I still have a couple vintage trucks with quadrajets, although I think it’s getting near the end of the line. I’ve been pretty good with them, but they’re getting so old that the worn linkages combined with the complexity just makes it harder to keep them working, at least for me. The best one I have now is a 1985 model from a heavy truck/motor home. In good condition and works well, but the electric choke has me mystified. I couldn’t get the original one to work properly, so I ordered a new one. Can never find the sweet spot. I have about 10 other coils, obviously the index marks won’t mean anything, but if it works, who cares. Here’s the question: is there a sort of generic electric choke coil that I could use? By 1985 obviously these carbs were about done and couldn’t pass emissions. Maybe that explains why it’s so temperamental. But I’m sure there’s about 5 million different variations, makes it hard to just start making guesses. I know for HEI vacuum advances I just use an AR12, and it works well. Has someone figured out something comparable for choke coils? Just hoping someone else has fought this battle already and came save me some trouble…
the choke is a complicated system...the electric heater is one small part of it. I've had problems with the vacuum pull offs on them, also with linkage binding.
X2 on check the choke vacuum pull off. It has to work for proper choke operation. Tightening or loosening the choke coil tension is also in relation to the pull off.
I've battled the electric Q-Jet chokes over the years, usually losing my mind in the process. In the past I could never get the electric ones to work correctly, they either didn't fully open or fully close. And they never seemed to 'snap' closed when pumping the pedal on a cold start. Only way I've gotten them to work, acceptably, is to get the engine fully warmed up and heat soaked and then adjust the choke spring to where it will keep the choke fully open but not over tensioned. This usually made the 'cold' setting not really closed. So even after the 2 pumps and twist the key, the pedal would still need some toe weight to keep the engine running after startup. IIRC Choke should have ~10Ω, anything more than 20Ω is a bad coil. Verify you are getting full battery/alternator voltage to the coil. Bad/missing grounds will not allow the coil to work properly. Verify the ground cables/bonding jumper for the engine and the intake are in good order.
Does the hot wire to the thermostat feed thru an oil pressure sensor or switch? Does the EFE or heat riser valve work properly? Is the heat crossover in the intake possibly plugged? These engines may have used the electric thermostat to open the choke early on but still depended on some amount of crossover heat to fully open the choke at full operating temperature.
Linkages and pull off are good. Years ago I had a whole series of 70s Cads and I had no problem dealing with them, even though they didn’t come with electric chokes. Just used later caddy carbs. This one just seems to have the rate and amount of travel all wrong. Just can’t find that middle spot where it works when fully hot AND cold. You can get one end working, but you give up the other. I know that’s a weird way to put it. I usually order my kits from mountain man, maybe I’ll run it by them.
Couple things to look at . Voltage to the choke , seal between the choke housing and carb body and as discussed choke pull off . If I’m not mistaken, the choke heater operates at the stator voltage . I just can not fully recall . The Qjet is one of the best carbs ever build , every circuit is fully adjustable and will work correctly .
That sounds like something Ford would do. Chevys (as mentioned by others) used oil pressure switch on those 1980s trucks to turn on the choke heater.
Mr . Squirrel , is probably correct with the 12v and the 3 terminal oil pressure switch . That would work superbly when wired correctly . You also need to verify the contact surface is clean between the choke housing and the carb body to allow for a good path to ground . Never use the same switched 12v wire to the ignition , the choke elements can short and so does the ignition if wired this way . Oil pressure switch 12 v switched wire is the answer . Fords use the stator voltage choke wires to heat the choke element , but 70s Fords used Qjets also . I have no idea how they were wired . It must also be through the oil pressure switch as GM . Only correct way I can see of safely doing it .
I run a Q-jet on my daily and converted it to manual choke using a universal kit. I too have never been able to get the electric choke to function well so I gave up trying years ago and simply swap on a cable operated system. Dorman HELP! 55101 Choke Conversion Kit
I did the same thing on a Pontiac 455 I had years ago. Never was able to figure out that setup, so I went with the manual choke. I also drilled a couple of 3/8" holes in the choke plate to allow some air to pass through it while fully closed, started and idled much better in my case.
Manual choke conversion? That’s just quitter talk. I thought we were all gluttons for punishment here… Voltages and everything else has been checked. No oil pressure switch, never seen one on a GM, but never say never. This carb came off a 78 burb 454, obviously a reman since it’s an 85. Installed on a 350 in a much older truck, I ran the wire myself. Electric choke qjets don’t have a housing seal. If they did the choke wouldn’t work because the coil won’t ground. Last summer I rebuilt a qjet from a 77 TA that went on a friends 68 GTO that he put a 428 in for some reason. It was a hot air choke, took the seal off and plugged the hole and made a guess as to which coil from my collection to use. Worked great and adjusted perfectly from day one. Unfortunately I realized my collection is still at his house… This coil is different. Thinner metal strips, more tightly wound, etc. Thought I was doing the right thing by using the correct one. That’s what I get for not modifying right from the get go, like I normally would. It occurs to me that kits are available to convert early divorced choke qjets to electric. Maybe I’ll figure out which generic coil they use.
I think some of them had both the hot air and electric coil to open the choke, but I could be mistaken, it's been a long time since I had to work on them. The divorced chokes from the late 60s-mid 70s usually can be made to work, if the carb isn't screwed up too badly.
I’ve never adjusted a heat stove or electric to close all the way. In fact my normal setting just enough to go one step up on the fast idle. It may take 2 pumps to start which is ok on colder mornings then I leave it running a minute or 2 before backing out of the garage. It’s more important for me to know it’s goes off. If the carb is a non-electric choke which I’ve added one I make sure there is a small hole somewhere to pull air thru like the original exhaust stove. If I use that original fitting I add a plug and a .030-.040” hole. CarbKing may have some thoughts on conversions.
Electric chokes have been around since the mid-1930's and are still (opinion) problematic. https://www.thecarburetorshop.com/Automaticchokes.htm I quit trying to fool with them on my own vehicles decades ago. Very easy to find a carb with a hot-air choke, and add a heat stove, if an automatic choke is necessary. https://www.thecarburetorshop.com/Heatstovefabrication.htm I converted all of my vehicles to manual choke (manual choke carbs, NOT the FLAPS one-size-fits-all-works-on-nothing manual choke conversion kits). Jon
My auto choke works great and I live in a northern area. First, I do not have the oil pressure switch. My choke is wired to my circuit panel to an ignition switched circuit (same as the AFB that was used prior to Qjet). Mountain Man provided the 1980's version core and built it as I requested. I installed it and worked fine immediately. I have since changed the spring and primary metering rods to lean the mixture at high vacuum (highway cruising).
I read somewhere that some parts houses are selling a 2 barrel version that fits but does not work for the Quad. Any quad electric will work on other quads. Supply 12 volts. As long as it heats right away should be good.
That's been my experience with electric Q-Jet chokes. They just don't do either correctly. Q-jet hot air chokes divorced and otherwise always worked fine for me. Snap closed when cold and stays wide open when hot. Fords use the Stator voltage for electric chokes. GMs use full battery voltage.
I use several of the 9800 series Carter Thermoquads on various vehicles. The electric chokes on these carbs work flawlessly. Once set, I never have any problems, always start and come off choke fairly quickly. Carter made 2 models with GM linkage, the 9800 and the 9810. If you can find a nice one-try it!
I think there were some GM models that picked up oil pressure at two different localtions on the engine. One was a variable resistance "sensor" that connected to the I/P oil pressure gauge. The other was a "switch" that was just either open or closed at a certain pressure. One would usually be mounted at the back of the block near the distributor. The other might be in the block above the oil pan rail near the oil filter adapter. The oil pressure "switch" controlled the I/P warning light, electric choke thermostat and on some models the in-tank electric fuel pump.
I made a hot water choke, works really well. This engine has OT vortec heads, with no heat crossover passages. Tried an electric coil, but it would shut closed before the engine had completely cooled down. This follows engine temperature much better. I used a new Ford housing.
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