Idle Stop Solenoid revisited

[CharlieB]

Bryan when it cuts off the rpms just quickly fall to zero. If I'm quick about it and hit the gas pedal I can bring the rpms back up enough to keep it running but on hills that's not possible. On the rare occasions when the car does not cut off, the rpms drop and then sort of "rebound" up to a normal level.
So to answer your question, I guess its more like the key was turned off...I guess.
But if I'm able to keep the gas pedal pressed, it will not cut off. So it's hard to say.
How's that for a crappy answer?!
Maybe I'll take a video and put on youtube.
Thanks Bryan
Charlie

[18Fiatsandcounting]

Actually, that's a good answer, although it still sounds to me more like a fuel issue. If an electrical issue were at fault, the engine would die but not recover. The fact that you can "recover" the idle issue by giving it gas tells me that the idle circuit isn't working properly. My guess is that this is connected to your non-operating idle shutoff solenoid, and also the lack of an idle jet at the end of that component. Perhaps it's just idling way too rich, and it doesn't take much to stall the engine? Still doesn't answer the cutout during right turns, and I remain stumped on that.

-Bryan

[CharlieB]

Yeah, the whole thing is baffling to me. So maybe I should replace the solenoid?
If so, is there a simple way to wire it?

[kilrwail]

Let's go back to Charlie's suggestion of replacing the coil. A few years ago I ran into a problem on the race track with my Porsche. It was cutting out on high speed right corners. I checked all the obvious things to no avail. I spoke to a mechanic at the track who suspected it could be related to the oil inside the coil being sloshed around and interfering with the operation. Then I spoke to friend over the phone who is as expert a mechanic as I've ever met. He asked me whether the coil's case might be grounded in its mounting bracket, when it shouldn't be. Sure enough the paint on the case had become chipped and scraped and a ground could occur there. I applied electrical tape to the coil's case and isolated it, solving the problem. Now our Fiat coils ARE grounded to the mounting bracket, but I wonder if the oil inside the coil is leaking into the transformer mechanism and causing a weak spark. If the spark is weak the engine might stall and extra gas might restart it, or not. This might explain the problem on right hand turns. Coils are cheap - it might be worthwhile changing it, especially if it's the original.

[18Fiatsandcounting]

Yeah, the whole thing is baffling to me. So maybe I should replace the solenoid?
If so, is there a simple way to wire it?

Charlie, I think you said earlier that the idle stop solenoid still had a wire attached to it, but that this wire was not attached to anything. Is this wire grey with a red stripe? For 1976, I believe that is what color it should be. How long is this wire, and does it look like the end was cut? If you can move that wire around by hand and see how far it reaches, perhaps you can see where it might logically reach when originally connected, and if you're lucky, there will be the other end of the grey/red wire there. If you can find it, this stub should have 12 volts on it with the ignition on, and no voltage with the ignition turned off, and that would be the best place to get your 12 volts for your new idle stop solenoid.

If you can't find the other end of this grey/red wire, the easiest place to find 12 volts when the ignition is on, would be the coil itself. There should be two small nut connections to the coil, one labeled B+ and one either blank or "-" (minus). The B+ connection would also be a source of 12 volts with the ignition on.

Also, I think you mentioned that you did not have a tachimetric switch. I have to admit I had never heard of this, but I did some quick searching and I believe it was only on California cars. It controlled the 12 volts to the idle stop solenoid. But, if your car was not a California car when it was first sold, you wouldn't have a tachimetric switch.

As for Kilrwail's suggestion about the ignition coil, I've never seen a coil fail in this manner, but I haven't exactly been able to fix your problem, so might be worth a try.

-Bryan

[SteinOnkel]

I would be concerned about using the supply wire from the coil, as these are usually run through a bias resistor and only receive 9V with the engine running.

I'm still curious about the no idle jet thing. And somehow this thing is running and driving?

[kilrwail]

Clearly Charlie should buy an idle jet and install it. That would remove one variable whether the solenoid is working or not. BTW on my '78 there are two wires going to the solenoid - one is pink and the other is black with a red stripe. The wiring diagram shows grey with red stripe plus another (no colour) going to ground.

[18Fiatsandcounting]

I would be concerned about using the supply wire from the coil, as these are usually run through a bias resistor and only receive 9V with the engine running.

The B+ connection on the coil should go directly to the ignition switch and thus be at 12 volts. At least on my Fiats, the bias resistor is on the negative side of the coil, with one side of the resistor to the coil and the other side to the tachometer and also to the points. Perhaps other model years are different?

Actually, I am concerned about transient voltage spikes on the B+ line to the coil, but for testing purposes, it should be OK for a while, and maybe longer. Ideally, the original 12 volt line to the solenoid could be found and reconnected. And perhaps there are better locations for 12 volts with the ignition turned on.

I'm still curious about the no idle jet thing. And somehow this thing is running and driving?

My guess is that it idles because the idle jet at the end of the solenoid is no longer there and thus it's irrelevant whether the solenoid is working or not. Seems like it would run way too rich, and perhaps that is true and part of the issue.

-Bryan

[kilrwail]

Just imagine, without that idle jet fuel would be flowing through the opening where the jet belongs, which is well above 1.0 mm in diameter, compared to the jet which is either 0.3 or 0.4 mm. With no throttle being applied, the carb would be flooded or at least extremely rich. No wonder it stalls out.

[CharlieB]

Hey thanks for suggestions guys.
My coil looks pretty bad, so I'm going to replace it anyway.
Peter you mentioned that the coil is grounded to the bracket, mine is not. I'll have to dig in deeper but I think it's grounded to the overflow pumpkin bracket.
Here's a pic of the top of my coil.
https://imgur.com/YxFtAXO
Mine doesn't have B+ & B-, it has "1" and "16".
Bryan, I'll track down the fast idle solenoid wire tomorrow but I think it just runs through the firewall and is taped off.
Here's a photo of my solenoid pulled apart.
https://imgur.com/4HNHTrd
Isn't that the idle jet?
Is there a certain spec I need to know before I buy a new coil? I know our main vendors sell coils and I use those guys all the time, but I feel like a coil from a local parts store would be ok...or is that a bad assumption?
Thanks again guys,
Charlie

[kilrwail]

Charlie - Don't worry about the coil's grounding, since it's been operating until now. The grounding I was referring to is not related to the wiring - it's just a random ground between the case and the bracket. Any brand should be OK, except MSD. MSD is too strong and would damage your wiring, points and plugs. Just ask NAPA for whatever they have listed for your car - we're in their system. The brown wire is on the Negative post.

That is your idle jet, although it looks shorter than mine (from memory). Just make sure that the passage (from left to right) and the tiny openings around the circumference are clear. Use carb cleaner and compressed air to clean them. If necessary, I use the core wire of a third or fourth guitar string to poke through the central passage. The solenoid wire (or wires) goes into the wiring harness immediately below the solenoid, where there's a large branch in the harness. If you're careful you can unwrap the tape around the harness and find the cut ends.

[CharlieB]

Thanks Peter, I'll take care of the coil this weekend hopefully.
Now I do remember about a year ago I checked the idle stop solenoid and the holes on the jet were clogged up. I cleaned it but I swear the car ran better when the jet was clogged. It's clean now though.
Thanks again,
Charlie

[18Fiatsandcounting]

After seeing the pictures of your coil, I now agree that replacement isn't a bad idea, given that it appears to have significant moisture issues (rust). Just FYI, the blue/black wire is the one to B+ (labeled 16) on your coil, and the minus side is the one with the brown wire labeled 1. Connection 16 should have 12 volts on it when you turn on the ignition.

If your fuel system is dirty, meaning anywhere from the gas tank up to the connection to the carburetor, small pieces of debris can periodically clog up your idle jet. It sounds like you've checked very recently that this idle jet is still clear, but if not, that would be the first step. The solution to clogging: Put a small inline fuel filter right before the inlet to the carb.

-Bryan

[CharlieB]

Thanks Bryan, I just thought it was odd that the car ran better with a clogged jet.
One question about the coil, do I need one with an external resistor?

[kilrwail]

No you don't need a coil with an external resistor.