Injector Test Sequence

1. ENGINE CRANKSHAFT WILL NOT TURN WHEN START SWITCH IS ON

Cause: Correction:

Battery has Low Output Check condition of battery. Charge battery or make replacement as necessary.

Wiring or Switches Have Defect Make repairs or replacements as necessary.

Problem with Engine Protective Make reference to ELECTRIC PROTECTIVE SYSTEM, in Form System SENR2984 or Form SENR2985.

Starter Motor Solenoid Has A Install a new solenoid. Defect

Starter Motor Has a Defect Make repair or replacement of starter motor.

Oil Pressure Switch For Prelubri- Make a replacement of defective switch. cation Pump Has A Defect

Prelubrication Oil Pump Has A Repair or replace pump components as needed. Defect

Inside Problem Prevents Engine If the crankshaft can not be turned after disconnecting the driven Crankshaft From Turning equipment, remove the fuel injectors and check for fluid in the cylinders while turning the crankshaft. If fluid in the cylinders is not the problem, the engine must be disassembled to check for other inside problems. Some of these inside problems are bearing seizure, piston seizure, or valves making contact with the pistons. 2a. ENGINE WILL NOT START - GOVERNOR TERMINAL SHAFT DOES NOT MOVE FUEL CONTROL LINKAGE

Cause: Correction:

Low Oil Level In Governor Check gauge and add correct amount of clean oil to WOODWARD UG-8 GOVERNORS. Check for plugged oil supply passages to CATERPILLAR 3161 GOVERNORS.

Too Much Binding In Control Engine can start cold, but with hot oil governor does not develop Linkage enough pump pressure to move linkage. Check linkage effort and correct.

Speed Control Shaft Setting Too Move control shaft toward high idle while cranking engine. Low (Low Idle Not set Correctly) Terminal shaft on properly operating governor will move fuel control linkage to the "FUEL ON" position.

Solenoid Stuck In Shut Off On UG8L remove top cover assembly and make sure shut down Position strap is up. Crank engine to start. Repair or make a replacement of faulty solenoid.

Problem with Engine Protective Make reference to ELECTRIC PROTECTIVE SYSTEM, in Form System SENR2984 or Form SENR2985.

Solenoid Energized in Shutoff Disconnect wiring harness to stop signal. Correct by Position During Cranking troubleshooting wiring to solenoid.

Low Oil Pressure In Governor The governor oil pump relief valve may be stuck open or leaking. Correct by governor disassembly and cleaning.

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2b. ENGINE WILL NOT START - GOVERNOR TERMINAL SHAFT OPENS AT LEAST HALF WAY OR MORE AT

CRANKING AS OBSERVED BY OUTBOARD SHAFT ROTATION

Cause: Correction:

Slow Cranking Speed Battery has low output, make reference to Item 29.

No Fuel To Injectors Check fuel tank and fill. "Prime" (remove the air and/or low quality fuel from the fuel system).

Install new fuel filters if necessary. Blocked or broken fuel lines should be cleaned or replaced.

Check the fuel transfer pump for damage or wear and make replacements as needed.

Control lever, on governor terminal shaft, not connected to the fuel control linkage such as improper assembly during overhaul. Make sure governor linkage is correctly engaged.

During cranking, the air-fuel ratio control will restrict injector rack to approximately 7 to 9 mm (.28 to .35 in.) which is below the fuel setting as set by the engine fuel setting screw. Once the lube oil pressure signal reaches the air-fuel ratio control from the engine, the rack will be further restricted to approximately 0 mm (0 in.). The engine must be running and generating boost pressure before the air-fuel ratio control allows more injector rack travel.

A worn or damaged start-up override valve in the hydramechanical protective system can also hold the governor in the shutoff position. On later engines, after a fault condition, the start-up override valve must be used to release the hydraulic pressure on the fuel shutoff actuator before the engine can be started again. Make a replacement and make sure the governor and control linkage move.

Bad Quality Fuel Remove fuel from the tank. Install new fuel filters and put a good grade of clean fuel in the fuel tank.

Fuel Pressure is Low. At starting rpm, the minimum fuel pressure from fuel transfer pump must be 20 kPa (3 psi). If fuel pressure is less than 20 kPa (3 psi) change the fuel filters. Look for air in the fuel system. If fuel pressure is still low, check the fuel bypass valve and the fuel transfer pump for correct operation.

Wrong Fuel Injection Timing Make adjustment to timing.

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3. ENGINE OVERSPEEDS ON START

Cause: Correction:

Fuel Control Linkage Improper assembly after overhaul, linkage not free, bound up in "FUEL ON" position, governor control lever not connected with stop lever of fuel control linkage. Make repairs or replacements as needed.

High Idle Setting Incorrect Start engine in mid speed position and make an adjustment of the high idle setting.

Compensation Needle Valve Adjustment Make an adjustment of the compensation needle valve to get stable governor operation.

Incorrect Governor Oil Used Oil viscosity is too high for ambient temperature starting conditions. Change oil to correct weight as recommended for the engine. In extreme low ambient temperatures DEXRON ATF can be used in UG-8 Governors only.

Dirty Governor Oil (Woodward UG-8) Oil is sludged slowing governor response. Oil should be changed before it gets too thick. Drain and flush with diesel fuel and add new oil.

Governor Not Engaged In Drive Coupling Make sure governor is driven by the engine. If necessary, remove and install governor to make sure it is engaged correctly with the governor drive. Also, check for worn or damaged drive components in the governor and engine.

4. ENGINE SPEED DOES NOT HAVE STABILITY.

Cause: Correction:

Air In Oil (Foam) in Governor Especially on Initial Open compensation needle valve and let governor Start With New Oil. oscillate for several minutes until air is vented from governor. Reset needle valve to approximately ½ to 3/4 open. Also make sure the correct grade of oil is used as recommended for the engine.

Low Oil Level Add oil to correct level in WOODWARD UG-8 GOVERNORS. Check for leaks, especially at drive shaft. Check for plugged oil supply passages for CATERPILLAR 3161 GOVERNORS.

Compensation Adjustments Incorrect Needle valve should be approximately 1/2 to ¾ open.

Negative Speed Regulation (Engine Speeds Up On governors with Isochronous droop setting, correct droop With Load Addition) setting on governor.

Linkage Is Binding, Or Worn With Flat Spots and Inspect and repair or replace linkage as needed. High Clearances.

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Cause: Correction:

Rough Governor Drive Worn splines and/ or high gear clearances can cause rough governor drive. Inspect and replace parts as needed.

Governor can also be out of alignment with drive. Loosen governor and adjust as needed for correct alignment with drive.

Engine Misfiring Make reference to Item 7.

Dirty Oil in Governor (Woodward UG-8) Oil is decomposed and sludged slowing governor response. Replace with new oil after flushing with diesel fuel. High operating temperatures may require heavier viscosity oils.

Pneumatic (Air) Speed Setting Adjustment Wrong If engine is equipped with pneumatic speed setting, improper adjustment or excessive play in the governor linkage can be a problem. Inspect and correct.

Power Piston Sticking Governors on engines that have not been run for long periods may develop rust in areas of the compensation pistons, etc. causing instability. Oil varnish also causes parts to stick. Correct by governor disassembly and cleaning.

Governor Worn Repair or replace governor.

Low Governor Oil Pressure Check correct oil level. Oil pump relief valve does not seat. Replace valve. Oil pump worn. Replace parts.

5a. ENGINE HIGH IDLE SPEED TOO LOW

Cause: Correction:

Speed Setting Shaft Not Against High Idle Stop Check speed control linkage and/or pneumatic controls for restrictions. Make repairs or replacement as needed.

Incorrect Adjustment of High Idle Governor speed setting shaft is against high idle stop and high idle is too low. Make adjustment to correct high idle. Also, check to make sure engine fuel setting is correct.

Speed Droop Adjustment Incorrect Internal adjustable speed droop is set at the factory. Make adjustment if necessary.

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5b. ENGINE LOSES HIGH IDLE AFTER START UP

Cause: Correction:

Normal RPM Loss Loss of approximately 20 rpm can be expected from average cold start to operating temperature.

A shift of 6 to 8 rpm can be expected on the UG8D. A continuous steady speed loss suggests a slipping motor clutch. Adjust motor clutch to 0.51 to 0.62 N m (4.5 to 5.5 lb. in.).

High Idle Adjustment Incorrect Make sure governor and engine fuel settings are correct. Make an adjustment of the high idle as needed.

6. ENGINE CANNOT BE SHUT DOWN THROUGH GOVERNOR.

Cause: Correction:

Bad Shut Down Solenoid Solenoid with a fault, shorted or broken wires, or stuck in open position. Inspect and replace as needed.

Wires Not Connected Correctly Shut down signal not connected with correct polarity to solenoid A positive (+), B negative (-) to 2 pin connector.

Hydraulic/ Pneumatic Shutoff Signal Too Low The signal must be 172 to 276 kPa (25 to 40 psi). The bellows may also be damaged. Measure signal pressures, inspect parts and make repairs or replacements as needed.

Governor Not Correctly Installed Make sure control lever on governor terminal shaft is engaged correctly with the stop lever of the engine fuel control linkage.

Governor Needs Repair Disassemble, clean and inspect governor for worn and damaged parts. Make a replacement of parts as needed.

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7. ENGINE MISFIRING OR RUNNING ROUGH

Cause: Correction:

Fuel Pressure is Low Make sure there is fuel in the fuel tank. Look for leaks or bad bends in the fuel line between fuel tank and fuel transfer pump. Look for air in the fuel system, sticking, binding or defective fuel bypass valve. Check fuel pressure. The outlet pressure of the fuel transfer pump must be a minimum of 415 kPa (60 psi) at full load speed. The pressure in both fuel manifolds must be 415 to 450 kPa (60 to 65 psi). If fuel pressure is lower than the above pressure, install new filters. If fuel pressure is still low, check the fuel transfer pump and fuel pressure regulator valve in the fuel manifold.

Air in Fuel System Find the air leak in the fuel system and correct it. If air is in the fuel system it will generally get in on the suction side of the fuel transfer pump.

Leak or Break in Fuel Line Between Fuel Manifold Install a new fuel line.

and Cylinder Head Defect in Fuel Injector(s) Temperature of an exhaust manifold port, when the engine runs at low idle speed, can be an indication of the condition of a fuel injector. Low temperature at an exhaust manifold port is an indication of no fuel to the cylinder. This can possibly be an indication of an injector with a defect. Extra high temperature at an exhaust manifold port can be an indication of too much fuel to the cylinder, also caused by an injector with a defect.

Wrong Valve Clearance Make adjustment according to Subject, VALVE CLEARANCE.

Wrong Fuel Injection Timing Make adjustment to timing.

Bent or Broken Push Rod Replacement of push rod is necessary.

Fuel Has "Cloud Point" Higher Than Atmospheric Drain the fuel tank, lines and fuel manifolds. Change Temperature ("Cloud Point" = Temperature the fuel filter. Fill the tank with fuel which has the Which Makes Wax Form In Fuel). correct "cloud point" and remove the air from the system with the priming pump.

In some installations it can be necessary to use fuel heaters to insure proper fuel flow and to prevent filter blockage from fuel wax. The fuel temperature at which flow is reduced and filter blockage occurs is usually dependent upon the amount of wax in the fuel or its cloud point.

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