My 72 L-48 has become fairly difficult to start when attempting to fire the engine up after it's only been shut down for a little while (anywhere between a few minutes to a few hours). I'm running a Holley 670 with electric choke, for the record - the car generally starts up just fine after it's sat overnight or for a similarly long period of time; a few cranks and some pumping off the accelerator gets it started pretty well. I think it has died on me a couple times unless I put just a little pressure on the accelerator for a short while.

The real problem is when the engine is still warm - it rarely fires up on the first try. Most of the time, it will almost start, as in the tach jumps but then it immediately dies. It then takes me another four tries or so, combining just cranking and pumping the accelerator, to get it started, and then I also often have to put a little bit of pressure on the accelerator to keep it started. Any idea what's going on? I think I need to raise the idle just a little, as it was recently set 50rpm below where it was before (now at 700-750rpm) to try and combat a dieseling problem I had. I believe I had the same problem before that, however...help!

 

Carb flooding maybe?

 

It's what you might think, but in the end I generally have to pump the accelerator to get it started...

 

Could be engine heat boiling the fuel out of the carb bowls. I have experienced the same thing on a previous car and will be adding a heat shield under the carb soon.

 

But, flooding is so common with the Holley that you would still suspect it. You should try to start it by simply flooring it and not letting up until it starts. You probably will find it is flooding.

 

Hmm, that's a possibility, and would explain why the engine used to diesel a little (before the idle was reduced, anyway). The bowl levels were checked and they were pretty much right where they should be.

wombvette, thanks for the tip. I'll try that next time If just keeping the throttle all the way down does work, what can I do to prevent the flooding? Didn't know these Street Avengers were prone to that kind of problem...

 

The only logical reason the car won't start when it gets warm is the choke. The next time you have to start it when it's in that warm condition...I suspect it's like going to the supermarket for groceries which lets the car sit for about 30 min...open the hood and remove the air cleaner and inspect the choke. Also open the throttle a couple of times to work the accelerator pump and make sure fuel is squirting out. Your problem could be an accelerator pump leak so you won't see any squirts, but you will be able to smell gas in the manifold...I've seen cars with manifolds FULL of fuel...puddled under the carb from an accelerator pump leak...oddly enough they will still start up if you hold the choke and throttle plates wide open so I can drive it to the store for a carb rebuild kit...been there...done that...got the T-Shirt. If this is the case then you need to rebuild your carb.

If you don't see any fuel in the manifold and the choke is open and the accelerator pump is squirting fuel out then you can try to start the car while working the throttle and choke manually...If your arms are long enough...make sure car is in park/neutral with parking brake set...then crank the car over while operating the choke and/or throttle. You should be able to start the car warm with two pumps of the throttle (one for each bank of cylinders) then crank the engine with throttle at idle position and a slight amount of choke. You may need to crank the engine over 8 times if your cylinders are leaking the air/fuel mixture that was in them when you shut it off. If this is the case then you might need to inspect the valves.

 

You might want to check out this thread.

http://forums.corvetteforum.com/show....php?t=1455245

 

My Holley SA is an electric choke and I have no start issues. When cold I pump the petal two times and she starts right up. I pump once when warm. You may have two problems going on, cold start and warm start. If it were me, I'd first replace the fuel filter just to eliminate it from the equation. Next, check the cold start problem by ensuring the choke is completely closed when the engine is cold by simply removing the breather and seeing that the choke is fully closed. When you turn the key on the electric choke is opens fully within 2 minutes on mine.


I've had two Vettes and both had warm start issues related to vapor lock and solved them by simply buying some fuel line insulation and running it over the line between the carb and fuel pump.

 

Oh wow. I'd noticed that thread before, but at that time the reply from the Holley rep hadn't been posted. My date code is 3464, which falls right into the possible range. Hopefully this is the cause of my problems...