enbay1 Posted September 13, 2017 Report Share Posted September 13, 2017 Hello, I've got an issue causing hard cold starts. I don't think my choke is engaging all the way. If I manually choke it while starting it (using two people, or a stick, or something) it always starts right up. The fast idle cam works, but maybe the spring on the fast idle cam doesn't seem strong enough to move the choke back up after sitting for a while. The choke does disengage all the way after warming up. Here's a video of the choke going from open to closed when the throttle is goosed, and what the free-play looks like. As always, thank you for your time. Video. 1 Quote Link to comment
datzenmike Posted September 13, 2017 Report Share Posted September 13, 2017 Depends on the year but earlier ones had 3 screws around the outer black plastic housing. Loosen and turn counter clockwise to set richer. The later 720s the choke was set and not adjustable. I think this one below was sealed. But... There was a tab that locked the black plastic choke housing from turning. I just ground the tab away and made it adjustable.... 1 Quote Link to comment
enbay1 Posted September 13, 2017 Author Report Share Posted September 13, 2017 Mine has the rivets. How possible is it to do this on the truck? Is there any merit to my spring hypothesis? It seems like if the little rotary spring on the shaft with the fast idle cam pressed up harder it would lift the choke into position. 1 Quote Link to comment
datzenmike Posted September 13, 2017 Report Share Posted September 13, 2017 The choke is controlled solely by a bi-metallic spring under that black cover. When cold it contracts and will pull the choke plate closed. There is an electric heater under it that warms the spring when the engine is running and it unwinds opening the choke. The fast idle cam is pulled up into position by a linkage connected to the choke plate. When the choke opens the fast idle cam is free to drop down out of the way by it's own weight. The electric heater is timed (about 8 min) to open the choke as fast as the engine warms up. It's efficient, fool proof and saves gas over the manual type. 1 Quote Link to comment
enbay1 Posted September 13, 2017 Author Report Share Posted September 13, 2017 What's the best procedure for drilling out, filing off, and adjusting without having spring-a-ma-things go places I don't want them to? I think this is my only option. 1 Quote Link to comment
datzenmike Posted September 13, 2017 Report Share Posted September 13, 2017 The 'spring is mounted inside that black cover. It has a hook shape that has to be hooked over the choke plate arm as it is put in place, then turned left or right to set the amount. If the choke is the kind that can't be adjusted you will find a small obstruction on the case. Just grind it away so the cover can be turned. 1 Quote Link to comment
bottomwatcher Posted September 14, 2017 Report Share Posted September 14, 2017 Before going crazy with all of that try cleaning up the shaft and pivot points. Carbs get gummy with varnish and deposits. Everthing works just sounds like the spring may be having an issue with friction. I may be wrong, but cleaning never hurts 1 Quote Link to comment
datzenmike Posted September 14, 2017 Report Share Posted September 14, 2017 True. I use WD-40 and spray anything that moves and then move everything through it's full range of motion. 1 Quote Link to comment
enbay1 Posted September 15, 2017 Author Report Share Posted September 15, 2017 I took out the two rivets and the phillips screw on the bottom, filed off the tab, and adjusted the choke. The inside of the spring housing was filled with what I can only describe as carbon deposits. Black, crusty, horrible stuff. I had previously cleaned and lubed everything THOROUGHLY. Based on one start-warmup cycle I can say the choke works now! 1 Quote Link to comment
racerx Posted September 15, 2017 Report Share Posted September 15, 2017 That's a good feeling isn't it when u fixed it. 1 Quote Link to comment
enbay1 Posted September 15, 2017 Author Report Share Posted September 15, 2017 Now if I can fix my throttle issue I can actually drive the silly thing. Quote Link to comment
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