Electric Choke Power Source??

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

97350

Member
Joined
Sep 2, 2012
Posts
38
Reaction score
0
Location
Canada
First Name
Duane
Truck Year
1983
Truck Model
C1500
Engine Size
406
I just installed a 406 and a Demon carb in my 83 Chevy 1/2 ton.I cut the connector that went to the factory electric choke and connected it to my + on my Demon carb. I'm not getting 12v from the connection and my choke light is on.Isn't this wire supposed to have power all the time?Also how do I get the choke light to turn off?

The truck was originally a 305 ESC but when I got it all of the original drive train had been removed.

Any help will be appreciated.
 

chengny

Full Access Member
Joined
Feb 22, 2012
Posts
4,086
Reaction score
1,008
Location
NH
First Name
Jerry
Truck Year
1986
Truck Model
K3500
Engine Size
350/5.7
That choke light is actually a low oil pressure indication. I'm not saying you have low oil pressure but the power over to the choke must first pass through the oil pressure switch. The oil pressure "switch" is the one with two connections - not the one that has a single connection and looks like a bell. That is the pressure "sender" for your gauge.

When the engine is started and oil pressure is developed (about 10 psi) the contacts in the switch close and power is supplied to the choke heater via the light blue wire.

Why there is no power on the light blue - IDK. Check your fuse block, there should be a 20 amp fuse for the choke. Check for 12VDC coming into the switch on the pink/white wire. The dark blue goes back to the dash and powers the choke lamp.

If power is available at the pink/white into the switch, pull the connector off and check for continuity through the switch while the engine is running.

If there is no continuity across the switch, and you are sure that you have at least 10 psi oil pressure - change the switch.
 

83kid

Full Access Member
Joined
Apr 13, 2014
Posts
321
Reaction score
1
Location
Massachusettes
First Name
John
Truck Year
1983
Truck Model
k10
Engine Size
350
Nevermind, Chengy has everything about it in his post!
 

97350

Member
Joined
Sep 2, 2012
Posts
38
Reaction score
0
Location
Canada
First Name
Duane
Truck Year
1983
Truck Model
C1500
Engine Size
406
When I installed the engine I never connected a low oil pressure switch.Would this tee off the connection for the oil sending unit? Also am I correct to assume that the wires coming/going from this switch are pink/white?I'll definitely check it out.I'll also check the fuse.

The truck is/was completely original until the engine was removed by the previous owners.The stock 305 threw a rod in 1989 and it sat until I got it about a year a go. 89k on it.

Thanks
 

chengny

Full Access Member
Joined
Feb 22, 2012
Posts
4,086
Reaction score
1,008
Location
NH
First Name
Jerry
Truck Year
1986
Truck Model
K3500
Engine Size
350/5.7
When I installed the engine I never connected a low oil pressure switch.Would this tee off the connection for the oil sending unit?

No, the oil pressure sender only provides a variable resistance to ground for control of the oil pressure gauge on the dash. The choke heater is in series with the oil pressure switch, it is not connected at all to the oil pressure sender.

Also am I correct to assume that the wires coming/going from this switch are pink/white?I'll definitely check it out.I'll also check the fuse.

Read my first post carefully, the colors and functions of the leads connected to the oil pressure switch are described in detail.

You must be registered for see images attach
 

MadOgre

Full Access Member
Joined
May 4, 2014
Posts
4,090
Reaction score
49
Location
NA
First Name
NA
Truck Year
NA
Truck Model
NA
Engine Size
NA
When I installed the engine I never connected a low oil pressure switch.Would this tee off the connection for the oil sending unit?

No, the oil pressure sender only provides a variable resistance to ground for control of the oil pressure gauge on the dash. The choke heater is in series with the oil pressure switch, it is not connected at all to the oil pressure sender.

Also am I correct to assume that the wires coming/going from this switch are pink/white?I'll definitely check it out.I'll also check the fuse.

Read my first post carefully, the colors and functions of the leads connected to the oil pressure switch are described in detail.

You must be registered for see images attach

So could a guy run 12 v ignition from the fuse block run it through the 2 tab oil pressure switch and over to the electric choke for an after market carb. I assume so as the OP has a demon carb ?
 

350runner

Full Access Member
Joined
Feb 9, 2013
Posts
2,858
Reaction score
224
Location
tx
First Name
Ceasar
Truck Year
82
Truck Model
c10
Engine Size
350
That's what I do.
 

chengny

Full Access Member
Joined
Feb 22, 2012
Posts
4,086
Reaction score
1,008
Location
NH
First Name
Jerry
Truck Year
1986
Truck Model
K3500
Engine Size
350/5.7
Yeah, that's exactly the way it works as designed by GM.

One thing to be aware of however, Rochester designed the heating coil (used to drive the choke open) to be grounded through the choke heater body. Only a hot lead is required to operate the heater.

On the other hand, the coil used on many after market carburetors has no path to ground within the choke heater body. That's why they often have two tabs. One is for the hot lead and the other provides a connection point for an external ground wire. That ground wire can go to any convenient spot on the engine.
 

97350

Member
Joined
Sep 2, 2012
Posts
38
Reaction score
0
Location
Canada
First Name
Duane
Truck Year
1983
Truck Model
C1500
Engine Size
406
OK thanks again.I pulled the 20A fuse today at lunch and it was fine.I need to track down the wiring that went to the op switch and go from there.There are quite a few wires that aren't connected,leftover from the esc/knock sensor.I can run a new wire but I'd like to use as much factory stuff if I can.
 

chengny

Full Access Member
Joined
Feb 22, 2012
Posts
4,086
Reaction score
1,008
Location
NH
First Name
Jerry
Truck Year
1986
Truck Model
K3500
Engine Size
350/5.7
The pink/white and the dark blue will come out of the harness loom and lead over to driver's side. They should emerge from the split in the loom somewhere around the distributor.

You must be registered for see images attach


The light blue wire (the one that eventually connects to the choke heater) will be in the side of the loom that goes towards the passenger's side. That one should be easy to find. If you have to, just start splitting the loom open over near the carb - you'll find it. When you do, just trace it back to the other end - or pull it out and run a new one.

The pink/white can be fed from any IGN energized feed. You only want the circuit energized when the key is turned to RUN (the IGN bank on the fuse block is hot only when the key is in RUN).

You must be registered for see images attach
You must be registered for see images attach
 
Last edited:

97350

Member
Joined
Sep 2, 2012
Posts
38
Reaction score
0
Location
Canada
First Name
Duane
Truck Year
1983
Truck Model
C1500
Engine Size
406
I finally had some time to check it out and found the unused connector.I installed a jumper to turn the light off.Thanks for the advice.
 

Scott91370

Full Access Member
Joined
Apr 2, 2018
Posts
924
Reaction score
899
Location
Burleson, Tx
First Name
Scott
Truck Year
1985
Truck Model
Sierra1500
Engine Size
350
You must be registered for see images attach

I know this is an old thread but what wire, if any, plugs in to the left side of the 'bell' shaped thing right behind the distributor hole?
 

AuroraGirl

Full Access Member
Joined
Sep 8, 2019
Posts
9,127
Reaction score
6,040
Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
I know this is an old thread but what wire, if any, plugs in to the left side of the 'bell' shaped thing right behind the distributor hole?
Woah your engine has quite the collection of gizmos and it looks like your gasket on intake might have a small leak. Could be my eyes failing me. Best thing I did was new intake and removal of all extra nonesense on top the motor. Still working on getting it perfect, but its better.


On my carb, I, in a pinch, sent power from another switched ignition off another circuit for my choke. I chose to use the power wire for the wipers. I justified it because Im not on the road and my wipers need serious overhall, (including new connector), so potentially compromising power on that line wasnt a huge deal. It runs straight across the motor, in the way sometimes. Ill eventually put a power point in my bay to power other accessories, that pull from a relay and battery so im not putting power on those circuits. I decided to ground my choke right on the bracket for the alternator. If its good enough for the battery, its good enough for my choke. Didnt even need to drill a hole, had a couple pre drilled openings.
 

chengny

Full Access Member
Joined
Feb 22, 2012
Posts
4,086
Reaction score
1,008
Location
NH
First Name
Jerry
Truck Year
1986
Truck Model
K3500
Engine Size
350/5.7
I know this is an old thread but what wire, if any, plugs in to the left side of the 'bell' shaped thing right behind the distributor hole?

That's oil pressure sender. Only used when equipped with a gauge package. There is just one terminal - that a TAN wire connects to:

You must be registered for see images attach
 

Latest posts

Forum statistics

Threads
41,859
Posts
903,668
Members
33,372
Latest member
83elcowes
Top