7.3 IDM Rebuilt: Hi-Voltage Hi-Current
7.3 IDM Rebuilt: Stock
7.3 IDM Testing
The IDM (Injector Driver Module) is basically a dumb box that fires the injectors in response to a signal from the PCM telling it which injector to fire, when to fire it, and for how long. It has some basic diagnostic capabilities for detecting short or open circuits, and reports any problems to the PCM via a simple serial communication link.

All in all, they are very well designed devices, except for a vent in the case intended to allow for changes in pressure due to elevation or temperature changes. The vent also lets water in, with no provision to let it back out. This kills the majority of IDM's, and also means that a large percentage of the cores which we get back are simply not rebuildable, which in turns pushes up the price of an IDM so we can cover these losses. International used an almost identical IDM in the T444E two-box (separate PCM and IDM) trucks, but they did not have a vent in the case. T444E IH IDM's cannot be interchanged with 7.3 Power Stroke IDM's due do differences in the connector pinout.

There are 4 main models of IDM's; in chronological order they are EDU-100A used in 1994-1995 vehicles, IDM-100 used in 1996-1997, IDM-110 used in early-99 and IDM-120 used in late-99 and newer vehicles. Within these 4 IDM models, are three very different circuit board designs, and several more minor revisions. As far as their functionality, all IDM's are 100% swappable / interchangeable between all model years of trucks, vans and Excursions.

The 7.3L Power Stroke

The 7.3L Power Stroke engine was released in the summer of 1994. It was considered to be the successor to the 7.3L Indirect Injection, although the only thing the two engines have in common is their displacement. Other than being 7.3 liters, not one single part is the same.

It's biggest distinction at the time is that it was the first computer controlled diesel engine sold in the United States.

A computer controlled diesel is the norm now; then it was revolutionary. Before then, the injection timing on a diesel was essentially fixed. You set it at 12* BTDC at idle, and it was still 12* BTDC at 3,000 RPM. It was 12* at -20*F below zero, and it was 12* at 250*F engine coolant temperature. It was 12* at zero PSI of boost, and it was 12* at 25 PSI of boost.

With the Power Stroke, the injection timing became infinitely variable: there were timing maps (lookup tables) that adjusted the injection timing for any altitude from sea level to 10,000', for any oil temperature from -10* to +290*, for any boost from zero to 21 PSI, and any injected fuel quantity from zero to 100 mg/cyl, and more...on the fly, updating the value every engine revolution.

The other new technology it pioneered was electronically controlled,  independent injectors. Prior to this, most diesels used either an injection pump that metered fuel to each injector, often called a Pump-Line-Nozzle system (PLN), or a Mechanical Unit Injector (MUI) where each cylinder had its own injector, but the injectors were activated by a camshaft or rocker arm  system the activated a plunger in the injector to pressurize the fuel. In other words, in a PLN system, the plungers are mechanically activated by a cam in the pump, and in a MUI system the plungers are activated by a cam on the injectors.

In the Hydraulic Electronic Unit Injector (HEUI) system on the Power Stroke, the force for activating the plungers in the injector came from engine oil pressurized by a High Pressure Oil Pump (HPOP), while when the injectors actually fired, how long they fired for, and at what pressure they injected the fuel, was all controlled by the Powertrain Control Module (PCM).

We break the 7.3 down into 4 generations:

First is the 1994.5-1997 F-Series trucks and 1994.5-1996 E-Series vans, which use a DPC-20x PCM.

Second is 1997 California F-Series and 1997 Vans, which use a DPC-31x PCM. Everything from 1994 through 1997 got a ZF 5-Speed manual transmission or an E4OD automatic transmission.

Third is the Early-99 F-Series trucks and Vans, both Federal/49-State and California Emissions, which use a DPC-40x or 41x PCM. Everything from Early-99 on got a ZF 6-Speed manual transmission or a 4R100 automatic.

Fourth is the Late-99 through early-2003, the end of production of the 7.3 in the US, which use DPC-42x through 49x PCM's.

Although Ford made trucks in 1998, there wasn't really a 1998 model year. In our view, if the truck has the old (square) body style, it's a 1997, and if it has the newer rounded-hood and fenders and an intercooler, it's an Early-99 / Super Duty, regardless of what the build date is.

If the build date is after 12-06-1998, then it is a Late-99 or 2000 model.

The Early-99 was a complete redesign of the entire cab, chassis and drivetrain, and some significant changes to the injectors, turbo, fuel system, etc on the engine. Then, after barely 6 months of production, for some reason Ford did another redesign, changing all sorts of other things, most of it for no apparent reason. (Why change the front wheel bearing unit hub flange from 3/8” thick to 10mm thick? It just meant that if you got the wrong unit bearing, your brake calipers wouldn't line up with the mounting bracket or brake rotor.)