hard hot start
Thread Starter
3rd Gear
Joined: Apr 2010
Posts: 3
Likes: 0
hard hot start
Hello,
I own a 1972 Corvette Coupe (350 cu. inch small block,stick-shift)for many years now and I am having a serious problem.
When I start the engine cold, there is no problem, not even after a long winter-stop.
A few turns and it runs great.
But when the engine is really hot after a long drive, it is very hard to start again.
Battery is OK.
Starter-motor is OK.
Carb. has been serviced.
Gasket between carb. and manifold has been renewed.
After about 20 minutes the engine just starts without problems.
Could this be vapor-lock ???
I never had vapor-lock before.
Nothing has been changed to cause vapor-lock.
Or could this be an ignition-problem ?
Today I had the same problem again.
Car ran great on an early spring day, so temperature was not high.
It was even chilly.
After I stopped the engine, I just couldn't start it for about 20 minutes.
After that no problem.
Starting, running, starting, running etc.
Was could be wrong ?
I own a 1972 Corvette Coupe (350 cu. inch small block,stick-shift)for many years now and I am having a serious problem.
When I start the engine cold, there is no problem, not even after a long winter-stop.
A few turns and it runs great.
But when the engine is really hot after a long drive, it is very hard to start again.
Battery is OK.
Starter-motor is OK.
Carb. has been serviced.
Gasket between carb. and manifold has been renewed.
After about 20 minutes the engine just starts without problems.
Could this be vapor-lock ???
I never had vapor-lock before.
Nothing has been changed to cause vapor-lock.
Or could this be an ignition-problem ?
Today I had the same problem again.
Car ran great on an early spring day, so temperature was not high.
It was even chilly.
After I stopped the engine, I just couldn't start it for about 20 minutes.
After that no problem.
Starting, running, starting, running etc.
Was could be wrong ?
Instructor
Joined: Sep 2008
Posts: 222
Likes: 0
From: penngrove ca
I'm assuming the engine cranks but will not turn over. Do a thread search of hot engine not starting. This issue comes up allot. Check the easy stuff 1st. Choke position when engine is hot? Connections at battery, starter, maybe the starter solanoid going bad.
Race Director
Joined: Nov 2002
Posts: 12,142
Likes: 54
From: Taylor Michigan
First, the starter is good as they don't die and suddenly come back to life....accessories draw very little amperage to work, ,lights, radio, ect. so those are not a good guideline to measure cranking ability. Before you start changing parts, clean all the grounds especially the one right under the battery on the transmission cross member..and then check the battery cables for corrosion if that don't satisfy the problem.
Instructor
Joined: Mar 2009
Posts: 187
Likes: 1
From: WA
Please describe what it does when hot. I wouldn't write off a starter because if that solenoid gets too hot, it needs to cool down a bit before working again. I've seen this many times especially with headers and 20 minutes is the typical time it needs.
Thread Starter
3rd Gear
Joined: Apr 2010
Posts: 3
Likes: 0
When, after a long drive, the engine is really hot and I park the car and shut off the engine, it fails to start again.
For example when stopping for gas.
The battery is OK, because the starter-motor is engaged properly.
The engine turns over and over and over, but just won't start.
Flooring the acc.pedal and keeping it to the floor won't help.
Pumping the acc.pedal won't help.
Not touching the acc. pedal won't help.
Then, after 15 or so minutes, the engine start without any problem.
Sometimes even within a second or two, just pressing the acc. pedal two inches will do the trick.
For example when stopping for gas.
The battery is OK, because the starter-motor is engaged properly.
The engine turns over and over and over, but just won't start.
Flooring the acc.pedal and keeping it to the floor won't help.
Pumping the acc.pedal won't help.
Not touching the acc. pedal won't help.
Then, after 15 or so minutes, the engine start without any problem.
Sometimes even within a second or two, just pressing the acc. pedal two inches will do the trick.
Instructor
Joined: Jul 2004
Posts: 202
Likes: 0
When, after a long drive, the engine is really hot and I park the car and shut off the engine, it fails to start again.
For example when stopping for gas.
The battery is OK, because the starter-motor is engaged properly.
The engine turns over and over and over, but just won't start.
Flooring the acc.pedal and keeping it to the floor won't help.
Pumping the acc.pedal won't help.
Not touching the acc. pedal won't help.
Then, after 15 or so minutes, the engine start without any problem.
Sometimes even within a second or two, just pressing the acc. pedal two inches will do the trick.
For example when stopping for gas.
The battery is OK, because the starter-motor is engaged properly.
The engine turns over and over and over, but just won't start.
Flooring the acc.pedal and keeping it to the floor won't help.
Pumping the acc.pedal won't help.
Not touching the acc. pedal won't help.
Then, after 15 or so minutes, the engine start without any problem.
Sometimes even within a second or two, just pressing the acc. pedal two inches will do the trick.
Racer
Joined: Nov 2009
Posts: 332
Likes: 1
From: Watkins Glen New York
The next time this happens and before you try too many times I would pop off the top of the air cleaner and manually work the carb linkage to see if you have any accelerator pump action. If you do, you'll see and hear a little "spritz" of fuel in the throat of the carb.
I had this problem once a long time ago and was told it was "vapor lock". In my case my inline fuel filter and some lines were too close to something too hot and this caused fuel to stop flowing.
You can prime the engine with an ounce of gas down the carb too. If it starts and runs briefly, you'll know it'll run with fuel flowing.
.
Anyway, you know it started before, so look for the basics. If you have fuel happening, take out one of those red hot spark plugs, lay it near a ground while in it's wire, crank her up and see if it's firing.
I had this problem once a long time ago and was told it was "vapor lock". In my case my inline fuel filter and some lines were too close to something too hot and this caused fuel to stop flowing.
You can prime the engine with an ounce of gas down the carb too. If it starts and runs briefly, you'll know it'll run with fuel flowing.
.
Anyway, you know it started before, so look for the basics. If you have fuel happening, take out one of those red hot spark plugs, lay it near a ground while in it's wire, crank her up and see if it's firing.
Last edited by Gilded_Splinters; Apr 13, 2010 at 09:52 PM.
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Instructor
Joined: Mar 2009
Posts: 187
Likes: 1
From: WA
The next time this happens and before you try too many times I would pop off the top of the air cleaner and manually work the carb linkage to see if you have any accelerator pump action. If you do, you'll see and hear a little "spritz" of fuel in the throat of the carb.
I had this problem once a long time ago and was told it was "vapor lock". In my case my inline fuel filter and some lines were too close to something too hot and this caused fuel to stop flowing.
You can prime the engine with an ounce of gas down the carb too. It it starts and runs briefly, you'll know it'll run with fuel flowing.
.
Anyway, you know it started before, so look for the basics. If you have fuel happening, take out one of those red hot spark plugs, lay it near a ground while in it's wire, crank her up and see it it's firing.
I had this problem once a long time ago and was told it was "vapor lock". In my case my inline fuel filter and some lines were too close to something too hot and this caused fuel to stop flowing.
You can prime the engine with an ounce of gas down the carb too. It it starts and runs briefly, you'll know it'll run with fuel flowing.
.
Anyway, you know it started before, so look for the basics. If you have fuel happening, take out one of those red hot spark plugs, lay it near a ground while in it's wire, crank her up and see it it's firing.
This is the closest explanation to the problem you are having. If the engine is turning over, you are right that it is definitely not a starter. I would say a timing or fuel delivery issue as my best guess. Good Luck!
Melting Slicks
Joined: Dec 2009
Posts: 3,229
Likes: 656
From: Thunder Bay
I had the same problem with my '79. It was worse some seasons than others. I think that had to do with changes in the fuel formulation. It turned out to be heat soak and I solved it with a change to an RPM Air Gap manifold, insulator plate under the carb, open element air cleaner, and insulation on the fuel lines where they run near the headers. this all also required a new hood with more clearance.
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,481
From: Southbound
Cruise-In II Veteran
Heat soak. The starter and solenoid are getting hot while driving. Once they cool enough, the car starts again. My '74 would do it.
Make sure the factory starter shield is in place. Check to see whether you have an exhaust leak near the starter.
Make sure the factory starter shield is in place. Check to see whether you have an exhaust leak near the starter.
Melting Slicks
Joined: Dec 2009
Posts: 3,229
Likes: 656
From: Thunder Bay
I don't think he has a problem with the starter. In one of his previous posts he says the starter turns the engine over fine, but the engine won't start. I like the suggestion to look for a stream of fuel from the accelerator pump to see if there is fuel in the float bowl. I think the fuel is boiling off.
Thread Starter
3rd Gear
Joined: Apr 2010
Posts: 3
Likes: 0
hard hot start
Thanks guys.
I always considered vapor-lock, but I just couldn't figure out why this didn't occur before, because I hadn't changed anything under the hood.
Any change in fuel formulation could be the reason as mentioned by drwet.
I'll keep you posted.
I always considered vapor-lock, but I just couldn't figure out why this didn't occur before, because I hadn't changed anything under the hood.
Any change in fuel formulation could be the reason as mentioned by drwet.
I'll keep you posted.
