FUEL INJECTOR TESTING AND REPAIR
Tools and Special Tools
Tool Kit, General Mechanic's, Automotive (WP
Adapter for Pressure Testing Valve Housing to
Battery disconnect switch in OFF position (WP
Keep hands away from nozzle spray. At opening pressure, velocity of spray could
puncture skin. Failure to follow this warning may result in injury to personnel.
Before testing nozzles, it is advisable to place them in a cold decarbonizing solution for at
least one hour.
After removing nozzles from solution, wash off exterior of all dirt and carbon.
Use clean filtered diesel fuel and standard type hand pump (equipped with a pressure
gauge having a capacity of at least 4,000 psi [27,579 kPa]) when testing nozzle
1. Connect nozzle loosely to hand test pump. Pump handle several strokes to flush out fittings; then tighten
2. CHATTER: Operate test pump and observe if nozzle chatters at opening pressure and if all orifices in the
nozzle tip are clear. Fuel should spray in an atomized mist and valve should emit a sharp high-pitched chatter.
If chattering does not occur, flush with test pump using rapid, complete strokes.
3. OPENING PRESSURE: Pump test pump handle a few strokes to clear air from nozzle and then raise pressure
steadily. Observe gauge pressure at which valve opens. Opening pressure should be between 3,500 to 3,600
psi (24,130 to 24,820 kPa). If pressure is below that specified, nozzle must be disassembled and reset by
addition of shims.
4. SEAT LEAKAGE: Wipe nozzle tip dry. Bring pressure up slowly to 500 psi (3,450 kPa) below nozzle opening
pressure and maintain this pressure for 5 seconds. Wetting of nozzle is permissible without formation of a