1970 Mustang Intermittedly Starts?

Hello to all and thanks in advance for providing any suggestions to help me keep this car issue figured out! Purchased this car almost two years ago and it would typically start up no problems after sitting overnight or for a few hours. However, after running the car and then say turning it off to pump gas or just for a short stop, it never starts up right away. Just this week I had it taken to a friends repair shop (yeah, I know) and was told they moved/adjust distributor caps and checked carb and that they saw no other problems and they had it starting it up every time. They had suggested that what I needed to do was run the old gas (its only been sitting about 3 months) and keep running premium until we are certain that nothing remains in the tank except new gas, but assured me that the car was good to go and they sent me on my way. Now, they didn’t charge me, which is great, but I got what I “paid” for when I took the car out for about a 45 minute cruise, stopped for gas, and without fail the dang thing wouldn’t start. A lovely citizen at the gas station raised the hood, fiddled with the carb, as he didn’t think it was a battery issue, and was able to get the car going and get me home, but again, car wouldn’t start about 20 minutes later. Hours later, out of curiosity, attempted and car started just fine. Suggestions? Ideas? And again, thanks!!!

Someone familiar with carburetors could likely get you up and running. I will suggest that the next time you wish to start the engine after a short stop, press the accelerator to the floor and hold it down while cranking the engine for up to 5 seconds. Don’t pump the pedal and of course release the pedal if it starts. There is a good chance that the pipe to the choke stove is bent or broken and the choke is held open by the vacuum pull off while the engine is running but quickly closes when the engine is turned off.

Could be a choke problem, like RK said, or an issue with the carb. Does it do this only in hot weather, or in cool weather too? If only in hot weather, it might be vapor lock. But I’m betting more on a carb problem.

This is most likely to be a problem with the carb.
In order to get it fixed properly, the OP needs to find a mechanic who is fully-skilled with carburetors, which usually means a mechanic over the age of 50. In this case, the older, the better.

Pretty good. Your 43 yr old car actually will occasionally start. Better than not starting at all

What engine is in your mustang, the 200, 250 straight 6 or the 302 or even a 351 ? ( not sure on the 351 ) All were available during this time…I had all 4 engines so might be able to give you any additional pointers, to the other positive replies. Old retired timer here. Currently own a 89 GT since new 112k and have done nothing under the hood except for plugs and wires and changing the oil every 6 months.
Runs like a champ and does not burn any oil…Will still smoke the tires in 1st and 2nd gear. car had a professional paint job done 5 years ago…was orginally black but went with a blue.

If the 302, those 2 BBL carbs had a problem, when you shut the engine off it would leak fuel into the intake and empty the carb bowl. …causing a flood condition. If running ethanol fuel I would try and avoid it…have a place here locally in Florida where I can get 87, 90 and 93 ethanol free pump gas.The ethanol fuels can cause a lot of problems for the older cars with carbs.Thats all that I run here for the car lawn mowers etc…but you pay extra $$$ per gallon…Well worth it. Nothing like having a 24 year old car since new and well taken care of.

1989 Mustang GT

rear view

Are you using gas with ethanol blended in?



Nice looking car. Glad you kept the stock look.

You really need to narrow it down to a spark or fuel issue. If it starts with a shot or 2 of starter fluid it is a fuel issue, if not a spark issue.

Just to clarify something, when you say the car will not start do you mean that the starter motor will crank the engine over and it will not start or do you mean that the starter motor will not physically crank the engine over?
This is just mentioned because of your reference to someone at the gas station thinking it was not a battery issue.

@Howie32703, that’s a slick looking Mustang you have. Very pretty car. :slight_smile:

From the original post I can’t tell if the starting motor is or isn’t cranking on the “hot” start attempts? If the starter isn’t cranking - I had a '67 Mustang (289 2bbl V8) and the starter on that motor isn’t very robust. It would develop an open circuit internally and work intermittently. Often it would work cold, but when hot the expanding metal would “open” the circuit so it wouldn’t run and therefore no cranking of the motor. I ended up carrying a spare starter in the trunk as it was easy to change the bad one out when it started to do this. I went through about 5 starters on the car over 15 years.

If the starter is cranking - then I suspect the heat of the motor is vaporizing the gas in the fuel line. My 2 bbl carb had a small fuel filter right where the fuel line entered the carb. I suspect the fuel is vaporizing there or somewhere in the fuel line between the fuel pump and the carb. You can try to wrap the fuel line with some insulating material. The test is when the car won’t start, open the hood and cool the fuel line, I used to pour water on it. After a couple of minutes to cool if the motor starts and runs then you have confirmed “vapor lock”. Which is fuel vaporizing in the fuel line. When this happens it in effect shuts off fuel to the carb and therefore the motor won’t run.

Another factor in “vapor lock” is fuel pressure. Fuel at higher pressure is less likely to vaporize. This means the fuel pump might be failing. If the pump isn’t putting out the spec pressure vapor lock can result. Another remedy might be to replace the fuel pump, a pretty easy job on that motor.

Thanks all! Stoveguyy You’re absolutely right in saying I’m lucky the 43 year old car starts at all and expected someone to say that…BUT I would like to have it as reliable as a car of this age can be. I knew the trick to hold the gas pedal down, not pump, but that doesn’t work to get it started. I haven’t yet tried the starter fluid on it as I haven’t had it handy when I’ve been stranded. Howie32703, then engine is the 302 so I will definitely look into the carb bowl/fuel intake issue and stay away from the ethanol fuels.
Again thanks to all who replied with suggestions and help, this PonyGirl appreciates it!