Ford 6.9L IDI Diesel Specs

Your Expert Guide to Ford X International’s 6.9L IDI Diesel Engine

Cast your mind back a few decades: in 1982 Ford, the globally renowned vehicle manufacturers, partnered up with agricultural giants International Harvester to transform the world of consumer trucking.

By utilizing International’s impressive 6.9 liter diesel engine within their range of trucks, they were able to economize fuel consumption, offer increased torque and provide improved components to their customers.

Today at ATVA Online, we’re taking a look at that now well-known IDI engine, examining piece by piece to cover all of its capabilities. Just about everything you could possibly wish to know about this perfect pairing, all in one article.


At A Glance - Everything You Need to Know

Ford 6.9L IDI Diesel 

Years Actively Manufactured:

1983-1987

Engine Design:

V8

Displacement:

6.9 Liters/20 cubic inches

Bore:

4 inches/101.6 mm

Stroke:

4.18 inches/106.2 mm

Cylinder Head:

Cast Iron; 5 bolts per cylinder

Engine Block:

Cast Iron

Connecting Rods:

Forged Steel

Pistons:

Aluminum Alloy

Camshaft:

Forged Steel

Crankshaft:

Forged Steel; induction hardened

Firing Order:

1-2-7-3-4-5-6-8

Compression Ratio:

1983

1984-1987

20.7:1

21.5:1

Fuel Injection:

Indirect fuel injection

Stanadyne DB2 Rotary Injection Pump

Mechanical Pintle Nozzle Injectors

TurboCharger:

None

Valvetrain:

OHV, 2 valves per cylinder

Aspiration:

Naturally Aspirated

Transmission(s):

3-Speed Select Shift Automatic Transmission

4-Speed Manual Transmission

Engine Oil Capacity:

(With Filter Change)

10 Quarts or 9.3 Liters

Cooling System:

Operating Temps:

Pressurized Series Flow

188-195 Degree Fahrenheit

Fuel:

Diesel

Fuel Capacity:

16.5 or 19 Gallon Front

19 Gallon (Behind Axle)

Horsepower:

j1983

1984-1987

161 Horsepower @ 3,300 rpm

170 Horsepower @ 3,300 rpm

Torque:

1983-1986

1987

307 lb-ft @ 1,800 rpm

The following ratings and advice are applicable to both conventional and Gooseneck/5th-wheel towing:

Maximum Towing Capacity - Manual Transmission*

Models

Rear Axle

Ratio

Max GCWR

Regular

Cab

Extended

Cab

Crew

Cab

F-250 HD 4×2

3.08

3.55

4.10

9,200 lbs

12,000 lbs

14,000 lbs

4,300 lbs

7,100 lbs

9,100 lbs

3,700 lbs

6,500 lbs

8,500 lbs

Not applicable

F-250 HD 4×4

3.08

3.55

4.10

10,500 lbs

12,000 lbs

14,000 lbs

N/A

6,600 lbs

8,600 lbs

N/A

6,100 lbs

8,100 lbs

Not applicable

F-350 4×4

3.08

3.55

4.10

10,500 lbs

12,000 lbs

14,000 lbs

N/A

6,600 lbs

8,600 lbs

Not applicable

N/A

5,900 lbs

7,900 lbs

F-350 4×2

3.08

3.55

4.10

10,500 lbs

12,000 lbs

14,000 lbs

Not applicable

Not applicable

3,400 lbs

6,100 lbs

8,100 lbs

F-350 4×2 DRW

3.08

3.55

4.10

10,500 lbs

12,000 lbs

14,000 lbs

N/A

6,700 lbs

8,700 lbs

Not applicable

Not applicable

*PLEASE NOTE: The above information is relevant only for F-Series trucks that are equipped with 4-Speed Manual Transmission, as well as the 6.9L IDI Diesel engine.

Maximum Towing Capacity - Auto Transmission*

Models

Rear Axle

Ratio

Max GCWR

Regular

Cab

Extended

Cab

Crew

Cab

F-250 HD 4×2

3.08

3.55

4.10

10,500 lbs

12,000 lbs

14,000 lbs

5,600 lbs

7,100 lbs

9,100 lbs

5,000 lbs

6,500 lbs

8,500 lbs

Not applicable

F-250 HD 4×4

3.08

3.55

4.10

10,500 lbs

12,000 lbs

14,000 lbs

N/A

6,600 lbs

8,600 lbs

N/A

6,100 lbs

8,100 lbs

Not applicable

F-350 4×4

3.08

3.55

4.10

10,500 lbs

12,000 lbs

14,000 lbs

N/A

6,600 lbs

8,600 lbs

Not applicable

N/A

5,900 lbs

7,900 lbs

F-350 4×2

3.08

3.55

4.10

10,500 lbs

12,000 lbs

14,000 lbs

  Not applicable

Not applicable

4,800 lbs

6,100 lbs

8,100 lbs

F-350 4×2 DRW

3.08

3.55

4.10

10,500 lbs

12,000 lbs

14,000 lbs

N/A

6,800 lbs

8,800 lbs

Not applicable

Not applicable

*PLEASE NOTE: The above information is relevant only for F-Series trucks that are equipped with C6 3-Speed Automatic Transmission, as well as the 6.9L IDI Diesel engine.

Further Information About Towing

Bear in mind that the maximum tow capacity for any F-Series truck with a 6.9L IDI Diesel engine is 9,400lbs. This figure should not be exceeded, and failure to heed this warning could result in serious injury or death. 

All of the information and specifications found in the above charts have been taken from the 1986 Ford F-Series Official towing guide based on the 1986 model - as such, it’s imperative that before you load a trailer up on to your truck, you consult the provided owner’s manual or seek out further information regarding your specific F-Series truck with an IDI engine. 

Remember: towing capacity is easily altered as a result of modifications made to your truck - it is always best to err on the side of caution. If you’re worried about exceeding the limit, try weighing your cargo before you load it, or make more than one trip if possible!

6.9L IDI Model Updates 1983-1987

IDI Diesel Engine Updates

1983

Ford 6.9L IDI Introduced

1984

6.9L IDI Block replaced

Compression Ratio increased from 20.7:1 to 21.5:1

Performance numbers increased

1985

Not applicable

1986

Final Year of Bull-nose Body Style

1987

Final Year of 6.9 IDI Manufacture

Body Style Change

International Harvester Diesel Engine, 6.9L - Key Features

A far cry from the technologically advanced behemoths we see nowadays, the 6.9L engine from IH is a mechanical design that is both naturally aspirated and utilizes indirect injection in order to function. 

Though it appears somewhat primitive to a modern mechanic, such components were revolutionary for their time period; the simplicity of it is a large factor in why it remains such a reliable choice even today. You can still find IDI’s running smooth!

For those not familiar with the above terminology, let’s go over it now:

Indirect Injection: as in the 6.9L IDI, an indirect fuel injection essentially means that fuel is inserted into what is known as a pre-chamber or ‘swirl’ chamber. In this small pocket, both air and fuel are able to mix, after which the combined solution is pushed through to the combustion chamber. Though this pales in comparison to the eco-friendly efficiency of a modern engine, it was a revolutionary fuel saving technology for the eighties, and ought to be respected!

Rotary Injection Pump: the 6.9L IDI’s fuel injection process is performed by the Stanadyne DB2 rotary pump; renowned for being a reliable choice, provided you keep them well maintained, there’s no reason they wouldn’t last for decades. Capable of delivering intense, high pressure fuel via the pintle-style hydraulic nozzles, the fuel is then atomized through the cylinder head to prepare for burning. When functioning optimally, these babies can work at levels as high as 2,100 PSI, though the pressure they are capable of will, naturally, fade over time. 

Natural Aspiration: quite simply, this means that the 6.9L IDI is entirely reliant on the intake of natural air in order to successfully combust fuel. This design has existed for decades - not falling victim to the lag of newer counterparts, you continuously receive the same amount of power, from the entire powerband. Despite that, this is where the engine shows its age a little: without a turbocharger, it isn’t capable of the higher-power performance and efficiency of more modern Ford trucks. As a result, naturally aspirated engines are falling out of fashion, gradually becoming obsolete and switched out for the smaller more efficient displacement engines of today. With one or more turbochargers, fuel emissions are much easier to keep within legal guidelines, as well as offering a significant boost in performance. Plus, they keep gas consumption down and your wallet fuller!

Transmission: as indicated by the tables above, there are two distinct transmissions utilized for the 6.9L IDI. These are Ford’s very own C6 SelectShift automatic transmission which is a three-speed, and T19 BorgWarner’s 4-speed manual.

Maintenance/Service

Miles

Kilometers

Change Oil

5,000 miles

8,000 km

Replace Oil

Filter

5,000 miles

8,000 km

Change Fuel

Filter

15,000 miles

24,000 km

Drain Fuel/Water

Separator

5,000 miles

8,000 km

Replace Air

Filter

30,000 miles

48,000 km

Flush Cooling

System

30,000 miles or once

every two years

48,000 km or once every

two years

Check Coolant

Nitrile Strength

15,000 miles or once

a year

24,000 km or

once a year

Adjust Drive Belt

15,000 miles

24,000 km

Inspect CDR

Valve

30,000 miles

48,000 km

Replace Auto

Transmission

Fluid

30,000 miles

48,000 km

Change Auto

Transmission

Filter

30,000 miles

48,000 km

Replace Manual

Transmission Fluid

60,000 miles

96,000 km

Drain & Replace

Transfer Case Fluid

60,000 miles

96,000 km

Replace Rear

Differential Fluid

100,000 miles

160,000 km

Replace Front

Differential Fluid

100,000 miles

160,000 km