Hot Start problem

[Guest Dave May]

I am finishing up a restotation on a 1960 Invicta with a 401 and Rochester carb. The engine and carburetor have been rebuilt, but I suspect the quality of the rebuild on the carb. The car cold starts just fine and runs well. The only problem I'm having is with Hot Starting, starting when the engine is up to temperature. The car will crank just fine but dosen't fire up untill it sits and cools down a bit.

As I said, I suspect the carburetor, but is there a specific issue with the carburetor that should be looked into that would cause this problem??? Or, could it be non-carburetor related??

Thanks

[old-tank]

Be sure you have spark when in the non start situation. Some ignition components like the coil and condenser will briefly give up when hot. Look down into the carburetor with the choke open and the throttle wide open. Today's volatile fuels will quickly evaporate and leave the carburetor dry or the fuel will boil and percolate into the manifold flooding the engine until it drys up. Also while looking into the carburetor work the throttle to be sure the accelerator pump is squirting 2 jets of fuel. Report back.

Willie

[MrEarl]

an old timer once told me "90% of all carburetor problems are electrical". check the coil.

[avgwarhawk]

The things to check as Mr Earl and old tank suggested, fuel, spark and air. One of these is not in the equation. I suspect the coil. Coils do go south under heat. In the new models usually the ignition module will die from the heat but work fine when cool again. What is your set up? Have the points system in the distributor or the replacement ignition system?

[Guest Dave May]

The coil is new and I've replaced the points with a Pertronix ign. system. The car has probably less than 10 mles on since the rebuild/restoration. When I did get it to start when warm, it was after using starting fluid.

"Old-tank"s recommendation to check the carb. for fuel seems to make sense. The gasoline in the car is winter formulated with high vapor pressure which could mean that it has boiled out of the carb when hot.

[avgwarhawk]

I would say it is your Pertronix. I have had plenty of electronics fail straight out of the box. Personally I would run the car until it gets to the condition of no start. Check for fire at the plug end. This will eliminate that portion.

What is the condition of the fuel pump? The fuel line in the engine compartment, how close to the any hot engine components? Vapor lock occurs in hot fuel lines.

Edited March 19, 2012 by avgwarhawk (see edit history)

[Guest brh]

Hopefully, I can save some time and $$$$. Had this problem with my 65 Lark, blamed the carb, tried all kinds of things. Problem- the car was overheating, which got the gas in the carb so hot, it was boiling out. Turned out my radiator was blocked, had it recored, end of problem. The way I could tell I was going to have a problem was it would start running bad, just before it was going to overheat. Shut it off and there was no way that car was going to start.

[Guest Dave May]

I think that may be a possibility. I've only driven the car twice aroound the neighborhood since its been finished. the last time I drove it, the "Hot" indicator light would go on occassionally for breif periods. It appears the car is running hot.

After I shut the car off and it cooled down, I checked the coolant level and it was down about a half gallon. I'll try running the car again to see if adding coolant helps the problem. The radiator was re-cored, so I'm guessing that is not an issue.

[Guest brh]

Make sure your cap is the right pressure range too. Mine would act up before the light came on, thats why it was such a puzzler.

[61polara]

If you have only driven it twice around the block and are half gallon low on coolant and the temp light flickers, you have a major leak if it was full when you started. The overheating could be causing all your problems. Find where the coolant is going! On these short drives, I don't think its the radiator cap. If it is the radiator cap, you will see coolant spitting from the overflow tube on the radiator when you stop unless the coolent level is to low. '

Fill the radiator to the correct level and start the engine with the cap off. Let it come up to temp. When the engine comes up to the thermostat temp, you should start to see the coolant flowing through the radiator. The engine should not overheat with the cap off at idle. I coolant starts flowing out of the opening, you have a blocked radiator or a lower hose that has collapsed. If you see major air bubles in the coolant after the thermostat has opened, you have a blown head gasket allowing compression gas to enter the cooling system.

By the way, my '60 Invicta was the first '60 Buick to receive the AACA Original award! They're geat cars. Never had an overheating problem with it. With the 401 they don't even know they have a Dynaflow behind them.

Trust me from experience, find the cause of the overheating first! Let us know what you find.

[Guest Dave May]

I was able to run the car yesterday with the radiator cap off. The radiator was recored last year and the car has only been driven about 3 to 5 miles since the recore. The engine was rebuilt also. I don't think my low coolant issue was a result of a coolant leak, I think I may not have filled the empty system completely, or after running the car, the coolant completely filled the system ??

Anyhow, after the car got up to temp., coolant started spraying/burped out of the open radiator. I surely did not expect this and shut the car off and replaced the cap. I started the car again and ran it for another 5-10 minutes. No "Hot" indicator lights. I shut the car off and restarted it again. No starting problems.

Could the coolant spray/burp be the result of an air pocket working its way out of the system??? Other than draining the system and checking the lower hose and radiator, is there another way to verify the system is not blocked??

Any help is appreciated.

[avgwarhawk]

I was able to run the car yesterday with the radiator cap off. The radiator was recored last year and the car has only been driven about 3 to 5 miles since the recore. The engine was rebuilt also. I don't think my low coolant issue was a result of a coolant leak, I think I may not have filled the empty system completely, or after running the car, the coolant completely filled the system ??

Anyhow, after the car got up to temp., coolant started spraying/burped out of the open radiator. I surely did not expect this and shut the car off and replaced the cap. I started the car again and ran it for another 5-10 minutes. No "Hot" indicator lights. I shut the car off and restarted it again. No starting problems.

Could the coolant spray/burp be the result of an air pocket working its way out of the system??? Other than draining the system and checking the lower hose and radiator, is there another way to verify the system is not blocked??

Any help is appreciated.

Yes, air can get caught in a cooling system making problems. Some new cars have a port opening at the high point of the system to burp the air. For these cars the high point is the radiator opening I would imagine and should be the spot air is released as coolant takes it's place.

The way I verify the system is blocked is waiting for the thermostate to open. If the engine is hot enough to open the thermostat and you see no flow through the radiator opening then suspect the thermostat. If the thermostat is ok but still no flow then suspect a blockage. I have found that behind thermostats as being the problem the radiator comes next. Sometime the radiator is half blocked as well.

[Guest Dave May]

After topping off the coolant, I took the car out for a rde last night. No "Hot" indicator light! My thinking is that previous temperature problems were caused by the coolant level being a bit low and an air-pocket in the system that was eliminated after running the car with the radiator cap off and "burping the system.

However, after the ride I backed the car into my driveway, which is inclined. The front of the car was pionting downhill. Leaving it running, I got out to go in the house for a minute or so and I noticed it was "stumbling"a bit. When I returned, the car had died out. I could not get it started until I squirted some gas into the carburetor. I backed it back into the garage and on a level surface, restarted it a couple of times with no problem.

The fuel pump is new, but it is a mechanical pump. I'm now thinking that because of the incline, the carb. got starved of fuel and pump could not effectively feed gas into the carb. causing a hard start???

Couple questions,...Shouldn't there be some sort of "back flow preventer" on the carb to keep the bowls filled with fuel??? Is this a typical problem with carbureted cars??? I don't have a lot of experience or knowledge of carburetors, since 1979 have had only fuel injected cars.

[avgwarhawk]

I'm not certain with your carb but some if not all have a check ball to prevent backflow. I'm not sure if you have rebuilt the carb that has a view of the carb parts but the exploded view of the carb should show a check valve or check ball if it has one.

This is not typical of engines with carbs. From my experience with the newer carbs anyway. Check balls are in the line somewhere. Not sure if the engineers of the 50's provided check balls in the fuel systems. Cars that are injected have a check ball/valve as well. Keeps the pressure up to the rails for better starting. Some have a prepump that cycles the fuel when the car door is opened. VW has this function.

Edited March 29, 2012 by avgwarhawk (see edit history)

[old-tank]

Probably volatile fuel like I noted in post#2. Maybe even vapor lock which happened to me while sitting in traffic with outside temp of 65*....shen I activated the electric fuel pump, it started. On hot days I anticipate vapor lock, but 65*? All of my Buicks have an electric fuel pump mounted near the tank.

Willie

[Guest Dave May]

I'm thinking installing an electric fuel pump may be a good idea.

Any recommendations???

[old-tank]

Airtex External Electric fuel pump: E8012S is the one I use, rated at 9 psi, but mounted at the tank, pressure at carb is 5.5 psi. They make lots of other ones.

Willie

[Guest Dave May]

Willie,

It sounds like you use the electric pump as an auxillary pump to the mechanical pump. Do you have it wired to a dash switch??

[old-tank]

Willie,

It sounds like you use the electric pump as an auxillary pump to the mechanical pump. Do you have it wired to a dash switch??

Yes, I use it to prime the carb after sitting for a few days or longer, flip the underdash switch as needed or in anticipation of a vapor lock situation.

Willie

[lrlforfun]

OK Dave: Have you checked the gas tank. From the sounds of everything you have said the sending unit could be clogged. That can easily produce intermittent symptoms of the no start. Remember, diagnose every aspect, isolate each component until all are trouble free. Mitch

[Guest shorttimer]

Is it possible the fuel level in the tank was low and the angle of the incline left the pickup in the tank high and dry?

Also, relating to your hot start condition, if your car has a Carter carb, do you have the steel insulator plate between the carb and intake manifold?