Vintage Gas Engine Oilers

By Staff
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Oilers you'll see on most gas engines include common oilers, check-ball oilers and sealed-type oilers.

There are several types of oilers you’ll come across working on vintage engines, some more common than others. For this article, we’ll look at three particular types and study them in detail.

The common oiler

Most often used on machinery shafting and many different engines, the common oiler is a simple reservoir with a means to regulate the flow of oil in drops per minute from the reservoir to the object needing lubrication. This can be either a machine or an engine. Most common oilers have a small sight glass below the reservoir so you can view the rate of oil drops. Common oilers are mainly used on shafts and bearings. Some are used on engine pistons, which is OK as long as there is no back pressure that would push the oil back into the reservoir. The top of the common oiler reservoir is open to the atmosphere, and the oil fill is often a sliding cover. If an engine has some compression loss or has a closed crankcase (like the F/M ZC or ZD engines, or the IHC M series), then a check-ball oiler may have to be used.

Common oiler operation: The reservoir is filled with the necessary oil through the fill hole (#10) in the upper cover (#14) to within 1/2 inch of the top, visible in the glass body (#12). The lever on top (#1) is lifted and is locked in place by spring tension (#5) on the metering needle (#4). The thumb nut (#3) on the oiler center tube (#6) is adjusted to raise or lower the metering needle (#4) to allow a certain number of drops per minute to ensure sufficient lubrication of the item being lubricated. When the top lever is lifted, it raises the metering rod (#4) off its seat on the oiler base (#19), thus allowing oil to pass through the oil port (#8), past the oiler base (#19) and into the supply pipe (#20). When engine operation is done the top lever is turned to one side, thus allowing the metering pin to seat in the base, shutting off oil flow.

Common oiler legend:

1) Oil stop lever
2) Oil metering pin retainer
3) Oiling rate adjuster
4) Oiling rate metering rod
5) Metering pin spring
6) Oiler center tube
7) Air equalizing inlet
8) Oil port
9) Oiler fill cover
10) Oiler fill hole
11) Oil
12) Glass reservoir body
13) Cork reservoir gaskets
14) Upper reservoir cover
15) Lower reservoir cover
16) Cork sight glass gaskets
17) Sight glass
18) Sight glass view port in oiler base
19) Oiler base
20) Mount coupling to engine or machine bearing/piston
21) Oil drop

The check-ball oiler

The check-ball oiler has the same style reservoir as the common oiler, but a different base. The check-ball oiler base has a captured ball bearing that fits into a ground seat under the oiler body. There is usually a steel pin under the ball to prevent the ball from falling out of the base.

Check-ball oiler operation: As with the common oiler, the metering rod is lifted and oil flows through the oiler assembly, past the check ball into the oiling passage to the engine piston. If there is blow-by or back pressure, the pressure blows the checkball upward into its seat in the oiler base, preventing oil already in the oil supply pipe from being blown back into the oiler body. When blow-by pressure drops, so does the checkball, thus allowing oil to again flow past the check ball into the oiling passage. Excessive blow-by can prevent oil from reaching the piston, thus starving the piston for oil and eventually creating even more blow-by due to excessive wear from a lack of lubrication. This is a vicious cycle that will cause excess wear to the piston, rings and the engine cylinder. If there is too much blow-by, then a sealed-type oiler may have to be used.

The check-ball oiler operates and functions in a similar manner as the common oiler and is constructed as follows: As noted, the upper body assembly is the same as the common oiler. The check-ball oiler base (#7) is machined to accept a ball (#5) within the internal diameter of the base, with clearance to allow oil to pass the ball. The top of the ball chamber is machined so the ball will seal against the oiler base when pressure is applied against the ball (#5). The ball is held in the chamber by a steel retaining pin (#6) pressed into a drilled passage in the base.

Check-ball oiler base legend:
1) Oiler body base
2) Sight glass port
3) Sight glass
4) Cork sight glass gaskets
5) Brass or steel checkball
6) Check ball bearing retaining pin
7) Machined check ball seat
8) Oiler base

The sealed-type oiler

 Sealed oilers are most often found on large-bore engines, as well as the IHC M type and some Fairbanks-Morse ZA, ZC and ZD engines. The sealed-type oiler uses pressure below the oiler to operate. As its name implies, the top of the oiler is sealed. Usually, the fill plug is threaded and gasketed, and there’s an O-ring to seal the metering pin to the oiling passage. The sealed oiler has a check ball in the base, as well. Back pressure can be blow-by, or in the case of some closed crankcase engines pumping pressure generated by the backside of the piston as it moves back into the crankcase.

Sealed-type oiler operation: Before blow-by can seat the checkball against its seat, some pressure is captured on top of the oil in the reservoir. Eventually, the pressure above the oil equals the pressure below the oil in the oil feed pipe. As the engine operates, the now pressurized oil is forced out of the reservoir when blow-by pressure drops. This ensures oiling of the piston.

The sealed-type oiler has some of the attributes of the common oiler base, but the upper section has a different construction. The upper oiler body is made of a heavy material (steel or brass), and the fill hole (#15) is threaded to accept a gasketed plug (#16). The plug often has a retainer (#17) attached to keep it from being lost. The metering shaft is machined internally to allow installation of an O-ring to keep the oiler body sealed against atmospheric pressure.

In operation, blow-by or crankcase pressure blows into the oiler body and is trapped against the oil by the sealed top. When the pressure below the oil level drops, the pressure above the oil in the reservoir forces oil into the oiling passage. The cycle is repeated at every power stroke of the engine.

Sealed oiler legend:

1) Oiler metering pin lever
2) Oiler metering pin retainer
3) Oiling rate adjuster
4) Oiling metering pin
5) Oiling pin O-ring compression washer
6) Oiling pin O-ring seal gasket
7) Metering pin spring
8) Oiler body center tube
9) Oil port/air inlet ports B/A
10) Top oiler cover
11) Bottom oiler cover/base mount
12) Cork cover gaskets
13) Oiler body glass
14) Oil
15) Oil fill hole
16) Oil fill plug and gasket
17) Oil fill plug retainer
18) Oiler base
19) Oil sight glass hole
20) Sight glass
21) Cork sight glass gaskets
22) Metering pin seat
23) Oil supply pipe to engine

2-stroke sealed engine oilers

There are two sealed-type oilers I think need their own explanations. These are the Powell-Boson oilfield engine oiler and the Detroit lubricator oiler used on the Detroit Engine Works 2-stroke engines. Each has its own set of operating functions.

Detroit Lubricator oiler operation: The oiler used on the 2-stroke Detroit Engine Works engine with low-pressure fuel injector is of a sealed-type design  and is built to operate in a specific manner that is essential for proper oiling on this engine. Engine crankcase pressure accumulates on top of the oil in the oiler reservoir, being blown in from a passage connected to the crankcase. At peak pressure, eventually the crankcase and oiler pressures equalize on the engine power/exhaust stroke (as the piston pushes back down the bore). On the compression/intake stroke, the piston travels up the bore, creating a vacuum in the crankcase. As the pressure falls off on the compression stroke the oil is forced out of the oiler into the piston/cylinder and into a slinger on the engine crankshaft that forces oil onto the big end connecting rod bearing. This positive/negative pressure cycle makes the oiler act as a low pressure pump, thus delivering oil to the needed areas. The original Detroit lubricator is a two-port oiler. If necessary, two single, sealed oilers can be used in its place. Simply mixing oil in the fuel will not be sufficient for the Detroit engines using the low-pressure fuel injectors commonly used on their stationary engines.

Powell-Boson oiler operation: On the engine compression stroke, as the piston rises in the cylinder a partial vacuum is created in the space behind the piston. This negative pressure allows air to push past the intake valve, lifting it off its seat, thus allowing gas to flow into the air as it passes the valve seat. After the engine passes top dead center the inlet valve seats, blocking off the gas flow and preventing the escape of the fuel/air mixture now captured within the cylinder, behind the piston.

As the piston moves back in the cylinder bore, it compresses the captured fuel/air mixture. The compressed mixture extends into the transfer passage at the top of the cylinder. The oiler is mounted at the top of the transfer passage, at the transfer port into the combustion end of the cylinder. The compressed fuel/air mix pushes past the air admission valve in the oiler (#32), and also pushes past the air admission check ball (#38), causing the top of the oiler reservoir to be pressurized. The oil outlet check ball (#27) prevents pressure from pushing oil back past the oiling metering pin, back into the oiler reservoir. When the engine nears bottom dead center, the exhaust port opens, allowing spent gasses to exit the cylinder. When the piston gets within 1 inch from bottom dead center the transfer port opens, allowing the compressed gasses in the space behind the piston to escape through the transfer passage and the transfer port into the combustion end of the cylinder. As this happens, the air admission check ball (#38) closes, trapping pressure on top of the oil in the oiler reservoir. This pressure forces the oil out of the reservoir, past the oiling metering pin (#20) and past the oiling outlet check ball (#27 and #28), and out of the oiler, and finally into the open transfer port where the oil is carried into the cylinder to lubricate the piston and cylinder. When the piston starts moving toward the combustion end of the cylinder it closes the transfer port, starting the cycle again. This time, the negative pressure allows the rising vacuum to force the once again pressurized oil in the oiler past the outlet check ball, causing more oil to leave the oiler. This oil now drops through the transfer port onto the piston body, which is now blocking the port, lubricating the piston and the rings. When the engines reaches top dead center compression, the oiling cycle starts again.

NOTE: Running the engine too lean or with excessive oil and fuel will cause carbonization of the intake and exhaust ports (coking). The ignition of fuel/air gases in the intake/transfer section of the engine, due to lean burn conditions, may cause damage to the gaskets, packings and the oiler, and even may lead to serious damage to the engine itself.

Using the Powell-Boson oiler

1) Remove oil fill plug (#4) and add SAE 50W oil to a point no closer than 1/4 inch from the upper oil level sight glass ferrule. Replace plug.

NOTE: If you overfill the oiler, it will jam the air inlet check and will not flow oil to the engine piston and cylinder. Do not run the engine with the oil fill plug removed – the engine will run poorly (if at all), and will blow oil out the opening.

2) Lift the oiler metering pin lever (#14) to the upright (vertical) position.

3) Fully open the air admission metering pin (#33) by turning the Bakelite handle at the bottom (#36) counterclockwise.

4) Loosen oiling rate set nut (#17) and back off the oiling rate body (#18) until you get approximately 10 to 15 drips per minute. Tighten the set nut.

5) Run the engine until warm and re-adjust the oiling drip rate to 10 to 12 drips per minute.

6) When engine operation is finished, shut off fuel to the engine. Allow engine to run until it stops. Turn the oiling metering pin lever (#17) to the horizontal position. The metering pin should drop until it hits its seat and the lever should not be in contact with the top of the metering body (#18). Shut the air admission metering pin (#33).

Powell-Boson oiler legend:

1) Bakelite fill plug handle
2) Handle retaining screw
3) Fill plug gasket
4) Fill plug
5) Oiler body
6) Oil
7) Oil must not be any higher than this level (1/4 inch from compression nut)
8) Sight glass mount tee
9) Sight glass installation cap
10) Upper oil level sight glass ferrule and packing
11) Lower oil level sight glass ferrule and packing
12) Sight glass elbow
13) Oil level sight glass
14) Oil meter shut-off lever
15) Meter lever retaining pin
16) Meter pin tension spring
17) Oiling rate set nut
18) Oiling rate adjusting body
19) Oil metering pin seal
20) Oil metering pin
21) Oil metering assembly tee
22) Oil metering flow adjuster seat
23) Upper oil metering sight glass ferrule and packing
24) Oil metering drip sight point
25) Oil metering sight glass
26) Lower oil metering sight glass ferrule and packing
27) Oil back flow check ball
28) Oil back flow check ball seat
29) Oil metering sight glass retainer gasket
30) Oil metering sight glass plug/oiling check outlet
31) Oil metering/check mount
32) Air admission regulator seat
33) Air admission metering pin
34) Air regulation pin ferrule and packing
35) Bakelite air regulation pin handle
36) Handle retaining screw
37) Air admission check housing
38) Air admission checkball
39) Removable air admission checkball seat
40) 3/4-inch threaded oiler mount

Contact Andrew K. Mackey at P.O. Box 347, Rockaway, NJ 07866;

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