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68 Mustang Will Not Start

The car will not start on its own when it is cold. I have to use starting fluid to get it started. Once it has started and runs then there is no problem.

I have replace the fuel filter, air filter and spark plugs.

Points, rotor and cap all look good.

Any ideal? I have purchased a carburetor rebuild kit - not sure if that would help the issue.

Once the car is up and running it runs great - no misses or anything.

I believe on that car the choke is controlled by a kind of temperature controlled spring. Look at that. You can actually adjust it by rotating the housing of the spring control, set it so it just barely opens at 35 deg? and go from there. As a start look at the choke in a cold start position, adjust it so it is just barely closing at that point and go from there.

That certainly sounds like a choke issue. Is the choke closing when the engine is cold?

I had a similar problem on my 1978 Oldsmobile Cutlass. The problem turned out to be a bad section of neoprene fuel line down by the gasoline tank. I could start the car by priming the carburetor and the mechanical fuel pump could overcome the bad section of the fuel line. However, when the engine was being cranked over by the starter motor, the pump wasn’t strong enough to overcome the bad section of the fuel line and was sucking mosgtly air.

Remove the air filter completely, housing and all…When cold, the choke plate on top of the carburetor should be closed. If not, open the throttle and it should snap shut…Turn the key and it should start. On the side of the carb is a black cover that covers the choke spring, a thermostatic coil…You can loosen the 3 screws and rotate the cover to adjust the choke…When cold, the choke plate should close all the way and a hair more. Tighten the screws there…Remember to hold the throttle open a little when adjusting the choke so the fast idle cam can move into position and provide a fast idle during warm-up. After the engine starts, the choke should open fairly quickly to avoid flooding the engine. Some cars have a vacuum choke pull-off, some use an electric choke heater to quickly heat that choke spring and open the choke. Some use both…You can help the choke by “pumping it”, the throttle, several times which hopefully will squirt some fuel into the engine and provide a quick start…

First Attempt:

Following the advice posted here still not successful. Looking at the Hayes book and instructions from the carb rebuild kit (which we have not done yet) it says to set the fast idle on the highest cam - did that and screwed in the adjustment screw all the way. Then using a 5/32 drill adjusted the plate. Still no go.

Some more information:

1968 Mustang 6 cylinder with an autolite 1100 carburetor 1 barrel. The choke is feed air from the exhaust manifold.

You didn’t post whether you have a 6 or V8 motor, or if it is standard or has been modified over the years. If it is still an original set up Caddyman is correct, you have an automatic choke.

The proper starting procedure in those days (I had a '67 289 2 bbl carb Mustang) was to press the gas petal to the floor once and let it up and remove your foot from the gas. This would set the auto choke to the closed position and also set the fast idle. Then you’d turn the key and the motor would start. In really, really cold weather if it didn’t start you’d turn the key and pump the gas petal once to 3 times to shoot some extra gas in from the accelerator pump. Folks who only know fuel injected cars have no clue what I’m talking about.

Shooting all this gas into the carb only worked if you had decent plugs, wires, cap, rotor, and coil otherwise you’d flood the engine and you were pretty much not going anywhere for awhile. My cars of the era were always given a winter tune up and started regardless of how cold it got, and -20 was not out of the question. In those days you needed to understand how to work the chokes and when to pump the gas and when not to pump or you never got your car started.

Today you just turn the key, or for some push the start button. Cars weren’t like appliances back in '68. So, when the car is cold in the morning push the gas petal to the floor once and open up the air cleaner. The choke should be fully closed. If it isn’t it needs some light weight lubricant on the hinges and linkages or is just out of adjustment. You might have to pump the gas petal a bit to get her going and keep her going. Once running the fast idle should have the motor turning about 1,500 to 2,000 rpm for about 30 sec. to 1 min. then you tap the gas petal and it should drop about 500 rpm. About 5 min. later the car should be idling at the normal idle speed for a warmed up motor.

1968 Mustang 6 cylinder with an autolite 1100 carburetor 1 barrel. The choke is feed air from the exhaust manifold.

That little heater tube is to warm the bi-metal coil in the choke housing. That housing has the 3 screws holding the plastic circle that hooks the outer end of the bi-metal coil. Loosen those screws and turn that until that choke flap is closed. You can even put preload on it.

Now before you start it…open the choke flapper manually and pump the gas. See if gas actually squirts from the accelerator pump. If you see fuel squirting …and the choke closes by itself, then there’s that end of the equation. Beyond that I’d play with timing to see if that’s on spec.

The choke must be closed when the engine is cold. There must be gas in the carburetor. The tube that connects the choke housing with the exhaust manifold is called the heat riser…A small vacuum passage inside the choke housing draws heat from the manifold to open the choke. There will be a vacuum operated piston inside the choke housing to pull the choke open a little when the engine starts…

For the engine to start normally, the carb must be full of gasoline. After a week or two, it is normal for this gasoline in the float chamber to evaporate or leak out. The engine will not start until the fuel pump has enough time to refill the carburetor. Carbs also have an accelerator pump. When you pump the gas pedal, you should be able to SEE the fuel squirt into the engine…If not, the pump is not working. There will be a new one in the rebuild kit. In the bottom of the pump chamber, there should be a little ball bearing that acts as a check valve and prevents fuel from being pumped back into the float bowl. This pumping action should allow you to start the engine even if the choke is set less than perfectly…

You, and everyone else seem to be concentrating on fuel issues. I wonder, have you done a compression check? A tired engine with low compression will run fine, but be hard to start when cold. Just a thought.

Did not realize that. That will be something else to check.

The next time you want to start it cold, first, look down the carburetor throat with a flashlight and pump the throttle a few times. You should SEE the accelerator pump squirting fuel in. After a few pumps, provided with this extra fuel, the engine should start…

If no fuel squirts in, the the pump is not working OR the float-bowl has drained (leaked) out.

And yes, a low compression tired engine will be difficult to start cold no matter what…100 psi is a good dividing line between serviceable and unserviceable engines…

Well we were able to finally get it to start with out the use of ether. Adjusted the choke so that it closed completely when hitting the gas peddle and making sure the fast idle was set correctly. But after letting it warm up the choke never reopened until i manually adjusted the choke. So now it appears that the automatic choke spring has sprung. So wondering if anyone know of a source to get a new one or I am open to the complete choke housing. I have done some searches on line but no luck so far. I am just doing a simple search using ‘68 ford mustang choke’

That “spring” is actually a bimettalic coil that opens and closes the choke with temperature changes. Yes, they can become weak over the years due to work stress and corrosion. You should be able to get a replacement from the same source you got your carb rebuild kit.

One caveat. the shaft on an old choke can develop wear grooves where the shaft goes through the housing body. The grooves can cause binding of the choke shaft, making it impossible for the bimettalic spring to open and close it properly. You need to evaluate these things before rebuild.

Other issues mentioned such as checking the function of the accelerator pump should also be a part of your repair process.

Honestly, if it were me I’d buy a rebuilt replacement carb and return the rebuild kit for refund. It should be easy to find one on the internet for this engine, along with good articles and instructions on how to adjust it. I’ve successfully rebuilt a few carbs but never one that age. The mechanical parts do wear including the needle valves that control flow to the bowl, the floats can become saturated or leaky, rubber parts such as the accelerator pump diaphragm can become tired and leaky…on a carb that age it may be better to just replace than rebuild.

Better to replace with a rebuilt carbeurator rather than have the fun of rebuilding the existing one yourself? What am I missing?

When people “rebuild” carburators today at home (or in the garage) what type of chemicals are used? I remember that the carb rebuild tank was some real nasty stuff. Myself I never found boiling then out in chemicals was required, just replace what is ruptured, tighten what is loose, adjust what is required, “carb OH” has always been a scam.

OK some Q-jets needed some TLC but that was more “carb reconstruction” than “carb OH”

Look for choke thermostat, I called NAPA, they said give them the carb number and they should be able to order one. Save the rebuild for when you need it.

There used to be kits available to convert an automatic choke to a manual choke. I made this conversion on a 1955 Pontiac that I owned when I had trouble with the choke. The kit included a cable and a knob that mounted on the bottom of the dashboard. The choke housing was replaced at the carburetor end of the cable with a device that operated the choke damper. On a cold start, I pulled the choke out and when the engine fired, I gradually pushed the choke in. I don’t know if such conversion kits are still available. I bought mine at the Western Auto store and they are long gone. However if a manual choke kit is available at some auto parts store, it is easily installed. You won’t have kept the car original if that is your goal.

If the choke is the only issue, install a manual choke kit (if you can find one) and drive on…

Millions of cars like this were modified with hand chokes when their finicky automatic chokes failed to work properly…

I know that pep boys carries the manual choke kit, put one on my 74 nova about a year ago. It’s in the section where you can buy inner door and window handles and other hard to find stuff. I also bought new hood release cables for the 59 bird.

The cables are about 6ft long so you trim to your needs.