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Finding the right diagnostic strategy for a hard start 6.0 Ford

Thursday, March 1, 2018 - 09:00
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Since the inception of the “electronic diesel” engine, the diagnostic path is a little different compared to an older mechanical engine, but the same questions must still be asked — is the engine cranking fast enough, is there proper compression in the cylinders, is the proper amount of fuel being injected into the cylinder and are the glow plugs working properly for the engine to start? In this article I will lead you through the diagnostic process for a cranks/no start that I have used many times over the years.

2005 Ford F550, manual transmission 4 Wheel drive drivetrain with a manual transmission. The vehicle is powered with the 6.0L Diesel engine.

Our example

Today in the shop is a 2005 F-550, with 77,000 miles on the odometer. The truck has a six-speed manual transmission with a four-wheel drive powertrain. Yes, this is a medium-duty truck, although the engine and transmission are the same as any 2005 F-250 that drives up and down the street. When being confronted with problems like this, whether you are working on a Ford or any other diesel engine, start with the basics and go from there.

The complaint on this vehicle is a no start. The owner states it started running rough and lost power. They stated the Check Engine light came on and he had cleared the codes with his pocket code reader. Don’t you just love those dime-store tools that make the vehicle owners feel good? Well, in a case like this where the engine will crank but not start, any codes that might have been stored are not of much value to me anyway. While cranking, the engine will fire once in a while in an attempt to start and a little blue smoke comes from the exhaust, but that is about all that happens. At this point, I want to see some scan data while cranking to get a direction on this problem.

For no starts/hard start problems, I will always start my testing with a scan tool. This is so I can gather a lot of information very quickly and since we are working on an electronic diesel, the information I need can be gotten very easily. I always take a look to see if there are any stored diagnostic trouble codes. In this case, there were no DTC’s stored to aid in a direction. Since this is a Ford 6.0 HUEI (Hydraulic Unit Electronic Injector) engine, the scan tool data needed will be the three voltages from the Fuel Injection Control Module (FICM), sync, FICM sync, Injector Control Pressure (ICP) voltage, RPM, Injector Pressure Regulator (IPR) percentage and fuel injector pulse width. With this information captured during cranking, I will know if I need to go look for a problem with the FICM, high-pressure oil system or fuel supply.

Before we get too far into this project, I want to take a minute and explain why I use the PIDs I use. “FICMlpwr” is the voltage to the module and it should be above 10 volts while cranking. “FICMmpwr” is FICM voltage to the injectors. This voltage should remain above 46V during cranking. “FICMvpwr” is vehicle power through the ignition switch. This should also remain above 10 volts when cranking. The RPM PID should be above 150 RPM (I like to see above 160), but this depends on the temperature of the engine. If the temperature is down to near 0˚F, your cranking will be slower.

The ICP voltage is very important. You should see 0.2 - 0.25 volts Key On Engine Off (KOEO), and when you start cranking the voltage should climb up to around 4.5 volts if the engine doesn’t start. The injectors will not be pulsed until this voltage gets to 0.8 volts. The pressure PID is an inferred value and it can read 2500 PSI when there is no pressure at all. That’s the reason for using the voltage PID instead. The IPR will start at 15 percent KOEO, and start climbing up to 85 percent on a long crank.

Last but not least is the Sync and FICM sync PIDs. This information tells you if the FICM module is properly synced with the PCM. If they both say “YES,” be assured there is a proper signal from both the CKP and the CMP sensors. By gathering this information during cranking, you have enough information to go to your next test.

So let’s test

With the scan tool hooked up, I checked for any DTCs stored, then moved on to the KOEO injector buzz test. This will tell me if the FICM is capable of pulsing the injectors and checks the electrical circuits to the injectors. While the test is being performed, I should be able to hear a faint audible click from each injector as it is activated. In this case, about half the injectors clicked. I ran the test three times; the results were the same each time. As with all other tests, be sure and write down the results.

Figure 1 - Scan data of cranks/no start. The engine will fire, and then die. The problem is caused by compression being blown into the fuel rail. This starves the engine for fuel.

The next thing is to select the aforementioned data PIDs and give the engine a 15-second crank (Figure 1). By examining the data, I can see the ICP voltage was between 0.2 volts and 0.25 volts KOEO before the engine was cranked. Once the engine started cranking, the ICP voltage increased as it should and the engine started and died. All three FICM voltages behaved as they should and the injectors were being pulsed. With this data, I know the high-pressure oil system is working properly. I can narrow the problem down to two areas: lack of fuel supply to the fuel injectors or all eight injector pintles are stuck and the injectors need to be replaced.

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