On my '71 LS5 I've got a new Rochester Quadrajet, new fuel pump and lines and old distributor with electronic ignition module in it. But I've got to crank the sucker over 7 or 8 times before she starts. When warm it starts on a dime, but when cold it's a bear to start the engine. I get good acceleration at speed and good response, so I know the acceleration pump in the carb is shooting fuel. Choke is in the closed postion at the front of the carb when cold, choke over the rear of the carb is open when cold, but I think that the rear is the secondaries right?

Steve

yes rear = secondaries

when your car does start "cold" is there any smoke??

this is fairly common.. not good but common..

you can have either fuel or oil slowly seeping into the cylinders..

in fact you need to check for smoke when this happens and the color of the smoke if any AND if the exhaust smells like unburnt fuel on a cold start.

|UPDATED|6/11/2004 1:07:30 AM (AZT)|/UPDATED|

And the air flap over the secondaries should be closed except when the car is warm and you have it floored, or close to it. It needs some attention. This may be part of your cold start problem.

kstyer said: And the air flap over the secondaries should be closed except when the car is warm and you have it floored, or close to it. It needs some attention. This may be part of your cold start problem.

i completely missed that when i read it..

damn insomnia.

Ben, happens to the best of them, and me too!

When you say, that the choke is closed when you try to start, is it completely closed, it should not be so when cranking, it should have .100 opening between the front of the air horn and the front of the choke butterfly to allow air into the engine, no air no start, have an assistant stick a flat tip screwdriver between the choke b.f. and air horn and see what happens, if it starts when cold it has to be adjusted, set the follower on the second step of the cam, bend the choke rod towards the top about 3/8" down from choke bellcrank to get adjustment

|UPDATED|6/11/2004 7:31:03 PM (AZT)|/UPDATED|

Thanks for the info guys. I don't see a lot of smoke after a cold start, but do smell some. Probably from all the pumping I'm doing on the accelerator pedal between cranks.

So then both flaps (big one over the primaries and smaller one over the secondaries) should be closed when the motor is cold? That's definitely not the case with the carb on my engine and my mechanic is a good one. Only the flap over the primaries is open, I'll check for some clearance between the flap and horn though. The rear flap is completely vertical. How do I adjust it so it's closed when cold? Is there a separate thermostat to control the position of the rear flap?

The old Rochester I have is sitting on a shelf and the rear flap on it is also completely open. Don't know if a carb that's off a motor is really worth comparing to though.

Steve

munkmunk said: The rear flap is completely vertical. How do I adjust it so it's closed when cold? Is there a separate thermostat to control the position of the rear flap? Steve

this is a question for KEN he is the quadrajunk king..

but im certain the secondary flap should be closed.

the action of opening is vacuum controlled.

i have three q-junks... one in service two in storage and all three have the flaps closed on secondary..

the only thing i can suggest is to make sure it isnt stuck.. follow the action of the linkage and make sure its all hooked up too..

The secondary butterflies that you speak of should be closed at all times except under wide open throttle at speed, you really have four secondary b.f.'s two at the trottle body at the base of the carb,and the two on top that are vertical at the top of the carb that should be closed, the job of the upper ones is to lift the secondary metering rods out of the secondary jets, it sounds like you might have a bent or hung up metering rod, the rods are held in place by the cam assy.held on by the small screw on top of the upper b.f.in the center, pull the screw and cam up with the rods and check, with the rods out the b.f.'s should close, PULL THE CARB and do it on the bench, if bent there is a number stamped on the rod, BUY NEW ONES, you'll never get them straight enough.

|UPDATED|6/12/2004 7:30:52 AM (AZT)|/UPDATED|