How many cranks to start engine from cold is normal?

[v8lee]

Owned my 1981 C3 since Feb this year. It's totally as it left the factory nearly 40 years ago! Rochester carb I think, 27k miles. Ever since I've owned car, it always takes about 10 cranks on the starter before engine fires into life and then runs perfectly on choke, until i blip the throttle to knock thr revs down a touch. To start car from cold and wet the choke, i depress the pedal slowly down once, then slowly release, all sets no problem...i can hear the click as the choke sets. The question is... is 10 or so kranks a normal amount to start engine from stone cold? One started it runs perfect, and once started will fire up on the button. I have previously owner a 75 and a 78 Pace Car and both fired up on the button from cold.
I have tried all other combinations for starting procedures..but most will make the starting even worse, so have stuck to correct operating manual procedure.
So, any ideas anyone?
Lee.

 

[v8lee]

Was thinking... maybe throttle position sensor ?

 

[Roscobbc]

My experience with C3's is (unless in regularly daily use) this can be a fairly typical scenario with the mechanical fuel pump simply needing the engine to turn a number of times to get fuel in to the carb.

 

[Daytona Vette]

Think of it as a benefit, you are getting the oil circulating before it fires up

 

[antijam]

There should be a check valve in the Quadrajet filter - if fitted the right way round! - to prevent fuel drain back. If it's not there or miss-fitted that could be a problem. Another common Quadrajet problem is the fuel bowl well plugs leaking allowing the fuel level to drop below the accelerator pump inlet.

That said, my C3 has a fully overhauled Quadrajet but if left for a few days it takes a lot of cranking to start. Starting the next day is instantaneous.

 

[RobsVette]

My 81 generally needs only 3 or 4 to start up even after a long stand, mind you it's an Edelbrock carb so whether that makes a difference?
Just in passing have you seen the 1981 Owners Group on FB? Loads of info there for our one year model

 

[Adriana1]

I have a 383 stroker engined car with a 950cfm double pumper carb- no choke- 2 pumps of the throttle and starts immediately
I do have the MSD electronic ignition so probably a bit more spark than normal cars

 

[v8lee]

Thanks everyone for your ideas! I will order up a new fuel filter with the check valve and new spring etc.. from Corvette Kingdom, I need a few other bits n pieces anyway. Will let you know how I got on.

 

[v8lee]

Update... Correctly fitted the new fuel filter into carb. There seems to be no difference, still takes 8 to 10 cranks of the starter motor from cold before engine starts. Anymore ideas anyone? I was thinking TPS throttle positioning sensor?

 

[Jimbo64]

My 72 SB 350 Auto, initially had it's standard Rochester carb, but on her inaugural drive home, carb failed and took the advice of others to fit a new Edelbrock 600 with electric choke. With two pumps of accelerator, she would start from cold, after 3/4 cranks. Have now fitted Pertronix electronic ignition and more powerful coil and after same two pumps, starts from cold, after 1/2 cranks.
After a short warm up, she will start straight off key, without any use of accelerator. Well happy ☺

 

[Sea5]

The 1981 C3 was the only model year to have the L81 engine fitted to all corvettes. The unique feature of this years' production was to include the "CCC - Computer Command Control" (first used in 1980 corvettes only sold in California ). This was GM's answer to pollution issues.This simple ECU technology has mophed into very complex computer management systems we see in all cars today. The original Rochester carb has 2 sensors which feed readings to the CCC. There is a module in the distributor that also tells the CCC timing info.
v8lee, your C3 is probably a rare example as you say it is 'original'. After nearly 40 years of use I suggest that most 1981's have been modified/upgraded. To my knowledge (limited!) most owners ditched the CCC system and the standard carb and put on a Holley, Edelbrock or maybe a Rochester carb from a GM truck!
I also have an '81 but it is not like yours or any other I am aware of. It is unusual because it has been highly modified - cam, roller rockers, SS headers and exhaust, MSD high energy distributor etc BUT it still uses the CCC and Rochester carb (with sensors). I also have 3 spare carbs (long storey, don't ask!) The car starts first time. I hadn't used it for over 6 months but it fired up on the button, first time.
So most of us cannot compare like with like but I would suggest you invest in a workshop manual or ditch the CCC system completely and modify it. Good luck.

 

[CaptainK]

Bit late to the scene here, but my 1968 with Edelbrock car and intake takes a fair few turning over before it starts. But I put it down to it hardly being used and thus sat there for a while between uses - and the mech pump has to pump fuel to it.

If I use it on a consecutive day or start it again later on in the same day then it starts first time.