The Stovebolt Site Forums The Shop Area Engine Shop 53 235 Very Difficult Hot Start

hi everyone,
i'm looking for suggestions for my problem before i do something unnecessary or bad.
i have read the top posts on the forum searching for hot start problems, so i think i have a few things to try already.
however i will give more specific details of my issue in hopes someone had the exact same problem i have and knows the solution.

My 53 GMC with the Chevy 235 (original engine for Canadian truck) has developed the "won't start hot" problem.
The problem is very consistent, it will happen every time the engine reaches sufficient operating temperature, a 20 minute drive on a summer day will do it.
In my case "hot" is normal operating temperature, the engine does not over heat, the temperature gauge is reading normal and it holds it's coolant well.

There is a non-original series resistors to the coil to convert it to 12V, i do not know if the coil is a 6V coil or a 12V coil i haven't touched it yet since i purchased it.
The truck starts perfect when it's cold or after it sits for about an hour once the issue occurs.
The engine cranks very well and fast at all times.
The glass on the fuel pump is always full of gas.
I have run the battery down a couple times trying to get it to start hot as if it was flooded, i don't see any signs that the engine is flooded, no gas leaking out the carb.
I have tried pumping and flooding it on purpose and cranking with the pedal to the floor, that also won't work.

what does work... if i can get the engine spinning fast enough by rolling it down a hill, it will start and run hot. once it's running it purrs just fine, no stuttering or missing.

if anyone recognizes this condition i would appreciate the help
thanks
-stan

Please tell us what carburetor you are running. Thanks

i think it's the original, a rochester
photo of it attached
thanks
-stan

Sometimes it has nothing to do with being "hot" and sometimes it does. Try running with gas cap off during next trip. Could be sucking a vacuum after awhile.

As far as the heat thing.
1. You say it turns over just as fast when hot, Right?
2. Not sure if "glass full" on pump means it's completing the pump to carb. Next time squirt gas down carb throat to see if it starts. This will identify or eliminate a few things.
3. Possible heat soak, boiling gas out of carb bowl.
4. Seems like you are saying you have a 12V system with a ballast resistor. That is correct for 12V conversion. It is a white ceramic block with one wire in and one wire out. Should not affect starting if bad. Should have two wires to the coil positive. Right? Foot start or key start?
5. Is your GMC positive ground?
6. I want to blame the starter or its wires, but only if it drags or is slow when hot.
7. Be sure that whatever type of choke you have is not closing due to heat.
8. Do you smell gas after hot shut down?

thanks for the prompt help,
1- yes it turns over just as fast or faster even when it's hot and easy spinning
2- good idea, i'll try that, i have a tiny gas can for just such occasions
3- i was thinking this, but wouldn't cranking it until the carb re-fills fix the issue?
4- its an old 12V conversion done by previous owner, it's a floor pedal foot start, there is no wire from the starter, the ignition powers the resistor in-series with the coil, original 6V starter hasn't been changed.
5- Negative ground in 1953, the Canadian GMC is a Chevy with only the front face changed to look like a GMC, it shares chassis, suspension, engine, pretty much everything behind the headlights to the back
6- there is no dragging or slowness, it spins just fine and fast because its the 6V starter running on a 12V battery, i actually dove it on the starter on the side of the road to get it into position to roll it down a field to get it going once and that worked!
7- manual choke, it has a new cable and it's wide open when pushed in to dash, closing the choke didn't help when it wouldn't go

Your coil needs a direct full 12V feed while starter engaged and a resisted 12V feed after start to protect the points.
I believe you need the button switch with the "side terminal" if the button switch on your starter does not have one. Easy to change and wire up.
Click
You don't even need to remove starter. Standard Motor Products SS521 Solenoid.
Two wires to coil pos. One from the ballast resistor and one from the side terminal.
You must be missing the full load 12V to coil and only have the resisted 12V to coil, which is 9V.
Starter demand, together with the fact that heat causes resistance all over the ignition system, nothing left for the points.
So advise if you have a button switch on starter with no side terminal.

ALWAYS take off the negative battery cable when working on the truck.

The next time it fails to start when hot, climb up to where you can see down the throat of the carburetor to see if you get a squirt of fuel when you goose the throttle. If not, you may have a marginally functional fuel pump. (Push starting makes even a marginally functioning fuel pump work much faster than the starter does, which might explain why a push start makes it fire right up.
If you pass the fuel test, attach a hot wire between the ignition key side of the ballast resister and the coil. A wire with alligator clips on each end works nicely for this. (You should keep one of these in your glove box anyway for when the ballast resister burns out. It will allow you to limp home.)
If it won't start then, attach the jumper wire from the big wire on the starter to the coil. If that doesn't work, you may a have a coil on the way out. They are prone to failing while hot. After the engine is shut off, and air no longer passes over the faulty coil and will soak heat from under the hood, making it fail until it can cool off.
It is possible to have an ignition coil and a fuel delivery issue at the same time.
BTW, these tests do not require any new parts.
Carl

Stan,
Before spending any time under the hood, I would suggest that you read Jon's "Hard Starting, Hot" section in the link below.

http://www.thecarburetorshop.com/Troubleshooting.htm#Hardstarthot

Implementing this technique may eliminate your hard start issue, at least it is worth the try. I don't know about you, but at first I had to relearn starting/operating old vehicles with chokes and carburetors. It has become second nature now.
Paul

If it is boiling the gas out of the carb. bowl, I would suggest getting a phenolic spacer between the carb and intake, it will really help insulating the carb from the intake. Also check the heat riser under the intake, if it is stuck closed it will make the intake very hot and cause the fuel to percolate out of the fuel bowl when the engine shuts down.

these suggestions all sound excellent, i will read that hard starting link and do the tests mentioned above
i'll report back in a few weeks to let everyone know what i find
thanks!
-stan

You might try carrying a small can of starting fluid. I've been doing that with my 261 after a long drive in 100 degree temps. It's an inconvenience, but starts right up.

When I first got my truck on the road I had the engine painted and in the engine compartment and had the same problem would start fine when cool go for a ride and would turn over great but not start . I began parking on a hill and letting the clutch out and would start right away . Ended up being a bad ground the strap by the starter was put on but had to clean away paint for a better connection .

I would not use starting fluid except in the direst of circumstances. You run the risk of breaking piston rings or even holing a piston if you over do it. These aren't Cummins diesels after all. Find out what's cuas9ing the problem.

It is a very common problem with the fuel evaporating under very hot conditions.
What is your solution to diagnose/fix this? Seems very straight forward and unavoidable if you drive for extended periods in very hot/humid temps. My trucks 261 never has this problem when it's in the 80's outside. But when it climbs up in the 90's and 100's, it can be hard to crank after a 10 mile drive into town. I have a spacer between my intake and carb, and fuel line is run in the standard location for the Rochester B.

I was not proposing using a 3-second burst of starting fluid that could cause damage upon start-up. I literally spray a 1/4 of a second mist over the top of the carb, and crank about 15 seconds later. I don't see how this could cause damage. And I rarely use that method at all, only if it absolutely will not crank after I let it cool off for 30 minutes or so.

I am all for testing and diagnosing. But not sure how you actually "fix" this problem.

Starting fluid will not harm a gasoline motor unless you try to run on it. Not a good idea on boat motors. It should only be used in an emergency in a blizzard. It is highly flammable and is in an aerosol can. Bad news.

Use a pump squirt bottle of gas. I assume you know where and how gas should be used.
The only advantage for starter fluid is you can carry it with you and it won't spill.
I use gas to clean all manner of parts, outside, no one here smokes.

Try this procedure:

Pump your accelerator pedal twice.
Pull out your choke cable half-way.
Press your throttle pedal (or, cable) half-way.
Press your foot-starter button
--- when it starts, let off a throttle cable/pedal; pr.
--- repeat procedure a few times

Or, yeah, make sure your ignition switch is on (which I forgot late at night recently, at Winchester).

Thank God.

We all saw that, Tim! Then we all admitted that we have been guilty of that too many times to say boo about it.

okay, i think it was a bad coil causing my truck to not start when hot
the coil in there looked older than me
put a new one in and it hasn't let me down yet

thank you everyone for the trouble shooting tips!
-stan