1952 mercury trouble, again

Hi again,

I have yet another question about my '52 merc.

I had it in the shop a few weeks ago and when I got it back it just ran like a top. The mechanic adjusted the float level in the carburetor and it just ran great. Now… it’s kind of doing what it was doing before. Once I get up to highway speed (sometimes) it will start chugging along slowing down and (sometimes) it dies… It will start again though.

When I’m just kind of idling along or driving about 30-40 mph it seems fine.

Keep in mind that it doesn’t always start chugging when I’m up to highway speed, lately it’s been most of the time though…

Is it probably that the fuel float level is still set too low?

Any thoughts would be greatly appreciated!

Since I have this car, I might as well have it run right…

Is the float itself in good condition? If it’s all brass they can leak, and if it’s plastic they can absorb gas.

Again I don’t think you cannot disregard vapor lock on this age vehicle and the current fuels available that compound the problem. Extra heat spacer on carb, insulate fuel lines from engine heat, and use the non-oxy fuel from stations that sell to boaters and old car enthusiasts. If the float was just adjusted, it most likely was checked for leakage since you have to dismantle the carb to set the float. Check the fuel pump pressure and volume delivery though and may want to consider an electric pump at some point.

If it did leak wouldn’t that cause the car to not run at all eventually?

The mechanic did check the fuel pump pressure and said it was good. I don’t really understand why the car worked so good when I first got it back and is now giving me trouble again… is the non-oxy fuel premium fuel? Would you just insulate the fuel line that goes to the fuel pump? How would you insulate the line?

I’ve used Armaflex closed-cell insulation (you can get it at HVAC supply stores) to insulate fuel lines. Most important is the line in the engine compartment, and anywhere it’s near the exhaust system. Vapor lock should affect it only once it’s hot - does the problem occur if you take it out first thing in the morning on the highway, before it’s hot? If so, then I’d suspect some kind of fuel obstruction - was a filter cleaned or replaced when he last worked on it? It could be partially plugged again.

I did just replace the fuel filter last week. The old one had a fair amount of sediment in it… it seemed to give me more trouble with the new filter. I will check next time I drive it to see if it bothers when first starting out.

Yeah, you are trying to keep the heat from the engine from heating up the fuel line. Used to wrap it with asbestos but can’t do that anymore. The Mobil station where I buy has the non-oxy as the premim and it is labeled for off-road use. The Minnesota Street Rod Association (MSRA) publishes a state-wide list of stations selling the non-oxy in Minnesota anyway so each state will be different. Local old car clubs or marine dealers should be able to help locate a local source. As far as the fuel pump goes, on those mechanical pumps you have to not only measure pressure but also volume. Pressure can be fine but won’t put out enough volume to keep the carb happy at higher speeds. Would have the same effect as too low a float setting. Just my 2 cents but sounds like you need to zero in on the symptoms some more. I 'spose a coil could also be cutting out when it gets over-heated too.

I wonder if you have rust in the gasoline tank which is being sucked up into the fuel system when you are pumping more fuel at highway speeds. The fact that you had quite a bit of sediment in the fuel filter may be an indication of rust and gunk in the gas tank.

I had the gas tank cleaned and lined, but there could still be rust in it somehow. Ethanol tends to clean all that stuff off and send it through anyway… I believe the mechanic did test for both volume AND pressure. I filled up with premium today, but that didn’t seem to make too much difference. I drove around for maybe 20 miles or so and it seemed to sputter mostly when I got up to 60-65 (I think my speedometer is off 5-8 miles - checking with an app on my smartphone) So more like 50-55. It only died for me once (when a vehicle was following me of course…) I just pushed in the clutch and pressed the starter button and after a little while it took off. It seemed to run fine at lower speeds - around 40-45.

I think I will have the mechanic check for junk in the carb again and possibly adjust the float slightly higher. Driving at higher speeds demands more fuel and if there’s junk in there I suppose it’s more likely to get sucked in then. When I let off on the accelerator and then slowing press down on it again that seems to “cure” it.

I talked with our local Napa man and he said that he knew more of vapor locking in the '60s and '70s cars but not really in cars from the early '50s…

The coil was replaced a few years ago when the old when died on me.

Now that I think about it, vapor lock would seem to be more of a problem at low speed, not cruising at high speed. At high speed you’ve got a lot of gas flowing through the line and air flowing by it, reducing the heat problem. Cars would vapor lock when you came OFF the freeway and stopped at a light, that kind of thing. But they did it in the 50s, for sure!

I’m still thinking it’s a fuel blockage problem, or maybe something in the ignition.

Are the non metal fuel lines and any seals new? One source could be old stuff deteriorating from the inside out due to ethanol. You may have to replace some lines and flush the carb.

The only non metal fuel line is a short rubber hose from the fuel line to the fuel pump that I cut and added a fuel filter to and this line is new.

I wonder if this hose is collapsing when you are having to pump more fuel. I hope it is a neoprene hose as opposed to rubber. Neoprene doesn’t deteriorate from petroleum products.
Another thought is that the fuel pump can’t keep up the fuel supply at higher speeds. If this is the mechanical pump, the pump may be fine but the lobe on the camshaft that moves the pump arm may be worn. I hope this isn’t the case, but it is a possibility.

It is a reproduction of the original hose, but I’m not sure what it’s made out of for sure… I do know the inside diameter is quite small - not that that matters…

The lobe on the camshaft probably isn’t worn or would have been noticed by the mechanic who put the motor back together when we had it rebuilt.

Could the rod be worn? I don’t think it looked worn when we had everything apart.

When I was a kid, we had a guy in the neighborhood with an old 49 Ford. He carried a jug of water with him so when it stalled, he poured the water on the fuel line and off he went again. Come to think of it though that was in town, not highway. Never had a vapor lock problem with any of our late 50’s 60’s or 70’s cars though. Yep, maybe just junk in the fuel system yet. I believe there is an “economizer” jet or circuit in the carb though that if junked up can cause a high end problem but I’ll be danged if I know where it is.

Today I had the misfortune of forgetting the key on in the car and I seemed to have burnt out the points (no spark anywhere). Along with this I noticed that when I cranked the engine there was plenty of gas coming and even when I stopped cranking the engine there seemed to be gas leaking from the float needle seat plug. I’m thinking the float level is actually set a little too high. Maybe? So that would mean there is probably some kind of sediment in the carb that needs to be cleaned out.

Thats interesting. Maybe the points were not set correctly to begin with or they forgot to clean the oil off the points when putting them in or forgot to lube the rub block. Junk in the carb could cause the needle valve to stay open and hold the float down but doesn’t mean the float is not adjusted properly.

I know you replaced the needle and seat, but debris in the bowl can cause failure at high speeds. It can settle and seems a plausible explanation. If all seems to have been done on the fuel side of the fence, after proper performance of the needle and seat, I would get a compression and leak down test done on the cylinders.

Well, now I don’t know what’s wrong… I’ve replaced the points, condenser, rotor, and the coil. I figured out there was a problem with the rubber fuel line last night and I’ve since repaired that problem as well. Last night the car would run (we put a coil for an H Farmell in the car when the one didn’t seem to work that I put in new 4 years ago and when we did that the car would start. Today I put the correct coil in the car. There is still no spark, at least when we pulled a plug out.

After I fixed the fuel line and tried to start the car (this was before I put in a brand new coil). the car did start well more it fired and ran a few seconds then died and now it will not spark or anything…

If it’s not the points, condenser, coil, or rotor, is there anything left??

Any ideas out there??? I’m now to the point where I’m just going to turn it over to a “real mechanic”.

Yesterday when the car ran, it just kind of shook when I would rev it up and even the little bit I was able to drive it.

Anyone who thinks owning a classic car is a bed of roses is sadly mistaken…