hard start/no-start diagnosis hard start/no-start

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INTRODUCTION

Since many computer-controlled and monitored components set a Diagnostic Trouble Code (DTC) if they

malfunction, perform QUICK TEST in TESTS W/CODES - 7.3L DIESEL article. Service DTCs as necessary.

NOTE: Testing individual components does not

isolate short or open circuits. Perform all voltage tests

with a Digital Volt-Ohmmeter (DVOM) with a minimum

10-megohm input impedance, unless stated otherwise

in test procedure. Use ohmmeter to isolate shorted or

open wiring harness.

HARD START/NO-START DIAGNOSIS

NOTE: Repair each problem detected before

going on to the next step. If repair corrects the

original complaint, it will not be necessary to proceed

to the next step or diagnostic procedure. However, if

complaint is not corrected, continue with the testing

until complaint is corrected.

HARD START/NO-START DIAGNOSIS > VISUAL INSPECTION > DIAGNOSTIC AIDS

Perform visual inspection to check general engine condition and look for obvious causes of hard start or no-

start conditions. Possible causes of a hard or no-start condition are:

Loose or leaking fuel supply lines could cause system to lose prime.

Kinked or blocked fuel supply lines.

Loose or damaged Camshaft Position (CMP) sensor and Injection Pressure Regulator (IPR)

wiring harness connectors.

1. Inspect fuel system, including fuel tank and fuel lines for kinks, bends and leakage.

Repair as necessary. Check oil lines and high pressure oil pump for leaks. Repair

as necessary. Inspect cooling system. Check radiator and heater hoses for leaks.

2. Check Powertrain Control Module (PCM) and Injector Driver Module (IDM) wiring

harness connectors for damaged pins, corrosion and loose wires. Repair as

necessary.

HARD START/NO-START DIAGNOSIS > CHECK ENGINE OIL > DIAGNOSTIC AIDS

Checking engine oil helps determine if there is enough engine oil to operate fuel injectors. If there is little or

no oil in crankcase, injectors will not operate.

1. Ensure vehicle is on level ground. Check engine oil. If oil is overfilled, engine may have been

incorrectly serviced, or oil is diluted with fuel and is filling crankcase. Repair as necessary.

2. Inspect oil color. A milky white color indicates possible coolant contamination. Determine cause

and repair as necessary. If oil level is low, top off oil. Ensure oil is correct type and viscosity.

ENGINE CONTROLS - SYSTEM & COMPONENT TESTS - 7.3L DIESEL

1997 Ford F-Super Duty 7.3L Eng

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3. Remove plug in top of oil reservoir and check oil level. If oil level is within 1" (25.4 mm) of fill hole,

level is okay. If oil level is not within 1" (25.4 mm) of fill hole, top off fluid. Attempt to start vehicle. If

vehicle starts, determine cause of low oil level and repair as necessary.

HARD START/NO-START DIAGNOSIS > CHECK FOR INTAKE/EXHAUST RESTRICTION >

DIAGNOSTIC AIDS

This is a visual inspection to determine if an air intake or exhaust restriction is contributing to a hard or no-

start condition. If engine does not start and a air intake or exhaust restriction exists, a large amount of

Black/Blue smoke will exist while cranking engine.

1. Inspect air cleaner assembly for proper installation. Ensure air ducting is not blocked or collapsed.

Inspect filter minder on filter housing to assure intake restriction is below Red marks. Replace filter

as necessary.

2. While cranking engine, inspect turbocharger exhaust backpressure butterfly bellcrank. Ensure

bellcrank is not closed. When tang is against the stop, valve is fully open. See Fig 1.




HARD START/NO-START DIAGNOSIS > CHECK FUEL SUPPLY & QUALITY >

DIAGNOSTIC AIDS

Purpose of this test is to see if fuel system is getting sufficient clean fuel to start and run engine.

1. Connect a hose to fuel drain line at bottom of fuel filter housing. Place other end of hose into a

suitable container. Open fuel drain. Crank engine and observe fuel. Fuel flow should be a steady

stream.

Fig 1: Identifying Open Exhaust Backpressure Control Valve Position

Courtesy of FORD MOTOR CO.



NOTE: Fuel should be straw colored, but not

cloudy. Fuel should be free of water and

contaminates. Fuel dyed Red or Blue indicates

off-highway fuel.

2. While cranking engine, check WATER IN FUEL warning light indicator. If warning light is on, fuel is

probably contaminated with water. Service fuel system as necessary. If engine oil is present in fuel,

injector "O" ring(s) may be defective. Perform INJECTION CONTROL PRESSURE LEAK TEST .

Repair oil leaks as necessary.

NOTE: Some sediment and water may be present

in fuel sample if fuel filter has not been serviced for a

prolonged period of time. A second sample may be

necessary to determine fuel quality.

HARD START/NO-START DIAGNOSIS > FUEL PUMP PRESSURE TEST > MECHANICAL

FUEL PUMP

NOTE: For fuel pressure specifications, see

FUEL PRESSURE SPECIFICATIONS article.

1. Connect Engine Pressure Test Kit (014-00761) and Adapter (014-00931-3) to Schrader valve.

Schrader valve is part of fuel regulator block. Connect fuel line between adapter and 0-160 psi (0-

1103 kPa) gauge (No. 6) at engine pressure tester. See Figure.

2. Crank engine (minimum of 100 RPM) for 20 seconds and observe fuel pressure gauge. If fuel

pressure is as specified, fuel pressure is okay. If fuel pressure is less than specified, replace fuel

filter and retest. Cycle ignition switch several times to purge air from system. If fuel pressure is still

low, check the following:

1. Check fuel level in gas tank.

2. Disassemble, inspect and clean fuel pressure regulator valve. See Figure.

3. Check for bent or damaged fuel lines. Check for blockage at fuel pick-up tube.

4. Check for loose fuel line on suction side of fuel system. If fuel line is tight, replace fuel

pump and retest.

HARD START/NO-START DIAGNOSIS > FUEL PUMP PRESSURE TEST > ELECTRIC

FUEL PUMP



1. Ensure fuel tank has fuel. Ensure fuel pump has power and ground. With ignition on, battery

voltage should be present at fuel pump for about 20 seconds. If voltage is as specified, go to next

step. If voltage is not as specified, perform CIRCUIT TEST FK in TESTS W/CODES - 7.3L DIESEL

article.









2. Remove cover and 1/8" pipe plug from top rear of left cylinder head. Install fuel pressure gauge.

Check fuel pressure with engine cranking or running. For fuel pressure specifications, see FUEL

PRESSURE SPECIFICATIONS article. If fuel pressure is not as specified, go to FUEL PUMP

PRESSURE TEST under ENGINE PERFORMANCE DIAGNOSIS .

HARD START/NO-START DIAGNOSIS > CHECK FOR DIAGNOSTIC TROUBLE CODES

If all steps under QUICK TEST in TESTS W/CODES - 7.3L DIESEL have been successfully completed, and

a System Pass (DTC P1111 on Federal vehicles or no DTCs on Calif. vehicles) is present, go to CHECK

PARAMETER IDENTIFICATION (PID) DURING CRANKING. If QUICK TEST has not been completed, perform

QUICK TEST. If any DTCs are present, service DTCs as necessary.

HARD START/NO-START DIAGNOSIS > CHECK PARAMETER IDENTIFICATION (PID)

DURING CRANKING > DIAGNOSTIC AIDS

Purpose of this test is to verify Powertrain Control Module (PCM) power-up during cranking. Lack of power

at PCM during cranking can cause a no-start condition and a fault code loss.

1. Check VPWR PID Connect New Generation Star (NGS) scan tool to Data Link Connector (DLC).

Using scan tool, access VPWR PID from PID/DATA monitor menu. See ADDITIONAL SYSTEM

Fig 1: Removing Fuel Pressure Regulator Valve (Vehicles With Mechanical Fuel Pump)







FUNCTIONS in TESTS W/CODES - 7.3L DIESEL article. Crank engine while monitoring PID

reading. If PID reading indicates more than 7 volts, go to next step. If PID reading indicates 7 volts

or less, check charging circuit, power and ground circuits. See CIRCUIT TEST A in TESTS

W/CODES - 7.3L DIESEL article.

2. Check RPM PID Using scan tool, access RPM PID from PID/DATA monitor menu. Crank engine

while monitoring PID reading. If PID reading indicates more than 100 RPM, go to next step. If PID

reading indicates 100 RPM or less, check Camshaft Position (CMP) sensor circuit. See CIRCUIT

TEST DG in TESTS W/CODES - 7.3L DIESEL article.

3. Check ICP PID Using scan tool, access ICP PID from PID/DATA monitor menu. Crank engine while

monitoring PID reading. If PID reading indicates 500 psi (3448 kPa) or more, go to next step. If PID

reading indicates less than 500 psi (3448 kPa), injectors are not being energized because of

insufficient pressure. Perform INJECTION CONTROL PRESSURE LEAK TEST .

4. Check Fuel Pulse Width Using scan tool, access FUEL PW PID from PID/DATA monitor menu.

Crank engine while monitoring PID reading. If PID reading indicates 1-6 milliseconds, go to GLOW

PLUG SYSTEM OPERATION TEST . If PID reading does not indicate 1-6 milliseconds and VPWR,

RPM and ICP PID readings are correct, Camshaft Position (CMP) sensor signal fault. See CIRCUIT

TEST DG in TESTS W/CODES - 7.3L DIESEL article.

HARD START/NO-START DIAGNOSIS > INJECTION CONTROL PRESSURE LEAK TEST >

DIAGNOSTIC AIDS

Removing Injection Control Pressure (ICP) sensor and inspecting level in oil rail will determine if oil is being

supplied to rail. Removing inspection plug in top of reservoir will help determine if reservoir is full. A

reservoir that drains back after engine has not been operated for a long period of time can cause a hard

start condition.


RIGHT CYLINDER HEAD CHECK

1. Perform step 3) under CHECK PARAMETER IDENTIFICATION (PID) DURING CRANKING (if not

already completed). Remove high pressure hose from right cylinder head. Using Fuel/Oil/Turbo

Protector Cap Set (T94T-9395-AH), install appropriate cap on high pressure hose fitting on

cylinder head. Using Oil High Pressure Leakage Test Adapter Set (D94T-6600-A), install plug into

high pressure hose.

WARNING: In the following step, engine may

start.

2. Install ICP/EBP Adapter Cable (D94T-50-A) between ICP sensor and sensor wiring harness

connector. Connect a DVOM between SIG RTN circuit (Black wire) and ICP Signal circuit (Green

wire) at ICP/EBP adapter cable. Observe DVOM and crank engine. Voltage reading should be 1-4

volts.

3. If engine starts, or if ICP PID reading indicates 500 psi (3448 kPa) or more, an injection control

pressure oil leak exists in right cylinder head. Inspect fuel system for oil contamination.

4. If no oil is present in fuel system, remove cap and plug, and reinstall high pressure hose to right

cylinder head. Remove right valve cover. Crank engine, and inspect injector body and injector

bore area for oil leakage. Repair as necessary. If engine does not start, or ICP PID is still less than

500 psi (3448 kPa), perform LEFT CYLINDER HEAD CHECK.











LEFT CYLINDER HEAD CHECK

1. Remove high pressure hose from left cylinder head. Using fuel/oil/turbo protector cap set, install

appropriate cap on high pressure hose fitting on cylinder head. Using oil high pressure leakage

test adapter set, install ICP adapter into high pressure hose. See Fig 1.

2. Remove ICP sensor and install sensor in end of ICP adapter. Install ICP/EBP Adapter Cable

(D94T-50-A) between ICP sensor and sensor wiring harness connector. Connect a DVOM

between SIG RTN circuit (Black wire) and ICP Signal circuit (Green wire) at ICP/EBP adapter cable.

Observe DVOM and crank engine. Voltage reading should be 1-4 volts.

WARNING: In the following step, engine may

start.

3. If engine starts, or if ICP PID reading indicates 500 psi (3448 kPa) or more, an injection control

pressure oil leak exists in left cylinder head. Reconnect high pressure hose to left cylinder head.

Remove left valve cover. Crank engine, and inspect injector body and injector bore area for oil

leakage. Repair as necessary.

4. If injection control pressure is still low after completing both right and left cylinder head checks and

no oil leaks have been found, remove high pressure hose from right and left cylinder heads. Using

fuel/oil/turbo protector cap set, install appropriate cap on high pressure hose fitting on each

cylinder head.

5. Using oil high pressure leakage test adapter set, install plug into each high pressure hose. Both

high pressure lines should now be blocked off. Using scan tool, observe ICP PID reading while

cranking engine.

6. If PID reading is still less than 500 psi (3448 kPa), replace Injection Pressure Regulator (ICP) with

a known good ICP and retest. If PID reading is now 500 psi (3448 kPa) or more, replace ICP. If PID

reading is still less than 500 psi (3448 kPa), high pressure pump or high pressure pump drive gear

is faulty. Repair as necessary.




HARD START/NO-START DIAGNOSIS > GLOW PLUG SYSTEM OPERATION TEST

Question: glow plug ohms

HARD START/NO-START DIAGNOSIS > GLOW PLUG SYSTEM OPERATION TEST >

DIAGNOSTIC AIDS

Insufficient glow plug "On" time will not allow enough heat to accumulate in combustion chamber resulting in

a hard start condition. If glow plug system "On" time is insufficient, probable cause is a faulty wiring harness

connector, bad ground connection or defective glow plug relay. If glow plug resistance to ground is high,

probable cause is an open circuit in Under Valve Cover (UVC) wiring harness or an open glow plug.

1. Connect a DVOM between ground and Black/Orange wire at glow plug relay. See Fig 1. Turn

ignition on. If battery voltage is present, go to next step. If battery voltage is not present, locate

and repair open circuit in Black/Orange wire between glow plug relay and starter relay.

Fig 1: Equipment Hookup For Injection Control Pressure Test


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2. Turn ignition off. Connect DVOM between ground and Brown wire at glow plug relay. Turn ignition

on and note how long is takes for glow plug relay to energize and de-energize ("On" time). Relay

will make a loud click noise when it energizes. If relay "On" time is not as specified, replace relay.

See GLOW PLUG RELAY SPECIFICATIONS table. If "On" time is as specified, go to next step.

GLOW PLUG RELAY SPECIFICATIONS

Engine Oil Temperature - °F (°C) "On" Time - Seconds

14 (-10) 120

68 (20) 70

122 (50) 40

131 (55) 60

Specification listed is with vehicle at sea level and battery voltage at 12 volts.

Specification is approximate.

(1)

(1)

Fig 1: Checking Power To Glow Plug Relay




NOTE: Each valve cover gasket has 2 fuel

injector connectors that are part of the gasket.

Each connector is responsible for 2 fuel

injectors. If connector is faulty, replace valve

cover gasket.

3. Turn ignition off. Disconnect all 4 injector connectors at valve cover gaskets. Install Glow Plug

Injector Adapter (014-00935) to any injector connector at valve cover gasket. See Fig 2.

NOTE: If all injector connectors are not

disconnected at both valve cover gaskets,

resistance measurements will be incorrect.

4. Measure resistance between ground and each glow plug test point at glow plug injector adapter. If

all readings are .1-2.0 ohms, go to next step. If any reading is not .1-2.0 ohms, probable cause is

an open in Under Valve Cover (UVC) wiring harness or an open glow plug. Repair as necessary.

5. Measure resistance between Brown wire at glow plug relay and each glow plug test point at glow

plug injector adapter. If all readings are .1-1.0 ohm, no problem is indicated at this time. If any

reading is not .1-1.0 ohm, locate and repair open circuit.

Fig 2: Checking Glow Plug Resistance





ENGINE PERFORMANCE DIAGNOSIS

NOTE: Repair each problem detected before

going on to the next step. If repair corrects the

original complaint, it will not be necessary to proceed

to the next step or diagnostic procedure. However, if

complaint is not corrected, continue with the testing

until complaint is corrected.

ENGINE PERFORMANCE DIAGNOSIS > VISUAL INSPECTION > DIAGNOSTIC AIDS

Perform visual inspection to check general engine condition and look for obvious causes of a loss of

performance.

1. Check for disconnected or pinched Manifold Absolute Pressure (MAP) sensor hose. Inspect fuel

system, including fuel tank and fuel lines for kinks, bends and leakage. Repair as necessary.

Check oil lines and high pressure oil pump for leaks. Repair as necessary.

2. Inspect cooling system. Check radiator and heater hoses for leaks. Check Powertrain Control

Module (PCM) and Injector Driver Module (IDM) wiring harness connectors for damaged pins,

corrosion and loose wires. Repair as necessary.

ENGINE PERFORMANCE DIAGNOSIS > CHECK FUEL QUALITY > DIAGNOSTIC AIDS

Purpose of this test is to see if fuel system is getting sufficient clean fuel for engine to operate properly. Fuel

should be straw colored, but not cloudy. Fuel dyed Red or Blue indicates off-highway fuel. Cloudy fuel

indicates fuel may not be a suitable grade for cold temperatures. Excessive water or contaminants may

indicate fuel system and tank may need to be flushed.

1. Connect a hose to fuel drain line at bottom of fuel filter. Place other end of hose into a suitable

container. Open fuel drain. Start engine and observe fuel. Fuel flow should be a steady stream.

Turn ignition off.

2. Turn ignition on. Check WATER IN FUEL warning light indicator. If warning light is on, fuel is

contaminated with water. Service fuel system as necessary. If engine oil is present in fuel, injector

"O" ring maybe defective. Perform INJECTION CONTROL PRESSURE LEAK TEST under HARD

START/NO START DIAGNOSIS. Repair oil leaks as necessary.

NOTE: Some sediment and water may be present

in fuel sample if fuel filter has not been serviced for a

prolonged period of time. A second sample may be

necessary to determine fuel quality.

ENGINE PERFORMANCE DIAGNOSIS > CHECK ENGINE OIL > DIAGNOSTIC AIDS

Checking engine oil helps determine if there is enough engine oil to operate fuel injectors. If there is little or

no oil in crankcase, injectors will not operate.

1. Ensure vehicle is on level ground. Check engine oil. If oil is overfilled, engine may have been

incorrectly serviced, or fuel is diluting oil and filling crankcase. Repair as necessary.

2. Inspect oil color. A milky white color indicates possible coolant contamination. Determine cause

and repair as necessary. If oil level is low, top off oil. Ensure oil is correct type and viscosity.




3. Remove plug in top of oil reservoir and check oil level. If oil level is within 1" (25.4 mm) of oil fill

hole, level is okay. If oil level is not within 1" (25.4 mm) of oil fill hole, check and repair cause of low

engine oil. Top off engine oil.

ENGINE PERFORMANCE DIAGNOSIS > CHECK FOR INTAKE RESTRICTION >

DIAGNOSTIC AIDS

This is a visual inspection to determine if an air intake restriction is contributing to a low power condition. If

engine has a high intake restriction, a large amount of Black or Blue smoke may exist.

ENGINE PERFORMANCE DIAGNOSIS > CHECK FOR INTAKE RESTRICTION > CHECK

AIR FILTER

Inspect air cleaner assembly for proper installation. Ensure air ducting is not blocked or collapsed. Inspect

filter minder on filter housing to ensure intake restriction is below Red marks. Replace filter as necessary.

ENGINE PERFORMANCE DIAGNOSIS > CHECK FOR DIAGNOSTIC TROUBLE CODES

Question: 7.3 eng miss

If all steps under QUICK TEST in TESTS W/CODES - 7.3L DIESEL have been successfully completed, and

a System Pass (DTC P1111 on Federal vehicles or no DTCs on Calif. vehicles) is present, go to FUEL

PUMP PRESSURE TEST. If QUICK TEST has not been completed, perform QUICK TEST. If any DTCs are

present, service DTCs as necessary.

ENGINE PERFORMANCE DIAGNOSIS > FUEL PUMP PRESSURE TEST

NOTE: If HIGH FUEL RESTRICTION indicator

light is on, a restricted fuel filter may be causing low

fuel pressure.

ENGINE PERFORMANCE DIAGNOSIS > FUEL PUMP PRESSURE TEST > MECHANICAL

FUEL PUMP



1. Connect Engine Pressure Tester (014-00761) and Adapter (014-00931-3) to Schrader valve.

Schrader valve is part of fuel regulator block. Connect fuel line between adapter and 0-160 psi (0-

1103 kPa) gauge (No. 6) at engine pressure tester. See Fig 1.







2. Start engine and allow it to idle. Observe fuel pressure gauge and briefly raise engine speed to

3500 RPM. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel

pressure is as specified, fuel pressure is okay. If fuel pressure is not as specified, replace fuel filter

and retest. Cycle ignition switch several times to purge air from system. If fuel pressure is still low,

go to next step.

3. Disconnect short fuel hose at fuel inlet line. Hose is located on left side of engine, close to frame

rail. The larger of the 2 lines is the fuel inlet. The smaller line is the fuel return. Connect Fuel

Pressure Adapter (014-00931-2) between fuel inlet line and vacuum gauge (0-30 in. Hg) of engine

pressure tester.

4. Start engine and allow it to idle. Observe vacuum gauge and briefly raise engine speed to 3500

RPM. If vacuum is 6 in. Hg or less, no restriction exist at this time. Check fuel regulator valve for

sticking or debris. If vacuum is more than 6 in. Hg, check for blockage between pump and fuel

tank. Repair as necessary.

ENGINE PERFORMANCE DIAGNOSIS > FUEL PUMP PRESSURE TEST > ELECTRIC

FUEL PUMP

1. Ensure fuel tank has fuel. Ensure fuel pump has power and ground. With ignition on, battery

voltage should be present at fuel pump for about 20 seconds. If voltage is as specified, go to next

step. If voltage is not as specified, perform CIRCUIT TEST FK in TESTS W/CODES - 7.3L DIESEL

article.

Fig 1: Identifying Engine Pressure Tester






2. Remove fuel line to inlet side of fuel pump. Install Fuel Pressure Adapter (014-00931-2) between

fuel inlet line and fuel pump. Connect fuel pressure adapter to vacuum gauge (0-30 in. Hg) of

Engine Pressure Tester (014-00761). See Figure.

3. Start engine and allow it to idle. Observe vacuum gauge and briefly raise engine speed to 3500

RPM. If vacuum is 6 in. Hg or less, no restriction exist at this time. Go to next step. If vacuum is

more than 6 in. Hg, check for blockage between pump and fuel tank. Repair as necessary.

4. Remove fuel pressure adapter and reconnect fuel line to inlet side of fuel pump. Remove fuel line

from outlet side of fuel pump. Install fuel pressure adapter between fuel outlet line and fuel pump.

Connect fuel pressure adapter to 0-160 psi (0-1103 kPa) gauge (No. 6) at engine pressure tester.

See Figure.

5. Start engine and allow it to idle. Observe fuel pressure gauge and briefly raise engine speed to

3500 RPM. For fuel pressure specifications, see FUEL PRESSURE SPECIFICATIONS article. If fuel

pressure is as specified, fuel pressure is okay. Go to next step. If fuel pressure is not as specified,

check fuel regulator valve for sticking or debris. See Fig 1. Repair as necessary and retest. If fuel

regulator valve is okay, replace fuel pump and retest.

6. Remove cover and 1/8" pipe plug from top rear of left cylinder head. Install fuel pressure gauge.

Start engine. Check fuel pressure with full load on engine. For fuel pressure specifications, see

FUEL PRESSURE SPECIFICATIONS article. DO NOT brake torque engine for more than 10

seconds. If fuel pressure is as specified, go to next step. If fuel pressure is not as specified,

replace fuel filter and retest. If fuel pressure is still low, replace left fuel check valve. Check valve is

located in front of left cylinder head between fuel inlet line and cylinder head.

7. Remove 1/8" pipe plug from top front of right cylinder head. It may be necessary to remove

generator and bracket to access pipe plug. Install fuel pressure gauge. Start engine. Check fuel

pressure with full load on engine. For fuel pressure specifications, see FUEL PRESSURE

SPECIFICATIONS article. DO NOT brake torque engine for more than 10 seconds. If fuel pressure

is as specified, fuel pressure is okay. If fuel pressure is not as specified, replace right fuel check

valve. Check valve is located in rear of right cylinder head between fuel inlet line and cylinder

head.









ENGINE PERFORMANCE DIAGNOSIS > CHECK FOR AIR IN FUEL SYSTEM > WITH

MECHANICAL FUEL PUMP

1. Disconnect fuel return hose at fuel filter. Install a clear fuel hose between fuel return hose and fuel

return hose fitting at fuel filter. Loop hose at a point higher than fuel filter. See Fig 1. While

observing fuel line, start and run engine for about 5 minutes. Fuel should be free of air.

2. If fuel is foamy, check for an air leak in fuel lines between fuel pump and fuel tank. Repair as

necessary. If no fuel flow exists, remove fuel regulator block, taking care not to damage "O" ring.

Inspect fuel return orifice screen for debris. Clean as necessary. See Fig 2.

Fig 1: Exploded View Of Fuel Regulator Valve (Vehicles With Electric Fuel Pump)






Fig 1: Checking For Air In Fuel System




ENGINE PERFORMANCE DIAGNOSIS > INJECTION CONTROL PRESSURE TESTS >

DIAGNOSTIC AIDS

Purpose of this test is to determine if engine oil is aerated and causing poor idle.

ENGINE PERFORMANCE DIAGNOSIS > INJECTION CONTROL PRESSURE TESTS > OIL

AERATION/POOR IDLE

1. Connect New Generation Star (NGS) scan tool to Data Link Connector (DLC). Turn A/C off. Using

scan tool, access ICP PID from PID/DATA monitor menu. See ADDITIONAL SYSTEM FUNCTIONS

in TESTS W/CODES - 7.3L DIESEL article.

2. Start engine and raise engine speed to 3400 RPM for 3 minutes. ICP PID reading should be 750-

1250 psi (5171-8619 kPa). If PID reading is not 750-1250 psi (5171-8619 kPa), change oil and

retest.

ENGINE PERFORMANCE DIAGNOSIS > INJECTION CONTROL PRESSURE TESTS > LOW

IDLE STABILITY (ICP PRESSURE)

1. Ensure engine is at normal operating temperature. Using scan tool, access ICP PID from

PID/DATA monitor menu. Start engine and allow it to idle.

Fig 2: Exploded View Of Fuel Regulator Block





2. Check PID value. See ICP PID VALUES table. If PID reading is not as specified, or idle does not

stabilize, disconnect ICP sensor. Sensor is located at top left side of engine.

3. If idle is now stabilized, fault is in ICP sensor circuit. Perform CIRCUIT TEST DD in TESTS

W/CODES - 7.3L DIESEL article. If idle still does not stabilize, replace Injection Pressure Regulator

(IPR) and retest.

ICP PID VALUES

Application psi (kPa)

Federal vehicles 550-700

Calif. vehicles 400-600

ENGINE PERFORMANCE DIAGNOSIS > CRANKCASE PRESSURE TEST

1. Ensure engine is at normal operating temperature. Remove turbocharger inlet pipe ducting.

Remove inlet pipe and elbow that connects to air filter housing. Using cap provided in Engine

Pressure Tester (014-00761), block air filter housing outlet. Install a protective screen over

turbocharger inlet.

2. Screw Crankcase Orifice Restrictor (5631) and Crankcase Pressure Test Adapter (014-00743)

into oil fill cap hole. Connect adapter to pressure gauge (No. 4) at Engine Pressure Tester (014-

00761). Ensure gauge has been zeroed.

3. Observe gauge and raise engine speed to 3400 RPM for about 30 seconds. DO NOT block hole

at top of crankcase orifice restrictor. Pressure should be less than 4 in. H2O. If pressure is 4 in.

H2O or more, check engine mechanical condition (compression rings, cylinder bores, valves, etc.).

Repair as necessary.

ENGINE PERFORMANCE DIAGNOSIS > CHECK CYLINDER PERFORMANCE

If KOER CYLINDER CONTRIBUTION SELF-TEST under QUICK TEST in TESTS W/CODES - 7.3L DIESEL

article has been successfully completed previously, go to CHECK FOR EXHAUST RESTRICTION . If KOER

CYLINDER CONTRIBUTION SELF-TEST has not been completed, perform KOER CYLINDER

CONTRIBUTION SELF-TEST. Possible causes for failing this test are:

Broken compression rings.

Burnt or bent valve.

Bent push rods.

Bent connecting rods.

Damaged rocker arms.

Faulty fuel injector assembly.

ENGINE PERFORMANCE DIAGNOSIS > CHECK FOR EXHAUST RESTRICTION

Question: exhaust back pressure buterfly on turbo wont open

ENGINE PERFORMANCE DIAGNOSIS > CHECK FOR EXHAUST RESTRICTION >

DIAGNOSTIC AIDS

This is a visual inspection to determine if an exhaust restriction is contributing to a performance problem.







1. Visually inspect exhaust system for damage. Repair as necessary. Start engine. Briefly raise

engine speed to 3500 RPM and inspect turbocharger exhaust backpressure butterfly bellcrank.

Ensure bellcrank is not closed. When bellcrank tang is against stop, valve is fully open. See

Figure.

2. Connect New Generation Star (NGS) scan tool to Data Link Connector (DLC). Turn A/C off. Using

scan tool, access EBP PID from PID/DATA monitor menu. See ADDITIONAL SYSTEM FUNCTIONS

in TESTS W/CODES - 7.3L DIESEL article.

3. Observe PID reading and briefly raise engine speed to 3500 RPM. If PID reading is 28 psi (193

kPa) or less, exhaust system is okay. If PID reading is more than 28 psi (193 kPa) exhaust is

restricted. Possible causes are:

1. Collapsed or plugged tailpipe.

2. Plugged or damaged muffler.

ENGINE PERFORMANCE DIAGNOSIS > BOOST PRESSURE TEST > DIAGNOSTIC AIDS

Perform this test to determine is engine can develop sufficient boost to obtain specific power. Possible

causes for low boost are:

Restricted intake or exhaust.

Pinched or disconnected MAP sensor hose.

Low fuel pressure.

Low injection control pressure.

Faulty injector driver module.

Faulty fuel injectors.

Faulty turbocharger.

Mechanical engine failure.

ENGINE PERFORMANCE DIAGNOSIS > BOOST PRESSURE TEST > WITH NEW

GENERATION STAR (NGS) SCAN TOOL

1. Ensure engine is at normal operating temperature. Connect NGS scan tool to Data Link Connector

(DLC). Turn A/C off. Using scan tool, access MGP PID from PID/DATA monitor menu. See

ADDITIONAL SYSTEM FUNCTIONS in TESTS W/CODES - 7.3L DIESEL article.

2. Observe PID reading and road test vehicle. Accelerate vehicle to achieve highest boost level

(2500-3000 RPM). Note PID reading. Boost level will level out after 3000 RPM. If PID reading is

15.5 psi (90 kPa) or more, boost level is okay. If boost level is not okay, see DIAGNOSTIC AIDS.

ENGINE PERFORMANCE DIAGNOSIS > BOOST PRESSURE TEST > WITHOUT NEW

GENERATION STAR (NGS) SCAN TOOL

1. Ensure engine is at normal operating temperature. Disconnect Manifold Absolute Pressure (MAP)

sensor hose at intake manifold. Install a "T" fitting between MAP sensor hose and hose nipple at

manifold. Connect a 0-30 psi (0-207 kPa) gauge to "T" fitting.

2. Ensure hose is long enough so gauge can be put inside cab of vehicle. Road test vehicle.

Observe pressure gauge and accelerate vehicle to achieve highest boost level (2500-3000 RPM).






Note pressure reading. Boost level will level out after 3000 RPM. If boost pressure is 15.5 psi (90

kPa) or more, boost level is okay. If boost level is not okay, see DIAGNOSTIC AIDS.

TURBOCHARGER > VISUAL INSPECTION

Perform visual inspection for:

Damaged intake hoses.

Loose hose clamps.

Loose exhaust clamps.

Damaged turbocharger.

Restricted intake or exhaust.

If a problem is found, repair as necessary. If concern still exists, go to SYMPTOM DIAGNOSIS .

TURBOCHARGER > SYMPTOM DIAGNOSIS > NO BOOST

Wastegate actuator not functioning. See appropriate SELF-DIAGNOSTICS article.

Compress air intake hose collapsed. Repair or replace as required.

Compressor manifold hoses leaking. Tighten hose clamps.

Turbocharger turbine or compressor wheel damage. Replace turbocharger.

Turbocharger bearings seized. Replace turbocharger.

Clogged air cleaner element or restriction upstream of compressor. Repair or replace as

required.

TURBOCHARGER > SYMPTOM DIAGNOSIS > LACK OF POWER

Low compression. Repair as required.

Wastage actuator not functioning. See appropriate SELF-DIAGNOSTICS article.

Clogged air cleaner element or restriction upstream of compressor. Replace the air cleaner

element. Remove the restriction.

Insufficient fuel supply. Repair or replace as required.

TURBOCHARGER > SYMPTOM DIAGNOSIS > EXCESSIVE FUEL CONSUMPTION (BLACK

EXHAUST SMOKE)

High fuel pressure or pressure regulator. Repair as required. For more information, see

appropriate SELF-DIAGNOSTIC article.

Fuel return line plugged or kinked. Clean or replace as required.

Injectors leaking. Replace injectors.

Powertrain control module malfunctioning. See appropriate SEFL-DIAGNOSTICS article.

TURBOCHARGER > SYMPTOM DIAGNOSIS > EXCESSIVE OIL CONSUMPTION (BLUE,

GRAY OR WHITE EXHAUST SMOKE)




Incorrect type or grade of oil. Drain and fill with specified oil.

Extended oil change intervals. Change oil as recommended.

Clogged air cleaner element or restriction upstream of compressor. Repair as required.

Engine wear (piston rings, valve guides). Repair as required.

Turbocharger oil seals leaking. See Turbocharger Internal Oil Leak Test under COMPONENT

TESTS.

Injector or injector "O" ring leaking. See appropriate SELF-DIAGNOSTICS article.

TURBOCHARGER > SYMPTOM DIAGNOSIS > NOISE OR VIBRATION

Leaks at turbocharger inlet and outlet connections. Repair as required.

Foreign object damage to turbine or compressor blades. Replace turbocharger.

Turbine bearing failure. Replace turbocharger.

TURBOCHARGER > SYMPTOM DIAGNOSIS > HIGH BOOST

Leak in exhaust system before muffler. Repair as required.

Malfunctioning wastegate. See appropriate SELF-DIAGNOSTIC article.

TURBOCHARGER > COMPONENT TESTS > TURBOCHARGER LEAK TEST

Check for loose connections or damage to air intake hoses and tubes.

Air leaks at the compressor manifold, intake manifold hoses or intake manifold covers can cause excessive

smoke, loss of engine power or a noise condition.

Exhaust leaks at the exhaust manifolds or in the turbine housing will also cause loss of engine power and a

noise condition.

Inspect turbocharger and components for loose connections or damage. Using a liquid soap on hose or

tube connections will aid in leak detection.

Exhaust leaks can usually be detected audibly or visually by a discoloration caused by escaping hot exhaust

gases.

TURBOCHARGER > COMPONENT TESTS > TURBOCHARGER INTERNAL OIL LEAK

TEST

Check the turbocharger compressor inlet for evidence of oil. If excessive oil is present, this indicates that the

failure is in the engine, not in the turbocharger; for additional information, see appropriate SELF-

DIAGNOSTICS article.

Check the turbocharger turbine outlet for evidence of oil. If oil is present in the outlet, remove the

turbocharger from the engine and examine the oil supply and return passages in the turbocharger pedestal

and engine block for restriction. If no restriction is found, replace the turbocharger.

TURBOCHARGER > COMPONENT TESTS > BEARING CLEARANCE CHECK

For bearing clearance check, see TURBOCHARGER OVERHAUL under FUEL SYSTEM in REMOVAL,

OVERHAUL & INSTALLATION - TRUCKS - DIESEL article.



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