hard start when hot

[piddler]

As you know, I am pretty new to the Corvair world. A couple of days ago I drove my '65 Corsa about fifty miles to a show. The temperature was in the high 70's to low 80's. When I got to the show I turned the car off for a few minutes to talk to some friends and when I tried to start it again it took a long time for it to start. I was beginning to get a little worried. The car has a Pertronix ignition. Any thoughts?

Any advice appreciated, Pete

[66vairguy]

As you know, I am pretty new to the Corvair world. A couple of days ago I drove my '65 Corsa about fifty miles to a show. The temperature was in the high 70's to low 80's. When I got to the show I turned the car off for a few minutes to talk to some friends and when I tried to start it again it took a long time for it to start. I was beginning to get a little worried. The car has a Pertronix ignition. Any thoughts?

Any advice appreciated, Pete

This issue came up a while back. The "HOT START" problem is a long running Corvair issue. A number or "tech" bulletins were issued by Chevrolet. Worst case is when the engine is hot and you turn it off and try to re-start it in 1-10 minutes. Basically the carburetors act like they are "flooded" from excess fuel.

The 65 carburetors had an idle vent (spring arm and rubber pad at the carburetor base) that helped. This "vent" closes as soon as the throttle opens. It is tricky to adjust and usually the rubber pad is hard or GONE (heat gets to it). Sometimes the hole is deliberately plugged. Many find trying to get the vent to work properly difficult. You can buy Bob Helt's Rochester book to learn about how to adjust the carburetor, however if you don't have the experience with carburetors I'd suggest do what many do. If you turn off the engine, the wait 15-20 minutes before restarting.

[bbodie52]

Check to be certain that the chokes are fully opening when the engine is warm and up to normal operating temperatures.

Also, have you had the carburetors off of the engine recently? If so, were the plastic insulators reinstalled or replaced along with the gaskets at the base of each carburetor? If the insulators were accidently left off the carburetors can build-up too much heat from the cylinder head intake manifolds, which can cause the gasoline in the float bowls or fuel passages to boil and vaporize (a form of vapor lock).

Ignition coils sometimes begin to fail with heat buildup. The original Delco-Remy coil is bolted directly to the right cylinder head, which gets very hot in normal operation and can transfer heat to the coil. An old coil can begin to fail under these conditions and may be showing signs of ignition system failure when the engine heats up. A weak or intermittent spark plug voltage could be the result. You might try relocating your coil away from the head, and remounting it on the perimeter frame in the engine compartment — away from the hot, vibrating head but still within reach of the distributor cap. If you suspect a faulty or failing coil, you could try replacing the coil.

Avoiding Ignition Coil Failures and Returns

By: NGK Spark Plugs
July 1, 2017


https://www.aftermarketnews.com/avoidin ... d-returns/

Ignition coils can vary greatly in size and shape but share three common parts. These are the primary windings, secondary windings and a non-conductive or dielectric insulation material that separates the two windings. The insulation material is typically a dielectric resin that is applied in a vacuum, so air bubbles are not formed. Air bubbles can create a path for electricity inside of a coil, and lead to premature failure.

Coils fail for a variety of reasons including heat, vibration, or issues on the secondary side of the ignition system. Coils are commonly found bolted to the cylinder head, either on top or inside of a cylinder specific well. Excessive heat and vibration can cause the insulating material to break down and create internal coil failure. Worn secondary ignition components such as spark plugs or wires can cause a coil work harder, require more voltage, and therefore significantly reduce the operating life of the coil.

When a coil fails, it is possible the electricity created is unable to reach its destination, the spark plug. When this happens, the electricity created inside of the secondary windings looks for the path of least resistance to ground. This path is commonly found through the boot or body of the coil. Carbon tracking happens when oil, dirt, or moisture is electrostatically attached to the boot or insulator and creates a path to ground. When carbon tracking is found, the coil and corresponding plug should be replaced. It is also possible that a failed ignition coil can cause damage to the engine computer, or ignition control module.

Aftermarket replacement coils are often engineered to prevent common pattern failures found with the original ignition coils. These improvements can include improved dielectric materials that better insulate the secondary and primary coils. Also, improvements can be made to the design of ignition control module, so the unit is able to withstand greater levels of heat and vibration.

Are you running the original 1961-style distributor, or has it been changed to the 1962-1969 version (with the screw-type cap attachment). If it is the newer design, has it been upgraded with an electronic breakerless ignition system? Electronic components can sometimes fail with heat buildup.


1960-61 distributor on the right. Electronic breakerless ignition systems will only fit 1962-69 distributors.



https://ssl.corvair.com/user-cgi/catalo ... IN&page=74


Ted in Atlanta has a lot of professional Corvair experience. I remember his recommendation...

...I love my Crane ignitions. I have only ever seen one that had failed. Something I can not say about the Pertronix units where failure is somewhat common from what I have seen.

Corvair guy since 1982. I have personally restored at least 20 Vairs, many of them restored ground up. Full time restoration tech and mechanic. https://www.facebook.com/tedsautorestoration

https://ssl.corvair.com/user-cgi/catalo ... ge=OTTO-21

DELCO ROCHESTER - Models H, HV Carburetor Service Manual.pdf

DELCO ROCHESTER - Models H, HV Carburetor Service Manual

(1.79 MiB) Downloaded 12 times

THIS BOOK IS HIGHLY RECOMMENDED...

How to Identify and Rebuild Corvair Rochester Carburetors Paperback – June 29, 2006
by Bob Helt (Author)

https://www.amazon.com/Identify-Rebuild ... 145&sr=8-1

The attached DELCO ROCHESTER - Models H, HV Carburetor Service Manual dos a good job of explaining the function of the different carburetor subsystems, had how the carburetors changed and evolved over the years.

DELCO ROCHESTER - Models H, HV Carburetor Service Manual.pdf

DELCO ROCHESTER - Models H, HV Carburetor Service Manual

(1.79 MiB) Downloaded 12 times

[piddler]

Wow. That is a lot of advice. The coil did come to mind with the hot start problem. I will start making some checks following what has been posted here.

Thanks, Pete

[66vairguy]

Wow. That is a lot of advice. The coil did come to mind with the hot start problem. I will start making some checks following what has been posted here.

Thanks, Pete

It is always a good idea to get the ignition coil off the engine block for longevity, but it is not critical. Usually a coil that fails due to a heat issue will cause the engine to run rough or miss under full throttle after the engine gets hot.

If the car starts fine, except just when you start the car a few minutes after shutting it off when hot, then that is the typical hot start problem. Another technique for a hot start condition is - DO NOT depress the throttle pedal until AFTER the starter is engage.