One of the best parts about owning an older diesel truck is you get to enjoy the power and torque of a turbo diesel engine without the steep monthly payments and higher insurance premiums that come with a brand new $80,000+ pickup. For the most part, a 15-year-old diesel can be just as reliable and nearly as capable as a brand new one, but occasionally they will have some issues which need to be addressed in order to keep the truck on the road. The Ford Superduty with the 6.0 Powerstroke diesel engine was made from 2003 to 2007, and it proved to be a powerful and efficient workhorse that can usually rack up hundreds of thousands of miles, but sadly the 6.0 Powerstroke also is one of the most problematic diesel engines made over the last two decades.
There are many ways a 6.0 can leave you stranded on the side of the road or in your driveway with a no-start condition, and the cause could be extremely simple, or it could be buried deep inside the engine requiring several hours of work to simply access the part. When diagnosing a no-start condition on a six-liter Powerstroke, it can be frustrating to get on the right path because there are so many systems that all need to function properly in order for the engine to run, but if you separate the systems into three major groups (electric, fuel and oil), your job of tracking down the cause of a no-start 6.0 can be much simpler, and today, we’re going to help walk you down the right path, starting from square one.
Even though a diesel engine doesn’t have spark plugs like a gasoline engine, it still needs an electrical system to function properly. When you turn the key to start your engine, a high amperage 12-volt DC electric motor (known as the starter) is responsible for spinning the engine so the combustion process can start. If you turn the key on your 6.0 Superduty and the engine does not turn over, we need to start the diagnostic process with the electrical system.
First, notice if there are any other lights that turn on in the instrument cluster, if the door chime is making noise, or if the headlights, horn, or radio work since they are all electrical components that require voltage to operate. If you have nothing come on, we need to head to the batteries and measure voltage using a battery tester or a digital multi-meter. Normally when the engine is off, each battery should have 12-volts as measured between the positive and negative terminals. Because a diesel uses two batteries, you must check each separately with the cables disconnected to get an accurate reading of each battery. If you have anything less than 10 volts and the batteries are a few years old, more than likely they need to be replaced (and you should always swap both at the same time). If both batteries show 12-volts and they can pass a load test, but you still have no lights on inside the truck, you need to look at the main battery cables to see if they are disconnected, worn through, or otherwise damaged on both the ground and positive side, and repair as necessary. After you verify the batteries are OK and the truck is getting voltage, the next step is to quickly throw a scan tool on the truck and check for trouble codes. Often, a crankshaft or camshaft position sensor can fail, or the computer can detect trouble in any number of areas and help you narrow down your search, so connecting a scan tool is a great first move.
If you have adequate battery voltage and electrical function in the rest of the truck but the engine still won’t crank over, the starter itself could be the culprit. Crawl underneath the truck with a test light or multi-meter and see if you have battery voltage at the main lug on the starter, and if you get 12-volts on the small wire of the solenoid when the key is turned to the start position. This will tell you if you have a wiring issue between the ignition switch and the starter, or if the starter itself is faulty. Starters are known to fail from time to time, and while it’s not a permanent fix, you can gently tap on the starter with a hammer which can sometimes coax it to start your engine a couple more times to get you back on the road or into your shop to make the repair.
If your engine cranks over but will not fire up, there are still a few more culprits in the electrical category we can inspect. The Fuel Injector Control Module (or FICM) is an electrical component that mounts on the driver’s side valve cover, and its responsible for amplifying the low current signal from the Engine Control Module (ECM) into a high current electrical pulse that can fire the solenoid on the fuel injectors. The FICM is known to be a failure item on a 6.0 which can cause a crank no-start condition, and if you remove the access cover on top, there will be four or seven screws underneath you can use to test for proper voltage. On the four-pin version you need to test the pin closest to the brake master cylinder, and on the seven-pin version you need the pin closest to the passenger side. In either version, you need to measure voltage between battery negative post and the correct pin with the ignition in the run position, and you should have about 48.5 volts. If it’s less than 45 or even zero (and your batteries test OK) the FICM has failed and needs to be replaced.
Every engine needs fuel to run, and while the 6.0 Powerstroke uses a somewhat complicated method to pressurize the fuel and force it into the combustion chamber, the low-pressure system that delivers the fuel to the engine is very straightforward. If your electrical system checks out, the next stop on the diagnostic train is the fuel system.
The first thing we need to verify is that there is fuel in the tank, and if its empty, simply fill it up and go, but I’m going to assume an empty fuel tank is already checked off the list. The next thing that we need to look for is fuel pressure at the engine. The 6.0 Powerstroke uses a frame mounted electric lift pump and filter assembly (known as the Horizontal Fuel Conditioning Module, or HFCM) to suck fuel from the tank and push it toward the engine. In the front of the valley of the engine is a fuel bowl which contains a pressure regulator, another fuel filter, and some lines that send fuel into the cylinder heads, and excess fuel back to the tank. In order to run properly, the 6.0 Powerstroke needs about 50 psi of fuel pressure being fed into the injectors, and the first step is to measure how much pressure is actually there. Alliant Power makes a fuel pressure test kit that works on the six-liter as well as its older brother the 7.3, and once its hooked up to the fuel bowl, turn the key and crank the engine for a few seconds. If you have between 40 and 50 pounds of pressure, the fuel supply system is working as intended, and the problem lies elsewhere, but if you have lower pressure, we need to find the reason. My next move would be to check the fuel filters for restriction. On a diesel truck, the fuel filter should be changed every 10 to 15 thousand miles, and because there are two on a Powerstroke, occasionally the lower one on the frame is forgotten. If a fuel filter is clogged, it can restrict flow and cause a no-start condition, so if it’s been a while, swap ‘em out for a fresh set and re-check fuel pressure.
If you have fresh filters but still no fuel pressure, the next culprit I’d look at is the HFCM. If you change your fuel filters regularly, you’re already familiar with the HFCM since it’s also what the fuel filter mounts in. There will be a small electrical connection on one side with two wires, and you’ll want to remove the plug and verify there are 12-volts while the key is turned to the run position. If you have voltage at the plug while cranking but the pump does not come on, then your HFCM has failed and needs to be replaced which should restore fuel pressure at the engine.
Finally, if you do have voltage at the HFCM and you can hear the pump spinning but still have no fuel pressure, you could have a broken fuel line somewhere along the frame rail, or even a cracked suction tube inside the fuel tank. One last note worth mentioning is if you have recently changed both fuel filters, sometimes the fuel system can become “air-locked” which is where the fuel lines drain completely out and fill with air. Typically, once the fuel filters are reinstalled and you cycle the key to the run position a handful of times, the HFCM will push enough fuel toward the engine to flush out any remaining air in the system through the return lines, but sometimes a dozen or more key cycles are required.
The majority of no-start conditions on a 6.0 Powerstroke will be caused by the high-pressure oil system which is responsible for creating the force required to inject fuel into the combustion chamber. The 6.0 uses a Hydraulic Electronic Unit Injector (HEUI) system, and inside the engine are two oil pumps: the first low pressure pump provides lubrication to critical engine parts like the crankshaft, connecting rods, camshaft and valvetrain at pressures of around 60-100 PSI. The second is called the High-Pressure Oil Pump (HPOP) and its only job is to pressurize engine oil to a maximum of 4,000 PSI and feed it into the top half of the fuel injectors. When an electrical signal is received from the FICM, a solenoid fires on the fuel injector which opens a valve and lets the high-pressure oil push down on a plunger which in turn forces fuel into the combustion chamber. While the theory is simple, there are a lot of parts that must work properly for a HEUI system to do its job and allow your Powerstroke to fire up.
The very first step you should take when diagnosing the high-pressure oil system is a simple one, but very critical: check the engine oil level. If the oil level runs too low on a 6.0 Powerstroke, the engine will not be able to run since the HPOP has no oil to pressurize and feed into the injectors. Once the oil level is verified, the next step is to hook up a scan tool and monitor Injection Control Pressure, or ICP. For a six-liter to fire up and idle, it needs to see at least 500 PSI of oil pressure, but usually it will be in the neighborhood of 800-1,000 PSI while cranking. If you have less than 500 PSI of ICP the first test is to see if it’s simply a bad sensor providing a false reading. If you simply disconnect the wiring harness to the sensor which is located on the passenger side valve cover and can now start the engine, that indicates a failed ICP sensor since the ECM defaults to 750 PSI when the sensor is disconnected.
If you still cannot start the engine, there are a few remaining things in the oil system that could be at fault, and the IPR valve is next up. It is attached to the HPOP which sits underneath the turbocharger, and its responsible for regulating the flow of oil into the high-pressure pump which in turn dictates output pressure much like the FCA on a CP3 pump. To test an IPR valve, you can remove it from the truck and attach an air hose to the bottom and listen to a change in flow as you apply 12 volts to the electrical connections. A working IPR valve will stop the flow of air when voltage is applied, and a failed one will have no change in airflow.
If the IPR valve checks out but you still have no injection control pressure, we need to check for leaks in the high-pressure oil system. They can come from several places like the standpipes and dummy plugs, branch tube connections, a failed STC fitting, or even the seal that connects the oil rail to the injectors. It can be very difficult (if not impossible) to visually see an oil leak, but air checking tools are available that will let you apply shop air into the oil rail at the ICP sensor port. This will pressurize the entire high-pressure oil system at the same time, and any leaks will show up as air escapes. You can unscrew the oil filler cap and listen for air leaks to narrow down the general area they are coming from, and once you determine which side of the engine to look at, you can remove the valve covers to further narrow it down and pinpoint the leak.
If you’ve gone through the work to eliminate all possible causes of leaks or failures in the high-pressure oil system, there are two possible remaining causes to your 6.0 no-start condition. The first is a bit difficult to test for, but a clogged IPR feed screen can restrict or block oil flow to the HPOP. Unfortunately, its mounted underneath the engine oil cooler which does take a bit of work to access. Finally, if the IPR screen isn’t the culprit, the one possibility remaining would be a failed high pressure oil pump.
Fix It Right the First Time
There is nothing worse than taking a “shotgun” approach to automotive repair because unless you’re extremely lucky, chances are you won’t get it right the first time with a guess, which means wasted time and money as well as added frustration that all could be avoided if you simply took the time to think though the diagnostic process, test a few parts along the way, and only replace what is necessary. I do however advocate a “while you’re in there” approach to vehicle maintenance, so if for example you have an oil rail removed to replace an injector O-ring, you might as well throw in an updated standpipe and dummy pug set since they can be prone to leaking and it could save you some headache in the future, as well as giving you added peace of mind.