no electrical power

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F-64

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1987
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R10 lwb
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That area with 1.3v is an issue.
Is there a fuse along that wire?

A battery normally sits at 12.6v when fully charged.
I'll add more when I have a chance.. at work right now.

Which part of the fuse box was 1.3v?

That circuit where 1.3v was on. If you take your red probe and move it along that wire towards the battery, the point where your voltage goes back up to 12.6 (or close) is where your issue is. The issue is causing the large voltage drop.

Remember, the circuit must be on( key on) and connected.
Disconnected wires will give the wrong reading.
 
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luna negra

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Definitely not battery. Took a RV battery out my gate opener and same result - nothing. I'll start at the fuse panel next. All under dash wiring is a rat's nest from PO. A new Painless harness is looking nice but not for $550.
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ByrdDog

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I'd take a pass on painless wiring. I used one of their universal kits to re-wire my 60 F250 and you can tell they cheaped out on a lot of stuff. My brother-in-law did his 72 K5 with American Autowire & that kit is miles above painless. This is one area I would not go cheap on. Running down wiring issues is EXTREMELY frustrating! There are lots of wiring diagrams available here - Buy some primary wire of the correct colors off Amazon & starting troubleshooting & replacing as you go.
 

Jgonick

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quick look at 79 wire diagram

I would check the voltage at junction block. If it has voltage, then look at red-2E and fusible link. That one feeds ignition (which feeds purple starter wire) It also feeds a portion of the fuse box. If no voltage at junction block check red-2B (&fusible link) at starter it feeds junction block. Red-2J at starter, feeds lights and portion of fuse box. See if your lights work.

before I begun -I might disconnect red wires from alternator - just to take it out of the loop.


Also- from your picture- it looks like you might be missing a fusible link at the starter on a pair of those wires.
 

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F-64

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You can check your grounds by turning your key on.
Meter DC V.
black probe on negative post.
red probe on engine block.
Reading should be as close to 0.0v as possible. Any higher than 0.5V then you have a marginal ground. The higher the voltage the worse it is.
This tests the quality of connection from the negative battery post to the engine block.

Move the red probe to a clean part of the frame( free of paint and rust).
Reading should be 0.0V.
Quality of connection from negative post to frame.

Move red probe to clean part of firewall.
Should be 0.0V as well.


Move the red probe to the negative battery clamp.
This will test the connection between the negative clamp and negative post. This will test for corrosion or loose connection at the negative clamp.
Should be 0.0V as well.

You can do the same on the positive side as well.
black probe on positive post
red probe on positive battery clamp.
Should be 0.0v.

Turn key off.
 
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luna negra

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Ok, I feel like an idiot now. New motor has an aluminum intake and the neg battery was grounded to the steel alternator bracket connected to that. I never checked ground with the key on but I got 11 V neg battery to engine when I did. Moved ground to the frame and it turned right over.

Last question - does it matter whether it's frame or engine grounded? Thanks for all the help on this. As you can tell, I need it.
 

squaredeal91

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Best to go from battery to engine with the big cable I believe. Then from engine to cab and from battery negative terminal to fender. Can't have too many grounds.
 

RustyPile

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The starter can surge upwards of 200 amps when it first engages.. In the 2 - 3 seconds before the engine actually "catches" the draw can be 150 - 180 amps.. The smaller ground straps grounding the engine to the body and frame cannot carry that much load.. The negative cable needs to be attached directly to the engine block and the best place is one of the bolts on the lower corner on the passenger side, very near the fuel pump.. Scrub the area around the hole down to bright metal with sandpaper. Apply a very small amount of grease to prevent rust. Don't use one of the exhaust manifold bolts as an attachment point. Rust and corrosion soon form and your problem returns.
 

F-64

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I ran 3 ground cables from the battery. All 3 awg. One to the intake manifold near the thermostat. One to the frame near the battery and one to the long alternator bolt. I need to run another to the firewall.

I also ran a 3 awg positive cable to the starter.

I was tired of a slow starter and marginal alternator charging at idle.
 

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Ncali

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I have had this problem, Check the red wire coming off the battery for battery voltage at the starter. then look at the wires with the fuse-able links. it is common for them to come in contact with the hot exhaust and melt. also the stud on the solenoid has been lose on mine and there has been corrosion on the wire and lug on the red cable
 

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