Anyone know how an electric choke works? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

DBLSPRT68 · 10-13-2004, 04:11 PM

Here is the deal, I had an 82 for several years and never had a choke. I put an 83 body on my 82 chassis and now I have the electric choke wire. When I put this truck together, I hooked up the wire to my Eldebrock quadrajet with electric choke. The choke light stays on all the time, and the choke dosent work

. If I unplug the wire, the light goes out. Any idea why it dosen't work? Thanks, David

cliffsta · 10-13-2004, 04:28 PM

reostat maybe? The automatic choke on ol red went out before i was born, and my dad just rigged up a manual. The choke itself isn't that expensive, just might buy a new one. When i rebuild my carb some Xmas time im gonna MAKE that auto choke work.

ElGracho · 10-13-2004, 05:53 PM

It's not the choke heater and there is no reostat in the circuit. Most likely your oil pressure switch is unhooked or not on this engine.

This is the diagram. The oil pressure switch is separate from the idiot light or gage sender.

DBLSPRT68 · 10-13-2004, 08:28 PM

Thanks ElGracho!

I will look into this. I don't remember seeing the switch above the oil filter. I will also check the other things. Many thanks, David

**swervin ervin** · 10-13-2004, 09:21 PM

Once again, Joe has given you great advice.

I only wanted to add that the oil pressure switch may be up top by the distributor. On my 85, the switch is in a brass tee at the back of the intake, drivers side of the distriblutor. The other thing in the tee is the oil pressure sending unit. The sending unit is the big, bell shaped one. Power for the choke needs to go through the switch. This design was used so the choke gets no power unless the engine has oil pressure. This keeps the choke from opening with just the ignition switch on and engine not running.

But as Joe said, some years had the oil pressure switch above the oil filter. It seems to me there is no rhyme or reason to it either. My 85's is up top but I have a 87 van and it's above the filter.

69 air cab · 10-14-2004, 07:16 PM

THis is interesting. I have an 84 that I just installed a new engine (replaced 305 with a 350) in and had an expert rebuild the original carb. My chock light will not go out either and the chock won't kick off. Note: the chock is not new but the chock light did not stay on prior to the engine replacement. I have an oil pressure unit as Mike described near the dist. but I also have a oil pressure down near the oil filter. The one near the dist. in a single prong and the one near the oil filter is double prong (round). There is also another double prong that looks just like the one on the near the oil filter but the harness does not look to be long enough to reach down to the other one...........wondering if I hooked the wrong one up. I do not know where the other hooks up. I did remove all emission stuff and have not checked to see if it came off of that.

**swervin ervin** · 10-14-2004, 10:14 PM

The small double prong is the oil pressure switch, what the choke needs. The big bell shaped single prong is the sender for the gauge. If the double prong switch isn't hooked up it means the choke light will stay on. If you have the power wire that goes through the switch to choke hooked up at the choke but not at the switch, then the choke isn't getting any power, thus the reason it won't open up like it's supposed to.

As a side note, GM started using the oil pressure switches for the electric fuel pumps when they went to TBI. No choke is involved but they needed a safety measure in case of a wreck. The switch keeps the pump from running if there is no oil pressure.

badone07 · 10-14-2004, 10:23 PM

Last week or so, I replaced my hot air choke setup with an electric choke setup, out of junkyard parts, on my quadrajet. Picked up a 2 wire pigtail off a van, 2 wire oil pressure switch from same van, electric choke housing, linkages and choke from a v6 Regal. You need a 2 terminal oil pressure switch to operate the choke. Or you can also use a 3 terminal oil pressure switch, which were used on mopars. If you use the 3 wire switch, you just replace yours and run the wires without a "t" fitting, top rear oil port. Think 2 terminals are gold and 1 is silver, so they are not confused and used incorrectly.

For a 2 wire, you can "t" off from the top rear oil port or find another port to use. There is a port by on top of the oil filer housing, or some blocks also have a port above the water pump, towards passenger side. Just temporarily move the alternator out of the way to get access to it. If your truck originally cam with an electric choke, the wires and pigtails should be on your harness.

If it didn't then you need to get 12 volts while the ignition key is in the RUN position, ONLY. You can use the pink with black stripe wire under the dash or the brown wire coming off the alternator. I would also run an inline fuse to the choke. I used the front oil port on my block, to mount the oil pressure switch. Since I converted my truck, I spliced into the brown alternator wire, added an inline fuse and connected to 1 of the pigtail wires for the oil pressure switch. Then connected the other wire coming from the oil pressure switch, to my choke. Works perfectly and much better than the hot air setup which didn't always disengage the choke.

Make sure your oil pressure switche is working correctly. Can easily be done with an ohmeter, while off the truck with an air source applied to the switch. Also make sure the wires going to the switch have 12 volts and the choke is getting 12 volts. Also when you use an electric choke, you do NOT use the choke gasket. Otherwise the choke will not ground and therefore will not open, while leaving your light on.

DBLSPRT68 · 10-18-2004, 08:03 PM

Thanks everyone for their reply . I've been working a lot of overtime and it's rained when I wasn't working. (My truck is outside). I looked at my POS 305 I pulled from my 83. It has the switch located above the oil filter, The cab has the wire going to it. The engine in my truck now is an 85 HD 350. It has a plug where I need to put my switch. As soon as I get time, I will swap that switch onto my engine and hook everything up. It should work! Many thanks! I'm sure glad I didn't cut that wire! . David

ElGracho · 10-19-2004, 01:21 AM

You will definately want to replace the switch, but until then you can jumper across the two sockets in that plug to make your choke work.

69 air cab · 10-19-2004, 07:35 PM

This thread has also helped me so I too thank everyone. When I changed out my 305 with a new 350 I somehow plugged the tranny wire into the oil pressure connection. Both look just a like until you look at the number of wires going into the plug............3 on the one that goes to the oil pressure and 2 on the tranny plug. Now I am wondering what the tranny plug does..........ha.
THanks to all

10-13-2004, 04:11 PM	#1
DBLSPRT68 Registered User Join Date: Nov 2000 Location: Ft. Mill, SC USA Posts: 931	Anyone know how an electric choke works? Here is the deal, I had an 82 for several years and never had a choke. I put an 83 body on my 82 chassis and now I have the electric choke wire. When I put this truck together, I hooked up the wire to my Eldebrock quadrajet with electric choke. The choke light stays on all the time, and the choke dosent work . If I unplug the wire, the light goes out. Any idea why it dosen't work? Thanks, David __________________ PROJECT TRUCK: 1985 SWB C10 Silverado Black/Charcoal, 1990 V2500 Suburban, 2018 Suburban, 2005 GMC 2500HD CCSB, 2014 Toyota Camry SE, HAD.....1968 Camaro RS/SS Family owned since new; 350 3 speed SOLD

10-13-2004, 04:28 PM	#2
cliffsta Stepsides RULE Join Date: Jul 2004 Location: Pineville, LA Posts: 1,921	reostat maybe? The automatic choke on ol red went out before i was born, and my dad just rigged up a manual. The choke itself isn't that expensive, just might buy a new one. When i rebuild my carb some Xmas time im gonna MAKE that auto choke work. __________________ 1981 Chevy C10 Custom Deluxe Stepside 350 V8, headers, side exhausts, 3-speed auto SOLD 1980 Chevy C10 Custum Deluxe Stepside 305 V8, Edelbrock Performer Intake, Edelbrock 1406 600CFM 4-barrel, TH350C. Bent rod. SOLD 1984 GMC Sierra Classic Longbed 6.2L Diesel SOLD 2009 Kawasaki KLX-250S too many mods for this signature 1999 Honda Accord EX 4-cylinder, 17" Motegi Wheels 215/45/17 Sumitomo tires, Tein S-Tech lowering springs, KYB GR2 shocks, Acura TL 20mm rear swaybar, debadged, blackhoused headlights, Short-Ram Intake Cardomain of the Accord

10-13-2004, 05:53 PM	#3
ElGracho Gentleman Jim Driver Join Date: Nov 2002 Location: Poulsbo, WA Posts: 1,550	It's not the choke heater and there is no reostat in the circuit. Most likely your oil pressure switch is unhooked or not on this engine. This is the diagram. The oil pressure switch is separate from the idiot light or gage sender. __________________ Joe '75 GMC Gentleman Jim '84 Chev C10 Short Wide - Super duper plain (manual steering, manual brakes, no dome light, no cig lighter) '85 Chev C10 Short Wide - Super plain Vortec 4.8 4L60E trans also: '81 K30, '83 C30 Crew Dually, '84 M1028 CUCV, '85 M1009 CUCV, another '85 C10 SWB, '89 R3500 Flatbed

10-13-2004, 08:28 PM	#4
DBLSPRT68 Registered User Join Date: Nov 2000 Location: Ft. Mill, SC USA Posts: 931	Thanks ElGracho! I will look into this. I don't remember seeing the switch above the oil filter. I will also check the other things. Many thanks, David __________________ PROJECT TRUCK: 1985 SWB C10 Silverado Black/Charcoal, 1990 V2500 Suburban, 2018 Suburban, 2005 GMC 2500HD CCSB, 2014 Toyota Camry SE, HAD.....1968 Camaro RS/SS Family owned since new; 350 3 speed SOLD

10-13-2004, 09:21 PM	#5
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	Once again, Joe has given you great advice. I only wanted to add that the oil pressure switch may be up top by the distributor. On my 85, the switch is in a brass tee at the back of the intake, drivers side of the distriblutor. The other thing in the tee is the oil pressure sending unit. The sending unit is the big, bell shaped one. Power for the choke needs to go through the switch. This design was used so the choke gets no power unless the engine has oil pressure. This keeps the choke from opening with just the ignition switch on and engine not running. But as Joe said, some years had the oil pressure switch above the oil filter. It seems to me there is no rhyme or reason to it either. My 85's is up top but I have a 87 van and it's above the filter. __________________ Mike 1985 Chevy C-10

10-14-2004, 07:16 PM	#6
69 air cab Registered User Join Date: Oct 2003 Location: Maryville, TN Posts: 477	THis is interesting. I have an 84 that I just installed a new engine (replaced 305 with a 350) in and had an expert rebuild the original carb. My chock light will not go out either and the chock won't kick off. Note: the chock is not new but the chock light did not stay on prior to the engine replacement. I have an oil pressure unit as Mike described near the dist. but I also have a oil pressure down near the oil filter. The one near the dist. in a single prong and the one near the oil filter is double prong (round). There is also another double prong that looks just like the one on the near the oil filter but the harness does not look to be long enough to reach down to the other one...........wondering if I hooked the wrong one up. I do not know where the other hooks up. I did remove all emission stuff and have not checked to see if it came off of that.

10-14-2004, 10:14 PM	#7
swervin ervin You get what you pay for Join Date: Dec 1999 Location: Cherryville, NC Posts: 4,798	The small double prong is the oil pressure switch, what the choke needs. The big bell shaped single prong is the sender for the gauge. If the double prong switch isn't hooked up it means the choke light will stay on. If you have the power wire that goes through the switch to choke hooked up at the choke but not at the switch, then the choke isn't getting any power, thus the reason it won't open up like it's supposed to. As a side note, GM started using the oil pressure switches for the electric fuel pumps when they went to TBI. No choke is involved but they needed a safety measure in case of a wreck. The switch keeps the pump from running if there is no oil pressure.

10-14-2004, 10:23 PM	#8
badone07 Project 2 Resume Join Date: May 2004 Location: Jim Thorpe, PA Posts: 884	Last week or so, I replaced my hot air choke setup with an electric choke setup, out of junkyard parts, on my quadrajet. Picked up a 2 wire pigtail off a van, 2 wire oil pressure switch from same van, electric choke housing, linkages and choke from a v6 Regal. You need a 2 terminal oil pressure switch to operate the choke. Or you can also use a 3 terminal oil pressure switch, which were used on mopars. If you use the 3 wire switch, you just replace yours and run the wires without a "t" fitting, top rear oil port. Think 2 terminals are gold and 1 is silver, so they are not confused and used incorrectly. For a 2 wire, you can "t" off from the top rear oil port or find another port to use. There is a port by on top of the oil filer housing, or some blocks also have a port above the water pump, towards passenger side. Just temporarily move the alternator out of the way to get access to it. If your truck originally cam with an electric choke, the wires and pigtails should be on your harness. If it didn't then you need to get 12 volts while the ignition key is in the RUN position, ONLY. You can use the pink with black stripe wire under the dash or the brown wire coming off the alternator. I would also run an inline fuse to the choke. I used the front oil port on my block, to mount the oil pressure switch. Since I converted my truck, I spliced into the brown alternator wire, added an inline fuse and connected to 1 of the pigtail wires for the oil pressure switch. Then connected the other wire coming from the oil pressure switch, to my choke. Works perfectly and much better than the hot air setup which didn't always disengage the choke. Make sure your oil pressure switche is working correctly. Can easily be done with an ohmeter, while off the truck with an air source applied to the switch. Also make sure the wires going to the switch have 12 volts and the choke is getting 12 volts. Also when you use an electric choke, you do NOT use the choke gasket. Otherwise the choke will not ground and therefore will not open, while leaving your light on. __________________ John 1984 C30 Chevy Crew Cab Dually 1998 Jeep Cherokee 4x4 2004 Chevy Trailblazer 4x4 (wife's) 1970 Mustang FB fully tubed (getting 521 BBF & powerglide) 1978 Nova 2dr (going BBCaddy & S.P. th400) 1984 Monte SS (circle track car)

10-18-2004, 08:03 PM	#9
DBLSPRT68 Registered User Join Date: Nov 2000 Location: Ft. Mill, SC USA Posts: 931	Thanks everyone for their reply . I've been working a lot of overtime and it's rained when I wasn't working. (My truck is outside). I looked at my POS 305 I pulled from my 83. It has the switch located above the oil filter, The cab has the wire going to it. The engine in my truck now is an 85 HD 350. It has a plug where I need to put my switch. As soon as I get time, I will swap that switch onto my engine and hook everything up. It should work! Many thanks! I'm sure glad I didn't cut that wire! . David __________________ PROJECT TRUCK: 1985 SWB C10 Silverado Black/Charcoal, 1990 V2500 Suburban, 2018 Suburban, 2005 GMC 2500HD CCSB, 2014 Toyota Camry SE, HAD.....1968 Camaro RS/SS Family owned since new; 350 3 speed SOLD

10-19-2004, 01:21 AM	#10
ElGracho Gentleman Jim Driver Join Date: Nov 2002 Location: Poulsbo, WA Posts: 1,550	You will definately want to replace the switch, but until then you can jumper across the two sockets in that plug to make your choke work. __________________ Joe '75 GMC Gentleman Jim '84 Chev C10 Short Wide - Super duper plain (manual steering, manual brakes, no dome light, no cig lighter) '85 Chev C10 Short Wide - Super plain Vortec 4.8 4L60E trans also: '81 K30, '83 C30 Crew Dually, '84 M1028 CUCV, '85 M1009 CUCV, another '85 C10 SWB, '89 R3500 Flatbed

10-19-2004, 07:35 PM	#11
69 air cab Registered User Join Date: Oct 2003 Location: Maryville, TN Posts: 477	This thread has also helped me so I too thank everyone. When I changed out my 305 with a new 350 I somehow plugged the tranny wire into the oil pressure connection. Both look just a like until you look at the number of wires going into the plug............3 on the one that goes to the oil pressure and 2 on the tranny plug. Now I am wondering what the tranny plug does..........ha. THanks to all



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