In the world of EFI gassers, making sure your injectors can provide enough fuel to handle horsepower upgrades often requires a fuel pump upgrade, since it’s the force that pushes fuel through each orifice. In the case of our 7.3L Power Stroke project truck, Old Soldier, however, the fuel pump is plenty powerful for our plans—it’s the other pump that actually powers the injectors that needs attention.
| big Oil Dieselsite Hpop adrenaline
Before we go any further, perhaps a little primer regarding exactly how 7.3L Power Strokes get fueled is in order. A standard multi-port fuel injection system, like those found on most gasser engines, relies solely on the fuel pump to ensure pressurized fuel is delivered to the injectors when the computer demands it. Diesel engines, however, run much higher compression to create combustion without an ignition system—so much higher injection pressure is required. Older diesels use a mechanical injection pump that directly actuates the injectors, but 7.3L Power Strokes do it a little differently, by utilizing a hydraulic electronic unit injection (HEUI) powered by a high-pressure oil pump (HPOP) that is geardriven off the camshaft. The fuel pump gets diesel out of the tank and into the fuel rails and injectors at around 60 to 65 psi—but that’s nowhere near what it takes. When the powertrain control module (PCM) signals for an injector to fire, the injector driver module (IDM) signals for a poppet valve inside the injector, which allows the HPOP to deliver engine oil at around 2,500 to 2,900 psi against an intensifying piston. This in turn exponentially pressurizes the diesel inside the injector to around 18,000 psi, which lifts the injector pintle from its seat and allows diesel to flow through the nozzle into the cylinder. Got all that?
The big point to take away is that most stock 7.3L HPOPs can’t maintain acceptable pressure for extended periods—even in stock form. Throw big injectors into the equation and ICP pressures can drop through the floor, resulting in poor performance, lots of smoke (the bad kind), and often a trouble code or two. But wait, you might remember that Old Solider is still running its original injectors, and we’ve got no plans to upgrade them. Big oil with stock sticks? You bet, and here’s why.
The popular opinion circulating around is that upgraded HPOPs are exclusive to the realm of trucks with larger injectors and aggressive tuning, and while it’s absolutely true that highly modified trucks will see large benefits, there’s much more to the story. Better pressures = better spray pattern = more efficient burn = more power, better fuel economy, and lower EGT. This is true no matter which level your truck is tuned to.
There are several choices on the market for wildly modified trucks requiring massive amounts of oil, but the vast majority of trucks with bolt-on parts and tuners will be more than satiated with our choice: DieselSite’s Adrenaline HPOP. Rather than big oil, think of this pump more accurately as better oil. As in, it’s designed to supply the volume and pressure that stock HPOPs should have all along while not shying away from injectors all the way up to 250cc hybrids.
Our pump wasn’t the strongest on the block, but it was certainly not to the point of causing driveability issues or increased visible smoke. To see exactly what the benefit of the Adrenaline was, we did a quick driveway swap. Tuning can mask the true benefits of any bolt-on part, so to avoid any diluting of the benefits, we’re sticking with our stone-stock tune for now for a seat-of-our-pants assessment of what the pump has to offer.
Review
We can honestly say we’ve never installed any part that resulted in a more immediately noticeable change in a truck. From the moment it cranked, we could tell a difference just by the sound of the idle—it sounded smoother and somehow more powerful. That was confirmed the moment we shifted into Drive, as we could feel the engine pulling against the brakes, even though we were at idle.
