Electric choke wiring

[Norwester]

On my '86, the PO installed a 350. While he did what looks to be a reasonable job, I'm still finding issues and am trying to clean them up.

I've been trying to adjust the choke on my Edelbrock 1406 with no success. Today I put a meter on it and found no voltage going to the choke.

I traced the wire and it eventually ends up somewhere in the dash. Choke light maybe? Regarding the light....it comes on when I'm cranking and then immediately goes out upon starting, regardless of outside temperature.

I found another thread about the choke wiring and it says the wire should be attached to the oil pressure switch. I have a mechanical oil pressure gauge and I found where it attaches to the engine and right beside it, there was what I believe to be the switch.

The problem is that it is so buried back there behind the distributor, I have no idea how I'd get in there to splice it in.

Being inherently lazy, I'm looking at what might be a better choice for switched 12V.

I've read where people have spliced into the wiper wiring. I put the meter on the wiper wiring and found all three wires registering 11.8V. This was the harness going into the motor. The colors were white, gray, and purple. None registered hot with the key off.

Would this be a good way to go? If so, does it matter which color wire I use?

If it's imperative to use the oil pressure switch, any hints as to how to get back in there? I'm an old fart and my body doesn't twist and turn as it might have 40 years ago.

I do appreciate any ideas you folks may have.....and MERRY CHRISTMAS!

 

[Quadrajet Power]

Any key on power source would work. Don't use ignition wiring though. Best would be to use the fuse block if you can.

 

[Norwester]

Any key on power source would work. Don't use ignition wiring though. Best would be to use the fuse block if you can.

I very much appreciate the advice. Thank you

 

[chengny]

If your choke light goes out as soon as the engine fires (and 10 psi of oil pressure is established), it is probably safe to assume a couple of things:

1. That the oil pressure switch is working (i.e. contacts are closing as designed) and

2. It is wired correctly - at least to the dash/choke lamp

The choke warning lamp receives power (as do all the other gauges and warning lamps like oil pressure, coolant temp, brake warning, fuel tank, voltage, etc.) from the 20 amp fuse in the slot labeled Gauge/Idle. It is supplied via a common PNK/BLK lead.

The choke warning light has one major difference, its other leg is not wired directly to ground - as is normal with most lamps. The other leg can be either a ground or an opposing power supply - depending on whether the oil pressure switch is back feeding to the lamp, or supplying power to the choke heater coil.

Power to the oil pressure switch is from the 20 amp CHOKE fuse on a pink/white lead.

The other side of the pressure switch has two leads coming out. One (a light blue) runs around the back of the distributor and is plugged into the heater coil. The other (a dark blue) heads back through the firewall and is connected to one side of the choke lamp.

The harness plug is misleading. It appears that it should connect to a 3 prong switch, but the DK BLU and LT BLU are spliced within the casing:

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The power supply to the choke heater coil is simply spliced onto the lead that runs back to the IP - from the switch - and controls choke light operation.

When the switch sees oil pressure, its contacts close - and both the BLU leads become hot. Consequently, the choke heater begins to assist in opening the choke plates and in addition the warning lamp in the IP goes out.

This is due to the fact that - with 12 VDC now being applied to both legs of the lamp - there exists no net flow of electrons through the filament.

I don't know how interested you are, but the wiring diagrams below explain what I mean.

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I hate to see the choke light wiring changed because - when lit, with the engine running - it is actually a visual indication that oil pressure is dangerously low (below 10 psi).

 

[Norwester]

If your choke light goes out as soon as the engine fires (and 10 psi of oil pressure is established), it is probably safe to assume a couple of things:

1. That the oil pressure switch is working (i.e. contacts are closing as designed) and

2. It is wired correctly - at least to the dash/choke lamp

The choke warning lamp receives power (as do all the other gauges and warning lamps like oil pressure, coolant temp, brake warning, fuel tank, voltage, etc.) from the 20 amp fuse in the slot labeled Gauge/Idle. It is supplied via a common PNK/BLK lead.

The choke warning light has one major difference, its other leg is not wired directly to ground - as is normal with most lamps. The other leg can be either a ground or an opposing power supply - depending on whether the oil pressure switch is back feeding to the lamp, or supplying power to the choke heater coil.

Power to the oil pressure switch is from the 20 amp CHOKE fuse on a pink/white lead.

The other side of the pressure switch has two leads coming out. One (a light blue) runs around the back of the distributor and is plugged into the heater coil. The other (a dark blue) heads back through the firewall and is connected to one side of the choke lamp.

The harness plug is misleading. It appears that it should connect to a 3 prong switch, but the DK BLU and LT BLU are spliced within the casing:

You must be registered for see images attach

You must be registered for see images attach

The power supply to the choke heater coil is simply spliced onto the lead that runs back to the IP - from the switch - and controls choke light operation.

When the switch sees oil pressure, its contacts close - and both the BLU leads become hot. Consequently, the choke heater begins to assist in opening the choke plates and in addition the warning lamp in the IP goes out.

This is due to the fact that - with 12 VDC now being applied to both legs of the lamp - there exists no net flow of electrons through the filament.

I don't know how interested you are, but the wiring diagrams below explain what I mean.

You must be registered for see images attach

You must be registered for see images attach

You must be registered for see images attach

I hate to see the choke light wiring changed because - when lit, with the engine running - it is actually a visual indication that oil pressure is dangerously low (below 10 psi).

As always, you're a wealth of good info. It sounds like I need to tap into that lt blue wire. I'll have a look and see if I can do that. Thanks for the reply.

 

[Juan Torres]

I know this is an old thread but just like me there has to be someone out there stuck on this problem. I have a 1984 c10 with the quadrajet electric choke. I understand how tutt his work but am having problems finding the right harness " pigtail connector " that goes into the oil pressure switch. The one with blue,light blue and pink. The oil pressure switch has two prongs and all the two prong connectors at parts stores only have two wires coming out of them. I dont have the idot light in cab either. Do I connect both blue wires to one side of pigtail and run the pink to other? Or only pink on one side and choke to the other side. Or do I need to find a connector with three wires the problem with that is all the three wires connectors have three prongs and my sensor only has 2. Been searching with no luck on the web alot of connectors you cant see the inside to know if it 2 or three prong.

 

[75gmck25]

The purpose for using the oil pressure sender for choke power is so the choke is not powered unless the engine is running. You could leave the key switch on but it would not provide power to the choke until you start the engine.

My ‘75 truck has a hot air choke and I installed an electric choke kit on my Quadrajet. I used the power lead to the relay for my dual batteries, but could have use power to the wipers instead (as many have done). The disadvantage is that it’s alway powered when the key is on, so you have current draw and the choke goes further open.

My point is that any key-on power lead will work, so don’t get too concerned looking everywhere for the proper terminals. As long as your oil pressure gauge works, and your choke works your don’t have any major issues.

I think you only need a two wire connector on the switch because you only have one lead with power in and one with power out. The power out wire is spliced/split into power feeds to the dash light and to the choke.

 

[Juan Torres]

Thanks I will buy the 2 wire harness run my pink wire " hot on key turn" to one side. Tie both blue wires to other side of connector wire. One to choke one to dash.

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