So yesterday the car ran fine, and we changed out some fluids and replaced the distributor cap, spark plugs (and wires), and rotor. Now it won't start, and doesn't even try. It makes no noise at all, and battery is new fully charged. I was told that it could be a fuse or the ignition switch. What do you think?

 

(1) Check fuse panel for blown fuse;
(2) Check wires for solid connections and routed correctly e.g. make certain you matched the spark plug wires to the correct firing order of the engine.

Can you hear the starter solenoid "click" when turning the IGN SW trying to start the vehicle? If not, suspect wire from horn relay distribution block to stater solenoid came loose.
The easiest way to troubleshoot this is with a circuit light tester. Begin by checking you have 12VDC from BATT to starter.

(3) Check & re-check your ground wire connections. >90% of electrical issues reside on the negative (ground) side of the electrical.

 

1) Is the shifter in PARK or NEUTRAL? Neutral start/backup lamps switch will prevent engine starting in any other position.

2) Take the battery cable terminals loose and clean them. Either wire brush or scrape with a pocket knife. Battery cleaning brushes are cheap at Harbor Freight.

3) Make sure the 10 gauge wire from the battery (+) terminal to the horn relay is in place and tightly connected.

4) Try putting the old parts back in. New condensers especially seem to be prone to failure or being bad right out of the box. Did you mess with points?

5) Normally I don't post these because I think people should have their own factory shop manual, but here's part of the 1965 Cutlass/F85 V8 wiring diagram showing battery, horn relay, ignition and NSS wiring.

 

After checking what previous posters mentioned above and thoroughly examining all of your work for a loose connection or wire, then check for voltage at the two purple wires on the neutral safety switch at the bottom of the steering column assuming this is a column shift automatic transmission car. Is it?

​Do the headlights work? What do they do whilst attempting to crank the car?

One purple wire from the ignition switch should get full battery voltage when the key is in the crank position and if the switch is good so should the other purple wire IF the car is in neutral or park.

 

What does "won't start" mean? Does the starter turn or not? If not, then pull out the test light or voltmeter and start tracing the purple wire START circuit until you find where the power stops. This isn't something that can be diagnosed over the interwebs. It takes you testing for power at each connection in that circuit.

 

The key turns but the car is absolutely silent, no clicks or anything, when I get back to it this weekend, I will definitely try all of these suggestions. Oh, and in terms of the headlights coming on or not, they haven't yet been replaced, so they didn't work before. Unless I change them out, I cannot use them as a guide to figuring this out (as one user suggested). Thank you!

 

So it ran before but none of the headlamps worked? Then it wouldn't do anything after the part replacement? I'd go to the battery connections first at both ends of each cable. You're very likely going to need a 12VDC test light or multimeter to figure this out but I'm guessing you are already well aware of that!

 

You need a test light as noted above. The starting problem and headlight problem are unrelated. I would start by testing for power at the threaded stud on the horn relay.

 

are you sure it's in Park ?? "neutral" safety switch ?

 

Post #3

 

She starts again! Turns out it was a bad connection in a wire somewhere, and the starter. We spliced the wire back together (bypassing a funky little box) and replaced the starter (because power was going in but not coming out), and now she starts first try!

 

Maybe you should post a photo of the "funky little box" to ensure you haven't bypassed something important.

 

Is this the "funky little box"? I've created an image of the engine bay you previously provided in another thread. I've created an image from the wiring diagram previously provided by Glenn (rocketraider), as well. Employing a modest amount of deductive reasoning I "suspect" that box is the horn relay/junction box? As Joe stated, a photo of that box would be helpful since it may be some other "funky little box".

 

The funky box is the horn relay.
you should have 4 wires attached to the post on it. there should be a two wire plug on it for the horns.
if you removed the 4 wires from the post then the horn will not work.
here is a picture that shows what each wire is.
in the picture my horn relay is not the same as yours. I had to have it replaced back in 1983.