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.
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.
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.
Before I start taking the engine apart, I want one more data capture with the scan tool. In Figure 2, I have reduced the PIDs to only ICP pressure, ICP desired pressure, ICP voltage, IPR percentage and RPM. This data verifies the high pressure oil system is working properly. The next step is to test for proper fuel supply.
Fuel supply testing
Since I am now looking for a fuel supply issue, I want to start testing the fuel supply. A quick way to verify fuel supply is to remove the top from the secondary fuel filter, (figure 3) then use the scan tool to turn the fuel pump on and see if fuel is being pumped into the fuel filter housing. This can also be done by just cycling the key, but it is easy to run the fuel filter over and cover the engine with fuel. In this case, there was a good volume of fuel to the filter.
You might ask why I didn’t use a fuel pressure gauge to test the pressure. Well, all a pressure gauge will tell me is the static pressure, and to get this engine started, all that is needed is fuel supply. Once the engine is running, then the volume and pressure can be tested easily on a test drive. All I want now is to get this engine started. In this case, the filter housing filled with fuel in about three seconds, I know the problem is not the fuel pump, or a plugged fuel filter. By the way, the owner has already replaced the fuel filters. With a fuel supply to the filter, the next question I ask is whether or not the fuel is passing through the filter. All that is needed for this test is to crack one of the steel line fittings on the bottom front of the filter and turn the pump on. If fuel squirts out, you have fuel supply to the cylinder heads. Now the problem has been narrowed down to the fuel injectors.
There are a few other tests I could do, such as a balloon test. To perform this test, a balloon is hooked to the fuel supply lines that go to the cylinder heads and the engine is cranked. This test is looking for compression being blown back into the fuel rail in the cylinder head. This compression could come through a defective fuel injector or from an injector that is not properly tightened into the cylinder head. In this case, I opted to pull an injector out and see if I could find anything there. Since only half of the injectors clicked properly, these injectors were faulty and needed to be replaced anyway.
I decided to pull an injector from the right cylinder bank, since this is the easiest one to get the valve cover off of. When the first injector came out, I saw someone had installed the injectors by lubricating them with grease (Figure 4). When installing injectors, they need some lubricant on the O-ring seals, which should be motor oil. The grease that was used on these injectors can get into the fuel system and plug up the injectors. As I continued to remove injectors, I found the #7 injector hold-down bolt only finger tight. When the injector was removed, I could see why the engine would not run. The injector was not sealing in the cylinder head and was letting compression blow back into the fuel rail. This blows the fuel out of the fuel rail and in effect, starves the engine for fuel. This engine has all the hallmarks of being worked on by someone that was not very conscientious about their work.
Any time you have a high-pressure oil rail off, give the high-pressure nipples a sideways push with your finger. If you can move them easily, the O-rings that seal them need to be replaced. Figure 5 shows the tool used to remove the nipple balls. If these are leaking and are put back in the engine, it won’t be long before the vehicle will be back or taken to another shop with a hard start problem when the engine is hot. There are a lot of places for high-pressure oil leaks in this engine.
As long as I am talking about oil leaks, there are two standpipes and two dummy plugs on this engine (Figure 6). Make sure you look these over very carefully and make sure the seals are in good shape. Any time these are disturbed, it is a good idea to replace them to prevent leaks. Doing the job right the first time will save your customer money in the long run. Before you put the oil rail back on the engine (Figure 7), take a look at the seals in the top of the fuel injectors. If the seals on the ball/nipples have been leaking, there is a good chance the leaking oil has eroded these top injector seals, too. These seals can be replaced without replacing the injectors.
With the high-pressure oil rails installed on the engine, it is always a good idea to hook air pressure to the ICP sensor port and pressure test the system. All you need is a fitting to screw into the place the ICP sensor goes (Figure 8), turn the key on — which pulses the IPR at 15 percent — and hook up air pressure. If you have a tight system, you will only hear a small amount of air leaking through the IPR, which means the system is tight and no leaks. It is a good thing to always air test before you install the valve covers. This might save you a lot of time and a comeback. Any time you work on the 6.0 engine, or any diesel engine for that matter, be very particular and do the job right the first time. These engines are getting some age on them and are still a very profitable engine to work on.
