Before the Power Stroke name existed, Ford trucks were already running diesel power under the hood, built by International Harvester, later Navistar. These indirect-injection engines, known as IDI diesels, laid the groundwork for the diesel dynasty that followed. Simple, rugged, and refreshingly low-tech, they still have a devoted following. Here is the story of the Fords before the Power Stroke.
What IDI means
IDI stands for indirect injection, a design in which fuel is injected into a small pre-combustion chamber rather than directly into the cylinder. This approach was quieter and simpler than early direct-injection systems, and it suited the technology of the era. IDI engines rely on glow plugs to aid combustion, especially for cold starts, and their mechanical injection needs no computer to run.
The 6.9L and 7.3L IDI engines
Ford's IDI story began with a 6.9L V8 built by International Harvester in the early 1980s, followed by a 7.3L IDI that carried into the mid-1990s. Later versions added a turbocharger for more power. These engines were never about big output; they were about dependable, no-drama service in work trucks, and they delivered exactly that for years of hard use.
Simplicity that owners still appreciate
The appeal of the IDI diesel is its mechanical simplicity. With no complex electronics, no high-pressure common-rail system, and no emissions hardware to manage, these engines are approachable and easy to keep running. Enthusiasts value them for that back-to-basics character and for the ease of working on them in a home garage. A healthy glow plug system and clean fuel go a long way.
The bridge to the Power Stroke
The IDI engines set the stage for Ford's diesel future. When the 7.3L Power Stroke arrived in the mid-1990s with HEUI injection and a turbocharger, it built on the foundation the IDI diesels had established, the International-built heritage and the reputation for durable diesel power in Ford trucks. Understanding the IDI era adds real context to the legendary engines that followed.
Living with an IDI diesel today
Owning an IDI diesel now is an exercise in appreciating simplicity. With no high-pressure common-rail system, no particulate filter, and no exhaust fluid to manage, these engines are about as approachable as a diesel gets, which is a large part of why enthusiasts still seek them out. The two things they care most about are a healthy glow plug system and clean fuel. Because IDI engines rely on glow plugs to aid combustion, fresh plugs and a working controller are the difference between an easy cold start and a frustrating one.
The trade-off, of course, is power and refinement. IDI engines were never fast, and by modern standards they are modest performers, even the turbocharged versions. But that was never the point. They were built to work dependably for years with minimal fuss, and a well-kept example still delivers on that promise. For owners who value mechanical honesty over horsepower, and who enjoy being able to understand and service their own engine, an IDI Ford is a rewarding and increasingly nostalgic piece of diesel history to keep on the road.
Frequently asked questions
What is the difference between IDI and the Power Stroke?
IDI diesels use indirect injection into a pre-combustion chamber with simple mechanical injection. The Power Stroke that followed used HEUI injection, firing injectors with high-pressure oil, along with a turbocharger and more power.
Do IDI diesels use glow plugs?
Yes. IDI engines rely on glow plugs to aid combustion and cold starting. A healthy glow plug system is important for easy starts in cold weather.
Who built Ford's IDI diesels?
They were built by International Harvester, later Navistar, the same partnership that would go on to build the early Power Stroke engines for Ford.
Restoring or maintaining one of these engines? Email our team at sales@coredieselparts.com with your year, engine, and VIN and we will confirm the correct part before you buy.