73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Fuel Systems and Drivability => Topic started by: greenmonster on January 06, 2008, 02:09:51 pm
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I have a 75 k10 with a 350 and I need to know where to wire the choke to.
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The choke is wired off of the oil pressure switch
(http://i6.photobucket.com/albums/y228/Sabaka454/choke-1.jpg)
PURPOSE
The electric assist choke helps to reduce hydrocarbon (HC) and carbon monoxide (CO) emission during start and warm-up periods--choke-on--by opening the choke more rapidly at ambient temperatures above 60-65°F, than it does at ambient temperatures below 60°-65°F.
OPERATION
System Components--Fig 39
Thermostatic Coil
Ceramic Resistor
Cover
Bi-Metal Snap Disc
Contact Spring.
Ceramic Resistor
The electrically actuated ceramic resistor--composed of a small center section for gradual heating and a larger outer section for rapid heating of the thermostatic coil--heats the thermostatic coil gradually relaxing coil tension allowing the choke valve to open.
The electric current is supplied to the ceramic resistor from the oil pressure switch when the engine is running and oil pressure is above the minimum value for the switch.
Air Temperatures Below 50°F
As current applied to the small section of the ceramic resistor allows slow opening of the choke valve--for good engine warm-up;
A bi-metal disc closes the spring loaded contact applying current to the large section of the ceramic resistor.
This increases heat flow to the thermostatic coil, opening the choke valve more rapidly .
Air Temperatures Between 50-70°F
Current is applied to the small section--or both the small and large sections--of the ceramic resistor, producing the heat required to control choke valve position for optimum engine operation.
Temperatures Near 60 to 65°F
Designed to open choke more rapidly when temperatures are 60 to 65°F or greater, than when temperatures are below 60 to 65°F.
Air Temperatures Above 70°F
Since leaner air/fuel mixtures are required for warmer temperatures current is applied to both the small section and large section--through the spring contact--of the ceramic resistor, to rapidly heat the thermostatic coil for quicker choke valve opening.
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I don't think I have an oil pressure switch.My truck has a gauge with a copper line running to the dash.
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find a Switch 12v lead...My truck didnt have one...Had to make one
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If i put it on a switched lead it will heat up if I am just listening to the radio.Then i don't know if it will start in the cold.
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Well...Hmmm..im sure i will be told im wrong...But i welcome it lol...Couldn't u just use a 12 lead and add a toggle switch?..
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That is an idea.Do you know how the factor choke was wired.Was the factory choke even electric.
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My 1986 Came with Electric choke.....But my oil pressure switch went bad..Didnt want to mess with it..So i just took a 12v lead and used it..
I would wait for chris or blazin or vile before u go cutting wires
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Thanks for the help. Hopefully one of them will read this and point me in the right direction.
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Just pick up an oil pressure switch from autozone and tap into the oil galley. You have 2 ports to tap in and if you have on already being used for your gauge or idiot light just run a brass tee. Most of them used the tap at the back of the block near the distributor for SBC.
PS115 $7.99
http://www.autozone.com/R,APP258748/vehicleId,1121804/initialAction,partProductDetail/store,5152/partType,00134/shopping/partProductDetail.htm
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That is a good idea.Are both of the oil taps in the back. THANKS for the help.
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as for the question "was the factory choke electric"...it would depend on what year truck you are dealing with. i wanna say 1976 and lower weren't electric...i think 1977 was the first year of the electric choke in GM pickups. before that they were simply a thermostat housing mounted to the factory intake...when the intake air got warm enough, they released...if they were working properly... ::)