Hey everyone,

I'm new the the forum. I just purchsed a 90% restored '84 Z28. It's a got a new engine, rebuilt 4spd auto, and rebuilt stock carb. The previous owner mentioned that the rebuilt carb would need to be replaced at some point. The car runs great, but sometimes the choke light flashes at me, especially when the engine is cold or I'm at a slow idle It's not all the time and it doesn't light up all the way, so I don't know if it's a carb issue or an electrical issue. Please help.

Greg

 

The choke light comes on when the alternator isnt putting out power.

Im guessing your alternator is on its way out.

 

Well, the light isn't "ON". It's flashing at 1/2 brightness or so and only does so intermittently.

 

loose wiring perhaps?
choke bad on the carb?
or alternator. How's voltage during this time? If <14.4V then alternator.

 

I didn't think about the alternator because voltage seems to be holding strong. Would a bad choke on the carb cause performance issues? If it's a wiring issue, I have no clue where it would be.

 

Check the wire that is connected to the alternator at he stud on the back. Mine had started to fray causing the smae thing. Also, as said above, put a volt meter on the battery while running to see if the alternator is putting out the required 14.5- 14.8 volts as this will cause the light to flash if it isn't. As for the wire, I cut the old ring terminal off and put a new one on and the problem went away. Check you choke wire and connector as well. Hope this helps..

 

A dim or flashing choke light probably indicates a bad or resistive electrical connection to the choke heater. This probably won't give you any problem during in warm weather because the engine block is hot enough to keep the "high idle cam" armature away from the throttle and choke levers.
However,
As far as the problems it causes, the connector on my electric choke heater broke (which would cause the choke light to not come on), it caused the engine to rev at about 1,500 - 2,000 rpm and would never "kick down" as it should.

I don't know how difficult it is to fix a bad electrical connection, but I'd assume its fairly difficult because unless it's something simple like a connector, it's pretty hard to find. I should rephrase, depending on ur setup, there may be several ways to fix the problem.

Hope this helps.

 

Thanks. I'll check these items tonight and let you know.

 

That says "alternator" to me. If it was the choke circuit itself, it would light all the time.

 

Wouldn't surprise me. The heat here in TX kills alternators and batteries. Would the alternator cause the problem so randomly, or would it consistently get worse? The the voltmeter on the battery a reliable test of the alternator, or do I need to take it to Firestone or someplace to have it tested?

 

My alternator/battery combo is really crappy and my choke light never comes on.

In the LG4 engines, the choke light is wired in series with the choke heater so that if there is a break in the connection, the choke light will not come on during the light test. If your choke is operational, the choke light comes on when your ignition is in the "ON" position but the engine has not been started. In fact, there is a relay that engages when the engine actually runs that directs power directly to the choke heater, effectively shorting the choke lamp connection. Therefore, the choke light should never come on while the engine is running (not just in the "ON" position, the engine must be running)

 

if I walk over to my carb, with the motor running, and pull of my choke wire, the choke light, lights up. The way it's supposed to.

At idle, check your voltage across the terminals, when the light is flickering preferably. A simple voltmeter will do. <13V is a bad alternator. >14 is good. mid 13's is dicey.

 

In that case, it could be a bad connection there. I'll have to look at it closer tonight.

 

I just read 87TAFrank's reply again. This IS happening when the engine is running. If that shouldn't be possible, what would cause it?

 

What would cause it? Underdrive sheaves, poor brushes/slip rings in the alternator, weak field (stator) current, failed (open) diode(s) in the rectifier bridge, and poor connections.

 

Sorry, Vader. That went right over my head.

Current reads strong at 14-14.5, but I couldn't get the choke light to come on this time. I do seem to have a parallel issue with the idle. When I start it after letting it sit 12+ hours, it idles really fast at over 2K RPMS. Faster than a normal fast idle and I have a tough time getting it down. Could this be related?

 

I assume you mean 14-14.5 volts. And I assume you used a hand-held voltmeter to check this at the battery, not relying on the voltmeter in the dash instrument panel.

You may have a weak choke thermostat or a weak connection somewhere in the choke power circuit. The lower voltage at idle could just be masking that problem. The idle should be higher when first started dead cold, but it shouldn't be higher than it is after 3-4 hours of cooling off. The choke may not be operating in its full range, so the previous owner crutched that by mal-adjusting the choke (not an easy thing to do because it had an indexing tab on it).

Make sure the choke mechanism is operating freely. This is best done when the engine is stone cold. With the air cleaner off, hold the throttle open slightly - the choke butterfly should snap fully closed, and the high idle cam weight (a green lever on the passenger side of the carb between the choke thermostat and the carb body) should come up fully. Keep holding the throttle open a bit and move the choke butterfly and high idle cam weight by hand - they should move freely and smoothly, and both go to the above-mentioned positions when you let go (with the throttle held open slightly). You should also check the choke pull-off - a vacuum mechanism on the front passenger side corner of the carb. It should hold vacuum (easy way to check it is to take the vacuum hose off of the carb end, press the mechanism fully in and then put your finger over the hose, and let go of the mechanism - it should stay in until you take your finger off the hose. If it goes back out, it's bad and should be replaced). When you depress the choke pull-off, it should open the choke butterfly slightly. Finally, when you start the car, the choke should slowly open and be fully open within 5 minutes or so. The idle won't come down unless you tap the throttle. Somewhere sometime in the past Vader posted resistance readings for the choke thermostat, you might try searching this forum for that info if you have a volt/ohm meter.

Any of these things not working properly would be reason for someone to make improper adjustments so they could at least drive the car.

(BTW, Vader was describing causes of low voltage in his post. )

 

BWWAAHHHAA! That IS funny!

5-7 called those round things stuck in the dash "instruments." That's like saying a claw hammer is a "surgical tool."

The term "instrument" usually carries the connotation of something with some accuracy and/or relative precision. The only "accuracy" of those things is how they fit into the dash, and even that is suspect. As far as how close any indication might be to any reality, the factory accountants made certain they saved LOTS of money in that area, despite any engineers' pleadings.

 

Yes in fact a faulty choke or faulty choke heater is probably responsible. I believe that your electrical connection to the choke heater is most likely resistive in that the choke heater will eventually heat up (eventually allowing the high idle cam to move away from the throttle and choke lever, and thereby allowing you to drop the idle with the accelerator), but it doesn't allow enough current for the choke heater to heat up quickly. I think that a poor electrical connection or bad relay contacts could cause this.

Possibly in your situation, the choke heater isn't functioning at all, but the heat of your engine block at 2,000+ RPM is moving the high idle cam spring (again allowing you to drop the idle but in a much longer time because the engine has to warm up rather than an electrical coil doing the heating) Anyone think this may be a possibility?

However, I'm not sure what would cause your choke light to come on while the engine is running. When I looked at the circuit diagram for the choke it appeared to me that the lamp should not come on when the engine is running. If I am incorrect about this someone please tell me as I don't want to mislead anyone.

 

Actually, I called it a voltmeter in the instrument panel. But, what you said pretty much defines why I expressed hope that the accountant's meter was not being used for diagnostic purposes.

A weak choke thermostat element is one good reason for a much higher idle when fully cold than only partially cold. It should close completely even if the engine isn't stone cold. The choke thermostat has to be doing something, because gravity will keep the fast idle cam "off" unless the choke thermostat moves it to "on".

As for the choke light while the engine is running - if you disconnect the alternator while the engine is running, the choke light will come on.

 

Frank,

Your read on the situation is dead on. After a few minutes, I am able to drop the idle to about 1000 RPM. When I took it out for a bit last night, the light never came on and I had no issues at all once it was warmed up.

As a side note, I'm going to replace the alternator regardless. It's too big a risk down here when I don't know how old it is.

 

As something else to check, I had a similar problem once (flashing choke light) and it turned out to be the choke relay chattering. There was also a noticeably clicking / buzzing coming from under the dash, right near the driver's right knee in the "convenience center" (another woefully misnamed part in these cars).

Vader, your comment about the factory gauges had me laughing out loud at work.

 

"Convenince Center." Yeah, that's a good one. It's "convenient" if you're two feet tall and can stand on your head for 20 minutes, hold a meter in your teeth, and use your third and fourth hands to keep the thing steady while you work there.

Glad I could brighten up your day just a little.

 

would the alt. cause the choke fuse to blow too, or is it more than likely a short?

 

oh thank god, I thought I was the only one having such a wretched time with that...

gasman - if indeed your choke fuse popped, it was probably shorted on something. I doubt the alternator could cause that...

 

Well, I've driven it at least a little bit every day this week since Monday when I purchased the car. I'm now inclined to believe that the issue was that he hadn't been driving the car much; less than 600 miles since the new engine and trans/carb rebuild. I had the air filter off and checked to make sure the choke was moving freely. Thanks for that advice, five7kid. I haven't seen the light come on since I posted this thread, and the more I drive it, the better it seems to run. Regarding the idle speed, it still idles too fast when started stone cold and takes 1-2 minutes before I can drop the idle down. I'll see if I can find a problem with the choke heater. Thanks for that one, 87TAFrank.