Tags: Fuel Pumps

Troubleshooting Fuel Pumps


The troubleshooting list in Table 1-3 contains the most common operating problems associated with fuel pumps and fuel units. Each problem is given in the form of a symptom, the possible cause, and a suggested remedy. The purpose of this list is to provide the operator with a quick reference to the cause and correction of a specific problem.

Table 1-3 Troubleshooting Fuel Pumps

Symptom and Possible Cause Possible Remedy
No oil flow to nozzle.
(a) Clogged strainer or filter. (a) Remove and clean strainer; repack filter element.
(b) Air binding in two-pipe system. (b) Check and insert bypass plug.
(c) Frozen pump shaft. (c) Remove pump and return it to the manufacturer for repair or replacement.
Oil leak.
(a) Loose plugs or fittings. (a) Dope with good-quality thread sealer.
(b) Leak at pressure-adjusting end cap nut. (b) Fiber washer may have been left out after adjustment of valve spring; replace washer.
(c) Blown seal. (c) Replace fuel unit.
(d) Seal leaking. (d) Replace fuel unit.
Noisy operation.
(a) Air inlet line. (a) Tighten all connections and fittings in the intake line and unused intake port plugs
(b) Bad coupling alignment. (b) Loosen mounting screws and shift fuel pump to a position where noise is eliminated. Retighten mounting screws.
(c) Pump noise. (c) Work in gears by continued running or replace.
Pulsating pressure.
(a) Air leak in intake line. (a) Tighten all fittings and valve packing in intake line.
(b) Air leaking around strainer cover. (b) Tighten strainer cover screws.
(c) Partially clogged strainer. (c) Remove and clean strainer.
(d) Partially clogged filter. (d) Replace filter element.
Low oil pressure.
(a) Nozzle capacity is greater than fuel pump capacity. (a) Replace fuel pump with one of correct capacity.
(b) Defective gauge. (b) Check against another and replace if necessary.
Improper nozzle cutoff.
(a) Filter leaks. (a) Check face of filter cover and gasket for damage.
(b) Partially clogged nozzle strainer. (b) Clean strainer or change nozzle.
(c) Air leak in intake line. (c) Tighten intake fittings and packing nut on shutoff valve; tighten unused intake port plug.
(d) Strainer cover loose. (d) Tighten screws.
(e) Air pockets between cutoff valve and nozzle. (e) Start and stop burner until smoke and afterfire disappear.

Priming Fuel Pumps


On occasion, the oil burner may fail to pump oil. When this occurs, check the oil supply line to the furnace for leaks. If there are no leaks, it may be necessary to prime the fuel pump. Pumps are self priming for single-stage, two-pipe systems and for two-stage pumps. A single-stage pump (one-pipe system) should be primed as follows:

1. Turn off the electrical power supply to the unit.
2. Read and follow the priming instructions provided by the manufacturer.
3. Prime the pump until the oil is free of bubbles.

When a new pump fails to prime, it may be due to dry pump conditions, which can be corrected by removing the vent plug and filling the pressure cavity slowly so that the fuel oil wets the gears (see Figure 1-29). Other possible causes of the pump failing to prime include the following:

• Suction inlet vacuum is greater than 15 inches of vacuum.
• Suction line is incorrectly sized.
• Oil suction line strainer or filter capacity does not match the pump suction gear capacity.
• Bypass plug is not in position on two-pipe installations.
• Plug(s) and/or suction line connections are not airtight.

webster fuel pump Priming Fuel Pumps