity. There will be hotness to the starter with the battery connected.

 

[RustyPile]

Finally buttoned up an engine and tranny swap in my '79 K5. Went to start it and it turned over fine, then quit working after about 30 seconds of total crank time. Now, I have no power anywhere - starter, lights, accessories. Thought it might be battery or cables but it has 12.7 Volts and good continuity & low resistance in both cables. Thoughts on where to look next? Didn't make any noise or smoke when it happened and I wouldn't think bad fusible links at the starter would kill the lights/accessories but maybe I'm wrong. Appreciate any insight on this, thanks.

Fusible links on an automobile are like the main breakers in the breaker box of your house. When they blow, all power is lost.

 

[luna negra]

Ok, thanks for the replies. I'll check the fusible links this weekend.

 

[luna negra]

Ok stumped again. I pulled the wiring harness from the starter, distr, and junction block. Tested all wires for continuity and resistance from terminal connectors back to firewall block. All were good. In the second photo, the 3 wires on the bottom were on the big solenoid stud with the positive cable. The one on top was on the small post closest to block. The battery will also jump off the old starter with jumper cables so don't think it's the battery. Thoughts?

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[luna negra]

Update - just hooked everything back up and still no power. Have 12 V at big starter lug but will not start even when shorting across the solenoid. Also, ignore the OL on the meter above - it wasn't hooked up at the time.

 

[Terry Wilkerson]

You could check for voltage on the fuel block inside the truck. See if you have voltage on the fuses by finding a good ground near the fuse block for the black lead of your meter and use the red to probe several different fuses. If you don't have any voltage there with everything hooked up you got a bad fuelseable link somewhere. Try it with key off and on in run position.

 

[WP29P4A]

First thing I would do is take a set of jumper cables and connect one side of the negative (black) to the negative battery post, then connect the other end of the negative cable (black) to a good bolt on the engine. Check for voltage, try the starter again. If you still get nothing, change all the connectors and fusible links your holding in your hand in the picture.

One of the most common mistakes that lead to electrical issues is forgetting to put ALL the grounds back in place after doing an engine swap, and tightening the grounds properly.

 

[F-64]

Continuity check is not a good indication of electrical connection.

You'll have to do a voltage drop test. Pretty easy.. connect the wires back to their locations.

The circuits being tested must be connected
Key on, Engine not running.
Meter on DC V
black probe on battery negative post(metal part of battery)
red probe on positive battery post
note voltage.

Move your red probe to the junction block at the top of the firewall.
Note voltage
a differance of 0.5v between the junction block and the battery is an issue.

You can move your red probe to each of the wires containing fusible links to test them, but the wires must be connected to where they belong.

Turn off key

If you measure continutity, you could have a 500 strand cable holding on by one tiny strand. Your meter will indicate continuity. This same joint will not pass full voltage. It may only read 1v instead of 12v under load. Hence the voltage drop test instead of continuity.

 

[luna negra]

Tried the 3 suggestions above:

1. 12.0 V at fuse box with key off. Max of 1.3 V on the hot side of the fuse box with the key on.

2. Nothing happened when connecting neg post to engine ground.

3. 12.65 V at battery. 12.65 V neg battery to firewall junction block. 12.65 V neg battery to fusible link at large solenoid connector. 11.63 V neg battery to fusible link at small solenoid connector, battery still 12.65 across terminals.

Also, left battery on a trickle charger overnight and voltage was 12.9 when I unhooked. It did make one click noise at the solenoid when I tried the key, then dead. In 10 minutes, voltage dropped to 12.65 doing nothing. Sounds like a battery issue but still don't understand why no accessories will come on but 1.3 V at fuse box might explain that. Any thoughts before I go buy a battery? Thanks for the help.

 

[Scott91370]

Doubtful at this time the battery is your culprit.. You'll need to trace the wire that feeds the fuse box. It should be the same voltage as the battery.

 

[RustyPile]

"One click at the solenoid, then dead"???? I'm with Scott in that you don't have a bad battery issue. This is the first symptom of dirty/corroded battery posts and cable terminals.. Clean 'em and start taking voltage checks all over the main power feed wire and fuse box terminals...