I have a 1972 Corvette that is having an engine issue. While driving, the engine will suddenly stop running. I am able to start it up again. After another mile or two, it stops again. I would appreciate any advice on what I should check that may be causing this.
I am not an auto mechanic but know my way around an engine good enough to check the various parts.

Thank you.

 

Moved to C3 Tech.

 

Does it appear to be heat related? Could be a failing coil or condenser. Is it fuel related? It could also be vapor lock, fuel filter clog or fuel tank sock or fuel pump?? Jerry

 

Welcome to the forum!

What kind of carburetor do you have? What’s your timing set to? Post some pictures of your engine bay with the air cleaner off so people can get a better idea of what you’re working with.

 

Welcome to the Corvette Forum Orange4one!

Welcome to the Corvette Forum as this is THE place to get answers to Corvette Questions! The more we know about your Corvette the easier it will be for all of us to help you. Take moment and fill out your "Profile" with as much detail as you can. This keeps the questions down to a minimum.

1.0 Older Corvettes used a gas tank with a gas cap that is vented. Yo are describing exactly what a plugged gas vent would sound like. The vent is in the middle of the gas cap and can be cleaned out easily. If your tank has a vent hose be sure it doesn't have a Mud Dauber nest in it.
2.0 The ignition coil is another very likely option as when they operate they warm up and then stop working randomly. I have had a problem with coils from MSD last the few years.
3.0 A faulty Ignition switch could cause the issue. They can develop loose connections and fail altogether.
4.0 A really dirty fuel filter including the bronze elements in your Holley or Quadrajet.
5.0 A bad fuel pump could cause issues stalling.
6.0 The Choke on your carburetor is not turning off. With the car turned off the coil cools off.
7.0 Really bad float settings.
8.0 What do you have your idle speed at? If it was too low the car might have issues and stall.
9.0 A weak or bad battery.

This might be a good starting list

 

10.0 Needle Valve, Seat and Float in the carb . . . . . . . .playing games.

If "they" stick in the upward position, no fuel will enter the bowl until the float drops again.

 

Welcome

 

Thank you for the suggestions. I think the battery may be the culprit as it seems to drain easily. It may not be charging correctly.

 

I had an "interesting" problem that gave me intermittent starts and stops. Somehow a piece of debris of some sort got stuck in between the pump and fuel filter. Now and then it would block fuel flow and the motor would stall. It would then fall back down and I could restart the car and run again.

 

It may not be the battery. Or it could be the alt. Once it starts, the alt. should take over. Put a meter on the battery before you start it and measure the voltage. After it starts, measure it again. There should be a step up in voltage after the car starts. Report back. Jerry

 

it seems that it would be electrical as it shuts off then restarts. How quickly does it restart. If it starts up rather quickly it wouldnt be fuel clog as they take a bit to clear, I had those issues as well. Most likely its a cap, coil, points or rotor issue. If its HEI then you have a bad HEI coil....

 

Hello again Orange4one,

Batteries are a really strange problem that can present itself in many ways. On a C3 Corvette the battery is there for Starting and Ignition only. The battery itself has a very low potential to make intermittent problems. Most issues are to do with the battery connections and the ground potential. On my C4 the ground cable is short and easy to check. IF there is ANY corrosion then you remove the hardware and wire-brush the metal until you see bare steel and then re-attach the ground wire and coat it with battery connection spray protector to keep it from corroding right away.

My favorite first test is to measure the battery voltage and then measure the voltage at the engine using the engine for the ground. The battery voltage and the voltage in the engine compartment should be very close.

Has the battery been left at a Low State Of Charge?
How old is the Battery?
Have you measured the DC voltage coming out of the alternator? Using the engine for ground, measure the DC voltage coming from the alternator. Then for kicks change the meter to read AC (Alternating Currant) and measure the output of the alternator. If any AC is found in the output then you might have a faulty diode bridge allowing AC to enter your DC wiring system. AC can mess up a ECU and other DC components. If AC is present then replace the alternator.

Disconnect the battery and connect a Battery Charger to it and let it go through a couple charging cycles. It works better to have a 15 amp or larger charger so you can push the cell voltages up towards 2.5 volts per cell which will cause the battery to gas off while it is charging. It is very important to be sure a battery gets fully charged if it will last a while. Before and after charging your battery be sure that it has enough electrolyte. Most conventional batteries are still the Flooded Lead Acid batteries and they should have a way to access the electrolyte to get the best life expectancy. If I can't access the Electrolyte then don't buy the battery.

Batteries can short out internally when the lead that has fallen off the plates builds up on the floor of the cell. This is dangerous because the lead can move and short out a battery internally. If a battery shorts out internally the lead is fused together and doesn't want to move away. This leads to a huge heat buildup and eventually the battery case will blow open or just split if you are lucky. It is not a nice mess to have to clean up from.

To me it sure sounds like a failing Ignition Coil though, or some kind of fuel issue.

 

years ago I had a sears battery back when they had a great warranty...it had a crack in a plate that would randomly open and the car would shut off. but it wouldnt restart right away....might be 30 minutes, might be a few hours...never did figure it out, just got a new battery and it was over......that was nightmare..

 

I had the same problem. Hard Left turn or U turn, the car would just power off.
Engine would restart without doing anything.
I did not find the problem until I pulled the motor for rebuild.
The problem was the fuse link at the distributor. older cars will rub the insulation of the link at the "dog house" or where it goes thru the fire wall.
I purchased a new link,problem could have be repaired with shrink tube

 

By any chance do you have an MSD ignition. Mine did the same thing. Now I know why racers run 2 units.

 

Which MSD do you have. I have an MSD6AL and never had issues...hoping I don't in the future now......

 

Nother time I had issues was with an electric fuel pump...thought it was a relay issue. It would do the on off on off thing until it gave up

 

You either have a fuel supply problem or you have an ignition problem. Either of these can have multiple causes. Fuel supply: kinked fuel hose between main fuel line and fuel pump; clogged fuel filter (in-line or in-carb); needle/seat problem in carb; float problem in carb, etc.
Ignition: bad electronic module (if electronic ignition); bad condenser (if points); worn/corroded points contacts; bad/damaged/worn distributor cap or rotor; bad ignition ground path thru distributor hold-down clamp (this is common when folks pretty-up the engine compartment and don't know that the dist hold-down clamp is the ground path for the ignition system on a points-type vehicle.

 

No MSD just orig stock chevy that came in my 70 454 vette.

 

Check the wires on the starter.

We went through hell last year with a members car. Loose wire on the started as that feeds the cars electrical system. Also check for a rubbed wire by the right head and firewall.