More starting issues

For the past 4 days I’ve had a problem with my 1972 351C 2v H code mustang where sometimes when I start it up the engine will turnover and start then immediately shut off, My guess was some sort of spark plus issue or something but I’m not too sure would could use some advice before I go around in the engine changing things that don’t need to be changed

Sounds to me you are loosing the feed at the coil. Check if you have 12v with key on. The contact switch is often prone to failure

Fabrice said:

Sounds to me you are loosing the feed at the coil. Check if you have 12v with key on. The contact switch is often prone to failure

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Thank you very much, i’m still learning how to do most repair stuff on the mustang any advice on how to test the contact switch

Do you own a mulitmeter?

will e said:

Do you own a mulitmeter?

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Nope

August07 said:

Nope

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You'll find a multimeter an invaluable tool when trouble shooting electrical issues. They seem intimidating but are actually fairly easy to use with the majority of your car trouble shooting efforts being in either a volts or ohm reading. When in volts reading you connect one end to a ground on the car (usually the battery) and the other to whatever you are testing. If there is 'power' it will read a number of volts, usually around 12 depending on what you are testing and if the car is running.

You don't need an expensive 'fancy' one for simple trouble shooting. Even the voltage reading itself doesn't have to be super accurate for most of our needs.

Pick one up and we can help walk you through the steps for the most basic trouble shooting before you start swapping parts.

will e said:

You'll find a multimeter an invaluable tool when trouble shooting electrical issues. They seem intimidating but are actually fairly easy to use with the majority of your car trouble shooting efforts being in either a volts or ohm reading. When in volts reading you connect one end to a ground on the car (usually the battery) and the other to whatever you are testing. If there is 'power' it will read a number of volts, usually around 12 depending on what you are testing and if the car is running.

You don't need an expensive 'fancy' one for simple trouble shooting. Even the voltage reading itself doesn't have to be super accurate for most of our needs.

Pick one up and we can help walk you through the steps for the most basic trouble shooting before you start swapping parts.

Click to expand...

Alright I spent the morning working on that and the battery read at 12.88 volts, my dad suggested that the choke could be not closing on cold start and his fix of pumping the gas and running the starter for 10 seconds worked to get the car started when before it wouldn’t start at all but i’m unsure if the choke is the full issue or just a symptom.

That's great. But I am now confused on the symptoms. Your original post indicated that it would start and immediately turn off. Your updated post seems to indicate it only happens when 'cold'.

I am not sure how much you know about old cars so bear with me.

It is not normal to crank for 10 seconds to get it to start. Even if the choke is not operating it should start fairly quickly. If the choke is bad It won't do a high idle and you might have to give it a bit of gas to keep it running until it warms up a little. I see you live in California so unless it is really cold the car shouldn't have much trouble starting without the choke working (if it is the choke..) My choke doesn't work and my car will start and, depending on the time of year, will run without me goosing the gas.

Assuming you have the stock carb (from your other posts) here's your normal 'cold' starting procedure:
1. Turn the key to 'run' (not crank)
2. Depress the gas to the floor and release. This does 2 things. It sets the choke and it 'shoots' a bit of gas into the intake for the initial start.
3. Turn the key to crank. The engine should start almost immediately. If it is cold and the choke is working it will go to 'high idle' and the choke will restrict airflow to the engine.

You do not need to keep pumping the gas to get it to start. Perhaps one more pump of the gas and if that doesn't fire it up and you have to crank and pump for 10 seconds you are probably having a fuel delivery issue. The most likely causes are the carb is leaking or boiling the gas out. The accel pump is not functioning or the fuel pump is weak.

The first thing I would check is that the accel pump is shooting fuel when you press the gas. With the air cleaner top off and the engine not running you should be able to 'see' fuel shoot into the carb venturi's when you move the throttle. If you don't the question is if it is because there is no fuel in the bowl or because the accel pump is weak. If the engine is warm and otherwise 'running' and you don't see fuel squirt then the accel pump is bad. If you see fuel when the engine is warm and running but not when the engine is cold then your fuel bowl is being drained while the car sits. Normally, unless the car has sat for a very long time, there is enough fuel in the fuel bowl to squirt gas into the carb and for it to idle for a bit.

How's the car running overall? Does it run and keep running once it is warm?

@August07 If you do not have a multimeter, buy one, but more invaluable and most simple tool you need, is a simple circuit tester.
which is basically 2 wires with a light bulb in between.

also, I did mention measure the feed at the coil. that the battery is ok is nice to know, but what matters is if there is voltage at the coil. During cranking, the column switch uses another connection/line. And if the starter turns, car starts, this means that your ignition works fine. however when you let the key go, so key is now in "ON" mode, the circuit at the switch is not the same. As said a frequent issue is that there is no voltage at all. as a result the car dies immediately after starting fine right before you let the key go.

As you are new to this. You also need to decompose what you see. first to be able to locate a problem, second, to describe to others the problems. For instance, you say it needs time to start. ok, but for instance, was it hard to start the first time you tried or did it become a problem after a few tries. ie. if you start/stop and pump, you start to have quite a lot of cold fuel into the intake and it becomes hard to start but is not related to the issue.

Once you have determined that the coil does receive 12v at the plus with key on on position( or bridge a wire from the battery plus directly to the coli + and try to start). Then you can remove this from the equation and as suggested above, go to next step that is fuel delivery/carb.

Harbor Freight has inexpensive voltmeters that work well. Just remember not to measure volts with the meter set on AMPs.