vapor lock (again)

[Guest hwess]

Is the gas-ethonol mix more or less apt to cause vapor lock, or no difference? Is there anything I can add to gas to prevent it? Expecting +100 next week.

[Phil 32DL6]

Why not install an electric fuel pump? When my newest DL6 arrived the previous owner had installed a rebuilt original fuel pump which may have worked okay out in CO but immediately gave me vapor lock problem here in hot humid CT. Fortunately he included the electric fuel pump he had removed. (It had been installed under the hood in plain sight by a previous owner.) I left the rebuilt pump for looks, by-passed it, and re-installed the electric pump hidden in front of the fuel tank.

Result? Goodbye vapor lock! Plus, I get better control priming the carb for start up, and purging the carb if I flood it. As a further bonus, the hidden toggle switch gives another ounce of theft protection.

My pump's a vintage Bendix of unknown age & reliability so I bought one of these to have an emergency back up: Fuel Pump Dodge Chrysler, DeSoto 1931 1930 1929 1928 | eBay

Edited July 18, 2011 by Phil 32DL6 (see edit history)

[Guest 1930]

I would put an insulator on the line where it runs next to manifold, you can buy the cloth wrap insualtor material cheap, comes in rolls and is avail online at companies like Jegs or Speedpro.

You can EASILY remove and use over as many times as you like and this way you are not altering from stock set-up

[Phil 32DL6]

Jason's right...you can add heat insulating wrap. Both electric pumps and wrap were solutions back in the day so either could be considered "original solutions."

I tried the wraps first and found them terribly ugly. Most folks don't notice I've by-passed the original mechanical pump.

The attached photo shows what Jason's talking about nicely presented on a 1931 Auburn Cabriolet.

It's good to have choices!

Edited July 18, 2011 by Phil 32DL6 (see edit history)

[Guest 1930]

I could be wrong Phil but I think Wess car is a couple of years older than yours which means a carb thats not quite as advanced as yours and in my experience prone to problems with electric pumps, that is why I suggested the wrap.

[Phil 32DL6]

Ahhh, I wondered about that. Out of curiosity, what year is it, hwess?

[Guest 1930]

The last time he asked a similar question it was for his 1913 case. It would appear he also has a 29 DA and a 36 as well

[Guest 1hooligan]

One comment, if going with a electric fuel pump get one that is low volume. Otherwise you will blow by the flout valve. max 2 gallons per minute. Place as low as possible, below the tank, not above it.

[lozrocks]

The first thing to look for when vapour lock is experienced is the fuel line. Especially with vacuum tank and gravity fed cars. The fuel line must always run downhill. Any fancy pigtail or trying to hide the fuel line should be eliminated.

[hwellens]

If you have gravity feed system there cannot be a vapor lock. The vapor lock (pressure bubble in the fuel line) will expand back into the tank which is not pressurized. The problem is when you have a fuel pump which has a one way valve and the carburetor with the needle seat closed, there is no way that the heated pressurized vapor can escape.

[lozrocks]

If you have gravity feed system there cannot be a vapor lock. The vapor lock (pressure bubble in the fuel line) will expand back into the tank which is not pressurized. The problem is when you have a fuel pump which has a one way valve and the carburetor with the needle seat closed, there is no way that the heated pressurized vapor can escape.

That’s actually not correct. A vapor lock in early cars with gravity feed is very common. The vapor lock is as you describe a pressure bubble, where liquid fuel essentially turns into a gas within the fuel lines. Any gas bubble will travel up the fuel line to the highest point. A gas bubble cannot travel downhill. In the case of a vacuum tank system the gas bubble will in most cases travel back up to the vacuum tank. However, if there is a pig tail or ‘kink’ in the pipe the gas bubble cannot go anywhere. It becomes trapped in the fuel line and prevents liquid from going past. The first step in any situation where you suspect a vapor lock is to ensure that any trapped vapor can escape. Remember vapor cannot travel downhill.

[hwellens]

I have a 27 Dodge with a vacuum tank and the line comes out of the bottom of the tank and goes downward to the carburetor and passes within an inch of the exhaust pipe - never vapor locks. I do not think there is any problem with vacuum tanks. The problem is as you stated. It is how people do the tubing by putting in unnecessary loops or for some reason running uphill. I also have two gravity feed cars that have no problem with vapor lock. If you run the drain pipes in your house uphill, the sink is not the problem.

[Guest 1930]

I have to agree with there being a problem with vapor lock even on vaccuum tanks no matter how un-obstructed the line is but this............If you run the drain pipes in your house uphill, the sink is not the problem. ...........is just plain funny. Thanks, I am still smiling

Atmospheric pressure is always present, when your inner canister dumps your lower canister is pressurized to a small degree, when you get the bubbles forming and there is even more fuel being dumped from your inner canister you have more pressure.

Just my thoughts and everyone has their own opinions. Thanks

Edited July 20, 2011 by 1930 (see edit history)

[Rusty_OToole]

Some have reported less vapor lock and more power and cooler running by adding kerosene to the gas. Low compression engines, like 7 to 1 or lower, 1O%. Up to 25% if your compression is real low like below 5 to 1.

Todays gas is too light and too high octane for old low compression motors, they need more heavy ends to develop full power.

[Phil 32DL6]

Some have reported less vapor lock and more power and cooler running by adding kerosene to the gas. Low compression engines, like 7 to 1 or lower, 1O%. Up to 25% if your compression is real low like below 5 to 1.

Todays gas is too light and too high octane for old low compression motors, they need more heavy ends to develop full power.

I found this an interesting article: Running Kerosene in a Gasoline Engine - Library

Of course, it's discussing straight kero instead of mixtures, but still...interesting.

[Guest hwess]

My original post was a general question, not for a particular model.

[Fred Zwicker]

Why not install an electric fuel pump? When my newest DL6 arrived the previous owner had installed a rebuilt original fuel pump which may have worked okay out in CO but immediately gave me vapor lock problem here in hot humid CT. Fortunately he included the electric fuel pump he had removed. (It had been installed under the hood in plain sight by a previous owner.) I left the rebuilt pump for looks, by-passed it, and re-installed the electric pump hidden in front of the fuel tank.

Result? Goodbye vapor lock! Plus, I get better control priming the carb for start up, and purging the carb if I flood it. As a further bonus, the hidden toggle switch gives another ounce of theft protection.

My pump's a vintage Bendix of unknown age & reliability so I bought one of these to have an emergency back up: Fuel Pump Dodge Chrysler, DeSoto 1931 1930 1929 1928 | eBay

Electric Fuel Pump to be used for priming purposes only?

About a year ago, my '55 Pontiac Safari fuel pump failed , probably due to gunk from ethanol. 1955 Pontiacs have a 12-volt system. As the car was going to Glenmoor the next day, I purchased a Carter P60430 electric fuel pump and then drove the 60 miles to and from the Glenmoor show. *Note that I disconnected the fuel line to the original mechanical pump, and am using the electric pump alone. The original mechanical pump is not being used, but still in place. I think the Carter P60430 is rated at 4 - 6 PSI. This pump is wired through the ignition and an then through a fused on-off switch under the dashboard and no pressure regulator. Everything is working perfectly with this setup.

I also have a 1958 Lincoln Continental and it previously had a Bendix 12-volt electric fuel pump that was installed by the prior owner in the engine compartment, and the mechanical fuel pump was not hooked up. This electric fuel pump was clogged , so I installed new fuel lines and had the gas tank"renewed". I then removed the faulty Bendix electric fuel pump from the engine compartment and installed a new Carter P60430 electric pump near the gas tank. Since the fuel line to the original mechanical pump had already been disconnected, I am using the electric pump alone.

I had the mechanical pump rebuilt on both of these cars and plan to connect each mechanical pump to carburetor as was done originally. The fuel line that is running from the electric pump in the rear will connect to the inlet side of the mechanical pump. Once hooked up, hope to use the electric fuel pump for priming only.

I am wondering if my mechanical pump on each car will pull fuel through the P60430, which is about 2" diameter and about 4 or 5" long? See attached picture. Both of my above cars are wired through the ignition switch and also through a secondary on-off switch below the dash. Neither use a pressure regulator and both perform flawlessly at present. I do not use a relay, nor do I use an oil pressure switch, as some recommend. I later plan to add a similar setup to a 1947 Ford (6-volt), but will use a relay for that hookup, since 6-volts draw more amperage.

Has anyone on this forum used a Carter P60430 or Carter P60504 12-volt electric fuel pump in conjunction with a mechanical pump without any type of bypass or check valve setup? (Both the P60430 and P60504 look about the same, although the P60504 is rated at 4 PSI) I have such a setup on my 1939 LaSalle, using the electric fuel pump for priming purposes only, and running off the original mechanical fuel pump (no check valve or bypass). The electric fuel pump is near the gas tank. This is a 6-volt system. I do not recall the name or part number of this electric fuel pump, although purchased it from Coopers in California a few years back. I did not use a relay on the LaSalle, although plan to add one in the near future, due to it being a 6-volt system.

In any case, since my cars sit for extended periods of time, feel that an electric fuel pump is perfect for priming the car and then can be shut off and let the mechanical fuel pump supply the fuel. (No more removing the air cleaner and pouring in gas or starting fluid into the carburetor). However I am not sure if the mechanical pumps will pull fuel through certain electric fuel pumps when they are in the off position. Some say yes and have no trouble of any kind without any bypasses, check valves, or pressure regulators. Since I want this setup for priming purposes only, I am trying to keep it simple if possible. I guess what I need are the names and part numbers of electric fuel pumps that have been used in this manner.

Thanks,