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. |
