I have a 1952 mercury that I occasionally take out for a drive. And almost every time that I’m out driving, once I get up to maybe 50 mph the car will eventually start to sputter and eventually die. I found out that this happens when there is too little gas in the tank, but that isn’t the problem now. I have removed the old tank and rinsed it out using clean gas, the inside looked very good. Also I did install a fuel filter last fall and haven’t driven much since so that shouldn’t be plugged either. The engine was rebuilt last summer and runs wonderfully otherwise. What could be the problem?
Have you blown out the fuel line? Carberater rebuilt? Fuel pump ok? If you blow out the fuel line you may need to change the fuel filter again if dirt is or was your problem. This forum needs some pretty extensive info for experts to help. I am not one of them, just a car buff.
Have you checked the pinhole vent in the gas cap to see if it’s clogged or has the gas cap been replaced with a non-vented model?
The fuel line was almost entirely replaced because the old one just rusted away. Carb is rebuilt, and fuel pump was brand new last summer. The gas cap has not been replaced and I really don’t know anything about the pinhole vent.
Easy test for the gas cap idea is to just loosen it, or leave it off, to see if that clears up the the problem. If it does, then fix/replace the gas cap.
What happens after it dies? Will it restart after some cranking?
One of the first things to check is the float bowl level. If it’s running too low, you’ll get starvation issues like this. Could be gumming in the bowl float/needle, incorrect float setting, clogged fuel filter, a partially ruptured fuel pump diaphram or some other pump issue leading to restricted supply.
Todays gasoline has “high vapor pressure” and tends to vapor-lock when used in older cars in the summertime…On these old flat-heads, is there an exhaust passage under the carb to heat the carb and manifold? You might have to block that off…Next time it happens, pour some cold water on the fuel pump and see if that cures it…
The car will start again after it dies. I usually just push in the clutch push the starter button, release the clutch and the car takes off again and it seems to drive fine after that.
Why not simply try loosening the gas cap and working that angle first?
I tried the gas cap thing, but that did nothing whatsoever. I also replaced the fuel filter and it had a lot of little pieces of stuff in it, but that didn’t do anything either! What else could it possibly be?
I’m voting float level too low or fuel pump even though it was replaced. Need to do a fuel pump pressure test and volume test on it. Other than that, try a tank of non-oxygenated fuel available at some stations for car enthusiasts and power equipment.
How would you adjust the float level on this vehicle?
There’s usually a spec measurement but I have no idea what it would be on a 52 Merc nor do I have a book that old.
There is a general rule of thumb that can be used and it works very well.
Remove the top of the carburetor and turn it upside down. This will allow the float to rest on the needle valve. Eyeball the float from the side and make sure it’s at least parallel and in-line with the carburetor top. Maybe even a tiny bit tipped downward would help. Make SURE the float is not angled upwards away from the carb top, or air horn as it’s called.
If the float must be adjusted do NOT adjust it by grabbing onto the float itself, Use a pair of needle nose pliers and bend the float arm that attaches it to the pivot pin.
While the top is off make sure the float bowl is not full of sediment. If you’re continuing to get junk in there this means that filters are going to clog up very quickly. What I would do on an old car like this is install a sediment bowl; something that all cars used to have. You can buy these at farm supply outlets since many tractors use them. They’re cheap, easy to install, and will prevent the gunk from getting to the carburetor in the first place. Hope that helps.
According to my Motors Manual for the 52, Holley Carb # 1901, the float level should be 5/32" in the closed position and dash pot setting is .040-.050. Pull the air horn off and invert it so that the float closes the needle valve, then measure from the flange of the air horn to the outer surface of the float (not the seam), then adjust if necessary by bending the tab as OK440 described.
Also, how about the choke closing on you, or a kink in the fuel line since it was all replaced, or screen at pump or carb, etc. somewhere clogged? Sure sounds like a fuel supply issue but then not sure if that would stall it out totally. Fords used to have trouble with the chokes sticking at least a few years newer in 57 at least and that would stall it right out but hard to start again without flipping the choke. Course I was only a kid so my memory is a little foggy.
I also replaced the fuel filter and it had a lot of little pieces of stuff in it, but that didn’t do anything either!
You still have junk/debris in the fuel system, and I’ll bet some got into the carb. You’ll need to have the carb looked at again. Chances are, there is some debris in the float bowls, clogging the jets.
One possibility might be that the fuel line has a small pinhole leak so that the engine is sucking air when you get up to 50 miles per hour. I just had a similar problem with my 1978 Oldsmobile.
I disconected the line from the carba and blew it out and also emptied the sediment bowl and cleaned some crud out of that too and now it seems to run just great! Must have been a combination of the fuel filter needing replacement and some junk in the carb.