Fusible Links Smoking

[mayolives]

19 hours ago, SteveJ said:

Has the TIU been disconnected? It doesn't work with your (@mayolives) setup anymore. 

TIU  ? What is that?

[Zed Head]

Ignition module.  By the fuse box.

[mayolives]

On 11/6/2021 at 3:19 PM, SteveJ said:

Has the TIU been disconnected? It doesn't work with your (@mayolives) setup anymore.

SteveJ...........Per your advice, sounds like I should disconnect my ignition module and test from there.  I'm supprised that Fast's instructions didn't give me a heads up about this.  They only mentioned bypassing all ballast resistance.  Is disconnecting the TIU just as simple as unplugging it?    

[Zed Head]

2 hours ago, mayolives said:

 Is disconnecting the TIU just as simple as unplugging it?    

It is.  It's a on a branched circuit, and 1978 has a nice protected plug.  Just unplug it and let it hang.

OR, disconnect the FAST module and reconnect the original one.  Not really clear why the FAST module was purchased and installed.  Might be a clue there.  The 1978 ignition module is pretty good.

[SteveJ]

28 minutes ago, Zed Head said:

It is.  It's a on a branched circuit, and 1978 has a nice protected plug.  Just unplug it and let it hang.

OR, disconnect the FAST module and reconnect the original one.  Not really clear why the FAST module was purchased and installed.  Might be a clue there.  The 1978 ignition module is pretty good.

And even when it's bad, it can be replaced by a GM HEI module pretty easily.

[mayolives]

On 11/6/2021 at 3:19 PM, SteveJ said:

Has the TIU been disconnected? It doesn't work with your (@mayolives) setup anymore. 

Following SteveJ's and Zed Head's advice.

On 11/6/2021 at 3:19 PM, SteveJ said:

The black/white wire that is hot when the key is in Start or On is on the coil positive. Why is the green wire on coil negative? It would either go to the distributor or to the TIU. Neither one is in service, so it could be pulled off the coil negative.

I disconnected the ignition module in the passenger foot well and removed the green and black w/ white stripe ones at my coil.  Also, I took a closed look at the Fast ignition module instructions and discovered that the original ignition module needed to be disconnected.  I sure missed that when I installed the system.  Also I discovered that when I was testing my fusible link connections, my headlight switch was turned to the on position for the parking light setting and the wiper switch is now stuck in place and is set on the first on position.  I'll need to address the wiper switch (combination switch) situation after I get this thing running.   

 

On 11/5/2021 at 4:08 PM, Zed Head said:

Those are the distributor "trigger" wires to the ignition module.  They only have voltage when the distributor is spinning.  Edit - actually those must be the wires up to the ignition module in the cabin.  So they're dead, no voltage.

This was Zed Head's response to me asking what the "small box with six sides" was that is mounted near the coil.  Should I disconnect the wiring for this trigger now that I have the Fast system installed?  I haven't tried to get the car running yet but I believe I'm getting close to this point.  

[Zed Head]

That box is the junction point for the wires from the distributor to the wires from the ignition module.  With the factory setup there would have been a green and red wire from the distributor connected there too.  On a reman distributor the wires are blue.

Since your ignition module is connected to your distributor in the engine bay, and the ignition module inthe cabin is disconnected, the wires at the 6 sided box aren't connected to anything.  They can just sit there.

Here's the 78 wiring diagram that somebody colorized.  They don't show the full shape of the terminal block.

[mayolives]

On 11/10/2021 at 5:25 PM, mayolives said:

I haven't tried to get the car running yet but I believe I'm getting close to this point.  

I did try to start the car today but had a fuse problem.  I'm using some in-line fuses to replace the original fusible links and as soon as I moved the ignition switch to the on position (not the start position) the front inside fusible link position blew the 30 amp fuse that was installed.  I tried again with a 40 amp fuse with the same result.  I know that position on the fusible link block controls the ignition switch.  Should I try a higher rated fuse?  Was the 40 amp one strong enough to support the ignition system?  I'm reluctant to go much higher and then do damage.  This car has be setting for a couple of years.  The ignition switch doesn't move very smoothly so I suspect it my be causing this problem.  I do have a new ignition switch on my shelf but I don't like tossing parts at a problem before I have an understanding of the cause.  Any thoughts?  

Edited November 18, 2021 by mayolives

[SteveJ]

Cut down some of the wiring you're trying to trace.

Pull the ignition relay. It's around the passenger kick panel

Put in another 30A fuse. Turn the key to ON. See if you smoke the fuse again. If not, get with me on tracing down the short downstream of the relay.

[Zed Head]

Don't go bigger on the fuses.  There's nothing on the Z's that will pull 40 amps through one circuit, I think.

You must have a short circuit after the ignition switch.  Could be the ignition/accessory relay or something after it like the ignition system (coil, etc.).

If your car was or is an automatic there are two inhibitor devices that could be shorting.  The simplest starting point is at the plug to the ignition switch.  Unplug it and check the black with white stripe for continuity to ground and the same for the black with yellow stripe.  That will split the system in to two parts.  You have a dead short after the switch.

SteveJ just posted.  Better see what he said...looks rational (of course).  So, there's two separate things that you can do to narrow things down.

[Zed Head]

Here's a picture of my old ignition relay, from a 76.

[Zed Head]

The Engine Electrical chapter shows all of the pins that you can check at the plug for a short to ground.  If it was me I'd just unplug that plug, set my meter to beep for continuity and poke, poke, poke.  The beep will be the problem circuit. 

Edit - actually, the beep would not be the best signal.  You'll get a beep through the relay solenoid.  Best to read resistance.  The one close to zero is the problem.  Then find that pin in the wiring diagram and follow it out. 

Here's another circuit, after the relay.  If you find that the ignition relay itself is good then check each pin after the ignition relay.  The relay will pass plenty of current to blow those fuses.

Edited November 19, 2021 by Zed Head