quadrajet ?for Lars or someone with qjet knowledge for 78 L48
03-22-2004, 11:28 AM
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quadrajet ?for Lars or someone with qjet knowledge for 78 L48
should i have vacum at the choke pulloff port or should i have to hook vacum to it? mine has vacum at the port already and the choke doesnt want to come off automaticly i have to kick it manually and as soon as you give it gas it resets itself. If its not suppose to have vacum there without the hose what could be the problem?thanks for any insight or help DRM78
03-22-2004, 11:46 AM
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Re: quadrajet ?for Lars or someone with qjet knowledge for 78 L48 (drm78)
The choke pulloff has a vacuum hose attached to it that goes to the choke vacuum port nipple on the carb. This port is manifold vacuum. The pulloff will not operate if the hose is not hooked up.
03-22-2004, 12:52 PM
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Re: quadrajet ?for Lars or someone with qjet knowledge for 78 L48 (drm78)
drm -
After re-reading your question I may not be understanding what the issue is. Here is how to check out your choke pulloff operation:
First, with the engine cold, verify that the choke snaps FULLY closed when you open the throttle. The black choke coil cover should be adjusted so that the alignment mark is on the second line to the "lean" side of the center mark. This should make the choke snap fully closed when the engine is cold.
Then, pull the short piece of vacuum hose off the pulloff (you should have a short piece of vacuum hose attaching the pulloff to the vacuum nipple on the carb). Attach a long piece of vacuum hose to the pulloff and suck on it. This should make the pulloff retract. The pulloff should hold a vacuum in this condition. If the pulloff does not retract, or if it will not hold a vacuum, you need to replace it.
With the pulloff fully retracted, apply very light finger pressure to the choke plate to simulate the light force of the air pushing on the plate. The lower edge of the plate should be open 1/4". You can measure it by slipping a 1/4 drill bit down bewteen the lower edge of the choke plate and the carb airhorn. Adjust the phillips head screw on the end of the choke pulloff lever to get this measurement right at 1/4".
With this set, hook up the short piece of hose again and start the engine. Fast idle speed is adjusted with the screw located unde the choke housing. Set fast idle to about 1200 rpm.
These are all the checkouts and adjustments to assure correct operation of the choke and fast idle system.
[Modified by lars, 11:53 AM 3/22/2004]
[Modified by lars, 11:54 AM 3/22/2004]
After re-reading your question I may not be understanding what the issue is. Here is how to check out your choke pulloff operation:
First, with the engine cold, verify that the choke snaps FULLY closed when you open the throttle. The black choke coil cover should be adjusted so that the alignment mark is on the second line to the "lean" side of the center mark. This should make the choke snap fully closed when the engine is cold.
Then, pull the short piece of vacuum hose off the pulloff (you should have a short piece of vacuum hose attaching the pulloff to the vacuum nipple on the carb). Attach a long piece of vacuum hose to the pulloff and suck on it. This should make the pulloff retract. The pulloff should hold a vacuum in this condition. If the pulloff does not retract, or if it will not hold a vacuum, you need to replace it.
With the pulloff fully retracted, apply very light finger pressure to the choke plate to simulate the light force of the air pushing on the plate. The lower edge of the plate should be open 1/4". You can measure it by slipping a 1/4 drill bit down bewteen the lower edge of the choke plate and the carb airhorn. Adjust the phillips head screw on the end of the choke pulloff lever to get this measurement right at 1/4".
With this set, hook up the short piece of hose again and start the engine. Fast idle speed is adjusted with the screw located unde the choke housing. Set fast idle to about 1200 rpm.
These are all the checkouts and adjustments to assure correct operation of the choke and fast idle system.
[Modified by lars, 11:53 AM 3/22/2004]
[Modified by lars, 11:54 AM 3/22/2004]
03-22-2004, 03:32 PM
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Re: quadrajet ?for Lars or someone with qjet knowledge for 78 L48 (drm78)
Lars i actually have vacum at the pulloff nipple with no hose attached to it so if im reading this right i should have no vacum there without a hose attached to it,thanks dale
03-22-2004, 03:52 PM
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Re: quadrajet ?for Lars or someone with qjet knowledge for 78 L48 (drm78)
You have vacuum at the choke pulloff with no hose on it...? That's not possible - the hose is the only source of vacuum for the pulloff - the pulloff can't produce it's own vacuum without being hooked up... Are you sure you're talking about the choke pulloff? Describe the part you're talking about - I don't think you're talking about the pulloff.
[Modified by lars, 2:53 PM 3/22/2004]
[Modified by lars, 2:53 PM 3/22/2004]
03-22-2004, 04:21 PM
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Re: quadrajet ?for Lars or someone with qjet knowledge for 78 L48 (drm78)
I just realized what you're looking at - that's not the choke pulloff....
Correct me if I'm wrong, but you're looking at the nipple that sticks out straight forward out of the round aluminum housing with the black round plastic side on it. That's the choke housing - not the pulloff. The nipple that comes out the front does not get hooked up to vacuum - it gets attached to the hot air tube that comes out of the manifold exhaust crossover. If you have it hooked to vacuum or not hooked up at all, the choke will never get hot, and it will never come off the "cold" setting. Thus your problem.
The nipple on the forward side of the choke cover needs to be hooked up to the tube coming out of the manifold exhaust crossover. The second tube coming out of the crossover plugs into the port on the back of the carb airhorn (inlet air). There is a small vacuum "leak" inside the choke housing allowing the choke housing vacuum to "suck" air from the rear carb airhorn location, down through the tube to the manifold, through the heat tube in the crossover, and into the choke housing through the forward nipple. This makes the coil hot, and makes the choke open up. This is not the pulloff.
The pulloff is the canister forward of the choke housing. It is hooked up to manifold vacuum with a short hose to the carb. When the engine starts, it retracts and cracks the choke open 1/4".
Both these systems must be correctly hooked up and operational in order for the choke to work. You can convert the hot air choke system to an electric choke, but cost to do this is about the same as the cost of new hot air tubes.
Correct me if I'm wrong, but you're looking at the nipple that sticks out straight forward out of the round aluminum housing with the black round plastic side on it. That's the choke housing - not the pulloff. The nipple that comes out the front does not get hooked up to vacuum - it gets attached to the hot air tube that comes out of the manifold exhaust crossover. If you have it hooked to vacuum or not hooked up at all, the choke will never get hot, and it will never come off the "cold" setting. Thus your problem.
The nipple on the forward side of the choke cover needs to be hooked up to the tube coming out of the manifold exhaust crossover. The second tube coming out of the crossover plugs into the port on the back of the carb airhorn (inlet air). There is a small vacuum "leak" inside the choke housing allowing the choke housing vacuum to "suck" air from the rear carb airhorn location, down through the tube to the manifold, through the heat tube in the crossover, and into the choke housing through the forward nipple. This makes the coil hot, and makes the choke open up. This is not the pulloff.
The pulloff is the canister forward of the choke housing. It is hooked up to manifold vacuum with a short hose to the carb. When the engine starts, it retracts and cracks the choke open 1/4".
Both these systems must be correctly hooked up and operational in order for the choke to work. You can convert the hot air choke system to an electric choke, but cost to do this is about the same as the cost of new hot air tubes.