7.3L DIT Anthology
Source:
Ford Motor Company Publication
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This article outlines some of the various changes to the 7.3L Power Stroke engine since its introduction in the 1994 1/2 model year.
From Ford Motor Company Publication FSC 12922JA.
7.3L DIT Anthology
Crankcase
The crankcase was redesigned starting with engine serial number 375549 with thicker valley walls to increase stiffness to the assembly which reduces radiated engine combustion noise.
The crankcase was also modified in the tappet shelf area.
Valve Train
The valve train was redesigned to replace the cam follower guides and retainer to redesigned cam follower guide assemblies which bolt delivery into the crankcase to hold the follower in place.
The redesigned roller follower guide assemblies are now held in place with a capscrew for each pair of tappets which has led to the elimination of the roller follower guide retainer.
This change occurred at engine serial number 375549.
Cylinder Head Gasket
Due to the change in the crankcase and valve train the cylinder head gasket was also changed.
The redesigned cylinder head gasket provides individual holes for each push rod which will guide the push rod ball seat into the lifter.
This redesigned cylinder head gasket can be used on previous engines.
Front Cover
A deareation valve was inserted in the front cover beginning with engine serial number 201681 through engine serial number 375549.
The front cover was redesigned starting with engine serial number 375549 to help keep the oil pump primed for initial start up.
To accommodate this change, the pump inlet port was rotated 90° which moved the pickup tube from the left to the right.
The front oil cooler header gasket was also redesigned because of the change to the front cover.
The front cover has been modified for the updated reservoir to front cover gasket and passages have been cast and drilled into the front cover to incorporate the standpipe.
The engine serial number that the standpipe was incorporated is 201681.
Oil Reservoir for the High Pressure Pump
As of engine serial number 187100 the reservoir has been cast and drilled to include the standpipe and is drilled, tapped, and spotfaced to use both a straight thread, o-ring sealed engine oil pressure sensor and inspection plug as sealing enhancements.
Oil Pan
Due to the relocation of the pickup tube the oil pan baffle was redesigned to allow the pickup tube to pass through it to the bottom of the pan. This was done as of engine serial number 375549.
Injectors
California calibration, model year 1996-1997, utilized a "Split Shot" injector that in conjunction with the proper PCM calibration provides rate shaping capabilities. Our rate shaping provides an initial charge of fuel early in the injection cycle, followed by a larger quantity of fuel to complete the injection cycle. During the 1997 model year Econoline utilized the "Split Shot" injectors in all Federal and California calibrations.
Rate shaping of injection provides for a longer duration of the injection process, providing a cleaner, quieter burn.
Federal "F" Series (49 State and Canada) injectors were unchanged through the 1997 model year.
Note: Injector solenoids are now white in color instead of the prior black units. No functional change exists in the solenoids.
Fuel System
The fuel system has been improved by new fuel supply pipe assembly and banjo fitting. The new fitting on 1997 Econoline and 1997 California "F" series incorporates an accumulator to steady fuel pressure for the "Split Shot" injection system.
High Pressure Oil Pump
The high pressure pump has had the drain check valve deleted. This brings the variation of high pressure pumps used on the DIT to three. The pumps may be identified by the absence or presence of the anti-drain check valve.
On 1994 1/2 and 1995 model year engines up to serial number 187099, the initial high pressure pump did have a drain check valve but did not have an edge filter. The edge filter was part of the injection pressure regulator.
On 1995 model year engines starting with serial number 187100, up to serial number 201680, the high pressure pump did have a drain check valve and an integral edge filter. The edge filter was deleted from the injection pressure regulator.
On 1996 model year engines starting with serial number 201681, the high pressure pump does not have a drain check valve but continues to have an integral edge filter.
High Pressure Pump Gasket
The high pressure pump gasket has been modified to seal the standpipe between the pump and front cover.
Note: The correct gasket must be used to prevent internal and external oil leaks.
Injection Pressure Regulator (IPR)
On all engines starting with engine serial number 187100 and above, the injection pressure regulator does not have an edge filter, but the high pressure pump does.
Note: There is now a service package for the IPR o-rings that allow you to replace them separately if needed.
Oil Pump
The engine lube oil pump has been modified to include the words "out" or "damper" on its face, that is to insure that the pump is installed correctly and no damage occurs to the front cover due to incorrect installation.
Wiring Harness and Glow Plug Relay
The wiring harness was redesigned starting with serial number 375549 to incorporate gold plated terminal pins to increase reliability and meet OBD II standards.
The sensors and connectors that received the gold pins were CMP, EBP, ECT, and ICP.
The UVC harness now incorporates a wire clip instead of plastic tabs to attach to the injectors for improved reliability and ease of removal.
The redesigned glow plug relay system is not affected by high operating temperatures. This redesign includes a new relay, relay cover, and mounting brackets,
The 1997 Econoline and 1997 California models also include a new housing post (GPC sensing) in the redesign.
Thermostat
The thermostat, along with being longer to seal the lower bypass seat, opens at a lower coolant temperature, 89° C (192° F) from 98° C (205° F) to allow the engine to operate at lower temperatures.
Water Pump
The water pump has evolved since the 1994 model year. Currently there are two part numbers to service the pre-January 1998 engines. The F7TZ-8501-ARM pump is to be used on all 1996 and 1997 model year engines with serial numbers starting with 201681 through January 1998 production. The F5TZ-8501-ARM is to be used on all engines from the 1994 model year serial number 000501 through 1995 model year serial number 201681. The F5 pump comes with a bolt package that is to be used to mount the replacement pump. The F5 pump also incorporates a larger bearing than the 1994 pump, all pumps, new and remanufactured, have an improved silicon carbide seal.
Camshaft Position Sensor (CMP)
The CMP sensor has also been changed to incorporate gold plated pins. There has also been changes in length and circuitry since1994. To identify each CMP sensor there is a part number suffix located on the top of the sensor near the sensor wiring connector. The CMP with a part number suffix of C96 is 1.152" ± 0.006" in length and has tin pins, this sensor was used in engines with serial numbers between 000501 and 033780. A C96 sensor should not be installed as a replacement sensor. The sensor with a C97 suffix is tin plated and 1.152" ± 0.006" in length. This sensor has improved circuitry over the C96 sensor. The C98 sensor is identical to the C97 except for the length, it is 1.142" ± 0.004" in length.
Due to the change in wiring harnesses three new sensors were made with gold pins. The C91 sensor is 1.152" ± 0.006" in length, which was used in engine serial numbers 375549 through 408253, and the C92 is 1.142" ± 0.004" in length, which was used in engine serial numbers 408253 through 623916. A sensor with a part number suffix of C93 has gold pins and a length of 1.142" ± 0.004", this sensor has improved circuitry over the C91 and C92 sensors. The C93 sensor is being used as of engine serial number 623916.
The camshaft position sensor circuitry has been updated to be less sensitive of clearance to the trigger wheel.
The part number suffix for the gold plated sensor is C93 and C99 for the tin plated sensor.
Crankshaft
The crankshaft's rear seal no longer utilizes a wear sleeve on production DIT engines beginning with engine serial number 201681. The service rear crankshaft seal does utilize a wear sleeve, no change has been made to the service seal package.
Oil Cooler Header Pressure Regulator and Filter Bypass
As of engine serial number 282299 the oil pressure regulator and the oil filter bypass is held in with a c-clip instead of staking.
Note: Bypass valves should be in place to avoid engine damage.
Intake Hoses
The hoes connecting the turbocharger discharge Y pipe to the intake manifolds have been changed as of engine serial number 2011681 to delete the humps and may used interchangeably.
Oil Pan Sealing
When resealing the oil pan, make sure than the silicone is applied properly. Extra sealant is required at the ends of the radius' on each end of the pan. Make sure to avoid applying too much sealant to pan rails since it can fall off in the pan and plug the oil pick up tube. Always use dowels (make locally) to locate the pan during installation. Whenever the oil pan is resealed, add a bottle of anti-foam concentrate to the oil available at Navistar dealers (P/N CH1824392).
Intake Covers
The number of bolts holding the intake covers in place went from eight (8) to ten (10). This change was done at engine serial number 174666.
Flexplate
The flywheel/flexplate, as of engine serial number 201681, used in conjunction with automatic transmissions has been changed for 1996. The flywheel/flexplate's thickness has been increased to improve strength.
Injector Torque
Injector bolt torque is 120 lbf/in (13.6 Nm). Failure to properly tighten the bolts may lead to engine damage if the copper washer at the bottom of the injector burns away and the lower o-ring melts, allowing fuel to pass the outside of the injector into the combustion cylinder. It is common for relaxation to occur and torque wrenches my indicate less than 120 lbf/in (13.6 Nm) on the bolts. If less than 50 lbf/in is measured with a wrench and an overfueling type concern exists, such as a knock, smoke, or fuel out the tailpipe, remove the loose injectors for inspection, and repair as necessary. Remember when servicing injectors to lubricate the bolt threads to obtain the proper clamp load and avoid overtightening the bolts since injector damage can occur.
Oil Capacity
The oil capacity on all DIT engines is 14 quarts when changing the oil and filter. When released in 1994, the oil level was described as 12 quarts with filter change. The dipstick was changed at the introduction of the 1995 model to indicate full when 14 quarts were installed. The benefit of more oil is less chance of aeration.
