Recommended fuel pressure regulator for gravity feed system??

[Rusty_OToole]

Some motorcycles have a vacuum operated gas shut off. Wonder if something like that might be available for cars.

[jdome]

What a mess. Looks like you have 3 unnecessary electrical devices between the fuel tank & carb to plug up or go bad. True gravity feed is just a tank of fuel with a pipe to the carb, not much to go wrong. Replacing the electricals with a pipe or hose is a good idea but you may not have a large enough diameter pipe. Since there is not much pressure behind the gravity flow its a matter of moving enough volume of fuel. A 1-cyl Cadillac, 98 cu in. has a 3/8 in. dia line. 9 liters of 1913 inefficiency is going to demand a large volume of fuel at speed. I would think that typical 1/4 line won't supply enough fuel without a couple pounds of pump pressure.

 

On the other hand, the brass pump on the side of the seat is for pressurizing the fuel tank. Gravity or fuel pump operate with a vented cap so air can enter the tank to replace the fuel as it is used up. If you want to pressurize the tank, you'll have to reseal the tank with a gasket under the cap, sealed tight and stick a wad of chewing gum over the vent hole.  The teen years are when the manufacturers transitioned from gravity to pressurized. Many early adopters were equipped with only the manual pump and that requires the driver to occasionally add more pressure, more frequently the faster you drive. There should be an air pressure gage on the dash that may read about 5 lbs. full scale. You want to maintain pressure in the middle two quarters of the gage. Some cars had an additional engine driven pump that would maintain pressure after the engine started. I don't know if the Marmon 48B is equipped with both pumps. 

 

With the Electrical pump gadgetry removed, it appears to me that your engine is now being starved of fuel do to narrow supply line and/or  pressurization malfunctions. 

 

[AHa]

Just so we have some clarity, the OP's car is a 1913. This would be before vacuum tanks came into widespread use. The gravity feed is from the tank to the carburetor and usually is no more than 5 or 6 inches. His car was provided with a pump but it is no more than a bicycle tire pump.  One would use the pump to pump air into the fuel system, creating pressure where very little would occur naturally. I'm not aware of any 1913 cars that had mechanical fuel pumps and most gravity fuel systems use more than 6" of rise to the fuel tank.

 

As an example, here is a picture of a similar year car with similarly placed gas tank. Notice the tank sets right down on the frame; the carburetor is just even with the bottom of the frame. This means there is very little head pressure created by the weight of the gas in the tank. Moreover, the gas is traveling through a horizontal line to the carb as opposed to a straight vertical line. The horizontal line creates more resistance for the gas to travel from the tank to the carb and if not installed correctly, could create an air lock in the system.

 

I hope this helps.

[intimeold]

I would think that  your carburetor, is not designed for any negligible pressure. 

 

All of my experience with gravity fuel systems; no sort of added, pump ever worked correctly. 

[Terry Harper]

As others have suggested if it were me I would get rid of the pump and regulator and either rely on just the gravity feed or restore the pressurized tank system. I would also check the float to make sure its doing its job and is at the correct height and lap the needle valve and seat. Is there a good filter? Even a tiny bit of material can cause the needle valve to not seat. Are the fuel lines the correct size? I had to replace the 1/4" lines with 3/8" on one of our machines.We also like easy to access fuel shut-off valves and make a habit of using them.

 

As others have noted deviations (i.e. "improvements) from the stock systems usually compound problems and often create their own.

 

Wonderful automobile! Love it and hope you have many enjoyable days with it!

[CatBird]

OK, I tried to run the original gravity feed and car would not start. The only difference between the original setup was an inline fuel filter.

Of course I previously drained the old fuel and replaced with clean fuel.The carb is below the frame attached to the "Y" shaped brass fitting.

The hand pump on the side of driver side did not help even though it is connected to a supply line to the gas tank. The seal in the hand pump is good, but not sure the gas tank filler tops does not seal, it has the two huge racing tops, about 7 inches in diameter.

So I put the old setup back on after finding out that the old electric pump failed. Electric stop valve did work  when power was applied to the pump and the stop valve. I replaced the dead pump with a new one that rated at 1 - 2 1/2 PSI. Pump ran a few seconds until the system pushed out the air and filled the carb.

The car ran for a few seconds and failed. I am going to try to check pressure and see if adjusting will the pressure regulator will help. I have cleaned the carb, and don't think it was sticking. There is an original setup does have an inline sediment setup. I drained and cleaned it. The was a bit of swarf and gluck. 

My car was had a major brass car guy for 39 years. I am going to call him and ask why it had the setup, see picture. It did run for many years including me when I bought it.

I would like to make the original setup to work. I don't like electric pumps.

[edinmass]

Bill, send it down to me for 18-24 months…….I’ll get it running and sorted……..I only need two weeks…….the rest is just for my pleasure! 👍

[AHa]

The fuel filter is your problem. It takes very little to clog it up. Take off the fuel filter and just run the sediment bowl. I had a fuel filter on my 1911 and it starved the carb.

 

 

[trimacar]

3 hours ago, AHa said:

The fuel filter is your problem. It takes very little to clog it up. Take off the fuel filter and just run the sediment bowl. I had a fuel filter on my 1911 and it starved the carb.

 

 

I agree, the fuel filter will rob you of the little head pressure you have.  Liquid is about 0.5 pounds pressure per foot of head, so you may have as little as one to one and a half pounds pressure at most. Small fuel lines don't help old cars either, particularly with new gas and a monster of an engine.

[Marty Roth]

43 minutes ago, trimacar said:

I agree, the fuel filter will rob you of the little head pressure you have.  Liquid is about 0.5 pounds pressure per foot of head, so you may have as little as one to one and a half pounds pressure at most. Small fuel lines don't help old cars either, particularly with new gas and a monster of an engine.

Agreed !

 

Ditch the fuel filter and pump - Gravity works!

Use a good sized sediment bowl with a decent screen.

Be certain as to the size, placement, and height of the Fuel tank.

I once saw a replacement/repaired tank, the lower 1/4th of which was lower than the carburetor, and when the tank was still 1/4 full, the car starved for fuel and quit running on the slightest hill during the 1997 Glidden Tour in south Georgia. The owner eventually added a "flow-through" style low pressure electric pump with a switch to get through the temporary issue, but learned not to let the tank get that low.

[jdome]

Looking at your engine and fuel tank, it is definitely configured for gravity feed. And that makes sense to me. I don't know anything about 13 Marmon but Cadillac had gravity tank in 13 and pressure in 14 - on. I don't know why someone added the brass pump to the side of the seat, other than it looks pretty. AS other have said, no filter, no restrictions on a gravity fuel lines. It is also important that the tank can breath. Typically there is about 1/8 inch vent hole thru the gas cap. If you are unsure if the tank is vented properly, leave the cap off and see if that improves operation. Also make sure that you have the correct carb or replacement carb that is properly sized for the engine, and that it is in good order.

 

I see another potential possibility that has nothing to do with fuel delivery to the carb. Some of these large displacement engines with long neck manifolds are susceptible to the venturi effect; moisture from the fuel/air mixture passing thru the manifold at high speed may condense & freeze on the wall inside the manifold, restricting passage to the engine. To prevent this from happening, Marmon designed the "Y" in the manifold with water passages and plumbed hot coolant from the block through the "Y".  I can't tell from the photo but there may be a valve at one end of the plumbing at the block to open/close the heat as needed. It is not always necessary, depending on operating conditions, and quality of fuel. Outside temperature is irrelevant.  It is more likely to occur in 100 degree, high humidity than 20 degree dry air.  It would be interesting to know the climate where the car came from compared to its present location. 

[Larry Schramm]

I had a similar problem to a car that I purchased.  The fuel line went up and down from the bottom of the tank to the carb. 

 

I took everything that was on the car out and pitched it.  I eliminated all of the rubber line, sediment bowl and all of the up & down bends in the fuel path.

 

I then put a steel line with fiberglass fuel line insulation over the line.   The line needs to be as straight as a ruler from the fuel tank to the carb.  The fuel line from the tank must run in a STRAIGHT LINE from the tank to the carb, all down hill.

 

I have never had a problem since.

[jdome]

Nothing wrong with gravity feed systems. Ford used a gravity tank all the way up through the Model A years, mounted high on top of the cowl. Ford switched to mechanical fuel pump with the 32 V8. They skipped past the pressurized tank and vacuum tank problems. 

[mechanician]

If the car is set up for a pressurized tank, make sure the tank is vented to atmosphere when not running pressurized or close the vent if you are going to run pressurized. I suspect the car may have a valve somewhere to do this, possibly at the bottom of the hand pump, I can’t make it out in your photo.  Even on a non-pressurized system a plugged gas cap vent can be a frustrating failure…at least until it happens to you once and you never forget it. Test by running it with the fuel cap off if you can’t ascertain that it is venting properly.

[AHa]

I started to address the venting in my previous post but didn't want to confuse the issue. In a closed system where there is a pump, there will not be a vent in the gas tank cap. You simply pump up the pressure, I had a friend who ran his car all day on one charge of air to about 4lbs, then watch the gauge and pump more air as the gauge indicates more pressure is needed. There should be a ball check valve on the bottom of the pump that allows air intake to the pump. If there is a vent, you will not be able to charge the tank with pressure.

 

Still, I believe your problem is the fuel filter. If the car was running fine before and suddenly started choking, it is the filter. The filter will likely look fine, like a new one, but be clogged enough even the electric pump cannot force gas through it.

[CatBird]

22 hours ago, edinmass said:

Bill, send it down to me for 18-24 months…….I’ll get it running and sorted……..I only need two weeks…….the rest is just for my pleasure! 👍

Sure, Ed, how much will you pay?

[trimacar]

41 minutes ago, CatBird said:

Sure, Ed, how much will you pay?

All kidding aside, a month at Ed’s would be a great investment in the car’s future drivability.  He’s able to walk the talk, and not all people attempting to sort out a car can…..

 

[CatBird]

2 hours ago, trimacar said:

All kidding aside, a month at Ed’s would be a great investment in the car’s future drivability.  He’s able to walk the talk, and not all people attempting to sort out a car can…..

 

You are right. But the car itself is sorted out. Running great except with the fuel problem. It was in the hands of one of the exceptional brass car guys for 39 years. Has turn indicators, brake/tail lights, it has been toured. Shifts, drives, stops, all the right stuff. Better and easier than my other brass cars. I think that Marmon had great engineers!

I have the utmost respect for Ed Minnie and will keep this in mind.

Last night I installed an electric pump with 1 to 2.5 psi. I do have a kill switch for it. The carb did not overflow and the car ran like new. I plan to get out soon and drive it as soon as the day warms up! 

[AHa]

Can we get a final report on this problem? Did the new fuel pump solve it? Did you take the fuel filter off? Have you got it running good?

[CatBird]

11 hours ago, AHa said:

Can we get a final report on this problem? Did the new fuel pump solve it? Did you take the fuel filter off? Have you got it running good?

The new fuel pump did solve it. Facet Low Pressure fuel pump. The Marmon has a large sediment bowl between the tank and the pump. With the new pump, I was able to start and run. Drove it about 15 miles with no issues.

I am not happy with this arrangement as I would like to have gravity feed as it was original. The hand pump that applies air pressure to the tank and this system seems to work like it should.

In re-reading the comments here, I may trying going back to the gravity system with no filter. It is quite possible that my having added in the fuel filter cause a restriction that made the gravity system fail to deliver enough fuel.

In 1913, apparently the hand pump pressurized the gas tank and began a flow to the carburetor. But there is no additional plumbing that would keep the pressure up. Information is sketchy about how this setup originally worked. My car is the only 48B speedster made in 1913. And the 48B was only made that one year.

But for now, it is running and a pleasure to drive.

[AHa]

Bill,

 

If the Marmon is typical of the era (I have not seen it) the gas tank and pump should make up a closed system. When the pump is used to charge the system with air, the tank should hold that pressure over a period of time. As the pressure is released through pressing the gas out of the tank to the carb, as noted on the fuel pressure gauge on the dash, a couple of pumps of the hand pump should recharge the system.

 

The system on your car must have encountered a problem at some point and the fuel pump was added. The fuel filter is not your friend. The relationship between the gas tank and carb allows for very little head pressure with the long horizontal gas line, especially when the tank is low on fuel. Everything has to be working properly for it to work at all. However, most all the early race cars used the exact same system and the gas tank would have been mounted higher if there was a problem. They did not have electric fuel pumps to add.

Edited February 21, 2023 by AHa (see edit history)

[raybelf]

This type of fuel system in not a Gravity feed system, this is a pressurized system. To start the car you would pump air pressure into the tank by means a hand air pump. Usually 1.5 to 2.0 psi, there should be a air gauge on the dash. Once the car is running there is usually a air pump off the exhaust or a pump that runs off the valve spring to maintain the air pressure. Because of the CID of the motor a gravity system could not keep up with fuel supply and the engine would stumble and die out.

An electric pump would work fine as long as the pump pressure is not to much to sink the float in the carburetor. This is why a pressure regulator is added to the system. 

 

[AHa]

Here is an example of a period correct dash mounted fuel pressure gauge. It turned on its side when loaded. As you can see, the gauge reads between 0 and 6lbs of pressure. This is a US Gauge from 1910-1911. It mounts into the dash and is plumbed from the hand pump. I've seen some that only read up to 5lbs but clearly 5lbs is not too much. The fuel float is attached mechanically to the carb body. I think it would take a lot of pressure to overcome the float attachment. However, not all early carbs are designed for this system.

[CatBird]

More information. The Pump has indicators for "Grav" and "Press" I guess you pump the pressure and move to gravity feed. Notice the diagram from my Marmon manual. I do have the pressure gage on my car. But it never moves, even when running. Didn't know what it does.

It is very interesting understanding old cars. Takes friends and being a detective.

 

Edited February 22, 2023 by CatBird (see edit history)

[AHa]

A couple of things to notice: the diagram shows a touring car set up. This is not a gravity feed but a full pressure system. The book from Marmon shows the predominate system. The car you have is a unique one year only offering that used much of the same parts. It relies on a hand pump to pump up pressure in the tank and a built in air pump on the motor with a pressure gauge on the dash but your car is also gravity feed. One or several of these parts failed, or the owner didn't understand it, and rather than repair it, an electric fuel pump was added. I would suggest a testing of the components. You could loosen the line from the pump on the motor, and while the car is running, check to see if it is pumping any air. If the lever on the hand pump is in the Grave position, any air will escape. Check to see if your hand pump is pumping air. If you check each piece and familiarize yourself with what they do, you can isolate the problem and decide what if anything to do about it. 

[Paul Dobbin]

Another friend with a vaccum tank and gravity system used this to great touring satisfaction.

The great 6 volt fuel pump is a Carter P4259, also available from NAPA under their number B-0110-E low pressure no regulator needed.  Life time warranty.  NAPA Stores can't find it without their part number.

[CatBird]

Good answers especially AHa. Will try your ideas. Old school is the best. 

The gas line from the tank is 5/16 and appears to have been there all along. But who knows?

Here are my gages. I softened up the leather cup inside and I pumped the "press" and could feel resistance. Pump is working, but the gage never moved.

[mechanician]

Looking at the tank that you have (which is not the same as the schematic, the schematic tank pickup requires “up hill” flow, the top line on your tank appears to be a pressurization line), it appears that you should run fine on gravity, but only if the selector on your pump is set to gravity, otherwise it will run for a bit and then pull a vacuum in your tank as your filler caps should not be vented in order for the pressure system to work. The tank is vented through the pressurization line. All of this said, there could be restrictions elsewhere, but it should not run properly on the “pressure” setting unless you actually pressurize the air in the tank.

[CatBird]

18 hours ago, Paul Dobbin said:

Another friend with a vaccum tank and gravity system used this to great touring satisfaction.

The great 6 volt fuel pump is a Carter P4259, also available from NAPA under their number B-0110-E low pressure no regulator needed.  Life time warranty.  NAPA Stores can't find it without their part number.

My electrical system has been upgraded to 12v
 

I am exploring and making the original system to work. Electric pumps seem to be prone to failure. A good friend and brass car guy is using a Holley 12-801-1 Red Electric fuel pump. He has seen dismal results with other electric fuel pump failure and this one keeps working. He is my "go-to guy" on brass cars. He has put more miles on a brass car than about everyone else put together! I sure trust his judgement.

I am buying one of these, and may stay in my toolbox unless needed. I am still trying to get the original system working.

Having to take a break. One of my fuel injected 350 Chevvy Crate engine is acting up in my thinly disguised race car. Thinking about a Holley 750 CFM mechanical secondaries and down leg booster. I have the mechanical fuel pump.

I have a lot of cars and they get jealous!

[Paul Dobbin]

Maybe NAPA can cross reference that 6 Volt part number for the low pressure pump to a 12 volt version.?   See my post above for that number.

[AHa]

The air/fuel system on your car is what is called a duel system. In theory, you turn the toggle on the hand pump to pressure and pump up pressure in the tank. The pressure should read on the dash gauge. If the toggle is in the grav position, any air you pump will go out the relief valve. With the toggle in the grave prosition, the gas tank will suck air through the relief valve. The relief valve is  nothing more than a hole with a small bearing in it. When pressure is applied to the back side, the bearing seals in the hole but if there is no pressure, the bearing backs off allowing air into the system. The bearing is very small and can easily fall out without notice if one is not careful and knows not what they are doing, thus, the part is put back together without it, and there is no way to pressurize the system. The gauge is a simple volume detector and should work if there is pressure to read.

 

My 1911 also has a 5/16ths gas line but I think 5/16ths is typical for the era. Obviously, if the car were being raced, you would need a greater volume of fuel delivered to the carb so you have a duel system. One for leisure driving and another for racing. I suspect the car is special built for racing. In those years, 11-14, several car companies built special cars for people what wanted to drive their cars and also race them. The Mercer is an example.

[CatBird]

On 2/24/2023 at 9:11 PM, AHa said:

The air/fuel system on your car is what is called a duel system. In theory, you turn the toggle on the hand pump to pressure and pump up pressure in the tank. The pressure should read on the dash gauge. If the toggle is in the grav position, any air you pump will go out the relief valve. With the toggle in the grave prosition, the gas tank will suck air through the relief valve. The relief valve is  nothing more than a hole with a small bearing in it. When pressure is applied to the back side, the bearing seals in the hole but if there is no pressure, the bearing backs off allowing air into the system. The bearing is very small and can easily fall out without notice if one is not careful and knows not what they are doing, thus, the part is put back together without it, and there is no way to pressurize the system. The gauge is a simple volume detector and should work if there is pressure to read.

 

My 1911 also has a 5/16ths gas line but I think 5/16ths is typical for the era. Obviously, if the car were being raced, you would need a greater volume of fuel delivered to the carb so you have a duel system. One for leisure driving and another for racing. I suspect the car is special built for racing. In those years, 11-14, several car companies built special cars for people what wanted to drive their cars and also race them. The Mercer is an example.

Very helpful info! I will be checking for leaks. Yes, the toggle on the pump "PRESS" is trying to pressurize the tank. When the toggle is straight down, you can't pump the pump, solid pressure. The pump is working! I guess it does what you said when moved to "GRAV."

Possibly my car was for sport touring, maybe racing. Researching was it owned by a wealthy socialite. Who liked fast cars

Edited February 26, 2023 by CatBird (see edit history)