6.9L, 7.3L IDI Diesel Injector Replacement Guide

IDI Injector Replacement Procedures, Injector Code Info

A dirty, worn, or leaking fuel injector (or series of injectors) will initially contribute to poor fuel economy, excessive smoke, and an overall rough running engine. However, worn injectors can also increase fuel dilution and wash the cylinders as they leak or the nozzles begin to stick. In a worst case scenario, neglected injector service can ultimately result in a burnt piston and/or scarred cylinder wall. Injectors are normal service items with a finite life and should be replaced as necessary.

When an injector becomes worn a number of symptoms can arise, which includes poor fuel economy, poor performance, excessive smoke under load, hard starting, rough idle, and related driveability concerns. Additionally, a worn injector can leak fuel into the cylinder while it sits, washing the cylinder and resulting in a dry start on that cylinder. For these reasons, injectors should be replaced as soon as it is suspected that they are worn. It is best to replace all 8 injectors at once and since the price of a set of injectors is reasonable on these engines, there's no reason not to. Identifying a single injector as the culprit is near impossible without removing the injectors and having them bench tested by a qualified shop. Furthermore, if a single injector fails you can expect that the remainder of the injectors are not far behind.

In order to promote injector and injection pump longevity, a fuel additive should be used at every fill-up on all IDI diesels. These engines were engineered long before the ULSD (ultra low sulfur diesel) mandate in the U.S. and were designed to run on LSD (low sulfur diesel). Sulfur plays a pivotal role in the lubrication properties of diesel fuel and thus ULSD does not provide sufficient lubricity to maximize the service life of injectors and the injection pump. We highly recommend Opti-Lube XDP or Archoil AR6200 diesel fuel additives. Both additives have earned high remarks and the cost-per-fill-up is more than reasonable.

6.9L & 7.3L IDI Injector Information

6.9L, 7.3L IDI Diesel Fuel Injector Codes

Injector Code

Model Year(s)


IDI diesel injector code location

A & AA


No longer manufactured. Engine serial number 59,207 and below.


1984 - 1992

Manufactured by Bosch


1984 - 1992

Manufactured by Delphi


1984 - 1992

Manufactured by Stanadyne


1992.5 - 1994

Naturally aspirated 7.3L IDI diesel only


1992.5 - 1994

Factory turbocharged 7.3L IDI diesel only

A and AA injectors were produced to identical specifications by two separate manufacturers. Similarly, B, BB, and D code injectors are built to the same specifications, but by different manufacturers (see chart above). A and AA injector codes, only used for one model year, have long been retired. B/BB/D code injectors feature an increased nozzle flow volume. Interestingly, B/BB/D series injectors have a lower ~1,875 psi opening pressure than the A/AA injector's ~2,075 psi opening pressure.

E and G code injectors are for 1992.5 to 1994 model year engines only. The injection pump on naturally aspirated engines was changed during this time and only E code injectors should be used. Likewise, only G code injectors are compatible in factory turbo applications. Do not attempt to put a naturally aspirated injector in a turbocharged engines. Engines from these model years will run best with the injectors they were designed with and if you're hunting for greater performance, injectors are not a viable solution for these applications.

IDI Diesel Fuel Injector Return System, Early Style vs Late Style

The fuel return system recycles excess fuel delivered to the injection pump and fuel injectors back to the fuel tank. In lieu of such a system, pressurized fuel from both the low pressure and high pressure fuel pumps would have no path and one or more parts of the fuel system would fail under pressure. It's rare for the return system to plug or develop a restriction, however the hoses and injector caps/headers have a tendency to leak with age. Thus, replacing the return lines and/or servicing as required is extremely important anytime the system is touched. Never replace fuel injectors without replacing the return line headers (caps), hoses, and related o-rings.

The routing of the return fuel hoses is different for naturally aspirated and turbocharged engines, however the operation of the system is the same and replacing the various parts is largely intuitive; simply trace the system and replace it one piece at a time as you move from cylinder to cylinder. The components are also extremely inexpensive, thus there is no reason to take shortcuts.

There are two injector return cap styles, referred to simple as the "early" and "late" style. The two styles are not directly interchangeable, however an early style return system can be retrofitted to the late style. While there's some debate surrounding the topic, the consensus is that there is little reason to convert one system to the other. The late style injector return cap was introduced during the 1989 model year to address concerns with fuel leaks. Early style return systems utilize a 3/16" hose while late style return systems feature 1/4" fuel hoses. The two styles are easily distinguishable and you can visually ensure that you are getting the correct parts for your application. The figure below will help you distinguish the early and late injector caps.

7.3L IDI and 6.9L IDI early vs late style fuel return caps

6.9L/7.3L IDI early vs late style fuel return caps

6.9L, 7.3L IDI Injector Replacement Parts List



Part Number


Delphi BB/D code injector

1983 - 1991
6.9L/7.3L IDI

Delphi 6760301

BB/D code injectors for naturally aspirated (NA) engines. For remanufactured Ford injectors, see: Motorcraft CMR5RM (Ford 2C3Z-9VE527-ERM).

Delphi E code injector

1992.5 - 1994

Delphi LJCK01101

E code injector for naturally aspirated engines. For remanufactured Ford injectors, see: Motorcraft CMR4RM (Ford 2C3Z-9VE527-DRM).

G code fuel injector

7.3L IDI Turbo

Motorcraft CMR3RM
(Ford 2C3Z-9VE527-ARM)

G code injector for factory turbocharged 1993 and 1994 model year engines.

Injector return line kit, early style

1983 - 1989
6.9L/7.3L IDI

Delphi 7135264

Early style fuel injector return hose is 3/16" diameter. All 6.9L diesels use this system. 7.3L diesels used this system until 1989, engine serial 630772 - 634154.

Injector return line kit, late style

7.3L IDI

Delphi 7135276

Late style fuel injector return hose is 1/4" diameter, header cap design is different than early style.

Anti-seize lubricant


Motorcraft XL-2

High temperature nickel anti-seize lubricant from Ford.

Recommended fuel additives

All engines

Opti-Lube XDP
Opti-Lube Summer+
Archoil AR6200

The IDI diesel was not designed with ULSD in mind. Using a supplemental fuel additive is a cost effective solution to prolonging the life of ALL fuel system components.

Glow plug repair kit

All 7.3L IDI


It is very easy to damage the glow plug connectors/wires as they become fragile and brittle with age; these are the replacement/repair options.

Glow plug connector set

All 7.3L IDI


How to Remove/Replace Fuel Injectors on a 6.9L or 7.3L IDI Diesel

Click any thumbnail to view fullsize, detailed image

IDI diesel engine, air cleaner removed

• Disconnect both negative battery cables so that the vehicle cannot be started unintentionally.

• Remove the air cleaner assembly and cover the intake manifold opening with a clean rag/towel.

• Use a vacuum or air nozzle to clean any debris (dirt, dust, grime) from the area around each fuel injector to prevent it from falling into the cylinder when the injectors are removed.

injector line clamps

• Remove the (4) injector line clamps/vibration damper brackets (11 mm socket). Each fuel injector has its own dedicated fuel line connecting it to the injector pump, i.e. there are no shared injection lines between fuel injectors. There are (2) injector line clamps for the left bank of cylinders and (2) injector line clamps for the right bank of cylinders.

fuel injector location on 7.3L IDI and 6.9L IDI diesel engine

• Disconnect (or cut) the rubber fuel hose for each injector return line. Fuel return system hoses and headers should not reused - always replace when the injectors are removed.

injector line removed

• Loosen, then fully remove the injector line from each fuel injector using a 16 mm flare nut wrench. Be extremely cautious not to kink any of the steel injector lines while handling them. You may wish to place a shop rag around the glow plug to collect any fuel that may leak when the injector line is removed.

return line cap removed from fuel injector

• Remove the fuel return header from the injector by pulling upwards away from the injector while rotating left-to-right gently. You may need to maneuver the fuel line aside at this time; do not kink the steel line.

removing fuel injector

• Remove each fuel injector with a 1 inch deep socket.

• Ensure that the copper crush washer came out with the fuel injector (at the base of the injector nozzle assembly). If it did not, you will need to fish it out of the injector bore with a pick or small screwdriver.

• Clean the inside of the injector bore in the cylinder head using a shop vacuum. We typically reduce the size of the vacuum hose using heater hoses of various sizes and plenty of duct tape. Do not blow the bores with shop air; remove debris using a vacuum.

fuel injector assembly

• Remove the protective cap from the nozzle of the new injector and install the copper crush washer. A small amount of anti-seize lubricant can be applied to one side of the copper washer in order to help it stick to the base of the injector nozzle during installation.

• Optional - apply a small amount of anti-seize lubricant to the injector threads. It will help the injector threads start easier and prevent corrosion, ensuring the injectors can be removed easily in the future.

new fuel injector installed

• Install the new fuel injector while ensuring that the copper crush washer remains secured to the base of the injector, i.e. does not fall into the cylinder head bore before being set into position. Always start the injector threads by hand, then torque to 35 ft-lbs.

Do not remove the protective cap at the top of the injector at this time. Repeat installation procedures for all 8 injectors.

return line cap o-rings installed

• Using a clean rag, clean the tip (flared end) of each injector line.

• Coat the injector return header o-rings (2 per injector) in clean engine oil, then install on each injector (reference image for proper position of the o-rings). Use caution as not to damage the injector o-ring on the sharp edge(s) of the threads and o-ring lands.

return line cap installed on fuel injector

• Install each injector fuel return header after removing the protective cap from the top of the injector. Rotate the header left-to-right while pressuring downwards firmly until it seats completely.

Note that the fuel return headers are not all identical; 90 degree headers are used to cross from the left and right banks while a single nozzle header is used where the return system stops.

injector line installed

• Install the fuel lines (high pressure steel lines) onto the new injectors. Always start the threads by hand, then snug up with a flare nut wrench.

return fuel line hose installed

• Cut new fuel return lines to length and reassemble the return fuel system using the hose and clamps supplied in the service kit.

• Replace the fuel filter.

• Reinstall the air cleaner assembly and reconnect the negative battery cables.

• Crank the engine in 10 second cycles, allowing the starter to cool for 30 seconds between cycles. Check for fuel leaks between cranking cycles. It may take several attempts before the fuel system primes and the engine runs. The engine can be expected to run very rough until all air is worked out of the fuel system.