Won't start when hot. Help!

Hey guys. I need a little help with a "wont restart when hot" problem with my Merc.

I have a 62 292 Y-Block. Edelbrock with three 94 Holleys. Center primary carb has a heat riser choke while the two secondaries are plugged idle circuits w/o chokes. The intake has a heat pass over that is open. I run and electric fuel pump with a pressure regulator set a 3lbs.
The car starts cold w/o a problem. Choke works fine and opens up when the motor gets warm. Temp gauge is right in the middle. Runs and drives well. Plugs are clean, timing set correctly.

However, when I shut it off...it will not restart. It doesn’t matter if it’s been running 5 minutes or an hour, just won’t start. Cranks and cranks...nothing. It will start an hour later.
Any ideas?

 

Check your condensor. Sounds like a typical condensor problem.

 

Check out the other current thread about vapor lock for possibilities.

 

Also check the coil. I just rode in a car on Power Tour that would "vapor lock" until everything cooled down. Turned out to be the coil.

-Brad

 

You first need to determine if you are losing spark or fuel. Try spraying carb cleaner or starting fluid down the center carb. If it fires, than u are losing fuel. If it doesn't fire then your need to see if you are losing spark. I normally take the number 1 spark plug wire off and put a spark plug in it. I place the end of the plug close to the block and have someone turn the engine over. You should have a white/blue spark jump between the plug and the block. If not, than you are losing spark. Also, I do not hold the plug wire with my hand, I use insulated pliers.

 

Is there a distinct gas smell around the carb when trying to start hot? Why? Because it sounds like you could be flooding the engine when it is shut down. The needle and seat could be worn and not sealing well. I would check the float level. Possible float leak too. If all of these are ok, then the dreaded vapor lock issue. Easy fix: try running a higher octane gas and see if this helps, vapor lock is more prone with low octane gasoline.

 

Seeing you're in NJ, and you folks have been haveing a bit of weather back there, what's the humidity been running back there? Hot and Humid would sure be indications of vapor lock.

2. Like was said before me, a condensor that gets hot will give the same symptoms, they start to break down.

3. You said your timing is nuts on, and plugs are clean. when you changed plugs last time, did you change the condensor too?

4. But when you say you're running an electric fuel pump, that would take care of any vapor lock and it would fill up the fuel bowl, even it it did bubble out, so that leans back to condensor or coil being the possible culprit.


HellRaiser

 

On mine..

Fuel percolation in plenum. If it will start without air cleaner then it is a good indication that heat is building up in manifold causing vaporization in plenum...causing very rich hard start. Took three attempts to start..and lots of rich..unburned gas smell.

Try an open top aircleaner like a K&N with filter exposed top. Also add aluminum heat shield under center carb with a phenolic spacer to keep bowl from percolating..

Blocking the water crossover does help somewhat but the manifold will still get hot..just takes longer. The crossover is to help cold running by heating the fuel quicker.

Worked decent on mine..small compartment with big motor. I need to vent the compartment better..but even here in southern AZ..it starts much better hot now.

 

had same problem was the coil check spark frist

 

Thanks gents, I'm headed out now to play with it.

It was a bad condenser. Thanks guys for the thoughts.