Inline 6 cold start issues

juuraslahti · Veteran Member

Inline 6 cold start issues

4SPEED427 · A Poncho Legend!

Next time it's cold, before you try starting it-

Remove the air cleaner.

While you are looking down the carburetor throat, manually pump the throttle linkage a couple of times. If you see a shot of gas each time you do that, you know the fuel bowl is staying full and also you know the accelerator pump in the carb is working.

My guess is you won't see a shot of fuel. It's likely either a bad accelerator pump or the fuel pump on the engine is allowing the fuel to drain back. I had a bad fuel pump that did that and it's very annoying having to crank and crank each time to get the carb bowl filled again.

seventy2plus2 · Canadian Poncho Superstar!

Another thing to check while doing what Carl Stevenson suggests is to ensure the choke plate is closing when the throttle linkage is operated. Because of the slow cranking speed, the fuel/air mixture MUST be very rich. The throttle plate should close (open maybe 1/8") to restrict the amount of air getting into the mixture - hence providing a rich mixture.

So it's a combination of ensuring the accelerator pump is providing shots of fuel, and the choke plate is closing to restrict the amount of air.

jim_ss409 · Guru

Another thing that can add to the problem is that summer gas is less volatile than the gas we get in the winter.
From what I've read it seems that it's the vapours in the gas that ignite first and winter gas has more of those "vapours" (I'm sure that's not the word they'd use to describe it but it's something like that)
I also gather that the vapours tend to evaporate over time and that makes old gas harder to light when it's cold.

This probably isn't the cause of your particular problem but a combination of older gas and summer blend gas might make it harder starting than normal.

juuraslahti · Veteran Member

Thanks for the tips. It wasn't too cold in my garage maybe around zero. I do recall watching the fuel going into the bowl before and it didn't squirt forcefully like I have seen with other carbs. It just kind of pooled in there and disappeared pretty quickly.
I will check to see how the butterfly behaves in a few days. Getting hit with a cold snap and my garage will be around minus 10

CdnGMfan · Canadian Poncho Superstar!

I can't recall if your 62 has the original carb, but I recall that it has an engine swap to the 194. The original carb for a 62 six cylinder would be a Rochester BC. It actually has a leather plunger in it, real 1930s technology! The leather could be dried out and cracked. The choke is not a vacuum choke, rather a sort of coiled up bi-metal strip inside a round housing (1954 technology). The choke changed to the more conventional vacuum choke for 1963 and the carb was now known as the BV. The carb itself remained the same old vintage piece. They made them through 1967 before being replaced with a new Rochester Monojet.

drae_man · Veteran Member

good info here, i have the BV, vacuum is sucked from ontop of the manifold (hot air) through the black gadget on the side of the carb and that will actuate the choke... when the air gets hot it releases the choke...

is the monojet a better carb>?

long stroke · Canadian Poncho Superstar!

CdnGMfan wrote:
I can't recall if your 62 has the original carb, but I recall that it has an engine swap to the 194. The original carb for a 62 six cylinder would be a Rochester BC. It actually has a leather plunger in it, real 1930s technology! The leather could be dried out and cracked. The choke is not a vacuum choke, rather a sort of coiled up bi-metal strip inside a round housing (1954 technology). The choke changed to the more conventional vacuum choke for 1963 and the carb was now known as the BV. The carb itself remained the same old vintage piece. They made them through 1967 before being replaced with a new Rochester Monojet.

Cam, you never stop amazing me with your knowledge of all things GM. Cam, when is your book about all things GM coming out ? It is always very welcome to hear all this great information you share with the C.P. brotherhood. Cheers. George

Canadian Poncho · A Poncho Legend!

I remember my 70 Biscayne had the bi-metal strip for a choke actuator. On really cold days you could hear it snap the choke plate shut from inside the car. I also remember how important it was to have the stove pipe from the manifold to the air cleaner working properly. Without it my 6 would pop and sputter when I tried to accelerate on cold days.

long stroke · Canadian Poncho Superstar!

Canadian Poncho wrote:
I remember my 70 Biscayne had the bi-metal strip for a choke actuator. On really cold days you could hear it snap the choke plate shut from inside the car. I also remember how important it was to have the stove pipe from the manifold to the air cleaner working properly. Without it my 6 would pop and sputter when I tried to accelerate on cold days.

Same technology on my 261 inline one barrel carb and it has always worked great.