Idle Stop Solenoid revisited

[18Fiatsandcounting]

However, just before I got home I shifted to neutral and hit the brakes hard. Just after I lifted my foot off the brake pedal, the car cut off.
I'm not sure what that means.

Glad I could be of some help! As for the engine dying when you work the brake, that usually is a sign of a leak in the brake booster system. The "assist" for the brake booster comes from the vacuum from the intake manifold, and if there are any leaks in the booster, the engine can cut off when you press or release the brake pedal.

Try this to test: Warm the car up and let it idle. While sitting in the driveway in neutral, work the brake pedal a few times, somewhat vigorously. If you see the idle speed drop as you do this (or if the engine cuts out), then it's likely a vacuum leak in the brake booster. If the idle speed doesn't change when you work the brake pedal, it's something else.

-Bryan

[18Fiatsandcounting]

I will go ahead and replace the Idle Stop Solenoid and rewire it...somehow.

Charlie, if the car doesn't "diesel" (keep running) when you turn off the ignition, one option is just to leave it as it is. As my dad used to say, "If it ain't broke, don't fix it." However, if it were me, I'd replace the idle solenoid. Just considering some options.

-Bryan

[CharlieB]

Yeah I'll check the brake booster like you suggested. If there is a vacuum leak in the booster does that mean I need a new one?
I'll hold off on the solenoid for now.

[18Fiatsandcounting]

If there is a vacuum leak in the booster does that mean I need a new one?

Yes, but another option is to plug up the vacuum hose to the booster and just live without power brakes. The brake pedal will be harder to push, but then again the car is light enough that power brakes aren't absolutely necessary. Some people even like the harder feel of non-power assist in a Fiat.

While replacing the brake booster isn't super difficult, it's not a 2 hour job either. Whatever you decide, I'd do some more tests to make sure the booster really is bad before going to the trouble of replacing. For example, making sure that the vacuum hose to the booster and its connections are good.

-Bryan

[SteinOnkel]

I'm going to disagree with Bryan. If a car never came with a brake booster, then it would have differently dimensioned calipers, different master cylinder, different pedal throw etc. The brakes would feel a little stiff, but nothing crazy. I've had cars that came from the factory like this and they felt okay-ish. When you upgrade those to power brakes you must also replace all the other stuff.

If on the other hand, your brake booster fails or you disconnect it, the brakes will feel like absolute junk. Regardless of how much the car weighs. This is because the system is setup for a brake booster and will not function properly without it. I've never gotten a car with a disconnected booster to lock up the wheels...with the booster you need, what 80 lbs of force on the pedal to achieve this? Without it, I'd venture a guess here and say you need 2.5x. It is sketchy to drive around like this.

What OP can do is disconnect the booster temporarily to diagnose his carburetor.

Or just replace it. I just re-did the brakes (booster, mc, calipers rebuilt, rotors, discs and fluid) on my 124 and the brakes feel absolutely amazing.

Cheers
Steiny

[CharlieB]

Well my brakes have always been stiff. So it's quite possible that my brake booster isn't working in the first place. I'll take a look over the next couple of days. I'll drive a friend's spider and see how his brakes feel.
Thanks guys,
Charlie

[SteinOnkel]

Well my brakes have always been stiff. So it's quite possible that my brake booster isn't working in the first place. I'll take a look over the next couple of days. I'll drive a friend's spider and see how his brakes feel.
Thanks guys,
Charlie

There is hardly any discernible difference between the brake feel on my 2014 Ford Focus and my 1978 Spider.

If it's stiff, something is broken. Most likely the booster.

This would also explain why your car likes to intermittently die. Especially when backing out of your driveway, I'm assuming you tap the brakes and then push the clutch in.

Also with the engine nice and hot, try idling it and pumping the brakes. If the booster is roached, it'll cycle up and down in idle rpm, stall etc.

[18Fiatsandcounting]

I actually agree with you Steiny! Just offering an option (perhaps bad) that Charlie could consider.

Also, one other test: Warm the engine warmed up and idling, insert your head down in the driver's footwell and press hard on the brake pedal with your hand. Make sure you're in neutral with the parking brake on. In addition to the diagnostics Steiny noted, if you hear a whistling or a sound like a vacuum leak up around the booster inside the footwell, that's a sure sign of a leaking booster. This test isn't foolproof as sometimes you can't press the brake pedal hard enough with your hand to the point where it starts to leak. But still, if you hear a vacuum leak sound, the booster is bad.

We can walk you through the steps to replace the booster if you choose to go that route.

-Bryan

[CharlieB]

Ok I finally got around to running the booster tests. There was no change in the rpm when I hit the brakes with the car idling.
However, if I tap the gas pedal, the rpms drop to zero and the car cuts off. Now I'm even more baffled.
By the way, I disconnected the booster and capped it and I don't feel any difference in the brakes. So, it looks like I have more than one issue going on. My booster is definitely toast though.
Any thoughts?

[dinghyguy]

Some q’s
Does the accel pump spray gas into the carb when you twitch the gas pedal? Look down the carb and see what happens. It should show a visible jet ( ask me how I know)

Have you removed the jets and emulsion tubes air correctors and perhaps put them back in the wrong places?

Is the choke operating correctly? Ie dropping to idle after warm?

Are the butterflies adjusted correctly to be closed the correct amount?

Is the throttle linkage adusted correctly? (Ask me how I know)

Is their an air leakage path into the carb past a shaft or at the base gasket?

Not saying any of these are the problem but maybe.....

Cheers
Dinghyguy

[CharlieB]

Dinghyguy,
I do have fuel spraying from the accel pump.
I did use a rebuild kit on the carb when all of my issues first started. I did put everything back correctly, I took pictures as I went along just to make sure. Butterflies are adjusted correctly.
When I pull the knob for the choke and start the car, the car starts up and the rpms go racing up as if the gas pedal is pressed to the floor. Obviously this is not ideal, so I never use the choke. I don't know where to begin to fix that.
I drove the car to my office this morning. It is still intermittently cutting out when i slow down, or the rpms drop to zero and it bumps itself back up.

[18Fiatsandcounting]

When I pull the knob for the choke and start the car, the car starts up and the rpms go racing up as if the gas pedal is pressed to the floor.

I'm on the road right and don't have access to all my manuals, but I would have thought a '76 spider was an automatic choke. If you have to pull a choke lever, is it possible that you have a different carb installed on this engine (in addition to the removal of all of the emissions stuff)? The number of the carb would be on the base "lip" of the carburetor, where it connects to the intake manifold, and on the side facing the intake camshaft. Sometimes you have to get a dental mirror down there to see it, or just remove the carb.

I think your '76 should have a Weber 32 ADFA carburetor, which has a choke driven by the coolant temperature. If you have something else, that could be the source of your issues.

By the way, having the engine "race" when the choke lever is pulled all the way out (on cars that have this) is not unusual. The solution is to only pull out the choke partway to start the car. With time, you'll get a feel for how far out to pull the choke depending on outside temperature, etc.

-Bryan

[18Fiatsandcounting]

I just thought of something: Some model years (mostly earlier) had a *throttle* lever that is often confused for a choke. All it does it give you a way to "give it gas" with your hand instead of your right foot (a pretty pointless feature, in my opinion, but that's Fiat for you). This throttle lever is on the right side of the steering wheel under the dash, whereas the choke (if your car has one) should be on the left side. If you are by chance pulling the throttle lever instead of a choke, that would definitely cause the engine to race!

And, if you're pulling the throttle and not the choke, and your coolant-driven choke isn't working, the engine will definitely misbehave until it gets fully warmed up.

-Bryan

[18Fiatsandcounting]

PS: Forgot to mention on the brake booster. Make sure you have the little one-way valve that's in the hose between the intake manifold and the brake booster. I think it's function is to prevent the brake booster from being blown apart should you have a backfire into the intake manifold (can happen with Fiats). If that valve is stuck in the closed position, your brake booster won't work.

-Bryan

[CharlieB]

Bryan,
I do have a 32 ADFA but I have probably used the wrong term in my previous post.
The knob I was referring to is the choke knob on the left side of the steering wheel.
Another thing I forgot to mention is when I decelerate, I hear a faint backfire through the tailpipe.
It's not a full blown backfire it's more of a quick puff...if that makes sense. It only seems to happen when I'm downshifting.
I'll take a look at the booster valve tonight, it's capped off for the moment.
Thanks
Charlie