pchalpin

Hello All:

The basics: '67 406 CI SB, Rebuilt Holley 3310-2, Pertronix


Last October car ran fine to a cruise night. Stayed about a half hour, when I decided to leave, car would not start. Engine was still pretty warm at this point. It Cranked fine, had gas flowing, checked for spark (which was there but not super strong) but would not fire. After a half hour of off and on checking stuff, more cranking and not firing, I gave up and took the next hour off.

Engine had cooled significantly by this time. I decided to try it again to see if I could get home. Got back in the car after the hour, and turned the key. It fired up instantly. I mean instantly. Ran great all the way home. I put the car away for the winter at that point.

Took the car out yesterday for a Spring test run and it was great. Started great, ran great, re-started great several times, no issues at all.

Went out again this morning. It started instantly. Stopped to get a coffee, it stated instantly again. Stopped at a friends to drink the coffees for about 45 minutes.

Went to leave, no start. Cranked like crazy, gas flowed, but would not fire. Engine was still warm at this point.

So we took his car to a show and after 4 hours got back to his house. My engine was good and cold by then and I decided to give mine one more try. Turned the key, it fired instantly, and, again, I mean instantly. And this thing runs really great once it starts.

It starts instantly when the motor is cold, and always has. It won't re-start when the motor is warm without essentially totally cooling down. This is new.

Where do I start?

Thanks Guys and Girls

Peter

Frankie the Fink

Sounds like classic 'heat soak' to me...with the car off for a while the underhood temperature rises and the gas may flow...but it percolates inside the carb resulting in a 'no-start' until everything cools down.

pchalpin

Thanks for your reply.

I do have a Holley heat shield under the carb cause I thought I had that problem three years ago. Had no problems even when it was 90 degrees after I installed the shield.

Also, that October day it was 40 degrees, and today it was 50 degrees, both days with zero humidity. And I had the carb rebuilt last November after I put the car away for the winter. Could under the hood really get that hot with those weather conditions? I have no clue.

But, and I'm hoping you are correct, since I already have the heat shield installed, what else can I do? Edelbrock?

Thanks again.

Peter

Frankie the Fink

I'm in unknown territory on a C2, and those ambient temps sound pretty low to have the sort of problem you describe....but the giveaway is how easy the car starts after sitting long enough to cool off. So the heat soak diagnosis still makes sense....although the weak spark could indicate an intermittent electrical issue.

A big problem is that modern gas has a lower boiling point...have you changed brands recently ? Do you have an exhaust heat riser and have you made sure it's not stuck shut ?

Bill Irwin

Think above posters are climbing the wrong tree with this one.
Look toward coil. That's what they do when going down and are hot. Bill.

Frankie the Fink

Good point - I didn't rule out electronics as I posted above. A quick check would be carrying a known good coil and doing a quick swap when the hard starting occurs...that should nail it one way or another.

62Jeff

pchalpin

Thank you all for your input. I just ordered a coil. Ecklers has them on sale for $15. Can't go wrong for that price!!!

66since71

We get used to newer fuel injection cars and forget the starting procedure for these old (carburated) cars.. I had the same problem last year and a friend in our local Corvette club reminded me to hold the throttle full open/pedal to the floor when the engine is hot. Fired right up every time thereafter. It's worth a try, before you start buying lots of new parts...

Harry

Kensmith

Or flood the carb if it doesn't start?

midyearvette

...also check that the 12v boost wire is connected to the starter solenoid ( left lug facing the starter) and the coil....

edb7

Hello,

I had this issue on my 1969 Camaro once upon a time. My money is on an issue with the starter solenoid. Check the ground on the starter and add some heat shield. You can buy the solenoid seperate from the starter, by the way. Good luck,

Ed

Godholio

It's just a jet of fuel, not a steady flow...that's what pumping the pedal will get you. Ahh, my first attempt at starting a carbed car...

pchalpin

Didn't mention this earlier because I did not think it was relevant. After the October problem, while it was put away for the winter, I replaced the flywheel ( had a couple of bad teeth on the ring gear) and the starter (those bad teeth didn't do the starter much good) with new, not rebuilt. So I'm pretty much ruling out any starter issue. Also, it cranks like a dream with that full set of teeth, just won't ignite when warm.

I'm going to put the new coil in, and hope for the best. The existing coil is original to the car, so I thinking my problem was the dying coil.

Thanks for all of your ideas.

Peter

wombvette

Classic Holley-itis.

Kerrmudgeon

Pick up a can of quickstart (ether) and the next time it won't start, put just a puff of it down the carb and try it again, that will tell you if it's a fuel delivery problem. Sounds to me more like a weak spark problem. If the coil is on it's way out, when it's hot it won't put out peak power. Just an idea....good luck!

John BX NY

I had the same exact problem with my 67 SB. Turned out to be a fuel percolation issue that went away when I wired the heat riser valve in the open position...........

Allcoupedup

Isn't cranking with carb WOT the way to reverse flooding? The cranking vacuum isn't enough to pull fuel from the main circuits so the A/F mixture should be mostly air causing fuel sitting in the manifold to evaporate.

Brian

64tux

i've had the same problem with daily driver a had a couple years ago. kept changing things. still wouldn't start when hot. finally figured out the starter was getting too hot and wouldn't start till it cooled off. put a shield between starter and exhaust and no problem!!

66since71

Actually, yes. Cranking it hot with WOT, presumes the pump shot will ignite or that there has been some fuel expansion out of the carb onto the floor of the mainfold. If it fires, then the engine starts to make some vacuum.

I know if you look down the venturis on mine when its hot, fuel is dribbling out of them. I have always presumed that's a percolation effect. Anyway, its probably closer to flooded than not in that case.

The 66 owners manual actually calls for 1/2 throttle for hot starts (more vacuum), and full for flooded. I just took my friend's advise, used full throttle and it works!

Harry