280 SE 4.5 Will Not Start

Need help from you experts! My 72 280SE 4.5 will not start, not only that but there is NO power to any of the systems (lights, horn, etc.). Is there a master relay or something else that could prevent power through the system? The battery is good, and it will not get power even with a jump. HELP!

[Tomguy]

Check and make sure your ground wire is making proper contact with your frame!

Where exactly might that be on this car?

[cth350]

Ground, as in negative battery terminal.
The +12v battery cable goes to the starter. From there two very hefty 10gauge red wires go to a 3-lug block on the passenger side of the engine compartment (follow the battery cable). There is a connection for the alternator at this point, and wiring goes to the fusebox and ignition.

First, find that 3-lug junction and see if there is 12v from there to the intake manifold. If it's 9v, you have one kind of problem. If it's 0v, you have another.

Second, check both sides of the #1 & #2 fuses using a volt meter to ground. One reads 12v all the time, the other only reads 12v when you turn the key. First measure stuff without turning the key. Then, turn the key one click clockwise and try again.

-CTH

Thanks, I saw the 3 lug terminal today when I R&R'd the battery. I thought perhaps the other post referred to a seperate engine to chassis ground. I will dig out the test equipment tomorrow. If I have 0 volts at the point where you indicated one sort of problem, what might that be? I have to take baby steps here, wiring is not my cup o'tea.

Guys,

Does this model employ fusible links?

[cth350]

No fusable link in the stock setup. If there is a little whip line coming off the +12 battery cable in addition to the heavy lead to the starter, that's a fusable link.

As for where to go, remember that voltage flows (well, sort of) down hill. Where the hill starts at your +12 battery post AND ALSO the Alternator's post and then goes down hill to ground.

That is a gross over simplification in some respects, But armed with a multimeter, you should see the voltage drop get smaller and small from ground to the point of measurement as you get further away (Circuit component-wise) from the 12v source.

When in doubt, leave it to somebody with prior experience. Preferrably, somebody who can spend some time with you explaining it. -CTH