BACK IN THE DAY

A short History of Ford’s first IDI and DI diesel pickups

It was the 1970s, and people were reeling from the shock of gas prices that had tripled in just a few short years. The effect was profound. We got a 55mph speed limit, the government began to mandate fuel economy standards and people were scrambling for vehicles with better fuel economy.

Diesel engines had not been much of a presence in the American car and light truck market up to then but were immediately eyed as a fuel economy answer. The collective American eyebrow rose at the idea of noisy, smelly, smoky diesels and the notable scarcity of diesel fuel stations back then. But the higher mpg and low-cost fuel were attractive, especially in the truck world where a torquey gasser meant sub-10mpg fuel economy.

In the light truck world, GM and Dodge were about tied in 1978 for being the first to offer a diesel pickup. The Chevrolet entry was a C10 with the notorious Olds 5.7L V8 diesel making 120 naturally aspirated horsepower. Dodge fielded a 4.0L (243cid) Mitsubishi NA diesel inline six with 100 rip-snorting horsepower in half- and three-quarter-ton 4×2 and 4x4s. Dodge dropped the Mitsu after 1979 and remained diesel-less until 1989. Chevrolet offered the 5.7L in C10s through 1981 and replaced it with the vastly better 6.2L in 1982. The stage was now set for a grand entrance by Ford.

Ford and International Harvester Team Up

IH started development work on a V8 diesel for medium-duty trucks in 1978. The architecture was based on the company’s own 446cid industrial gas V8. “Ack!” you may say. “A conversion!” Not really. The diesel merely adopted similar block dimensions that made tooling up easier. It isn’t exactly clear when Ford Motor Company’s interests were piqued by the IH diesel, but in 1981 a $500 million agreement was signed for IH to develop the engine for Ford light and medium-duty trucks and to supply engines for five years. Because it was a hefty engine, more than 900 pounds, it was soon clear this was going to be a three-quarter ton and up powerplant. When the diesel option emerged for 1983 it cost $2,225.

The Ford diesel light trucks debuted in late 1982 as ’83 models. The lightest duty truck in which the 6.9L (420cid) diesel was available was the F250HD (8,600-pound GVW) and they went all the way up the light line, including the E-Series vans and into the Ford medium duties. The first advertised rating was just 161 hp and 307 lb-ft with a 19.7:1 compression ratio. These were likely preliminary specs because 170 hp and a 20.7:1 compression ratio very soon became the advertised norm.

Cranking out 420 cubic inches from a 4-inch bore and a 4.18-inch stroke, the 6.9L featured oil-cooled pistons, four-bolt mains, a massive forged crank with a 2.2-inch rod and 3.1-inch main journals, valve rotaters, roller tappets, gear-driven cam and injection pump. It was naturally aspirated and indirectly injected using the Ricardo V combustion chamber. Injection came from a Stanadyne (Roosa-Master) DB2 rotary pump and pintle-type injectors that were popped at 2,100 psi. Issues with cold starting came right away, so in ’84 the compression ratio was raised to 21.5:1. Torque increased to 315 lb-ft as a result. That’s where output would stay for the remainder of the 6.9L run that lasted through 1987.

The engine got a makeover for 1988. The bore was increased 0.18-inch and that boosted displacement to 7.3L (444 cid). The heads, head bolts, head gaskets, rocker gear and combustion chambers got a workover and the glow system was completely revised. The injection system also got some tuning alterations. As a result, the engine was boosted to 180 hp at 3,300 rpm and 338 lb-ft of torque (some spec sheets show 345 lb-ft). In mid-year 1992 power output was increased to 185 and torque went up to 360. The 1992 model year also brought a serpentine belt system.

The revisions in the 7.3 were largely successful but there were some stumbles. The overbore and cooling system changes resulted in an increased tendency toward cavitation damage on the cylinder walls in the water jacket. It was manageable using the right anti-corrosive coolant additives (called SCAs, supplemental coolant additives) but it became a well-known problem.

The IDI reached its zenith late in 1993, when the first 7.3L turbo was introduced. It mounted a Garrett wastegated turbo with an A/R of 0.82. Advertised power and torque were 190 hp and 385 lb-ft, but this engine was somewhat underrated. If you look at the nearby power chart, you will see it’s mysteriously cut off at 3,000 rpm vs. the NA engine going to 3,300. The power line looks to still be climbing at 3,000 and extrapolations show the turbo engine was somewhat over
200 hp at 3,300. Speculation within the IDI enthusiast community is that with the new 210hp Power Stroke engine on the horizon Ford marketing wanted to make sure the new engine looked “better” than the old one. The IDI turbo engine was hyped more for its high-altitude performance than its raw power, but tweaking in the intervening years has shown that the IDI turbo is fully capable of 250 hp with only minor tuning.

Internally, the IDI turbo was given improved head gaskets with a heavier fire ring. The pistons were given keystone rings and anodized crowns. The wrist pin diameter was increased from 1.110 inches to 1.308 inches. Inconel exhaust valves were added and the oil cooler bundle was increased from 24 fpi (fins per inch) to 30. The injection pump calibration was altered and new injectors were used. Minimum boost was 5 psi but most developed around 8-10 psi in service.

The Turbo IDI and the Power Stroke shared the stage in ’94 and sales overlapped a little after the PSD’s mid-year intro. In reality, the Power Stroke is very much the IDI engine’s progeny. Especially in the first-gen PSDs, the IDI heritage is pretty clear and there are even a few interchangeable parts.

The IDI Today

Nearly 1.5 million 6.9L and 7.3L IDI engines were produced by International Harvester and its offspring, Navistar International. They are truly one of the cornerstones of the growth of diesel power in pickups. The IDI is an old-school engine and can’t hold a candle to the modern electronic engines in the power department, yet it has a large following. There are still gobs of them on the road, some still even in commercial livery. And they just go on and on. One IDI diesel fan has been heard to say, “This thing will have parts availability until the sun runs out of hydrogen!” That may be an exaggeration, but the IDI Ford is nowhere near the end of the road.

The Ford Package: 1983-1986—The Bullnose Era

Ford had debuted a new line of trucks in 1980 and the diesel entered the game right in the middle of that ’80-86 generation. Today, this era of Ford trucks is often called the “Bullnose” for its broad snout. It came in a Standard (base) trim, XL and the full-boat XLT. Body styles ranged from regular-cab longbed, SuperCab longbed and, in some years, a crew-cab longbed. “Lariat” was added to the XLT designation in ’85.

In this era you had the choice of two transmissions, the Warner T-19 four-speed or the legendary C-6 automatic three-speed. If you ordered four-wheel drive, it came with a BorgWarner 1345 transfer case. Axles varied by year. To mid-’85 the rear axle was a Dana 61 or 70 axle. In mid-year ’85 the 10.25-inch ring gear Ford Sterling debuted in semi or full-float versions (full-float only on the diesels). F-350 DRWs most often had Dana 70 HD axles but there are DRW Sterling axles out there too. Up front, the Twin I-beam non-driving axles carried the load for 4x2s. The F-250HD 4×4 had a twin traction beam (TTB) Dana 44 as standard with a Dana 50 TTB optional. The F-350 came standard with the stronger Dana 50 TTB. In ’85 the Dana 60 solid front axle was introduced and most F-350s had it. Only two axle ratios were offered for the diesels, 3.55 and 4.10:1. This was to remain the practice all the way through the IDI era.

1987-1991—The Flatnose Era

In 1987 Ford undertook some restyling without changing the basic body shape all that much. To IDI diesel nuts these trucks are known as the “Flatnose” or “Bricknose.” Flattening the nose and using flush headlights achieved a more aerodynamic look. Fender well shapes changed as well as the interior. A small “Diesel” badge appeared under the driver’s headlight. Trim levels changed a little, the base level being called “Custom,” but the things included in each of those levels also changed, generally moving upmarket.
The 6.9L engine soldiered on for ’87 but was replaced by the 7.3L IDI for ’88. A big innovation that occurred later in ’87 was the ZF five-speed manual trans option. At first it was a choice between the standard T-19 four-speed, the five-speed and the C-6 automatic. Later (by ’88) the T-19 was dropped and the five-speed became the only manual option. Like the T-19, it had a taller first gear than the gas engine version.

For ’89 the E4OD overdrive automatic was offered in the diesel line. That was a big innovation, offering the mpg improvements of overdrive to those desiring automatics, but it had taken Ford a while to build one stout enough for use in the higher GVW light trucks. There was a mix of three-speed C-6 and E4OD automatics that year and it remained that way through 1994, though in later years the C-6 was available only in the commercial cab-and-chassis lines. Suspension and axles stayed the same as the previous trucks, but in this era the Dana 44 TTB was dropped and the F-250HD inherited the Dana 50 as the standard front end for 4x4s. With a few exceptions, F-350s still used the Dana 60.

1992-1994—The OBS Era

The front wrap changed again for ’92 but, again, the basic body shape didn’t change much. This time the front end was more rounded. For some reason, Ford diesel fans are calling this generation IDI the “OBS” for “old body style.” We suppose that’s because the Power Stroke also used this body well into the ’90s. The interior got a big makeover again. The powertrain options changed little.

The big news came in ’93, when the turbocharged version of the IDI diesel became an option. The NA IDI continued as the baseline diesel option but the output had increased to 185 hp and 360 lb-ft, the highest power and torque levels the NA IDI would achieve in factory trim. The Power Stroke was a mid-year entrant for ’94 and the IDI trucks were soon in the “Oh, by the way” category.

FREQUENTLY ASKED QUESTIONS

What are the potential issues related to cavitation in the 7.3L IDI, and how can they be mitigated?

Understanding Cavitation and Its Impact on the 7.3L IDI

Cavitation poses a significant threat to the 7.3L IDI engine. This phenomenon occurs when tiny vacuum pockets form on the cylinder walls, leading to potential damage. These pockets result from the rapid motion of the pistons, which creates vibrations and a rocking effect. Though each vacuum pocket exerts a minor force, their persistent and frequent collapse can gradually wear down the cylinder walls.

Potential Issues Arising from Cavitation

1. Cylinder Wall Erosion: Over time, the continuous collapse of these vacuum pockets erodes the cylinder walls, compromising the engine’s integrity.
2. Risk of Perforation: If left unchecked, cavitation can eventually create a hole in the cylinder wall, leading to severe engine damage.
3. Increased Susceptibility: Diesel engines, particularly the 7.3L IDI, face a heightened risk due to their high compression ratios, making them especially vulnerable to this type of damage.

Mitigation Strategies

1. Use of Coolant Additives: Incorporating a supplemental coolant additive (SCA) or diesel coolant additive (DCA) into the engine’s cooling system can effectively prevent the formation of these damaging vacuum pockets. These additives help maintain a protective layer on the cylinder walls.
2. Regular Maintenance: Ensuring the cooling system is routinely checked and maintained is crucial. This practice keeps the protective additives active, preventing cavitation-related issues.
3. Opting for Extended Life Coolants (ELC): Some extended life coolants come pre-charged with protective additives and can last over 300,000 miles without requiring frequent maintenance. These coolants offer a convenient solution for long-term protection against cavitation.

By understanding and addressing the effects of cavitation, owners of the 7.3L IDI can effectively prolong their engine’s lifespan and performance. Regular maintenance and the use of specialized coolants are key strategies in mitigating these potential issues.

How does the 7.3L IDI’s mechanical injection system function?

The 7.3L IDI diesel engine incorporates a straightforward yet reliable mechanical injection system. At its core, the system utilizes a rotary-style injection pump, a pivotal component for delivering fuel to the engine.

Key Components:

1. Injection Pump: This pump plays a crucial role in the process, transferring fuel to pintle-type injectors. These injectors are responsible for spraying fuel into the combustion chamber.
2. Fuel Delivery: Fuel is supplied to the injection pump via a mechanical fuel pump. This pump is camshaft-driven and strategically mounted on the engine block’s passenger side.

System Reliability:

The mechanical nature of this system is praised for its durability and efficiency. Maintenance and repair costs tend to be reasonable, making it a favored choice for those looking for a dependable diesel engine. However, the introduction of Ultra Low Sulfur Diesel (ULSD) has posed some challenges. The lower lubricity of ULSD can potentially shorten the lifespan of the injection pump.

Maintenance Tips:

To mitigate the effects of ULSD, it’s recommended to regularly use a fuel additive. These additives help restore lubrication, ensuring the longevity and reliable performance of the entire fuel system.

In summary, the 7.3L IDI’s mechanical injection system is a dependable mechanism with a few easy maintenance steps that can help maintain its efficiency despite challenges presented by modern fuels.

What is the impact of ULSD fuel on the 7.3L IDI’s injection pump longevity?

Impact of ULSD Fuel on the 7.3L IDI’s Injection Pump Longevity

The 7.3L IDI engines have generally built a reputation for robust reliability. However, the introduction of ultra-low sulfur diesel (ULSD) fuel has posed a challenge, particularly affecting the longevity of their injection pumps.

ULSD has significantly lower sulfur content, leading to reduced lubricity. This lack of natural lubrication can result in premature wear and tear on the injection pumps, which rely on a certain level of lubrication for optimal performance.

To mitigate these effects, it’s recommended to consistently use a fuel additive designed to enhance lubrication. Products like Stanadyne, Power Service, or similar third-party lubricants can play a critical role in prolonging the life of the injection pump by compensating for the lower lubricity of ULSD. Frequent use of these additives appears to successfully counteract most of the wear issues associated with ULSD fuel.

Key Recommendations

• Regularly add fuel lubricantsto your diesel to maintain pump health.
• Monitor pump performance, adjusting the dosage of additives if necessary.
• Consider periodic inspectionsto detect and address wear early.

By proactively managing fuel quality, many 7.3L IDI owners continue to enjoy long service life from their injection pumps despite the challenges posed by ULSD.

What are the historical significance and legacy of the 7.3L IDI diesel engine?

Nearly 1.5 million 6.9L and 7.3L IDI engines were produced by International Harvester and its offspring, Navistar International. They are truly one of the cornerstones of the growth of diesel power in pickups. The IDI is an old-school engine and can’t hold a candle to the modern electronic engines in the power department, yet it has a large following. There are still gobs of them on the road, some still even in commercial livery. And they just go on and on. One IDI diesel fan has been heard to say, “This thing will have parts availability until the sun runs out of hydrogen!” That may be an exaggeration, but the IDI Ford is nowhere near the end of the road.

Simplicity and Reliability

The legacy of the 7.3L IDI is deeply rooted in its simplicity and reliability. These engines are known for their straightforward design, which makes them easier to maintain and repair. This simplicity is a key reason why they continue to operate smoothly decades after their release.

Longevity and Historical Significance

Properly maintained, the 7.3L IDI engine stands the test of time, serving as a testament to its longevity. While it may lag behind in performance compared to modern engines, it represents an era when durability and dependability were paramount. This historical significance adds to its enduring appeal, making it a beloved choice among diesel enthusiasts who appreciate its storied past.

A Legacy That Endures

Despite the advancements in diesel technology, the IDI holds a special place in automotive history. It met and exceeded the needs of its time, establishing a legacy that continues to be celebrated by those who value its honest and robust performance. As a result, the 7.3L IDI remains an iconic engine that has left an indelible mark on the diesel landscape.

Why is the 7.3L IDI engine still relevant today?

Its lasting reputation for durability and ease of maintenance keeps it relevant, with many enthusiasts and operators still valuing its robust performance.

Did the engine meet the needs of its era?

Yes, it more than satisfied the requirements of its time, offering a balance of simplicity and reliability that was highly valued.

What is the historical reputation of the engine?

The engine is remembered as an honest and reliable workhorse that fulfilled the needs of its era, securing its place in automotive history.

How does the engine compare to modern standards?

While it doesn’t match contemporary engines in terms of performance, the 7.3L IDI was designed to meet the demands and expectations of its time.

What are the defining characteristics of the 7.3L IDI engine?

The 7.3L IDI engine is known for its straightforward design, dependable performance, and ability to last for many years with proper maintenance.

What are the detailed specifications of the 7.3L IDI diesel engine?

The 7.3L IDI debuted in 1988 and touted a number of improvements. Power was advertised at 180 hp and torque bumped to 338 lb-ft. The engines looked similar on the outside and initially they only came naturally aspirated; 7.3L blocks can be distinguished by a 10809000C1 casting number. With the heads off, you can ID them via round coolant ports at the corners of the block deck vs. The triangular ones on the 6.9L. The 7.3L also got larger head bolts (1/2-inch vs. 7/16-inch) and of course the larger bore. The thinner cylinder walls, changes in coolant flow, and a tendency towards core shift made the 7.3L vulnerable to cavitation and pinholes from the water jacket into the cylinder. The oil filler was cast into the pump gear cover. This is a ’92-and-later engine, which featured a very desirable serpentine belt system.

Detailed Specifications of the 7.3L IDI Diesel Engine

• Manufacturer: International Harvester, Navistar
• Production Years: 1988 – 1994
• Applications: Ford F-250, F-350, F-Super Duty; International medium duty trucks
• Displacement: 444 CID, 7.3 liters
• Configuration: 90° V-8
• Bore and Stroke: 4.11 inches x 4.18 inches
• Compression Ratio: 21.5:1
• Firing Order: 1-2-7-3-4-5-6-8
• Engine Materials: Cast iron block and heads

Fuel and Injection System

• Injection Type: Indirect injection (IDI)
• Injection Pump: Stanadyne DB2 mechanical pump
• Injector Type: Mechanical with pintle type nozzle
• Nozzle Opening Pressure: Minimum 1,425 psi

Aspiration and Performance

• Aspiration Variations: Naturally aspirated and turbocharged (1993-1994)
• Horsepower:
  • Naturally aspirated: 185 hp @ 3,000 rpm
  • Turbocharged: 190 hp @ 3,000 rpm
• Torque:
  • Naturally aspirated: 338 lb-ft @ 1,400 rpm (1988-1992 models)
  • Turbocharged: 388 lb-ft @ 1,400 rpm

Additional Specifications

• Cold Start Aid: Solid state glow plug system
• Thermostat Temperature: Opens at 192°F, fully open at 212°F
• Oil Capacity:
  • Ford F-Series: 10 quarts with filter change
  • International trucks: 16 quarts with filter change
• Fuel Types: #2, #1, or winterized diesel; biodiesel not advised
• Idle Speed and Governed Speed: Idle around 675 rpm; governed speed varies with load

Physical Dimensions and Weight

• Engine Weight: Approximately 995 lbs dry
• Dimensions:
  • Length: 30.0 inches
  • Width: 27.0 inches
  • Height: 27.0 inches

These detailed specifications enhance our understanding of the 7.3L IDI diesel engine’s robust design and performance capabilities, making it a staple in its class during its production years.

What are the aspiration options and specifications for turbocharged models?

The engine is available naturally aspirated and with turbocharged variations. Turbocharged models from 1993 to 1994 used a Garrett T3 internally wastegated turbocharger.

What type of fuel and injection system is used?

The engine uses an indirect injection system with a Stanadyne DB2 distributor type mechanical pump.

What materials are used for the engine block and cylinder head?

Both the engine block and cylinder head are made from cast iron.

What is the firing order of the engine?

The firing order is 1-2-7-3-4-5-6-8.

What is the compression ratio?

The compression ratio is 21.5:1.

What is the engine’s bore and stroke?

The bore is 4.11 inches, and the stroke is 4.18 inches.

What is the exact displacement of the engine in cubic inches and liters?

The engine has a displacement of 444 cubic inches (443.65 cubic inches actual) and 7.3 liters (7.27 liters actual).

What are the applications and production years for this engine?

This engine was used in Ford F-250, F-350, and F-Super Duty trucks from 1988 to 1994, as well as in various International medium-duty trucks during the same years.

Who manufactured the engine?

The engine was manufactured by International Harvester and International Navistar.

What types of transmissions were used with the 7.3L IDI in Ford F-Series trucks?

“Ford had debuted a new line of trucks in 1980 and the diesel entered the game right in the middle of that ’80-86 generation. Today, this era of Ford trucks is often called the “Bullnose” for its broad snout. It came in a Standard (base) trim, XL, and the full-boat XLT. Body styles ranged from regular-cab longbed, SuperCab longbed and, in some years, a crew-cab longbed. “Lariat” was added to the XLT designation in ’85.

In this era, you had the choice of two transmissions: the Warner T-19 four-speed or the legendary C-6 automatic three-speed. If you ordered four-wheel drive, it came with a BorgWarner 1345 transfer case. Axles varied by year. To mid-’85, the rear axle was a Dana 61 or 70 axle. In mid-year ’85, the 10.25-inch ring gear Ford Sterling debuted in semi or full-float versions (full-float only on the diesels). F-350 DRWs most often had Dana 70 HD axles but there are DRW Sterling axles out there too. Up front, the Twin I-beam non-driving axles carried the load for 4x2s. The F-250HD 4×4 had a twin traction beam (TTB) Dana 44 as standard with a Dana 50 TTB optional. The F-350 came standard with the stronger Dana 50 TTB. In ’85, the Dana 60 solid front axle was introduced and most F-350s had it. Only two axle ratios were offered for the diesels, 3.55 and 4.10:1. This was to remain the practice all the way through the IDI era.

In the Ford F-Series, the 7.3L IDI was mated to a series of robust transmissions, enhancing its versatility. For the manual transmission enthusiasts, the ZF 5-speed offered precision and control. Automatic options included the C6 three-speed, though it became increasingly rare after the introduction of the E4OD four-speed automatic in the 1989 model year. The latter two, both overdrive transmissions, significantly improved fuel economy and highway driveability, especially given the common 4.10 final drive ratio in these trucks. This setup ensured that engine speeds remained reasonable, contributing to a smoother and more efficient driving experience.”

What is the impact of the 4.10 final drive ratio on engine performance?

The 4.10 final drive ratio is common with the 7.3L IDI, and having an overdrive gear helps to maintain reasonable engine speeds.

When did the transition from C6 to E4OD occur?

The transition from the C6 to the E4OD took place for the 1989 model year.

Which transmissions are overdrive and what are their benefits?

The E4OD and ZF 5-speed are overdrive transmissions, which enhance fuel economy and improve driveability, especially at highway speeds.

What specific transmissions were paired with the 7.3L IDI engine in Ford F-Series trucks?

The 7.3L IDI engine was paired with a ZF 5-speed manual, a C6 3-speed automatic, and an E4OD 4-speed automatic transmission.

What are the performance characteristics of the 7.3L IDI diesel engine at high elevations?

“The IDI turbo engine was hyped more for its high-altitude performance than its raw power, but tweaking in the intervening years has shown that the IDI turbo is fully capable of 250 hp with only minor tuning. Originally, this engine was designed to maintain peak performance at elevations up to 10,000 feet above sea level—making it a reliable choice for those tackling mountainous terrains.

Despite not being a race-winning powerhouse, the 7.3L IDI turbo’s high compression ratio ensures a ‘snappy’ throttle response, essential for dynamic driving. Its robust design enables it to haul heavy loads efficiently while maintaining reasonable fuel economy. The naturally aspirated version of this engine delivered 185 horsepower and 358 lb-ft of torque, while the turbocharged variant stepped up to 190 horsepower and 388 lb-ft of torque.

These specifications highlight the engine’s inherent versatility, providing a solid foundation for those seeking both performance and reliability. Whether you’re climbing steep inclines or cruising at high altitudes, the 7.3L IDI turbo proves to be more than just a historical footnote in diesel engineering.”