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Baffled a bit (but no longer)Thank you!


Terry Harper
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This one has me baffled a bit. Here is an excerpt from a 1921 circular sent out by a manufacturer advertising certain points about their product.

 

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Note the reference to a gasoline pressure pump "... so that constant air pressure is carried in the tank..." Also note reference to  "... an emergency hand pump..." in addition to the gasoline pressure pump.

 

I am familiar with early cars having hand pumps to pressurize the fuel tank. But what I am not familiar with is an engine driven air pump that pressurizes the fuel tank. 

 

Engine driven compressor for dealing with flat tires. Yup! We see those quite often. But an engine driven pressure pump to pressurize the fuel tank? That's a new one for me at least.

 

Any thoughts? Anyone ever run across this before?

 

 

 

Edited by Terry Harper (see edit history)
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Pierce-Arrow used an engine-driven air pump thru 1928, except for the 1925-28 Series 80/81 which used vacuum tanks.  Of course, when engine is off, the fuel tank must be pressurized to start by using the dash hand pump to build up (on my 1918 48) at least 1.25-1.5 psi to enable the car to start.  I wouldn't call that an "emergency" pump.  I have had my passenger use it to keep us going on one occasion (here's your "emergency"), because the trailer ride enroute to the tour site caused the fuel tank cap to vibrate loose just a smidge.  We quickly learn to keep at least a half tank of fuel at all times!  And now I give a tightening twist to the gas cap before unloading the car from a trailer.  I bleed off the pressure if I will be away from the car or stopped for 30 minutes, thus requiring hand pumping for restart.

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My 1924 Cadillac has the same fuel tank pressurization system.

You use the dash-mounted hand pump to pressurize the tank for start-up. The engine-mounted compressor maintains fuel tank pressure once the engine starts.

 

This is a tiny, single-cylinder air pump mounted on the timing cover,  not anything like the engine-driven tire pump.

I was taught to turn the engine off by venting the fuel system to prevent potentially feeding pressurized fuel onto the hot engine if the carb leaks.

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Terry, prior to the invention of the vacuum tank most big cars used that system unless they had a gravity feed tank. There was usually a tiny compressor on the engine, often driven by the camshaft, that produced 2 or 3 pounds of pressure. Even though the vacuum tank was good, it wasn't as simple and a lot of cars continued to use it right through the 20s. My 27 Cadillac had such a system as did the Silver Ghost and I imagine many of the other expensive cars. Cadillac also had a compressor mounted on the transmission...that was intended to inflate the tires and I don't believe it was connected to the fuel system (at least mine wasn't).

 

Rather than a compressor, some cars used exhaust to pressurize the tank. The hand pump on the dash was mostly used to start the car since it couldn't be expected to hold pressure for a long time when sitting. The starting drill was to pump up about 2lbs of pressure, then hit the starter. When the system leaked, you could keep pumping...

 

The system on my Cadillac leaked. At the time I bought it, (I was 19 and had absolutely no exposure to old cars at that point) I'd never driven a standard transmission car so I got one of my friends to drive it home while I kept the pressure up...

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They forgot to mention that if you run out of gas, or stop to fill the tank, you must release the pressure from the tank to put in more gas. Then you need to pump up enough pressure to get started.

 

V8 or V12 motors carry the carburetor higher than inline engines, at least, in the days of updraft carburetors. And have more need of a fuel pump of some kind.

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33 minutes ago, Rusty_OToole said:

They forgot to mention that if you run out of gas, or stop to fill the tank, you must release the pressure from the tank to put in more gas. Then you need to pump up enough pressure to get started.

 

V8 or V12 motors carry the carburetor higher than inline engines, at least, in the days of updraft carburetors. And have more need of a fuel pump of some kind.

Actually, Rusty, only after owning the 1918 for two years did I find that there's enough gas in the carb to start after a fill-up without manually re-pressurizing the tank.  As you say, upon arrival at the pump we need to relieve any pressure to add gasoline to the tank and thus the gas pressure gauge on the dash will read zero.  On my car, there's an arrow on the round pressure pump knob:  9 o'clock for zeroing out pressure, 12 o'clock while pumping, and 3 o'clock to hold pressure.  So when starting after fueling, I turn the knob from 9 to 3 without pumping, and the remaining gas in the carb bowl is enough to start the engine, and the engine-driven pump immediately takes over.

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Thank you!

 

Great response and I am now no longer baffled!

 

At the moment its gravity feed from a 60 gallon tank. If we want to return the beast's fuel system back to original what are the chances of finding an engine driven fuel tank pressure pump? I have seen the hand pumps around but not the engine driven units.

 

Also, I would love to see some photos of an engine driven pump if possible.

 

The more I dive into this project the more impressed I am with the sophistication of what is just a large tractor  - electric start, dual ignition (mag and distributor) full pressure lubrication with a crazy oil pump that is three pumps in one and fully a counter balanced crankshaft. 

 

Again, thank you so much!

 

Best regards,

 

Terry

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Might help if you told us what kind of vehicle or motor it is. If it had a pressure system from new the pump would have been built into the engine somewhere unless it used exhaust gas pressure as some did. Could a small air pump be part of that crazy oil pump? Some cars had a vacuum pump in the oil pump to run vacuum wipers, and this in the fifties.

Are you sure you even want that type of fuel system? They were largely supplanted by vacuum tanks until they figured out how to make modern fuel pumps, then everyone quickly went over to the fuel pump. The air pressure system always struck me as the most complicated, expensive inconvenient and dangerous solution to the problem of supplying fuel to the engine.

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1 hour ago, Rusty_OToole said:

Might help if you told us what kind of vehicle or motor it is.

Well... its not a car... ....... its a whole 18,850 pounds of fun.

 

We are developing a punch list and prepping it to move to the museum. Here are a couple of photos - mostly of the engine. It was kind of crammed into the shed so it was difficult to get a good overall shot. The motor is the original Sterling Model FT manufactured by the Sterling Engine Company of Buffalo, NY. The engine is a 6 cylinder (5-1/2"x6-3/4") T-head rated for 140 hp at 1,500 rpm. The oil pump is internal but easily adjustable from the outside. It's one unit but contains two scavenger pumps (one for each end of the sump) and a service pump. When new it also had a 10 gallon oil reservoir which fed into the crankcase via a drip feed monitored by a oil site gauge on the dash panel. It had dual ignition using a magneto and an Atwater-Kent distributor which went missing at some point. The crankshaft is fully counter balanced. Its a very, very smooth running beast and not your average tractor engine of the period and it likes lots and lots of gas.

 

 

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Edited by Terry Harper (see edit history)
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1 hour ago, Rusty_OToole said:

Probably made to run on low octane tractor gas. Check with local oil dealers that supply farms, it may still be available although farm tractors went to diesel years ago. Tractor gas is cheap and has no road tax.

Do you know if it came with an air pump originally? Or a vacuum tank, or just gravity feed?

It runs on regular gas. The engine is actually based on Sterling's model 'F' marine engine with modifications to the lubrication system and cooling system, and exhaust manifold.

 

According to the factory literature (as posted above) it had an air pump. Earlier versions were gravity and later versions had vacuum tanks. Fortunately there is enough height difference that we can run it via gravity unless its a fairly steep hill. It would just be nice if we could set up the ignition system and fuel system as original. 

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The marine version

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Edited by Terry Harper (see edit history)
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Guys, The 1915 Dodge Brothers used a air pressurized fuel system. There was a hand pump and pressure gauge on dash for starting up and a small pump operating off the rear cylinder exhaust cam to keep up pressure while driving.1684433301_15Interior003.jpg.7889ea45c94688d0c43adcc9c1143f73.jpg

 

'15 engine RH.JPG

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  • Terry Harper changed the title to Baffled a bit (but no longer)Thank you!
On 9/22/2022 at 9:01 PM, Terry Harper said:

Thanks! That helps a lot. I believe it could be mounted on top of the crankcase as long as there is a drive gear on the cam correct? 

I can't find a good image to show, but the Cadillac design uses an offset pin on the camshaft to drive the air compressor via a small connecting rod.

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