Project Box Hauler: Dynomite Injector Install

July 22nd, 2010

By: Kevin Wilson

Photos: Kevin Wilson

The Injection Connection
Project Box Hauler Gets New Dynomite Diesel Performance Injectors

For those of you who have been following our Project Box Hauler series, you’ll remember our high-miler, ’01 Ford F-350 dually with 200,000-plus miles on it, was diagnosed with a couple of dead cylinders, more specifically No. 3 and No. 8. Upon his initial diagnosis, Nate Brekken at Strictly Diesel in Scottsdale, Ariz., guessed the problem would more than likely be bad injectors on those cylinders since injectors get fairly tired and worn out on the 7.3s after about 150,000 miles. On the other hand, two dead holes could mean more serious issues, such as bad valves or poor compression from worn-out piston rings, or even a cracked cylinder head.

When Injectors Go BadThere are two areas on the 7.3L injector that can have trouble: The fuel side and the high-pressure oil side. Regular fuel and oil system maintenance is key to keeping these babies alive. “
So what kills injectors? Plenty. You can have failures due to fuel contamination, usually from water in the fuel, O-ring failures or even from air in the fuel system. But according to Nate at Strictly Diesel, poor maintenance is the No. 1 killer of 7.3L injectors and injectors, in general.

Contaminated or dirty oil, which is pumped through the high-pressure oil pump into the injector, does damage, so Nate recommends doing regular oil changes using a quality 15W-40 motor oil. Also, he’s seen poor oil pressure from “cheapie” oil filters that drop oil pressure to the point where drivability issues crop. Why? Since the 7.3 injectors are operated via oil pressure, a lack of oil pressure directly affects fuel delivery and leads to drivability issues. As a result, Strictly Diesel uses only factory oil filters on the trucks they service. Also, it never hurts to consider an injector service as the mileage accumulates.


Last month, we changed out the glow plugs on the Power Stroke. While we had the valve covers off, a compression test was done to truly diagnose the dead cylinder situation. The glow plug holes are used to access each cylinder for the compression test. According to Strictly Diesel, compression on a diesel should be 400 psi or above. On this truck, we had three cylinders at 425; three at 395; one at 400; and another one at 420—not bad for a 200,000-mile motor. So the initial diagnosis that was some bad injectors in the mix was correct.

Unlike today’s common rail setups, the 7.3L Power Stroke utilizes a unique injection system referred to as a HEUI setup. The HEUI system essentially utilizes engine oil to hydraulically actuate the truck’s fuel injectors. Timing is controlled electronically, as is the firing sequence and duration. The oil that actuates the injectors comes from a high-pressure oil pump, which is driven off the engine’s camshaft gear. The injectors are huge, having both pressurized fuel section and a high-pressure oil section. To top it off, they are located under the valve covers, in a high-heat environment. No wonder they have a tendency to get tired after 150,000 miles.

For Project Box Hauler, we had several options: Replace them with stock injectors from Ford for big money, or turn to the aftermarket for a simple upgrade. We chose the latter. Dynomite Diesel Performance in Monroe, Wash., is probably best known for its injector work and selection. We called them about our project, and told them we were looking for more power, but were kind of hamstrung by the fact that Arizona has diesel emissions testing that includes an opacity test, where they measure exhaust smoke.

The crew at DDP recommended a variation of their Stage I injector for the Power Stroke. Normally, a Stage I injector is rated at 75 hp, but for us, they “detuned” them slightly to be rated at 50 hp, which will keep the smoke situation near stock while still providing some added power and fuel economy. Our custom injectors started as a full set of new Alliant Power injectors, which are the best in the business. Dynomite then fine-tuned the delivery tips and nozzles with a unique process that’s almost like extruding, which ensures accurate fuel flow and delivery. The end results are perfect nozzle delivery holes. Like all DDP injectors, each injector was then flow-benched before being shipped out.

The 8th Injector
On ’99-’03 Ford 7.3L Power Strokes, the firing order fires cylinders No. 6 and No. 8 back to back. Both are located on the driver-side cylinder head. Since the high-pressure oil system and fuel side have a tough time keeping up with the immediate pressure drop from side-by-side cylinder openings, Ford installed what is called an AE or Long Lead injector to help level out the fuel delivery and injection timing. They are usually stamped “LL” on the top of the body.

When pulling your old injectors, double-check to make sure you get and replace the LL injector in the No. 8 hole with another LL injector, as opposed to the regular ones you just installed in the other seven cylinders. Dynomite sells these AE injectors so you can do the job correctly.


Installation is fairly straightforward, especially once you get the valve covers off the truck. Another oddity of the 7.3 is that the injectors and glow plug wiring harness is part of the valve cover gasket. R&R is pretty straightforward once you pull the high-pressure oil galley plugs to drain the oil so it doesn’t run in the cylinders when you pull the injectors. Also, Strictly Diesel cleans and inspects each injectors “pocket” before installing the new ones. The following photos highlight a typical 7.3 injector swap.

Once we got the truck buttoned up, and all the excess oil burned out of the cylinders, which takes about 10 miles of hard driving, the end result of the new DDP injectors was remarkable. The engine was much quieter and had noticeably more power, even on the stock tune. Exhaust smoke was minimal at wide-open throttle. Once we get some gauges on the truck, we’ll let you know about EGTs and get some mileage numbers, as well.

If your Ford’s odometer has more than 150,000 miles on it, and your 7.3 is not running as smoothly as it used to, the simple solution is to add a set of Dynomite Diesel Performance injectors. They offer a wide selection of choices, so doing an injectors upgrade is a simple R&R deal.

Dynomite Diesel Performance (DDP)
(360) 794-7974

Strictly Diesel
(480) 922-8768

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