Dodge D250 1990 Service Manual page 432

Fuel System
DODGE Turbo Diesel
Fuel System Malfunction - Diagnosis
Page 14-13
Failure of the needle valve to lift and close correctly can cause
the engine to misfire and produce low power. Fuel leaking from
the open nozzle can cause a fuel knock, poor performance,
smoke, poor fuel economy, and rough running.
17mm
Caution: When bleeding a line, be sure to tighten the fuel
line nut before proceeding to the next Injector.
To find which cylinder is misfiring, operate the engine and
loosen the fuel line nut at one injector and listen for a change in
engine speed.
Note: A drop in engine speed indicates the injector was
delivering fuel to the cylinder.
Check each cylinder until the malfunctioning injector is found.
24mm
Remove the malfunctioning injector to tester replace it.
If the engine continues to misfire after replacing the injector,
check for leaks In the high pressure line. Also check for a
defective delivery valve that lets the fuel drain back into the
injection pump.
Carbon build up in the orifices in the nozzle will also cause low
power from the engine. Remove and check the spray pattern or
replace the injectors.