85 K10 Choke

[crysalis]

Hello all! First post. I have an 85 K10 with an Edelbrock 1406 on a 350 and trying to figure out what PO did. Many strange things have been uncovered, but current task is the electric choke.

Truck does not start very easy. When cold, it will fire off immediately and die as fast as it starts. Then after 10-15 seconds of starter, it will eventually fire off and idle. When I bought it, the electric choke was half-way hooked up with the ground leg disconnected (almost everything electrical was disconnected). I hooked the ground back up and fixed the choke mechanism. As seen in pics, the light blue (now green) coming from oil pressure switch is spliced with the Pink/Black (circuit 39?). Choke is getting 7-8v with key on.

Now, the choke light in instrument cluster stays on when the truck is running. I understand the dark blue wire from pressure switch goes back to gauge to complete a circuit. If oil pressure good, then both sides of choke lamp get 12v and light goes off. I'm guessing my oil pressure switch may be bad, but I'm more concerned about the pink/black wire connected with light blue wire at the choke heater. Isn't this just bypassing the oil pressure switch, making the choke heat BEFORE engine start? Should I disconnect pink/black?

 

[Ricko1966]

You need to check, do you have 12v to the O P switch? Do you have continuity on the OP switch with the engine running. If so plug the O p. switch back in and disconnect the mystery wire. You should have 12v to the choke positive,double check. If all those don't pass post back so we can dig deeper and figure out why not. You want to check continuity at the switch, not for power on both terminals. You could check for power on both sides if you can provide power to one side but leave the other side disconnected from everything. Otherwise backfeed could give you false readings.

 

[Jgonick]

I have an 85 K10 with an Edelbrock 1406 on a 350

Exact same setup I have.

Now, the choke light in instrument cluster stays on when the truck is running. I understand the dark blue wire from pressure switch goes back to gauge to complete a circuit. If oil pressure good, then both sides of choke lamp get 12v and light goes off. I'm guessing my oil pressure switch may be bad, but I'm more concerned about the pink/black wire connected with light blue wire at the choke heater. Isn't this just bypassing the oil pressure switch

Sounds like you understand how it is suppose to work. See attachment.

Follow @Ricko1966 advice.

Once you confirm the oil pressure switch is good and 12V at choke don't forget to adjust the electric choke itself (might have to tweak fast idle- but thats later).

 

[crysalis]

Sorry for the delay. I don't get too much time to work on the truck during the week. Thanks for the input!

Disconnected oil pressure switch and put a meter on it. Started up the truck and got 0.1 ohms, and eventually open circuit, so I'll be getting a replacement pressure switch shortly. Once that is in place and assumed good, I should have 12v at the carb and can remove pink/black. When I started it today, I only had 3-4v at the heater so that choke isn't gonna open anytime soon.

EDIT: Any preference on brand of the pressure switch?

 

[crysalis]

Thanks for the help fellas! New switch installed. Choke light is out and 14v at the choke. Opening like it should now.

For anyone in the future, I used Duralast PS115 and was 1/4” thread. Added a layer of pipe thread tape.

I used a Lisle 13250 1-1/16” sensor socket and an 11” ratchet. Changed it in 5 minutes.