The Fuel Pump



The fuel Pump moves the fuel oil from the fuel tank to the fuel nozzle. The pump uses a meshed gear set to squeeze the fuel through the pump at about 100 psi.
Equipment manufacturers may set fuel pumps at different pressures – up to 125 psi or more. Pump pressure is read at the gauge port and adjusted with the pressure adjusting screw.


Note: Most fuel pump problems are due to either improper installation or clogging with debris. Guaranteeing a clean fuel supply will do more than anything to prolong fuel pump life.

Important: Constant readjustment of pressure or other settings on the fuel pump will result in unreliable fuel pump action.

Inspect The Fuel Pump


A lot can be determined by simply looking over the fuel pump. Here is a checklist for fuel pump inspection.

· Check to see if the fuel pump is properly seated in the burner or bracket. Misalignment will side load the seal area, causing excessive wear, possible leakage, and inability to prime. This extra load is passed to the drive motor, causing motor heating over normal levels and increased amp draw.
· Check to see that the fittings connecting the lines to the pump are straight and seated properly. Make sure the fuel lines are not kinked or blocked. Fuel or vacuum leaks can result from improperly seated or cross-threaded fittings and reduction in pump capacity or pump damage may result. This can also cause the pump to not produce fuel flow. Air leaks in the fuel system will have similar effects to air leaks in the water system.
· Check to see if the fuel pump shaft has some end play and whether it has some freedom to slide in and out. If not, the pump is end loaded and will require excessive starting and running torque. The pump should be securely seated all the way in the housing but not seated so tightly that end loading will result. In most cases the pump coupling will not bottom out if the pump is completely inserted and tightened and end loading will not be a problem.


Important: The fuel pump is lubricated by fuel oil. Running the pump dry or with water in the fuel will cause pump failure. If the pump has been removed, care should be taken not to strike the end of the shaft. If the shaft is bent, binding and/or wobbling will occur when the pump is restarted. This can damage the gears, end plates, mounting hub or seal. Fuel pumps in a one-pipe system bypass fuel internally.


Self-Lubrication & Potential For Damage
Fuel pumps are basically self-lubricating; the flow of fuel oil through the pump lubricates and cools its moving parts. Operating a fuel pump with no fuel or a clogged strainer will starve the Pump. Without the lubricating and cooling effect of the fuel oil, the pump will overheat and seize up. When the pump seizes up, a drive coupling may break or trip a thermal reset.

The Right Fuel


The pump must have a proper supply of fuel oil to operate correctly. Fuel oil pumps are designed for use with clean fuel oil or Kerosene. Other substances not only will burn less well but also may damage the pump, which depends on fuel passing through it for lubrication. Other types of fuel or other liquids will not be pumped at all.

Important: Use of improper fuel may cause fuel pump damage or failure. Fuel oil or kerosene is the standard fuel for most oil-fired units. No other substance – especially water – should be run through the fuel pump. Make sure all water is flushed from the fuel tank and purged from the fuel lines and pump.

Clean And Flush The Fuel Delivery System If Contaminated.
If another fuel or fluid enters the fuel tank, the pump should be flushed and the tank cleaned and drained. The easiest way to flush a pump is to clean the tank and fill it with clean fuel, connect a different return line and stick it into a separate container and let the system run. The clean fuel from the tank will flush the pump and the contaminated fuel will be delivered out of the return line to the new container.

If the return line is not directed to a separate container, the trash will simply be flushed back to the fuel tank. The debris or improper fluid can then return to the fuel pump through the inlet line and again obstruct or contaminate the fuel pump. Do not flush the pump through the bleed valve. Oil from the bleed valve comes directly from the gearset and won’t flush the pump valving areas. The tank and the fuel strainers must be kept clean.

Internal Strainer Blockage


Blockage of the internal fuel pump cannot be detected with a gauge because there is no port to check for vacuum beyond the strainer. Removing the fuel pump inlet cover allows inspection of the strainer. If it is coated or covered with debris, it should be cleaned or changed.

Water Can Cause Pump Freeze-Up.
Water in the pump will stop burner operation and the fuel pump will rust while it is out of service. Surface rust can cause the piston to rust cylinder is light, the pump will continue to operate, allowing the piston to move back and open the port to the nozzle. The piston may not, however, close completely. If the machine is stored in this condition, fuel may siphon or drain out of the fuel nozzle, collecting in the burner or dripping out of the floor.

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