Packard Forum Index » Pre-War (1899-1942)

I have a 1940 120, which I have just been able to check out recently, although I bought it over a month ago. The car starts instantly, and runs strong and smooth, with oil pressure to the right of center on the gauge, however, after driving at 50-60 mph for 15 to 20 minutes, the engine begins to hesitate and eventually just peters out. If allowed to sit for a while, it starts right up fine and runs OK for a while, then exhibits the same failure. I have to assume the interuption in performance has something to do with the engine or some of its components getting to a certain termperature? Maybe the coil gets hot and fails. Maybe a fuel problem (vapor lock). Any suggestions? Since my heat gauge not working; I guess I may have to get that part going to help me in my diagnosis of this problem?

Could be vapor lock but I'd think it would have to be awfully warm to act up that quickly--unless the steel tube is right on the exhaust manifold. Do you have a fuel filter where you can see if any gas present?

I had a very similar problem on a 54 and it turned out to be the flex fuel hose was old and brittle. Apparently the inside lining was cracked and loose. Suction was enough to periodically let a piece move and close off. Without the engine running, it would relax and open the line again.

And, as you said, the coil could also be acting up when hot.

HH56
Thanks for the response. I do have a clear bowl filter just ahead of the carb, and it does not appear to be void of fuel when this sputtering occurs, so I am less inclined to think that it is a fuel starvation problem, but your example may have some merit so I'll have to check the entire fuel line more closely.

I can imagine the frustration. The coil should be easy to check: no spark = no engine runnin'. If you consider the history of Packard coil locations from the early 30's to 40 you will note from atop the engine to aside the engine to the horn bracket and finally back to the firewall in 41. Does that give you a sense that hot coils are not a good thing? Is there such a thing as a "weak" coil? I am told so, but I am not an expert in this area. Obviously a fresh set of points and condensor are cheap and easy.
Spark Yes, Fuel No = Fuel delivery issue. Do you have a fuel pump and/or a carburetor heat shield? Is the insulator gasket present between your carburetor and the intake manifold (its 1/4" thick, not just the thin gasket), along with a heat shielded fuel line. These are elements of the street term "vapor locking" which with todays alchohol fuels makes our cars more susceptable to fuel "boiling" problems.
Fuel pump strong? Not normally heat affected from my understanding. Is there a fuel filter that needs changing somewhere in the system? Please consider properly installing an electric "backup" pump.
Finally, and this is important - check the heat choke valve in the exhaust manifold - that heat spring weighted shaft thing above the exhaust pipe. If this is stuck in the closed position, as soon as the engine really starts to warm up, you could be diverting a huge amount of heat up, where you don't want it any more, contributing to cooking the fuel in the carburetor.... Well, this is an open forum for armchair quarterbacks, so that's my .02 worth. With a few more clues, I am confident you will get more than a second opinion.

I had the same issue with my boat, it appeared to have fuel bucause I could see it in the glass filter, but yet it would peter out, after about 20 minutes of running it. It turned out that there was a ceramic fuel filter in the carburator just upstream of the needle valve that was partially clogged, I removed it and have been boating for hours on end without any problem.

flackmaster:

Thank you for giving me so many areas to check. I have to agree about the location of the coil; on this 120 it is mounted right to the left side of the engine, just below the head with a pretty hefty bracket that must be fairy efficient at transferring a lot of engine heat to the coil. I did try disconnecting the coil from this mount and tying it to the horns, where it was well away from the engine and got the same sputtering result.

I don't believe my 120 has a heat shield above and forward of the fuel pump like my 1948's have, nor do I know whether they were ever outfitted with one.

I did check to see whether or not the damper valve in the exhaust manifold beneath the carb was moving freely and had a spring attached, but did not follow through by watching its performance in the warm-up process.

Again, you give me a lot of things to check up on.

Is your gas cap vented? Cars from before about 1970 had a vent hole in the gas cap to allow air in. If the hole is plugged or the wrong cap used, the engine will run until the vacuum in the tank is equal to the pressure of the fuel pump, then the engine stalls out.

Next time it stalls open the gas cap and listen for a "hiss" of air.

Rusty:

Thanks for the suggestion regarding the gas cap; I would never have thought of that. The car has a locking type gas cap and doesn't appear to have any vent. This will give me one more possible solution to check out the next time it acts up!

G'day all, If the engine is just dying ( fuel)and not backfiring ( ignition) I would suggest fuel pump. The next time it happened I would immediately disconnect the centre lead from the coil, then disconnect where the fuel line enters the carby and get someone to crank the engine for 30 seconds while you check for a consistent fuel flow from the fuel pump (carefully dispense it into a metal quart coffee can or similar, not onto the exhaust mainfold). If this fuel flow and delivery is satisfactory. I would reconnect the fuel line and the coil output lead. I would then disconnect the coil lead going into the distributor and hold it about 1/4 inch from the block and get someone to crank the engine with the ignition ON for 30 seconds and check for a strong and consistent spark.
I am more inclined to believe that it is your fuel pump as those internal valves do wear out and a hot motor would bring out this fault. Also check that you do not have an alien blocked filter fitted in the fuel line between the tank and your fuel pump. I had a blocked alien fuel filter in one of my cars and it nearly drove me crazy trying to figure out why my car was pinging on hills. ( it was running lean due to a blocked fuel filter near the tank). Of course a blocked fuel cap vent and others mentioned are also good candidates. Best regards Peter Toet.

Dan
My moneys on the heat riser being stuck closed. My 1940 120 acted exactly the same. I was afraid to drive it anywhere. I would have to wait sometimes an hour or more before it would restart. Finally it would fire up and run great for awhile then the same thing. Good Luck keep us posted.