FORD POWER STROKE DIESEL NO-START DIAGNOSIS

1 How do you approach a fa-miliar NO-START or drive- ability problem? Do youjump right in, relying onpast knowledge of com-mon problems, or do youfollow a set diagnostic strategy to ensurenothing is about when a vehicle manufac-turer makes changes to the engine man-agement system? Do you take time tounderstand the system first or do youdive right into the diagnostic process,hoping your experience wins out? Whathappens if your first couple of educatedguesses don t resolve the problem?Effective and efficient repair of to-day s vehicles requires an understand-ing of how each system operates be-fore the diagnostic process begins.

2 It sFORD POWER STROKE DIESEL NO-START DIAGNOSISDon t Start Something You Can t FinishBYBOBPATTENGALES ervice opportunities on DIESEL -poweredvehicles are on the rise. If your shop is lookingfor additional revenue, taking on the oil-burnerscould be the ticket. But to be successful, you llneed the right tools and 2011 Photoillustration: Harold A. Perry; images: Thinkstock & Wieck Media37 November 2011nice to have troubleshooter tips, butthere s no substitute for a firm grasp ofhow the components relate to one an-other and what happens when every-thing is working assume top driveability tech-nicians quickly diagnose problems be-cause they re able to complete all thetasks in a fault tree the fastest or be-cause they know all the common is-sues.

3 The truth is they re able to lookat the symptoms, make a logical deci-sion on where the diagnostic processshould begin and then follow the bestpath for opportunity to repair DIESEL vehi-cles is on the rise, and if your shop islooking for additional revenue, dieselrepair can be it. To be successful youneed to have the right tools and techni-cians who understand how DIESEL sys-tems DIESEL truck repair is a good op-portunity. It s also an excellent exampleof how things can change very the past 10 years, Ford has offeredfour different platforms , , and now the and althoughthe basic combustion process for each issimilar, how the fuel is supplied to thecylinders is very article will focus on a commondriveability complaint with the DIESEL engine, then explain howthe fuel delivery system differsfrom the and NO-START complaintsare a common issue with Ford engines.

4 And experienced techni-FORD POWER STROKE DIESEL NO-START DIAGNOSISFig. 1 This illustration shows the low-pressure and high-pressure oil systems for the DIESEL engine. The fuel systemmust have the correct oil pressure to operate, so oil-related problems are common causes of hard-start/ NO-START 2011 Courtesy Ford Motor Reservoirfor High-PressurePumpHigh-PressureOil PumpICP SensorIPR SensorDrain to CrankcaseHigh-PressureOil RailsFuel Injectorscians are able to determine the rootcause very quickly. But they can do thisonly because they understand how thesystem with limited experiencewill most likely begin with the HardStart/No Start Diagnostic Guide devel-oped by Ford.

5 We don t have the spaceto reproduce it here, but it can be foundat Thiscomprehensive guide is designed to pro-vide a logical diagnostic flow and helpthe technician avoid overlooking poten-tial issues, which from Ford s perspectivewill ensure that the vehicle is repaired ef-ficiently and correctly the first using this guide will lo-cate the root cause, but they may notunderstand why they re performing thesteps listed. One example is step 2: Check Engine Oil Level Check forcontaminants (fuel, coolant), CorrectGrade/Viscosity, Miles/Hours on oil,correct level.

6 Engine oil quality andlevel are critical for correct operation ofthe fuel injectors and a common causeof hard-start/ NO-START issues. Why is theengine oil so critical?Fig. 1 on page 38 shows a simple oilflow schematic for the DIESEL en-gine. In order for the fuel injectors tooperate, a minimum of 500 psi oil pres-sure is required for start-up. The high-pressure oil pump can deliver up to3600 psi, but only if the low-pressure oilsystem delivers the oil to the high-pres-sure the low-pressure andhigh-pressure oil systems is critical fordiagnosing hard-start/ NO-START problems,so let s take a closer look at these sys-tems in low-pressure oil system beginswith the oil pump drawing oil from theoil pan.

7 Oil pressure in excess of 70 psibetween the pump and oil cooler isvented back to the oil oil travels from the oil pump tothe oil cooler and any pressure greaterthan 25 psi is diverted around the oilcooler to the oil filter. The benefit is pro-viding an alternative oil flow path duringhigh oil flow oil travels from the oil cooler tothe oil filter, and any pressure greaterthan 20 psi bypasses the oil filter andtravels to the high-pressure oil filter housing contains two criti-cal valves: One is an oil change drainvalve that opens when the oil filter isremoved, allowing the oil to drain backinto the pan.

8 The other is an antidrain-back valve that uses a one-way checkvalve to keep oil in the housing with theengine off and the filter installed. Thisensures that oil is available on oil travels to the high-pressurereservoir, where approximately 1 quart ofoil is stored. The high-pressure oil pumpdraws oil from the reservoir through a 3-in. screen designed to catch debris. Thephoto above shows what can happenwhen preventive maintenance is neglect-ed. Keep in mind that once this screen isdamaged, debris will enter the high-pressure pump and be carried throughthe high-pressure high-pressure oil pump is drivenby the camshaft and produces the high-pressure oil needed to properly operatethe fuel injectors.

9 The pump is capableof producing more volume and pressurethan is needed for normal operation,and the excess volume is controlled bythe powertrain control module (PCM).Next in line is the injection controlpressure (ICP) sensor, which measuresthe oil pressure leaving the pump andreports this to the PCM. The PCM usesThis is what can happen when a customer skips preventive maintenance. Oilsludge builds up and can damage the reservoir filter screen. Once the screen iscompromised, debris can enter the high-pressure 2011 Photo courtesy Automotive Training Group, low- andhigh-pressureoil systems iscritical fordiagnosinghard-start/ NO-START information from the ICP sensor toregulate the oil pressure using the injec-tion pressure regulator (IPR).

10 This is aduty-cycle-controlled solenoid thatopens and closes to achieve the desiredoil pressure. The IPR duty cycle for anormal hot idle engine is approximately30%. In order to maintain the correctoil pressure, excess oil is diverted backto the oil engine start-up, the PCMneeds to see at least 500 psi. If the pres-sure is too low, the PCM increases theduty cycle percentage; in other words, itcloses the IPR, creating a restriction toincrease the oil pressure. If the PCMcommand reaches 85%, the IPR is fullyclosed, which indicates a major problemin the oil supply photo above left shows a dam-aged IPR where the debris catch screenis almost completely gone.