The Oil Pump

Many will say they understand pumps, which come in several types.  Here are a few: Centrifugal pump– This pump is not self priming pump. The fluid is sent to the center of the pump’s eye and is moved via rotation of its impeller to the outer walls of the pumps housing. By the fluid’s movement against the outer walls, pressure will be built up at the pump’s outlet.

Piston pump– This is applied to applications that require liquid to be provided at high pressure to the outlet of the pump. The unit can often be found when water feed is required in large steam boilers.

Gear pump- This pump is most often used when a specific suction and pressure is required. Generally speaking, as the gears rotate and disengagement takes place, suction takes place. As the gears mesh, pressure is created and forces the liquid from a discharge port.

The high pressure oil burner pump- This is the unit we are most familiar with.

This pump has some basic principles and components. First, the unit must be able to create a specific vacuum to draw oil from a storage tank. Secondly, it must be equipped with a valve to regulate the unit’s pressure to support the proper atomization through the oil nozzle. And finally, we have become quite accustomed to seeing an electric solenoid valve that supports positive fuel cut off and a clean combustion process.

I work with several heating components, pumps being one, and I must say the manufacturers are doing an excellent job eliminating many of the problems that were so common many years ago. How can I tell? I see very few pumps being returned. Some that are can often be found to be trouble free once the strainer in the pump is replaced.

Before condemning a pump, make sure you do some quick checks. Check the pump coupling for slippage, make sure the suction and return lines are connected properly (sometimes they get reversed), check for a damaged or crimped oil line, is there water in the oil? And last, but not least, is there oil in the tank?

Often the pump, besides being neglected from lack of service, is often expected to do more than it was designed to do, for example, excessive lift and horizontal run of the piping or a wrong application for the installation. Sometimes a single stage pump is applied when a two stage pump is required for the application. Keep in mind that when a pump is operating on a two pipe system, the full capacity of the pump is used and on a single pipe, the capacity of the nozzle is used.

The best oil pump guides are provided by the pump manufacturers, (Free for the asking!) and these guides will give you all the information required to select the proper pump for a given application.

On occasion I get calls from technicians that say the burner seems to be losing the flame, and most often this can be caused by an air leak somewhere in the fuel line. Keep in mind that too many fittings, check valves and bends in the tubing can create more resistance for the pump to overcome and create a higher vacuum. This in turn can lead to air separation in the oil, noisy operation and an unstable flame pattern. Always look for compression fittings somewhere in the line and remove them. 

Oil pumps also become stressed when the viscosity (thickness of the oil) becomes too high and causes the oil’s ability to flow to be more difficult. If this is a problem, call on one of the many companies that manufacture additives, as an additive can help to eliminate this issue.

Proper tools are a must when servicing pumps: a liquid filled pressure and vacuum gauge set; Allen set; 3/8″ and ½” brass flared liquid eye as they are often called to visually check for air in the line from the tank; pump bleed hose and a combination wrench set. Don’t use pipe wrenches or Teflon tape when working on a fuel unit.

As a final note, make sure that you have a current burner OEM Guide to verify the proper pump pressure for the application you’re working on. You will find there are oil pump pressures set well beyond the140 PSI range. I have witnessed new burners that are operating at pressures in the 290 PSI range. I would also agree with co-writer George Lanthier when it comes to eliminating two pipe systems whenever possible.