Dolore Nel Culo! Ignition switch!

[wetminkey]

What a PITA!
My '79 2000 (carbureted, auto tranny) has always started on the first turn of the crankshaft, until about a week ago when it sputtered a bit, then stumbled with the second try, then refused to spark at all. You could turn that engine all day, and it would not fire, period.
A check for voltage at the coil + showed no more that about 2V! A lot of troubleshooting ensued, and I found that I could get the car running, with everything working once it was, by jumping 12V from the battery + to the coil +. Once the car got started, it would run just fine even without the jumper attached, and would even start a time, or two, after the car was shut off, but then when the key was turned, the charging and oil pressure lights in the speedometer glowed quite dim, and the car would turn, but not spark.
More troubleshooting and I found that the car starts and runs perfectly with number 1 (A) fuse pulled, but when in place the loads on the other side of #1 draw down the coil + voltage to that same 2V level. In addition, the car will continue to run when #1 is re-inserted while running, but does not have enough coil + voltage to restart if turned off. I figured this out yesterday and have gotten no further.
I have a list of the loads on #1 in my shop manual, and I suspect I'll be checking for grounds on each one, but I thought I'd see if any of the other members had any suggestions that might help shorten this process,...
All of the loads on #1 seem to be working when the fuse is in place (whether the the car is running or not), although I have a driver's backup light and front fender running light out at the moment (possible suspects to start with, for sure), and the seatbelt warning buzzer has been disabled in some manner since I got the car (another suspect). And with #1 pulled, I get a nicely glowing charge indicator before turning over the engine, and it nicely goes out (indicating a charging system) once the engines begins to run. The battery is nearly new, and has a full charge.
Any ideas of how to look for shorts in the load circuits individually, or just general advice?
Thanks, Todd.

[AriK]

I would love to go the easy way and lay blame on the internals of the ignition switch. Check terminal C31 (the white 6 prong plug that connects the the switch to the dash harness) and inspect for discoloration from overheating on the pink wire. That would be your proof but i'd swap in another ignition switch regardless.

[wetminkey]

Thanks, Arik, but C31 is no more. The PO replaced it by hardwiring the thing with crimp connectors. And the ignition switch works just fine. The only time the car has low voltage to the coil + is when #1 fuse is in place. Any other ideas?
Todd.

[spider2081]

I know there are some differences in wire diagrams. The diagram I have shows the back up lights are on fuse 1. So I would check there first.
The coil and charge indicator are on the "Hot in start and run" position of the ignition switch but are not fused. The "hot in start and run" position of the ignition switch also feed fuse 1.
I believe Fuse 1 has two output terminals on it one has a blue/white wire the other has a white wire. If you can get your head up under the panel and pull them off one at a time it will help you isolate the problem.
It would be good if you could make voltage measurements at the ignition switch itself. Terminal 30/1 is a black wire that feeds the switch. Terminal 15/54 is a pink wire that is "hot in start and run" position of the ignition switch.
If the voltage drop is on the black wire then your problem is before the switch. If the black wire is good 12Volts with the switch in the "Run" position but the pink wire has 2 volts then the ignition switch is bad.

[wetminkey]

Thanks spider2081! I appreciate any input I can get.
The one constant I find is that if #1 fuse is in place, I get about 2V on the pink wire that feeds the coil + and no spark. If that same fuse is removed, I get 12V on the pink wire, at the coil +, and the car will start on the first turn of the crankshaft, every time.
If #1 fuse is in place, I get no charge light or oil pressure light when the key is in the "on" position (prior to turning the key to the start position) and I assume that's due to the large drop in voltage due to the #1 fuse loads that are energized when the key is turned to the "on" position. If that fuse is removed I get a bright charge light (and no oil pressure light, since it is #1 fused) and the car will start easily.
I WILL be checking that non-functional backup light, and the front running light before proceeding,...either could be malfunctioning due to a major short when the key is in the "on" position. I will also suspect the disabled seatbelt warning system.
I did have the interior out, and then I re-installed it, just prior to this incident, but the car ran just fine after I got the console back in (and I tuned it at that time), so I feel this is just a coincidence,...however, I'll keep that at the back of my mind as I troubleshoot.
One detail that stumps me is that the car starts and runs just fine with #1 fuse removed, and will continue to run and function perfectly if #1 fuse is re-inserted while already running,...which makes me think relay or capacitor in the system,...
Thanks again, Todd.

[azruss]

The ignition switch is still my #1 suspect. By pulling the fuse, you are just lightening the load on the switch.You can test this by by passing the ignition switch. Use a beefy jumper from the battery or top starter lug to the upstream side of the fuse panel. You may also want to load test the battery. If you have a massive load on the fuse, it should be blowing the fuse. This is why i think it is a power issue, not a drain issue.

[spider2081]

I agree:
If there is a short or too high a current draw in a circuit protected by Fuse 1 the fuse should blow. Do you have the proper value fuse in the fuse 1 position. My diagram shows an 8 amp fuse.
The fact once the car starts with the fuse removed the fuse can be replaced and the car continues to run sounds like the ignition switch is at least part of your problem.


Wires for removed seat belt warning circuits should have ends insulated and secured so they can not be a future problem.

[wetminkey]

That all makes good sense. And would explain how all this started while turning the key, without previous symptoms.
Is it true that brown feeds the switch through terminal 30, and supplies voltage to terminal 30/1 black, and 15/54 pink, when the key is in the "on/run" position? And supplies voltage to terminal 50 red, when in the "start" position? Does it sound like I've got that right?
That would make spider2081's recommendation of:
"If the voltage drop is on the black wire then your problem is before the switch. If the black wire is good 12Volts with the switch in the "Run" position but the pink wire has 2 volts then the ignition switch is bad."
:make perfect sense.
I'll have a bit of difficulty checking voltages, since the connector plug from the ignition switch to the dash harness has been replaced with insulated crimp connectors, but perhaps it's time to replace those hardwire connections with electrical crimp male to female plug-ins,...
Thanks to the three of you for all your help! I think I've been "not seeing the forest because of the trees"!
I'll report back later.
Hope you both have a great holiday weekend. Todd.

[wetminkey]

Geeze! I never even got to checking voltages,...I just tried that ignition switch a great number of times, and, fuse in or out, that damn thing worked, and then it didn't, and then it did!
I know the Spider's ignition switch is notorious for failure with age, and I'm convinced (I also see a new post on here about a fellow who had to hold his in the "start" position just to keep his car running!).
I guess I'm in the market for a new ignition switch.
I'll be supporting the aftermarket Fiat parts suppliers again for this one item. Any suggestions who I should get it from,...now that there is a market FULL of competition (unlike when I worked on this vehicle 14 years ago and there was ONE Fiat parts supplier (Bayless) and another that no one wanted to do business with,...)? And I'll start replacing the hardwire crimp connectors for M to F plug-in connectors.
Thanks to spider2081, azruss, and Arik, for helping me "see the forest" once again! Sometimes it's too easy to complicate simple things!!
Thanks, all!
Todd.

[spider2081]

A lot of people keep the weak ignition switch and let it activate a 40 amp contact rated Bosch type relay that connects the black wire to the pink wire.

[wetminkey]

I see that I can get the relay and pigtail for about $10 online, rather than replace the Fiat's switch for $120!
But what does what I call "big brown" do at terminal 30 of the ignition switch? Does it only supply terminal 50 red, to activate the starter solenoid when the key is in the "start" position? And does L blue/black get it's voltage when the key is in the "run" position from 30/1 black at the same time as 15/54 pink?
I NEED to understand this part of the ignition circuit, and the diagrams do not illustrate how the switch makes contacts when it's position is moved. I sure appreciate your help with all of this!
Thanks, Todd.

[perthling]

Rebuilding the switch is not hard, you just need to get some small bolts to hold it together after drilling out the long rivets. Clean up the contacts with an emery board or sandpaper and reassemble.

[AriK]

While trying to service the old ignition switch doesn't sound like a bad idea, one of my switches had a fracture in the plastic casing that surrounded the terminals. I don't know if it was a fluke or if heat created that, but in my case the switch had to be changed. I then got a new aftermarket one from Germany that lasted only one year. I won't buy another aftermarket unless someone like Csaba or Mark chimes in and convinces me that my case is isolated and those units are in fact reliable. My current switch is a used genuine Sipea brand from ebay.

[wetminkey]

Dug around a bit and found this, posted by aj81spider:

"My 81 had an ignition switch wired (and named) as follows:

Pin 30/1 - Black wire (power into switch)
Pin 30 - Brown wire (power into switch)
Pin 15/54 - Pink wire (power out on start and run - powered by black wire on 30/1)
Pin 50 - Red wire (power out on start only - powered by brown wire on 30)
Pin "Int" - Light Blue/Black wire (power out on start and run - powered by brown wire on 30)"

So it sounds like 30 brown, supplies power to 50 red and 'INT' when the key is in the "start" position and to 'INT' when the key is in the "run" position. 30/1 black supplies power to 15/54 pink in both the "start" and "run" positions of the key. This is what I wanted to understand,...the wiring diagrams provide the rest of the power flow information.
Hail to the members of this forum and the information they provide to us all!!
Thanks to all of you!
Todd.

[TStark]

How I reed the diagrams, and according to the schematic of the ignition switch tumbler, the brown wire feeds the lighting circuit separately from the rest of the car. Ignition and accessories feed from the black wire.