Tach/ Idle Solenoid Linked?

Gotta love that wiring . . .
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HOLLYWOODSPIDER

Tach/ Idle Solenoid Linked?

Post by HOLLYWOODSPIDER »

So I've had this problem getting my car to idle smoothly. I can get it to idle, but not very smoothly. Also, the car sometimes dies during hard braking. Application of the brake pedal can occasionally cause the rpm to drop very low, but it usually comes back up before the engine dies. I don't think the booster leaks air, as there's no suction noise, and the idle stabilizes after a second.

Disconnecting the idle solenoid on my carb does not affect the idle speed. I read in the manual that the solenoid is controlled by a tachimetric switch that energizes it under 2600 rpm. My tach is currently disconnected. Would disconnecting the tach disable the Idle Solenoid circuit?
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manoa matt
Posts: 3442
Joined: Thu Oct 26, 2006 4:28 pm
Your car is a: 1978 Fiat 124 Spider 1800
Location: Honolulu, Hawaii

Post by manoa matt »

If you disconnect the idle solenoid the car should shut off. The idle solenoid is energized when you put the key in the ignition and turn on the electric.

Try this: Disconnect the idle solenoid wire. Put the key in and turn the electric on. Go to the engine and hook up the wire, you should hear a click.

Aside from the idle solenoid electronics going bad there is another posible problem that can happen to the idle solenoid.

Remove the idle solenoid and check the small brass jet at the end. It should be conical in shape and uniform. If one side appears worn then fuel can leak past the jet and cause a rough idle.

Hopefully you have the smaller diameter idle solenoid. The jets are avilable for about $5. If you have the larger solenoid then you have to buy the whole thing.

On a 78 the solenoid should only have one wire going to it. If you have two wires that are crimped into a single connector then it is wired up wrong. Not shure about the 79

Matt
mdrburchette
Posts: 5754
Joined: Wed Jan 25, 2006 5:49 am
Your car is a: 1972 Fiat 124 Sport
Location: Winston-Salem, NC

Post by mdrburchette »

You can also eliminate the booster as being faulty by disconnecting the vacuum hose and plugging it.
HOLLYWOODSPIDER

Post by HOLLYWOODSPIDER »

My main question is " are the idle solenoid and the tach linked?" I.e., am I going to be able to get it to idle smoothly without replacing the tach? Is this "tachimetric switch" mentioned in the manual text actually inside the tach? Connecting/disconnecting the solenoid produces no results. Carb is adjusted to idle without the help of the solenoid, thus it is idling without the help of the idle circuit.
racydave

Post by racydave »

You can check for voltage to the solenoid with a test light.
So Cal Mark

Post by So Cal Mark »

to idle without the idle circuit, rpm would have to be over 1200. Most likely scenario is that the tip of the idle cutoff switch has been cut off, leaving the idle jet open whether the key is on or not. Tach is not connected to the idle cutoff switch
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