General Description

DESCRIPTION AND OPERATION

Engine Description
The 7.3L diesel engine is:
^ a four-cycle turbocharged V-8 with overhead valves.
^ 7.3 liter (444 cubic inch) displacement.
^ separated into two banks, the right bank numbered 1, 3, 5, 7 and the left bank numbered 2, 4, 6, 8.
^ rated at 215 horsepower at 3000 rpm.

The cylinder block has been designed to withstand the loads of diesel operations by using:
^ four-bolt main bearing caps.
^ internal piston cooling oil jets.
^ a forged steel crankshaft.
^ heavy-duty forged steel connecting rod.

The piston and rings are:
^ made of aluminum alloy.
^ fitted with an upper keystone compression ring.
^ fitted with a lower rectangular compression ring.
^ fitted with oil control rings.

The piston pins are:
^ a free-floating type permitting the piston pin to move/float freely in the piston pin bore.
^ retained in the piston and rings by piston pin retainers.

The camshaft is:
^ supported by five insert-type camshaft bearings.
^ driven by the crankshaft through the use of the crankshaft gear and the camshaft gear.

The hydraulic valve tappets:
^ minimize engine noise.
^ maintain zero valve lash.
^ incorporate camshaft follower guides.
^ incorporate a roller follower design that reduces camshaft wear.

The cylinder heads are designed:
^ to incorporate electronically controlled/hydraulically actuated fuel injectors.
^ to locate the fuel injectors in the center of the combustion chambers between the rocker arms.
^ with integral high-pressure oil galleries.

The glow plug system is:
^ designed to preheat the cylinders for faster cold weather starts.
^ controlled by the Powertrain Control Module (PCM).
^ mounted directly into the cylinder heads.
^ activated by the glow plug control module.

The manifold intake air heater:
^ is designed to preheat intake air to reduce smoke and odor during cold weather starts.
^ is controlled by the Powertrain Control Module (PCM).
^ is mounted into the compressor manifold to heat intake air.

The optional block heater is:
^ designed to heat the engine coolant and oil for improved cold weather starts.
^ located near the oil filter in the oil cooler.
^ powered by a 120-volt external power source.
^ not repairable; a new block heater must be installed.

The fuel injection system used on the engine:
^ is controlled by the powertrain control module.
^ utilizes an electric in-line fuel pump.
^ circulates through a combination fuel filter, fuel heater and water separator assembly. uses eight electronically controlled/hydraulically actuated fuel injectors.
^ maintains operating pressures between 448-482 kPa (65-70 psi).

The engine lubrication system:
^ is divided into two systems:
^ the low-pressure system lubricates the engine, the high-pressure system actuates the fuel injectors.
^ maintains pressures between 69 - 414 kPa (10 - 60 psi) for the low-pressure system and 2,758 - 20,685 kPa (400 - 3,000 psi) for the high-pressure system.
^ is cooled by an engine oil cooler.
^ in the high-pressure system uses an Injection Control Pressure (ICP) sensor and Injection Pressure Regulator (IPR) valve to maintain and control pressure.
^ actuates the exhaust back-pressure warm-up system integral to the turbocharger.
^ in the high-pressure system is used to inject fuel.

7.3L (DIT) Engine (Part 1):

7.3L (DIT) Engine (Part 2):

7.3L (DIT) Engine (Part 3):

7.3L (DIT) Engine

7.3L (DIT) Crankshaft, Camshaft And Piston:

7.3L (DIT) Crankshaft, Camshaft And Piston

Engine Identification

Engine Labels (Part 1):

Engine Labels (Part 2):

Engine Labels

Vehicle identification, the location of the vehicle rating and data plates, and engine code information is fully covered in Vehicle / Application and ID. For specific and exact engine identification, an engine calibration code label is affixed to the B-pillar. Refer to the illustrations for examples of engine identification labeling.

Calibration Code Label
Refer to Computers and Control Systems.

Lubrication System - Low-Pressure

Low-Pressure Oil Flow (Part 1):

Low-Pressure Oil Flow (Part 2):

Low-Pressure Oil Flow

The lubrication system is comprised of a low-pressure system and a high-pressure system. The low-pressure system provides primary engine lubrication while the high-pressure system provides the hydraulic pressure required to actuate the fuel injectors.

The gerotor oil pump draws oil from the engine oil pan through the oil pump screen cover and tube into the oil inlet passage in the front cover. The gerotor oil pump then pumps the oil back out through the outlet passage in the front cover. The oil separates into two paths.

One flow path sends oil into the high-pressure pump reservoir possibly through the short circuit valve during cold start. One feed leaves the short circuit valve and enters the front cover. From there it enters the high-pressure oil reservoir. The second feed exits the short circuit valve and enters the left bank valve lifter oil gallery.

After leaving the front cover outlet passage, the second oil path sends the oil through the oil cooler. Once inside the rear oil cooler housing, the pressure relief/regulator valve may open to vent excess pressure and oil back into the oil pan. After the oil has been circulated through the oil filter, the oil feed then enters the main oil gallery (integral to the cylinder block). Once in the main oil gallery, the oil is routed to the five crankshaft main bearings through five drilled and machined fed galleries (integral to the cylinder block). The five camshaft bearings receive the oil feed through five vertically drilled and machined feed galleries connected to the main bearing feed galleries. The front main bearing feed gallery also supplies oil to the right bank valve lifter oil gallery through a vertically drilled and machined oil feed gallery (integral to the cylinder block). The rear main bearing oil feed gallery also supplies oil to the turbocharger assembly through a vertically drilled and machined oil feed gallery (integral to the cylinder block).

Pressurized oil entering the turbocharger assembly is utilized to actuate the exhaust back-pressure warm-up system. The exhaust back pressure regulator controls the oil leaving the turbocharger to actuate the back pressure device during cold ambient temperatures. The oil drains back through the turbocharger mounting pedestal and back into the oil pan. The valve lifter oil gallery supplies pressurized oil to the valve tappets and to the piston cooling oil jets. Oil from the valve tappets is routed upward to the cylinder head valve train through hollow push rods. Once in the cylinder head, the oil drains back to the oil pan through return ports at each end of the cylinder head.

Lubrication System - High Pressure

High Pressure Oil Flow (Part 1):

High Pressure Oil Flow (Part 2):

High Pressure Oil Flow

During cold start, the high-pressure oil pump receives oil from the left side valve lifter oil gallery possibly through the short circuit valve. Once the engine starts or during warm engine starts, the short circuit valve closes and the high-pressure oil pump receives filtered oil from the high-pressure oil pump reservoir. The high-pressure oil pump pumps the oil under extremely high pressures (2,758-20,577 kPa [400-3,000 psi]) through the left and right side high-pressure supply hoses to the high-pressure oil rails (integral to the cylinder heads). Once in the oil rail, the oil is fed to the fuel injector bores through four oil feed galleries drilled and machined in the cylinder head. The high-pressure oil then actuates the fuel injectors. The IPR valve controls and maintains the high-pressure oil. The PCM uses the information from ICP sensor to adjust the pressure in the system.