Regardless of how well we take care of our trucks, one thing is for sure – they are going to have parts fail. Parts don’t last forever and they will eventually let us down. With that being said, the beloved 6.0-liter Power Stroke, and its predecessor, the 7.3-liter, are getting on in years, which inevitably leads to issues. To learn more about what issues arise, we reached out to the Power Stroke experts at Strictly Diesel to gather their thoughts.

Dennis Schroeder, co-owner of Strictly Diesel, has actually been working on a Strictly Diesel Blog for enthusiasts to go for troubleshooting and diagnostic help. Specifically for trucks with modified fuel systems. With this information so easily available, we had to share their latest post for all of you Ford enthusiasts out there. So what did Schroeder have to say?

Strictly Diesel – The Experts

In a blog post, Schroder says: “After nearly 20 years of building and selling custom fuel systems for 7.3-liter and 6.0-liter Power Stroke diesel engines, it’s pretty safe to say that I’ve done my fair share of troubleshooting. Probably the most common statement from truck owners that are experiencing some kind of issue with their fuel system is, ‘I think the regulator is bad,’ or ‘I need to buy a new regulator.’ When I ask what kind of problem they are having, it’s always some version of ‘the pressure is too low.’ I’ve lost track of how many fuel pressure regulators I’ve sold from both Aeromotive and Fuelab over the years, but I can count on one hand the number of times that we had an actual regulator functionality problem, and I will still have fingers left over.”

The blog continues to explain how fuel pressure regulators are actually a very simple device. Schroeder regularly tells their customers that think they have a regulator issue to simply take it apart and look. There aren’t many parts inside these regulators and, per Schroeder, if you pay attention during disassembly, putting them back together isn’t challenging at all.

What I hope this accomplishes is for you guys diagnosing a low-pressure fuel issue, maybe you can attack these issues yourself and have that sense of DIY, you know? Strictly Diesel even offered a few photos of some fuel pressure regulators disassembled so you can see the orientation of how they do it and how simple it really is to reassemble.

“The second most common comment I gave to customers over the years has been, ‘If you don’t have fuel leaking from the brass nipple, the regulator is working,'” ” Schroder says. “The single most common issue with one of these bypass fuel pressure regulators is diaphragm failure, and even that isn’t very common. This always comes in the form of a hole or tear in the flexible portion, and always includes a steady stream of fuel leaking from the brass nipple (boost reference port) in the top half of the regulator. This is why our fuel systems include a length of poly tubing. If the diaphragm fails, we don’t want fuel spraying all over the engine. If you have fuel leaking from the boost reference port, you just need a diaphragm. If not, you’ve got another issue.”

Although you may hear a culprit often from other enthusiasts, that doesn’t always make it your culprit. As mentioned before, Strictly Diesel has been toying with these engines for going on for over two decades. I would say it is safe to trust the word and experience these guys are offering.

How Does A Regulator Work?

To better understand why the regulator would or wouldn’t be operating properly, we need to have a better understanding of how it functions. Not only will this give us a better understanding, but this may also make it easier for disassembly/assembly. As you can see in the picture above, the base of the regulator has three ports.

The side ports are plumbed to become part of the fuel rail in these Power Stroke trucks. The fuel that passes through the rails in the cylinder heads is then directed into each side of the side ports in the regulator. In the center of the base of the regulator, you’ll see the seat that leads to the return port on the bottom.

Schroeder then explained the operation of the internal side of these regulators. “The diaphragm has a ball that sits in and seals against that seat,” he began. “When the pressure coming from the side ports reaches the set point of the adjustable regulator, it lifts the ball off the seat and fuel exits the bottom port of the regulator and returns to the tank. The varying level of flow that is directed back to the tank is what controls the fuel pressure. If the flow coming into the regulator drops (because the injectors are spraying more fuel under heavy throttle, for example), the diaphragm will close against the base of the regulator to maintain the correct pressure.”

“If the flow increases (because you lifted off the throttle), the diaphragm will open and let more fuel return to the tank to continue to maintain the correct pressure,” he continued. “This happens very quickly and smoothly, such that even with a gauge in the cab, you rarely see the needle move as the situation changes. The spring and adjuster screw on the top of the regulator is used to set the pressure required to lift the diaphragm off of the seat. As long as all of the parts are still in the regulator, in the correct order and orientation, and you don’t have fuel leaking from the boost reference port, the regulator will be operating as designed.”

Schroeder pointed out a common internet theory, one that suggests a problem with these regulators could be a broken interior spring. He says in all of his years of diagnosing these issues, not a single time has it actually been the spring in the bypass fuel pressure regulator. “Anything is possible, but this is extremely unlikely, and easily verifiable by simply taking the regulator apart,” he said.

So, Why Is The Pressure Low?

According to the Strictly Diesel Blog, the key to diagnosing a low fuel pressure situation is understanding that in order to have pressure, you must have adequate flow at the regulator.

“If your fuel flow is reduced for some reason, it can lead to the pressure being lower than desired,” Schroder said. “There are a number of things that can lead to a decrease in flow. The pump may be old and getting weak. You could have a voltage issue slowing the pump down. There could be a blockage in the suction line from the pump back to the tank, or, if your pressure problem is only under heavy throttle, your pump may just not be large enough for the injectors and tuning you have in the truck.”

Hopefully, the information and images offered by Strictly Diesel will help you better understand these regulators and give you the confidence to open one up and check it out if you think you are having a problem. Generally speaking, these regulators need no maintenance. If the diaphragm fails, replace it and keep on going. If one of the fittings leaks, just replace the o-ring. Should you have a reason to take it apart, just clean it and make sure there is no debris inside before you put it back together.

Zero PSI, But The Pump Is Running

Like most fuel plumbing, if you’re not getting pressure and you should be, there is a reason. If you’re showing zero psi at the fuel pressure gauge and the pump is running, there should be pressure. If you’re making the adjustments to the adjuster screw, so much adjustment that it is maxed out and you still aren’t seeing a pressure jump, chances are you’ve got a wrong hose connection.

“If you have turned the regulator adjuster screw clockwise until it stops, but the pressure never changes, there is a high probability that hoses at the regulator are incorrectly connected, ” said Schroeder. “Before going through a bunch of other diagnostic procedures, make sure that the regulator hoses are connected where they should be. The side ports on the regulator should be connected to the hoses coming from the cylinder heads, and the bottom port should be connected to the hose that goes back to the fuel tank.”

When it comes to this zero PSI issue, Schroeder explained that there are usually two situations that cause this. First, the installer has swapped the fuel supply and fuel return hoses (typically on a fuel bowl delete setup). If you connect the fuel supply from the pump to the bottom of the fuel pressure regulator and connect the fuel return line to the bowl delete distribution block, you will have zero pressure. The flow is going in the wrong direction.

“Secondly, another common issue is the installer will swap a cylinder head return line and the regulator return line,” offered Schroeder. “If you connect the cylinder heads, return them to the bottom of the regulator and the regulator return to one of the side ports of the regulator, you will have zero pressure too. (because the return to the tank is connected to the fuel supply without a diaphragm between them)

Strictly Diesel Can Help Even More

If you managed to reach this point and all of these easy go-to items check out, you can proceed to diagnose this issue further. Per the experts, chances are you’ll catch these issues dead in their tracks with these tips and tricks. Remember, don’t always blame the regulator. If you’re interested in Strictly Diesel’s upgraded parts for your truck, be sure and check out their website.

For more tips and tricks that can keep your truck alive, be sure and check out the Strictly Diesel blog about common Power Stroke issues. For more part reviews, tech stories, event coverage, and truck features stay tuned right here to Diesel Army.