Automatic choke issue on 85' C20 350 4bbl

6Sixathome · March 19, 2014

I bought an 85' C20 last night 2WD 350 4bbl. The truck will run great with the choke held open but as soon as you let the choke go it will close and dog out the engine, it's not going to full open when warm. It is the Quadrajet carb. The vacuum lines look OK as far as I can tell. Any tricks to get the choke to function correctly?

Also I noticed the reservoir for the rear brakes was empty so I put fluid in and worked the pedal but the fluid will not go in the lines so I can see where the leak is. Any ideas? Thanks.

txab · March 19, 2014

Check the choke pull-off servo. It's supposed to tug on the choke linkage to pull it open. Also make sure you have the choke spring set correctly and and adjusted. You need to find documentation showing how to set the choke adjustments and how to adjust the choke pull-off

6Sixathome · March 19, 2014

Will do, maybe a manual choke is an option? Is there a good place to hook up the cable on the choke from the cab?

grampadirt · March 20, 2014

This info is for an '86,'85 should be similar.

http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c1528004c521#hd1-1-5

Join up at Autozone,tons of info there

As for the reservoir issue maybe connect a vacuum hand pump to the bleeder fitting at the wheels and see if you can draw the fluid in? or maybe disconnect both ends of the brake line and shoot some compressed air through it?Be sure to have an empty bottle or can handy.

Lots of rags too

Could be plugged with rust if it's been sitting a while.

idahoruss · March 20, 2014

The choke pull-off should open the choke a small amount when the spring is cold. The choke spring is heated by pulling exhaust through it or by an electrical heater in the choke cap. If there is a wire terminal on the choke cap, check for power when it is running. If no terminal, check for a small metal pipe going from the intake manifold to the choke housing. The rubber coupling could be missing or the tube broken or plugged. Good luck.

6Sixathome · March 20, 2014

Thanks guys, we have a couple nice days coming so I'll probably work on it and see what's up. Here's a couple pics the day I brought it home. Not too bad for $600.00

grampadirt · March 20, 2014

Sounds like you got a pretty good deal.It's cost leaves some room to fix it up.I'd love to find a 4x4 like that

6Sixathome · March 23, 2014

Well I got looking at the electric choke on the Quadrajet and I want to install a manual choke but the electric choke cover is held on by rivots, do I drill the rivots out so the electic choke assembly will come off the carb and once it's off where is the best place to attach the manual choke cable? Thanks.

grampadirt · March 23, 2014

I've drilled 'em out in the past but only to remove the cover and clean inside and make sure the spring is attached to the linkage lever and re-assemble.Get self tapping screws to match the drill bit size.

As far as the mounting of the cable I don't know,never done it.

lynnamiller · December 10, 2019

My 1988 3500 truck with a 5.7 350 v8 engine started having starting problems when the weather turned cold this fall, and the "service engine soon" light was on despite a tune up and nothing found on the computer readout. I finally replaced the $17 engine coolant temperature sensor and now it starts right up in sub-freezing temperature and the "service engine soon" light went out. This engine does not have a choke at all, its computer just adjusts the gas/air mixture depending on the temperature of the coolant.