Tele_Man

Can't seem to get my 427 to start from cold. The battery is new and I've also replaced the plugs. Sometimes I can eventually coax it to start, and then it runs fine. If I shut it down after driving for a while, it starts again with no trouble. I'd appreciate any ideas you might have to help me troubleshoot the root cause. Thanks. :confused:

PRNDL

The 2 obvious things to check are, 1) Your choke - only reason it exists is to start the engine when cold, and 2) Carb could be leaking gas so on cold starts there is no gas in carb. Try pumping the gas several times before cold start. (I used to pump 5 full times before cold start w/o flooding carb). MJ

Tele_Man

I've tried pumping the gas pedal a few times and that doesn't seem to help. I'd like to check the choke as you suggested. How can I check it for proper operation? Thanks for your help.
:seeya

Corey_68

An ignition box such as a MSD or a Crane would also help.

:cheers:

mandm1200

It could also be the accerator pump in the carburator. It takes a lot richer mixture to fire a cold engine on a cold day. Yes the choke is a must to keep the mixture rich after it fires up, but you said it did not even start. Take off the air cleaner and make sure the choke plate is open. Have someone else press on the accelerator pedal while you look down the throat of the carb. You should see gas squirting in. Do the above WITH THE VETTE TURNED OFF. Another symptom of a bad accerator pump on a carb is that it will bog down for a split second as you mash the throttle wihile driving, but with a BB you may not notice it as much with all the power you got.

Another thing you can try to do if it won't start is to dump a cap of gas down the carb before trying to start it. By a cap of gas I am referring to a 1/4 ounce to maybe 1/2 ounce. If it starts up, then you know that it is not getting gas as you pump the pedal.
Hope this helps in narrowing down your problem.

You could probably eliminat the choke as the culprit. You don't need a choke to start the engine. As stated before, the choke is needed to keep it running until the engine is warm. I ran a 425hp 350ci without a choke in PA and never had a problem starting it on the coldest day. Of course I had to stay in the car to give it some throttle so it would stall out, but it started up right away with only a few pump of the pedal. As for ignition, sure it wouldn't hurt to upgrade that, but chances are it won't fix the problem either.

I always look at it this way. If you got Air/fuel, spark, and compression; it will fire. If it doesn't fire, then it most likey is Air/fuel, or spark. Since it starts fine after it is warm, you are probably fine in the spark area and it is the Air/fuel causing the issue.

Mike


[Modified by mandm1200, 8:57 PM 3/13/2004]


[Modified by mandm1200, 9:08 PM 3/13/2004]

Tele_Man

The Q-Jet that I'm running was just installed last May. It's a rebuilt unit and the choke coil was also replaced. I don't put a lot of miles on this car. What are the chances that the accelerator pump in the Q-Jet has already gone bad?

Regarding your suggestion to put a cap of gas in the carb, I assume you mean down the primary barrels. Right?

mandm1200

It would be rare for the accelerator pump to be bad if the carb wasn't rebuilt. It should not matter much is you dump the gas in the primary or secondary. Either way it will hit the bottom of the intake and once the engine is cranked it will be picked up by the incoming air. I would give it closer to the 1/2 ounce due to the large displacement of the engine. But it would still be best to see if the carb is squirting gas when the pedal is depressed.

I should have mentioned in the earlier post, you can move the throttle yourself while checking to see if the pump is squirting.


[Modified by mandm1200, 10:27 PM 3/13/2004]

Tele_Man

Eureka - she started!!! I took your suggestion to pump some gas into the carb by moving the throttle arm by the carb. I opened the "butterfly" to see the gas spitting into the primary barrels. By the way, the gas spitting little squirts in the barrles. Not really long squirts. Is that the way it's supposed to work.

I had to squirt about 10 pumps into the carb and then it fired up for me.

So, I think, with your help, I solved the mystery, but is is normal to have to pump the acclerator so many times to squirt enough fuel to start the car?

Thanks for all your help. Very much appreciated. Enjoy the rest of your weekend!

:steering:

geezer

It sounds like you acc pump is bad or the pump lever is installed wrong. The rod that is attached to the acc. pump lever should be in the hole the closest to the acc. pump rod. This will give you more travel of the acc. pump and a longer shot of fuel.
Also the way a Q-jet works at cold stat is you give it about three pumps and then keep your foot OFF the gas! The choke plate should now be completely shut and the fast idle cam will be set. When you crank the engine the vacuum below the choke plate will pull fuel out of the float bowl through the primary nozzles and walah the beast is alive!
Things to check:
1) Engine off, air filter off. Pump gas once, choke plate should slam shut. If not figure out why and fix it.
2) Engine running, up to operating temp. Choke should be wide open. If not adjust choke setting but do not over adjust or it may not close at cold start up.
P.S. Be prepared to have two choke settings, one for spring and fall and one for summer. My '69 BB did and this and this was probably normal for the car. Remember we are now spoiled by EFI in our daily drivers and don't have to do this "normal" stuff anymore!


[Modified by geezer, 11:24 PM 3/13/2004]

73 LS-4

If you have a properly set up quadrajet you should be able to get it to fire without even touching the accelerator pump. I tap my gas pedal just enough to hear the choke snap shut and then turn the key and it will fire every time without ever touching the gas pedal. As others have mentioned quads have a tendency to leak causing thier main wells to go dry while sitting for a long period of time, espeicially noticeable if it's hard to start overnight but not hard to start an hour or two later even on a cool engine.

:cheers:
Pat Kunz

Tele_Man

Thanks for your tips.

Forgive my ignorance, but where can I find a detailed diagram of my model of Q-Jet? I vaguely understand your instructions, and I'm afraid to start tinkering with the wrong gizmo on that carb. It looks very complicated. My engine is the L-36; 427ci, 390hp. Are there any good instruction manuals out there somewhere?

geezer

Hey Tele_Man you're only about an hour or so away! Your car is the same one that I had, '69 -L36-390 h.p, so I know it like the back of my socket wrench. I sold it but I know I've got some diagrams around here that I could scan and send to you in Adobe Acrobat format (.pdf). If that doesn't work I could maybe make a house call!
Send me an IM with your e-mail and I'll get the info together along with a more detailed MS Word file of instructions.