FORD POWER STROKE DIESEL NO-START DIAGNOSIS

FORD

POWER STROKE

DIESEL NO-START

DIAGNOSIS

BY BOB PATTENGALE

Service opportunities on diesel-powered

vehicles are on the rise. If your shop is looking

for additional revenue, taking on the oil-burners

could be the ticket. But to be successful, you¡¯ll

need the right tools and training.

H

ow do you approach a familiar no-start or driveability problem? Do you

jump right in, relying on

past knowledge of common problems, or do you

follow a set diagnostic strategy to ensure

nothing is overlooked.

What about when a vehicle manufacturer makes changes to the engine man-

36

November 2011

agement system? Do you take time to

understand the system first or do you

dive right into the diagnostic process,

hoping your experience wins out? What

happens if your first couple of educated

guesses don¡¯t resolve the problem?

Effective and efficient repair of today¡¯s vehicles requires an understanding of how each system operates before the diagnostic process begins. It¡¯s

Photoillustration: Harold A. Perry; images: Thinkstock & Wieck Media

Don¡¯t Start Something

You Can¡¯t Finish

November 2011

37

FORD POWER STROKE DIESEL NO-START DIAGNOSIS

High-Pressure

Oil Rails

Oil

Filter

Oil Reservoir

for

High-Pressure

Pump

HighPressure

Oil Pump

Oil

Cooler

IPR Sensor

ICP Sensor

Drain to Crankcase

Fig. 1 This illustration shows the low-pressure and high-pressure oil systems for the 6.0L diesel engine. The fuel system

must have the correct oil pressure to operate, so oil-related problems are common causes of hard-start/no-start issues.

nice to have troubleshooter tips, but

there¡¯s no substitute for a firm grasp of

how the components relate to one another and what happens when everything is working right.

Many assume top driveability technicians quickly diagnose problems because they¡¯re able to complete all the

tasks in a fault tree the fastest or because they know all the common issues. The truth is they¡¯re able to look

at the symptoms, make a logical decision on where the diagnostic process

38

November 2011

should begin and then follow the best

path for resolution.

The opportunity to repair diesel vehicles is on the rise, and if your shop is

looking for additional revenue, diesel

repair can be it. To be successful you

need to have the right tools and technicians who understand how diesel systems work.

Ford diesel truck repair is a good opportunity. It¡¯s also an excellent example

of how things can change very quickly.

In the past 10 years, Ford has offered

four different platforms¡ª7.3L, 6.0L,

6.4L and now the 6.7L¡ªand although

the basic combustion process for each is

similar, how the fuel is supplied to the

cylinders is very different.

This article will focus on a common

driveability complaint with the Ford

6.0L diesel engine, then explain how

the 6.4L fuel delivery system differs

from the 6.0L.

Hard-start and no-start complaints

are a common issue with Ford 6.0L

diesel engines, and experienced techni-

Courtesy Ford Motor Co.

Fuel Injectors

Oil

Pump

Photo courtesy Automotive Training Group, Inc.

cians are able to determine the root

cause very quickly. But they can do this

only because they understand how the

system operates.

Technicians with limited experience

will most likely begin with the ¡°Hard

Start/No Start Diagnostic Guide¡± developed by Ford. We don¡¯t have the space

to reproduce it here, but it can be found

at . This

comprehensive guide is designed to provide a logical diagnostic flow and help

the technician avoid overlooking potential issues, which from Ford¡¯s perspective

will ensure that the vehicle is repaired efficiently and correctly the first time.

Technicians using this guide will locate the root cause, but they may not

understand why they¡¯re performing the

steps listed. One example is step 2:

¡°Check Engine Oil Level ¨C Check for

contaminants (fuel, coolant), Correct

Grade/Viscosity, Miles/Hours on oil,

correct level.¡± Engine oil quality and

level are critical for correct operation of

the fuel injectors and a common cause

of hard-start/no-start issues. Why is the

engine oil so critical?

Fig. 1 on page 38 shows a simple oil

flow schematic for the 6.0L diesel engine. In order for the fuel injectors to

operate, a minimum of 500 psi oil pressure is required for start-up. The highpressure oil pump can deliver up to

3600 psi, but only if the low-pressure oil

system delivers the oil to the high-pressure pump.

Understanding the low-pressure and

high-pressure oil systems is critical for

diagnosing hard-start/no-start problems,

so let¡¯s take a closer look at these systems in detail.

The low-pressure oil system begins

with the oil pump drawing oil from the

oil pan. Oil pressure in excess of 70 psi

between the pump and oil cooler is

vented back to the oil pan.

The oil travels from the oil pump to

the oil cooler and any pressure greater

than 25 psi is diverted around the oil

cooler to the oil filter. The benefit is providing an alternative oil flow path during

high oil flow conditions.

This is what can happen when a customer skips preventive maintenance. Oil

sludge builds up and can damage the reservoir filter screen. Once the screen is

compromised, debris can enter the high-pressure pump.

The oil travels from the oil cooler to

the oil filter, and any pressure greater

than 20 psi bypasses the oil filter and

travels to the high-pressure reservoir.

The oil filter housing contains two critical valves: One is an oil change drain

valve that opens when the oil filter is

Understanding

the low- and

high-pressure

oil systems is

critical for

diagnosing

hard-start/nostart problems.

removed, allowing the oil to drain back

into the pan; the other is an antidrainback valve that uses a one-way check

valve to keep oil in the housing with the

engine off and the filter installed. This

ensures that oil is available on initial

start-ups.

The oil travels to the high-pressure

reservoir, where approximately 1 quart of

oil is stored. The high-pressure oil pump

draws oil from the reservoir through a 3in. screen designed to catch debris. The

photo above shows what can happen

when preventive maintenance is neglected. Keep in mind that once this screen is

damaged, debris will enter the highpressure pump and be carried through

the high-pressure system.

The high-pressure oil pump is driven

by the camshaft and produces the highpressure oil needed to properly operate

the fuel injectors. The pump is capable

of producing more volume and pressure

than is needed for normal operation,

and the excess volume is controlled by

the powertrain control module (PCM).

Next in line is the injection control

pressure (ICP) sensor, which measures

the oil pressure leaving the pump and

reports this to the PCM. The PCM uses

November 2011

39

FORD POWER STROKE DIESEL NO-START DIAGNOSIS

Here are two examples of where oil pressure may be lost in the high-pressure system. Injection pressure regulator (IPR)

damage (left photo) and O-ring issues (right) are very common causes of hard-start and no-start complaints.

the information from the ICP sensor to

regulate the oil pressure using the injection pressure regulator (IPR). This is a

duty-cycle-controlled solenoid that

opens and closes to achieve the desired

oil pressure. The IPR duty cycle for a

normal hot idle engine is approximately

30%. In order to maintain the correct

oil pressure, excess oil is diverted back

to the oil pan.

During engine start-up, the PCM

needs to see at least 500 psi. If the pressure is too low, the PCM increases the

duty cycle percentage; in other words, it

closes the IPR, creating a restriction to

increase the oil pressure. If the PCM

command reaches 85%, the IPR is fully

closed, which indicates a major problem

in the oil supply chain.

The photo above left shows a damaged IPR where the debris catch screen

is almost completely gone. IPRs are

common failure items and will normally

point to additional problems. For example, if you find the high-pressure oil

reservoir screen is damaged, then the

IPR will likely have debris present, and

if the IPR screen is damaged or

40

November 2011

clogged, the high-pressure oil reservoir

screen is likely damaged as well.

After leaving the high-pressure oil

pump, the oil travels through a series of

branch tubes, standpipes, passages,

During engine

start-up, the

PCM must

see at least

500 psi. If the

pressure is too

low, the PCM

closes the IPR.

high-pressure oil rails and finally the fuel

injectors. Keep in mind that these connection points will have O-rings sealing

the system. Fig. 1 cannot properly

demonstrate all the possibilities, but if

you look at where the lines connect to

the components described, each point

would likely have an O-ring. O-rings

should never be reused under any circumstance. We¡¯ll discuss how to check

for leaks later in the article.

Steps 1 through 6 in the ¡°Ford Hard

Start/No Start Diagnostic Guide¡± deal

with visual inspection, engine oil quality,

intake/exhaust restrictions, fuel quality

and fuel pump pressure and volume.

Steps 7 through 9 cover checking for diagnostic trouble codes (DTCs) and performing KOEO tests.

Experienced technicians will check for

DTCs first. If the following DTCs are

present¡ªP1378, Fuel Injection Control

Module (FICM) voltage circuit low;

P0611, FICM Internal Failure; P0261,

P0264, P0267, P0270, P0273, P0276,

P0279 and P0282, All Fuel Injector Circuits are low; and/or U0105, Lost communication with FICM¡ªthe most likely

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