Jeep Cherokee 2000 Service Manual - page 692
DESCRIPTION AND OPERATION
ENGINE
DESCRIPTION
The 2.5 liter (150 CID) four-cylinder engine is an
In-line, lightweight, overhead valve engine.
This engine is designed for unleaded fuel. The engine
cylinder head has dual quench-type combustion cham-
bers that create turbulence and fast burning of the air/
fuel mixture. This results in good fuel economy.
The cylinders are numbered 1 through 4 from front
to rear. The firing order is 1-3-4-2 (Fig. 1).
The crankshaft rotation is clockwise, when viewed
from the front of the engine. The crankshaft rotates
within five main bearings and the camshaft rotates
within four bearings.
The engine Build Date Code is located on a
machined surface on the right side of the cylinder
block between the No.3 and No.4 cylinders (Fig. 2).
The digits of the code identify:
• 1st Digit—The year (8 = 1998).
• 2nd & 3rd Digits—The month (01 - 12).
• 4th & 5th Digits—The engine type/fuel system/
compression ratio (HX = A 2.5 liter (150 CID) 9.1:1
compression ratio engine with a multi-point fuel
injection system).
• 6th & 7th Digits—The day of engine build (01 - 31).
FOR EXAMPLE: Code * 801HX23 * identifies a
2.5 liter (150 CID) engine with a multi-point fuel
injection system, 9.1:1 compression ratio and built on
January 23, 1998.
LUBRICATION SYSTEM
DESCRIPTION
A
gear—type
positive
displacement
pump
is
mounted at the underside of the block opposite the
No. 4 main bearing.
OPERATION
The pump draws oil through the screen and inlet
tube from the sump at the rear of the oil pan. The oil
is driven between the drive and idler gears and
pump body, then forced through the outlet to the
block. An oil gallery in the block channels the oil to
the inlet side of the full flow oil filter. After passing
through the filter element, the oil passes from the
center outlet of the filter through an oil gallery that
channels the oil up to the main gallery which
extends the entire length of the block.
Galleries extend downward from the main oil gallery
to the upper shell of each main bearing. The crankshaft
is drilled internally to pass oil from the main bearing
journals (except number 4 main bearing journal) to the
connecting rod journals. Each connecting rod bearing
cap has a small squirt hole, oil passes through the
squirt hole and is thrown off as the rod rotates. This oil
throwoff lubricates the camshaft lobes, distributor drive
gear, cylinder walls, and piston pins.
The hydraulic valve tappets receive oil directly
from the main oil gallery. Oil is provided to the cam-
shaft bearing through galleries. The front camshaft
bearing journal passes oil through the camshaft
Fig. 1 Engine Firing Order
Fig. 2 Build Date Code Location
1 – NO. 4 CYLINDER
2 – NO. 3 CYLINDER
3 – DAY
4 – MONTH
5 – YEAR
6 – MACHINED SURFACE
9 - 2
2.5L ENGINE
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