Dying in drive when warm, and choke woes...

Hey guys, got one for you.

This weekend, I am tinkering with the Skylark. I rebuilt the carb, but had a mystery tube left over that I didn't have to begin with, so on to carb #2.

With the old carb and the new carb, I have the same basic issue. The one common denominator here is the disconnected cold choke (well type in intake manifold).

When the car is cold, it runs fine. So yesterday, I am driving the car for a shakedown run, and it is fine. It gets to normal operating temperature, and the idle is super high when I get to a stop. I have to just about heel-toe when I come to a stop as well, which might be a float issue on this carb (numbers say a '74 Chevy with auto trans- my carb is a '73). So, I turn the idle down. I run to the store with it. The thing dies as I coast in to the parking lot. No biggie.

I do my business, and go to start it up, and the thing runs super low (like 100-200 rpm...Seriously!), and when I give it gas, it chokes out (possible secondary linkage adjustment issue?). I let it set a few minutes, and viola, it starts with some gentle right foot coaxing. It runs super rough from idle to about 1200 rpm. I drop it in gear, and it barks the tires, and dies. My dad came with his truck and chain yesterday, and we sat in the parking lot playing with this thing. He said he didn't see fuel dump into the primaries. This carb has a good accelerator pump, and I redneck rigged the fuel line (remember, the '73 Buick carb has a center fuel inlet, the '74 Chevy's is cocked to the passenger's side), by cutting the metal fuel line and splicing rubber fuel lines to accomodate the different fuel inlets. So my guess is a.) fuel evaporating, or b.) fuel pump taking a dump. So the disconnected choke is the high idle issue.

Other points of interest, the ignition dwell and timing are good. Plugs and wires are also good, so we can rule out ignition. The '74 has a 3/8" NPT fitting on the back of the carb where the nipple for the EGR valve is on the '73 carb. I put a brass plug in it as well, but like I say, the '73 carb was exhibiting similar behavior as well..

So, that's the news with my bomber buick this week. I got the headlights working (relays from starter were melted) ou:, now this carb issue is keeping the car from going to Gulfport with me this week. Arrgh...

I am taking the '73 carb with me to G'port to finish rebuilding. I can't for the life of me figure out where this brass tube came from. It is about 1/16 in diameter by an inch or so. My guess is that it is a sleeve insert on a passageway. It is too small to fit around a metering rod. I was nutso focused on this carb when I was rebuilding it, I mean, Mr. Myagi Zen with dental tools, and I was shocked as hell when I had parts left over. This is my first rebuild, so its a learning curve. The part wasn't on the instruction sheet, and every diagram I could google didn't have that damn thing listed...Arrgh!

Any words of wisdom for setting float hieght? I didn't touch it at all when I was rebuilding this thing...
KFD

 

1. Sounds like you've got problems with the fast idle cam. The fast idle cam should be disengaged from the fast idle screw when the engine is warm--choke fully open. Curb idle is set with the screw (and solenoid, if used) combination on the left side of the carb; fast idle is set with the screw on the right side of the carb. First Guess: The choke is not being held fully open, and if the choke blade is partially shut, the fast idle cam engages.

2. Post a photo of your "mystery tube". I can't think of any brass tube in a Q-jet that'd only be an inch long. Sure it isn't a broken section; and the rest is still inside?

 

I believe that the tube is a feed tube, for either the off idle or the idle ciecuit. If you remove the air horn, I believbe that the situation will self-solve, as you will see where the missing tube goes. I would start there. Find the position of the extra tube. Ray