PISTON & ROD GP 1777878 - Caterpillar

can be several causes for constant low fuel delivery from the separate injection pumps of pump housing groups during testing on Fuel Injection Test Benches. The first is worn or damaged plunger and barrel assemblies. Test bench operators can install new plunger and barrel assemblies and check the fuel delivery again.
If fuel delivery is still low, check the master valve (special fuel injection valve with a flat seat used as the standard resistance against which the fuel injection pump must work). To do this, exchange the master valve with a master valve that shows normal fuel delivery.
If the master valve checks correctly, look for a restriction at the ends of the fuel injection lines. Generally, restrictions are caused when the line fittings are tightened too tight or if they have been used for long periods of time. A .062" (1.57 mm) drill can be used to clean the lines of these restrictions.
Troubleshooting problems like these will be added to Special Instruction Form GEG00451-01, "Using the Caterpillar Fuel Injection Test Bench", when revisions are made.