Diagnostic Procedure

NOTE: If not directed here from another diagnostic, DO NOT perform this procedure. Only perform this test when fuel is more than 65°F (18°C).

Were you directed here from one of the following?
- Diagnostic Procedure for DTC P1094.
- SURGES &/OR CHUGGLES symptom under SYMPTOM DIAGNOSIS under SYMPTOMS (DIESEL) in TROUBLE SHOOTING - NO CODES - TRUCKS article.
- ROUGH, UNSTABLE, OR INCORRECT IDLE & STALLING under SYMPTOM DIAGNOSIS under SYMPTOMS (DIESEL) in TROUBLE SHOOTING - NO CODES - TRUCKS article.
- FUEL INJECTOR BALANCE TEST WITH TECH 2
If yes, go to FUEL PRESSURE REGULATOR GRAPHING . If no, go to next step.
Remove air duct from air cleaner assembly and turbo inlet.
Remove air intake pipe.
Remove fuel injection pump fuel return rubber hose from junction block. Cap fitting on block with a 3/8" rubber cap to prevent fuel leakage.
Attach a rubber hose with a barbed fitting to fuel injection pump return hose and insert other end into a one gallon clean fuel container.
Remove Ignition 1 relay using Relay Puller Pliers (J 43244).
Remove glow plug controller/relay.
Remove fuel line retainers.
Remove banjo bolt from left rear cylinder head.
Install Black hose of (J 45873) to left rear cylinder head and install other end of hose into one of (J 45873) graduated cylinders.
Remove banjo bolt from leak-off block.
Install other Black hose of (J 45873) to leak-off block and install other end of hose into another (J 45873) graduated cylinders.
Remove banjo bolt from junction block.
Crank engine for 15 seconds while observing fuel pressure relief valve on junction block for fuel leakage. If fuel is leaking from fuel pressure relief valve, replace fuel pressure relief valve. If no fuel is leaking from fuel pressure relief valve, go to next step.
Crank engine in 15 second intervals, with one minute cooling time between, until fuel starts to flow into one or both of (J 45873) graduated cylinders.
Elevate hoses to retain fuel in hoses, and empty graduated cylinders into a suitable container.
Install hoses into 2 graduated cylinders.

NOTE: Engine cranking speed must be more than 150 RPM.

Crank engine for 15 seconds.
Measure quantity of fuel in each graduated cylinder. If there is more than 12 ml of fuel from either cylinder bank, remove valve cover from that bank. For valve cover removal and installation procedure, see 6.6L V8 DIESEL article in ENGINES. Go to next step. If there is less than 12 ml from each cylinder bank, replace fuel injection pump and repeat steps 15- 19 . If fuel injection pump has already been replaced in this repair and there is less than 12 ml of fuel from each bank, go to step 39.

NOTE: When fuel injector pressure lines are removed, debris will fall into fuel injector inlet fitting. Vacuum debris from inlet fitting of fuel injector.

Remove return line from injectors.
Install 4 Yellow hoses from (J 45873) to injectors and other end of hoses into each (J 45873) graduated cylinder.
Install 4 injector supply lines. Tighten supply lines to specification. See REMOVAL, OVERHAUL & INSTALLATION - 6.6L DIESEL article.
Connect fuel injection control module wiring harness connectors to enable starter.
Install fuel supply hose. Push hose in until it locks.
Install Black hoses from (J 45873) into same container that fuel injection pump return hose is in. Prime fuel system 30 times to remove air from fuel system. Air will be forced out of system within 2 minutes.
Crank engine in 15 second intervals, with one minute cooling time between, until fuel starts to flow into one or more graduated cylinders.
Elevate 4 hoses to retain fuel in hoses, and empty 4 graduated cylinders into a suitable container.
Install hoses in graduated cylinders in numerical order.

NOTE: Engine cranking speed must be more than 150 RPM.

Crank engine for 15 seconds.
Measure quantity of fuel in each graduated cylinder. Repeat steps 25- 30 for all fuel injectors. If there is more than 4 ml of fuel flow from any fuel injector(s), replace high flowing fuel injector(s). After replacement, go to next step. If no fuel injector has a flow of more than 3 ml, install valve cover. After installing valve covers, go to next step.
Were both banks of fuel injectors tested with steps 25- 30 ? If yes, go to step 40. If no, go to next step.
Reassemble fuel return line and valve cover.
Ensure hoses are still installed as they were in steps 10) -13) .
Prime fuel system 30 times to remove air from fuel system. Air will be forced out of system within 2 minutes.
Crank engine in 15 second intervals, with one minute cooling time between, until fuel starts to flow into one or both (J 45873) graduated cylinders.
Elevate hoses to retain fuel in hoses, and empty graduated cylinders into a suitable container.
Install hoses into 2 graduated cylinders.

NOTE: Engine cranking speed must be more than 150 RPM.

Crank engine for 15 seconds while observing fuel pressure relief valve for fuel leaks. If relief valve leaks, replace relief valve and repeat steps 35- 38 .
Measure quantity of fuel in each graduated cylinder. If there is more than 12 ml of fuel in either cylinder, perform steps 25- 30 on bank of fuel injectors with high fuel flow, then go to next step. If both cylinder have less than 12 ml of fuel, go to next step.
Install all disconnected and removed components.
Start and idle engine. You may have to prime fuel system before engine will start.
Connect scan tool to DLC.
Command fuel pressure control to 160 MPa with scan tool. If fuel pressure is more than 145 MPa, system is okay. If fuel pressure is unable to increase to more than 145 MPa, replace fuel injection pump.