From '94-1/2 to '96, all 7.3L Power Stroke engines came equipped with single-shot HEUI injectors. When fired, the single-shot injectors would deliver all of their fuel in a single shot--hence the name. The '97 7.3L Power Stoke trucks sold in California received a new injector design that used a split-shot system for lowering emissions. The split-shot injectors work by dividing the fuel delivery into two parts in order to make the engines run cleaner. By the time the '99 Super Dutys came out, all 7.3L engines were built with split-shot injectors.
While it can be argued that the split-shot injectors are better for near-stock applications, they are usually ditched in favor of performance-enhancing single-shot units when an owner seeks more power. In the aftermarket segment for the 7.3L Power Stroke, running single-shot injectors has always been a common way to go when more power is desired.
Split-Shot vs. Single-Shot:
For emissions purposes, 7.3Ls built for sale in California after April of 1996 came standard with split-shot injectors (AB codes as opposed to AA), which flowed approximately 130 cc of fuel (on a 1,000-count test). By converting to AC-code single-shot injectors, considerable gains in power can be had, as they flow 160 cc of fuel. And because only one injection event occurs (as opposed to a split-shot event), they also require less high-pressure oil to fire.
It should be noted that all of the following modifications can also be performed on all '94 to '97 Power Stroke engines. With a few quick phone calls, a set of single-shot injectors was on the way, as well as a new 17-degree high-pressure oil pump and some fuel system upgrades. While under the hood at John Wood Automotive in Holtville, California, we also took the time to perform a little preventative maintenance on the old Power Stroke.
Tuning For Single-Shot Injectors
One of the most important things to keep in mind when going from split-shot injectors to single-shot units is tuning. To be specific, it's in the timing. Split-shot engines typically use 1 degree of timing advance at idle, while single-shot engines require 11 degrees. After our install was complete, we pulled the F5 chip attached to the powertrain control module (PCM) and had John Wood Automotive reburn it with DP Tuner's programming, which allowed the new, single-shot injectors to work problem-free both at idle, and on the throttle.
 Included in our install was...  Included in our install was a set of new AC-code Alliant injectors, a new Bosch Rexroth high-pressure oil pump (HPOP) and reservoir, four new fuel injector wiring harnesses, new under valve cover harnesses (UVCH), oil rail plugs, a regulated fuel return system, and a fuel bowl delete from ITP Diesel that was retrofitted to the older Power Stroke engine. |  Since we planned to install...  Since we planned to install a fuel bowl delete and a regulated fuel return system from ITP Diesel, we disconnected all the fuel lines from the fuel filter reservoir and removed it. |  The turbo had to be pulled...  The turbo had to be pulled in order to gain access to the fuel lines at the rear of the cylinder heads. We removed the air intake, intercooler tubes, unplugged the under valve cover harness plugs, and glow plug relay solenoid. After this, we removed the turbo up-pipes to measure our new fuel lines and gain access to the fuel rail plugs in the rear of the cylinder heads. |