Hard starting after a week or two sitting.

jimlj66

Well-known member
After sitting for a week or so, my Mustang is hard to start. After several seconds cranking and pumping the gas, it will start and idle fine. If I drive it every day, it will start right up. This makes me think the gas is draining out of the carburetor. I think the gas is running back to the tank as I don't smell it in the oil, and it is not leaking on the outside. I rebuilt the carburetor (Autolite 1100) with a el cheap NAPA kit a couple years ago. I have since purchased a (what I think is a quality) made in USA kit and plan to do another rebuild.

So, while I have the carburetor apart, is there anything to look for that might cause the hard start issue? Is fuel draining out of the carburetor a possible cause?

Also, can someone explain how to adjust the float level? The kit I used had measurements to adjust to, but I'm not sure were to take the measurement from.
 
:) Hi jimlj66.From what you describe,it sounds like the fuel is just evaporating from the fuel bowl,and the pump has to refill it before the motor will fire.This is normal.BTDT.
HOWEVER,someone with more knowledge than I will hopefully chime in and correct me if I`m wrong.
Good luck.Have fun.Be safe.
Leo
 
X2 on the evaporation all those early cars before mid 70's were just vented to the atmosphere. So that is normal you would need to install a later closed fuel system (non vented and a big job too) to be able to change that.

Float is set with carb top turned over so float is facing upward with no extra pressure other that gravity and weight of the float on the needle and seat. Measurement is 1 3/32 inch with the stock nitro type float (a 66 carb?). If it's been changed to a brass float set it at 1 inch + or - 1 /32 inch. Measure from the gasket flange surface (without gasket) of carb top to top front edge in the center point of the float with your scale or a machinist ruler etc. If you have to adjust the measurement carefully bend tab to adjust, for sure don't plush down on float assembly when installed it will cause damage to the needle and not work correctly. :nod: I have used hundreds of the NAPA carb kits over years without problems of course I don't know if they are still made in the USA or not.
 
Thanks for the quick reply's. I had not thought of evaporation, but that makes sense. It had never been a problem with other old cars I have had, but they weren't "old" cars then, and they would have been daily driven.

I didn't mean to bad mouth NAPA kits, I guess I was just repeating what the salesman had said that sold me my current kit. If my problem is indeed evaporation it is not a problem with the kit.

Bubba, when you say to measure to the "top" front edge of the float, are you talking the top with it inverted, or the top of the float as it would be installed on the carburetor?
 
Just to clarify...'stock' float is brass, nitrophyl are replacements.



Be sure you use the correct needle. The GP Sorenson kit comes with two different lengths...too long will result in too little fuel in the bowl (lean), too short will result in needle binding during float travel.

Last time I had a carb do that was last spring/summer, and I'm sure evaporation contributed to it, but turned out to be a pourous/holy ;) area developed in the aluminum bowl casting...leaked or more like leached the fuel out over a week. I occasionally go a couple weeks without driving the car after swapping back to a good casting and haven't had the 'several seconds cranking to refill the bowl' issue come up since. Good luck (y)
 
X2 on a porous or rotted out casting that does happen sometimes too.

when you say to measure to the "top" front edge of the float, are you talking the top with it inverted, or the top of the float as it would be installed on the carburetor?

That would be the top of the float when it's Inverted. :nod: Good luck

Oh and I did not take any offense about the NAPA kits in fact am curious if the quality has went down. With move to the EFI cars for severial decades now have not bought a carb kit for probably 15 years so don't know, But was planing to get a couple soon for my old projects.
 
I wonder if there is a connection to EFI and closed fuel systems with regards to the the fuel formulation used?

Sorta how the oils reduced the ammount of zinc over the years to clean up emissions with the addition of roller cams and rockers being in most engines. Maybe the formulation has changed to reduce additivies that helped with evaporation?
 
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