QuestionHello,
I am 29 and just bought my first Mustang. I didn't know much about engines and still know very little but am trying to learn something new everyday.
I have a 69' Mustang Coupe 351W. I have replaced the starter, alternator, regulator, added an electronic ignition and replaced the transmission. Car drives like a dream but has a very very cold start. I have to pump the pedal 5-10 times just to start and sometimes 5-10 more times to start. Once started I have to hold my foot on the gas so the engine won't die. If I let go of the gas the engine just drops out like it is choking...(I also had choke adjusted). If I keep my foot on gas for 2-3 minutes then the car idles beautifully and runs great. Once running it is easy to start up. Once the fluids are going and engine is warm everything works great. Is the cold start problem a fuel filter/pump issue or a carb problem?
If it is a carb problem; do you recommend a rebuild or a complete Holly replacement?
AnswerThere is nothing wrong with your fuel filter or pump, and there is very little wrong with your carburetor. The only problem is that the automatic choke is not working properly, or possibly not working at all.
I'm glad to see you have interest in learning more about this car. My advice is to buy the rebuilding kit for your carburetor (you'll have to determine which carburetor it has first) and follow the instructions in the kit for adjusting the automatic choke. You don't have to take anything apart or change any parts - you just have to read the directions and perform the steps, in order, that are listed. This, of course, is only if your car has the correct original carburetor, which is part number C9ZZ-9510 followed by the letter A, B, C or D, depending on whether it is a 2 bbl or a 4 bbl, and whether the car has an automatic transmission or a manual shift. (A is for 2bbl, manual, B is for 2bbl, Automatic, C is for 4 bbl manual, D is for 4 bbl automatic). The correct kit is part number CBAZ-9A586 followed by D for a 2 bbl or E for a 4 bbl. Once you have the kit and the instructions, keep it in a safe place for the day you might need it - but that day isn't here yet!
To diagnose your problem further, perform the following steps:
Next time the engine has been off long enough to have completely cooled off (for instance overnight) remove the air cleaner and look at the top of the carburetor. The front section of the carburetor should have a metal flap that is closed so as to block off air flow. If it is not already closed when you first look, get in the car, and without touching anything else, pump the gas one time. Now inspect the flap. If it is still not closed, the choke is not working at all. If it is closed, but not all the way, it is mis-adjusted.
Since some parts of the car have been modified , I cannot tell you exactly what to do after this diagnosis because I do not know what carburetor is on the car. If the carburetor has been replaced since the car was new, someone may have installed one with an electrically assisted choke, and if the choke is not working at all, it may be simply disconnected electrically.
If the choke is not electrically operated, but is not working at all, probably the reason is one of two things, either the air cleaner has been overtightened, warping the top of the carburetor so that the flap cannot move when the air cleaner is on, or some linkage has become disconnected or is not connected correctly.
If the choke appears to be working when you do the first test (the flap being closed), try starting the car with the air cleaner removed. If it now starts and idles the way it should (and when it is cold it should idle quite fast for the first few minutes), the problem is caused by the air cleaner - either due to being overtightened, or perhaps it has the wrong air cleaner on it, and the choke flap is being prevented from closing due to some interference between parts. It is normal, by the way, to have to pump the gas a few times (typically 3 times), to start an older car.
Younger folks don't realize that modern cars have computers that do all this for you (cold enrichment via the fuel injection system), so you have to be re-educated to drive an old car.
If the test shows that the flap is somewhat closed, but not all the way, the choke needs to be adjusted for a richer starting mixture.
If the flap is closed, but the idle is still too low after a cold start, the cold idle speed adjustment is incorrect - this is a simple screw adjustment somewhere on the carburetor, but without seeing the carburetor myself, I cannot tell you which of the many screws it is.
The bottom line is, you need to either get the shop manual or the kit so you can adjust it, or take the car to a mechanic who knows what he is doing, and leave it there overnight so he can adjust the choke correctly when the engine is ice cold - there is no other way to correct any of the above problems.
To answer your last question - I definitely do NOT recommend a carburetor rebuild - I don't think you need it anyway, but if for some reason you conclude that the carburetor needs to be replaced, buy a new one. Rebuilt carburetors are usually worthless, in my opinion. The only exception to that is when the owner rebuilds the carburetor himself. I would not suggest this to everyone, but I can tell from your question that you are interested and bright, and I'm sure you are able to follow the detailed directions and do it yourself. All it takes is simple hand tools, a clean well lit place to work, a can of spray carburetor cleaner from the auto parts store, and good eyesight. However, I repeat, there is nothing wrong with your carburetor that requires a rebuild at this time - just get the choke working and properly adjusted and you'll be quite pleased with the results.
I also advise you to buy the factory issued shop manual for this car- it will give you all the above information (how to adjust the carburetor) in addition to every other thing you will ever need to know about the car. These run on eBay frequently, or you can just contact one of the auto literature dealers and buy one directly. I use Ed Faxon at www.faxonautolit.com, but there are many others.
I generally try to dissuade people from modifying cars from the original - it makes it very difficult to troubleshoot for problems, and electronic ignition is almost impossible to troubleshoot - I hope you saved the original ignition system so that you can put the car back right if/when the new system acts up. That does not appear to have anything to do with your current problem - just a warning for the future.
Dick
