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Re: Anybody got the end all cure for vapor locking?
#21
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1929PackardGuy
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Quote:

DavidM wrote:
I would assume that your 1929 Packard is in good running order under all normal conditions, as were my two 1929 Packards. Mine started, idled and ran well under all conditions except when it was particularly hot weather and then they sometimes vapor locked.
Vapor lock does not happen all the time, only under adverse conditions. When it happens the engine will run for a second then starve for fuel for a second and keep doing that until it either corrects itself or the engine stalls. It might happen on a long steep climb and be fine when it is back on the flat and not working so hard. It might happen in stop start conditions when there is less air flow through the radiator. It never happens in cool or cold weather.
The problem is caused by the fuel in the carburetor boiling. When that happens the fuel drawn into the engine is intermittently either normal atomised liquid or vapor from the boiling fuel. The vapor has little energy so the engine starves and misses.
The problem starts in the vacuum tank where the fuel is heated by its proximity over the exhaust manifold and from engine bay heat. The fuel will boil in the vacuum tank. I have proved this by removing the top when it has happened on my car. Even though it is boiling it flows under gravity to the carburetor where it continues to boil. The boiling fuel is drawn through the carburetor to the engine as a mixture of liquid and vapor which is what causes the erratic running. There is negligible energy in the vapor so the engine starves for fuel.
Fixing the problem is not entirely possible under worst case conditions. Everything possible must be done to reduce the temperature of the fuel and that is far from easy. A heat shield under the vacuum tank is essential. An electric pump bypassing the vacuum tank is probably the best solution as there will be far less fuel exposed to the very high engine bay temperatures so it will be cooler when it reaches the carburetor. An electric pump feeding the vacuum tank does nothing to solve the problem. Getting the fuel to the vacuum tank is not the problem.
Another solution is to raise the temperature of the boiling point of the fuel. The fuel does not have a single boiling point like water, it is a mixture with many different boiling points, the lowest being around ambient temperature on a hot day. Mixing kerosene with the fuel raises the average boiling point of the fuel mixture, it dies not change the boiling points of the fuel components, it simply provides more higher boiling point fuel. I have spoken to fuel companies who have confirmed its effectiveness and that it is not detrimental to the engine. However the fuel needs to have at least 10% kerosene to make any difference, 20% is better. Such quantities can be difficult to obtain.
Another solution, although hardly practical, is use Avgas, available at airports. Avgas has a much higher average boiling point for obvious reasons.
These comments only apply to the models with vacuum tanks for fuel delivery. The problem may be different on cars with mechanical fuel pumps,


Exactly what was occurring, both days I was suffering vapor lock issues last week, it was 88 degrees outside with humidity levels in the mid-sixties. As stated, my vacuum pump is dead and just along for the ride, they restored it externally but it has no guts in it, so, the car has been running strictly off an electric fuel pump for at least the last twenty years.

The car has been in much cooler climates, however, than Louisiaiana. Most of its life was spent in Minnesota, then the last fifteen years in Tennessee. Kerosene is not a problem down here in redneck land except for the expense of it. I poured a quart of kerosene in the tank with about 14 gallons in it, and it was seemingly running much better and cooler, until my recent electrical issue arose, so, I'll continue the kerosene experiments on the other side of that.

I've also read that the issue was with the fuel vaporizing in the intake manifold above the carburetor before it reaches the cylinders, which also seems plausible as turning up the psi on the electric fuel pump doesn't seem to have any effect on whether or not the car was vapor locking. The major issue it was demonstrating was just staggering and stalling when coming to a stop after an extended period of cruising along at 40-55 mph. Adjusting the idle up also did nothing to stop this. Continuously working the gas pedal did, and would keep it from stalling, but, that's rather a pain.

The big tell-tale that this is a vapor lock issue, to me, is that it will not do it when idling with the hood open on hot days, but, close the hood, and in a few minutes, it begins to stumble and if left to its own, it stalls. When the carburetor is pulling in cooler air, even mildly cooler air, she'll idle all day long. Hood down, on an 85+ degree day, maybe one or two minutes and she stalls.

Thanks!

Posted on: 1/4 9:23
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Re: Anybody got the end all cure for vapor locking?
#22
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DavidM
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I missed the point that your vacuum tank does not work. Does your electric pump bypass it? If not it should however I would recommend you fix the vacuum tank. The electric pump should only be switched on to overcome vapor lock otherwise it can overcome the carburetor cut off and flood the carburetor. Much has been written about that.
Your experiences with opening the hood are exactly the same as mine. Also when I parked my cars in summer I always left the hood open otherwise the car would be hard or impossible to start unless they had hours to cool down.
Someone mentioned diesel instead of kerosene. I tried it once on a long trip in hot weather when the car was constantly vapor locking, I can't remember the % added but it was a lot. It made no difference good or bad.
On that trip I improvised a way of holding the hood sides up a couple of inches while driving. The increased airflow into the engine area significantly reduced the problem. Later in the day a cool change occurred and the vapor lock problem instantly stopped. I have driven one of my 1929's in light snow and it never ran better.
Another time I had to drive when it was just over 100 deg. I constantly had to stop to wet the carburetor and vacuum tank to cool them. That provided instant but very short relief.
I should add most of the time my 1929's were great cars to drive. I drove the 633 Roadster on many long-distance tours over twenty years. It did not have an electric fuel pump, only the vacuum tank. The other car was a 633 Sedan and I fitted it with an electric pump bypassing the vacuum tank. So when it vapor locked I switched on the pump giving almost instantaneous relief most of the time. On very hot days nothing much works. Stay home or stop and wait for the sun to go down!

Posted on: 1/4 16:10
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Re: Anybody got the end all cure for vapor locking?
#23
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1929PackardGuy
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We are very much on the same page! Eventually I will rebuild the vacuum pump, but right now, literally, I have nothing in there to work with. When you open it up, it's just an empty can, there are NO internals in it - was merely plumbed and externally restored for good looks (previous owner, not me).

The electric pump is mounted back by the rear axle and directly feeds the carburetor with a regulator that is set alternately at 1-1/2 psi or sometimes 2-1/2 psi - I've tried to figure out where the car likes it better but honestly can't tell much difference. It's been running on the straight electric fuel pump setup since 2000 when the restoration was finished, but the previous owner only put 300 miles on it from 2005 to August of 2020 when I bought it. I've already put 420 miles on it since then just tinkering with it and experimenting!

I want to make her into a fun tour car, maybe do some weddings with it (it's a club sedan) and just generally have fun with it. Not looking to go to the Amelia Island Concours, just want it to be a fun and reliable driver. Which for us primarily means late September through March only - after that it's far too hot down here. We've been cheated quite a bit this year, it's been exceptionally hot and we just had our first day below freezing (30 degrees) yesterday. Had three days in a row last week where the daytime highs were 88 and 89!

Oh well, hopefully I'll get it all figured out before the winter is over. I was hoping to repaint her this winter but looks like I'll have to put that off until early summer now - probably be for the best anyway. Thanks for all the helpful advice!

Posted on: 1/4 16:23
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Re: Anybody got the end all cure for vapor locking?
#24
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DavidM
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The fact that your pump feeds directly to the carburetor is interesting. That should overcome most vapor lock events. If you are using fuel with ethanol that could explain the problem. I found it made the problem much worse.

Posted on: 1/4 17:48
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Re: Anybody got the end all cure for vapor locking?
#25
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1929PackardGuy
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Nope, non ethanol gas, just heat I'm afraid.

Posted on: 1/4 21:16
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Re: Anybody got the end all cure for vapor locking?
#26
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5540Packards
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Maybe ethanol-free fuel? Just guessing.

Posted on: 1/4 22:27
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Re: Anybody got the end all cure for vapor locking?
#27
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29tons
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Vapor lock has been happeninng at least since the 40s. I have an owners manual from a 40s car that i own that states how to start the car if it vapor locks. Its not a Packard but I was suprised to read that in the owners manual.

Posted on: 1/5 6:22
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Re: Anybody got the end all cure for vapor locking?
#28
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DavidM
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The Packard company issued this letter to its dealers in 1931 giving instructions about modifications to avoid vapor lock. It states that the fuel had become more susceptible to vapor lock. The fuel today is far more "susceptible to vapor lock" than it was in 1931. The problem is that it vaporizes or boils at a much lower temperature. It is certainly not a new problem

Attach file:


pdf Packard tech letter re vapour lock.pdf Size: 876.67 KB; Hits: 55

Posted on: 1/5 16:17
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Re: Anybody got the end all cure for vapor locking?
#29
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1929PackardGuy
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Quote:

DavidM wrote:
The Packard company issued this letter to its dealers in 1931 giving instructions about modifications to avoid vapor lock. It states that the fuel had become more susceptible to vapor lock. The fuel today is far more "susceptible to vapor lock" than it was in 1931. The problem is that it vaporizes or boils at a much lower temperature. It is certainly not a new problem


Wow! Packard actually sent out a tech letter in 1930 telling dealers to remove the fuel filter to help move the gas along? That seems like a fairly drastic measure for that time!

Posted on: 1/6 9:43
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Re: Anybody got the end all cure for vapor locking?
#30
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Duane Gunn
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I currently have 2 running Packards here in Phoenix, Arizona, a 1955 Clipper Custom and a 1940 160 Sedan. I have mechanical fuel pumps on both cars. Near the gas tank, I have electrical fuel pumps. In the winter I drive without the electrical fuel pump on. In the summer, I only turn on the electric fuel pump when the car is bucking, like it's out of gas. I do drive in temperatures of over 100F. I know, no AC, and my wife won't be in the car. On the freeway is where I have most of the problem, until I turn on the electric fuel pump. This is my end all cure for vapor locking. I have over 70,000 miles on this set up so I know it works.
Good luck finding yours.

Posted on: 1/6 15:23
1955 Clipper Custom
1940 160 Touring Sedan
1953 Patrician
1948 Super 8 Limo
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