Carb choke coil question
Thread Starter
Instructor
Joined: Nov 2013
Posts: 166
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From: Acworth GA
Carb choke coil question
I don't seem to be able to get the setting of my choke coil to get both ends correct. If I adjust it to be fully open when the engine is hot, the choke does not fully close when it's cold (even very cold as in 20 degrees). If I adjust it to be closed at 20 degrees the it's not fully open when the engine gets hot (when the thermostat opens). Is this normal? I've looked but I cannot find a replacement coil on line.
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
Your profile and post provides no info on what car, year, engine, or carb you have... impossible to provide you info with no carb or engine data...
Lars
Lars
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Instructor
Joined: Nov 2013
Posts: 166
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From: Acworth GA
Its a 1978 std not the higher hp version.
The rebuild you did on the carb several years ago is still working great. I just cannot seem to get the choke setting dialed in. I don't know what kind of carb, I thought they probably all got the same one in 78. If they didn't I'll look for some kind of identifying tags or numbers on it.
Last edited by Rich123; Nov 2, 2020 at 04:11 PM.
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
Oh - you're Rich G...
The 1978 uses a hot air choke, and the operation is dependent on a proper hot air supply to the choke. If I remember right, your carb had indications of someone not getting the choke to operate correctly before, because your carb had the choke pulloff removed along with the airvalve linkage. The choke intermediate rod was also disconnected.
Questions and issues would be:
If you post up some photos of the choke side of the carb I may be able to spot the issue.
If all items are hooked up, and the choke housing is getting hot, you may have a defective hot air choke coil. It that's the case, I can send you a good used one to try out. Let me know.
Lars
The 1978 uses a hot air choke, and the operation is dependent on a proper hot air supply to the choke. If I remember right, your carb had indications of someone not getting the choke to operate correctly before, because your carb had the choke pulloff removed along with the airvalve linkage. The choke intermediate rod was also disconnected.
Questions and issues would be:
- Do you have both hot air tubes hooked up?
- Are you running a stock intake manifold with open (not block-off) manifold gaskets?
- Is the heat exchanger in the manifold crossover intact?
- Is the heat exchanger open and unplugged so it can flow hot air?
- Does the choke housing get hot after 10 minutes of engine operation?
If you post up some photos of the choke side of the carb I may be able to spot the issue.
If all items are hooked up, and the choke housing is getting hot, you may have a defective hot air choke coil. It that's the case, I can send you a good used one to try out. Let me know.
Lars
Last edited by lars; Nov 2, 2020 at 05:42 PM.
Thread Starter
Instructor
Joined: Nov 2013
Posts: 166
Likes: 8
From: Acworth GA
Lars,
I will take a look at those items that I can figure out what they are. I know that the ones that have anything to do with the cross over on the exhaust are not going to be there as I have side pipes. I did put baffles in each side pipe and had a cross over welded between then.
Thanks
I will take a look at those items that I can figure out what they are. I know that the ones that have anything to do with the cross over on the exhaust are not going to be there as I have side pipes. I did put baffles in each side pipe and had a cross over welded between then.
Thanks
Tech Contributor
Joined: Aug 1999
Posts: 14,376
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From: At my Bar drinking and wrenching in Lafayette Colorado
None of the items mentioned in my post above have anything to do with the exhaust system.
Lars
Lars
Last edited by lars; Nov 2, 2020 at 11:18 PM.
Thread Starter
Instructor
Joined: Nov 2013
Posts: 166
Likes: 8
From: Acworth GA
Oh - you're Rich G...
Questions and issues would be:
If all items are hooked up, and the choke housing is getting hot, you may have a defective hot air choke coil. It that's the case, I can send you a good used one to try out. Let me know.
Lars
Questions and issues would be:
- Do you have both hot air tubes hooked up?
- Are you running a stock intake manifold with open (not block-off) manifold gaskets?
- Is the heat exchanger in the manifold crossover intact?
- Is the heat exchanger open and unplugged so it can flow hot air?
- Does the choke housing get hot after 10 minutes of engine operation?
If all items are hooked up, and the choke housing is getting hot, you may have a defective hot air choke coil. It that's the case, I can send you a good used one to try out. Let me know.
Lars
I drove the car until I was certain it had reached operating temperature and the temperature of all components had stabilized. After I drove into the garage, within 3 minutes I took the temperature of several components.
plastic cover on the choke 150f
housing behind the plastic 143f
top of the carb 125f
intake manifold 192f
exhaust manifold 525f
upper radiator hose connector on the intake manifold 210f
I found a picture of a 78 Vette engine and compared it to my setup. The major difference I saw was the EGR valve on mine is not connected to a vacuum switch. A couple of years ago I found that the EGR valve was defective so I replaced it. After I put the new one on the car ran very rough. I took the new one off and put the old one back on and the car ran well again. The old one, as I recall, had a vacuum leak and was completely frozen or rusted together internally.
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years ago I had a chev Impala with the same problem. the passage way in the intake manifold was plugged shut with carbon build up. your temp readings indicate that perhaps your exhaust passage through the intake manifold is blocked or plugged. pull your intake manifold. make certain you use the correct gaskets that do NOT plug off said exhaust crossover. clean out the crossover passage in the intake manifold. clean up everything and reinstall.
Last edited by 4-vettes; Jan 2, 2021 at 03:40 AM.
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Joined: Jan 2020
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From: Va.Beach Va.
I would pop the line off at the choke and see if there is vacuum coming from the housing when the engine is running Use a small piece of paper and see it will draw itself up to it. Then put compressed air on the line away from choke housing to see it its clear. A clogged line wont allow vacuum from the housing to draw in the heated air needed to make the coil work.