BELT TENSION
Note. Serpentine belt tension is maintained automatically by a spring-tensioned idler pulley. No adjustment is necessary.
ENGINE COMPRESSION
| Application | Compression Ratio |
|---|
| 2.5L (VIN E) | 8.3:1 |
| 2.8L (VIN R) | 8.9:1 |
| 3.1L (VIN D) | 8.9:1 |
| 3.8L (VIN L) | 8.5:1 |
| 4.3L |
| VIN W | 9.1:1 |
| VIN Z | 9.3:1 |
| VIN Z Turbo | 8.35:1 |
| 5.0L (VIN H) | 9.3:1 |
| 5.7L (VIN K) | (1) 9.1:1 |
| 6.2L Diesel (VIN C & J) | 21.3:1 |
| 6.5L Turbo Diesel (VIN F) | 21.0:1 |
| 7.4L (VIN N) | 7.9:1 |
| (1) 8.3:1 - Over 8500 lbs. GVW. |
| (1) | 8.3:1 - Over 8500 lbs. GVW. |
COMPRESSION SPECIFICATIONS
VALVE CLEARANCE
Note. All models are equipped with hydraulic lifters. No adjustments are required.
IGNITION COIL
| Application | Ohms |
|---|
| All Models | 500-1500 |
HIGH TENSION WIRE RESISTANCE
| Application | Ohms |
|---|
| All Models | 30,000 Maximum |
HIGH TENSION WIRE RESISTANCE
SPARK PLUGS
| Application | AC |
|---|
| 2.5L (VIN E) | R43CTS6 |
| 2.8L (VIN R) | R43TSK |
| 3.1L (VIN D) | R43TS |
| 3.8L (VIN L) | 41-600 |
| 4.3L |
| VIN W & Z | CR43TS |
| VIN Z Turbo | CR42TS |
| 5.0L (VIN H) | CR43TS |
| 5.7L (VIN K) | CR43TS |
| 7.4L (VIN N) | CR43TS |
| Application | Gap In. (mm) | Torque Ft. Lbs. (N.m) |
|---|
| 2.5L (VIN E) | .060 (1.52) | 17 (23) |
| 2.8L (VIN R) | .045 (1.14) | 22 (30) |
| 3.1L (VIN D) | .045 (1.14) | 18 (24) |
| 3.8L (VIN L) | .060 (1.52) | 20 (27) |
| 4.3L |
| VIN W | .045 (1.14) | 22 (30) |
| VIN Z | .035 (0.89) | 22 (30) |
| VIN Z Turbo | .045 (1.14) | 11 (15) |
| 5.0L (VIN H) | .035 (0.89) | 22 (30) |
| 5.7L (VIN K) | .035 (0.89) | 22 (30) |
| 7.4L (VIN N) | .035 (0.89) | 22 (30) |
SPARK PLUG SPECIFICATIONS
Firing Order & Timing Marks (2.5L). Scheme 1
Scheme 1: Firing Order & Timing Marks (2.5L)
Firing Order & Timing Marks (2.8L). Scheme 2
Scheme 2: Firing Order & Timing Marks (2.8L)
Firing Order & Timing Marks (3.1L). Scheme 3
Scheme 3: Firing Order & Timing Marks (3.1L)
Firing Order & Timing Marks (3.8L). Scheme 4
Scheme 4: Firing Order & Timing Marks (3.8L)
Firing Order & Timing Marks (4.3L). Scheme 5
Scheme 5: Firing Order & Timing Marks (4.3L)
Firing Order & Timing Marks (5.0L, 5.7L & 7.4L). Scheme 6
Scheme 6: Firing Order & Timing Marks (5.0L, 5.7L & 7.4L)
Firing Order (6.2L & 6.5L Diesel). Scheme 7
Scheme 7: Firing Order (6.2L & 6.5L Diesel)
IGNITION TIMING
Note. For timing adjustment procedures, see ADJUSTMENTS article in the ENGINE PERFORMANCE Section.
| Application | (1) Man. Trans. | (2) Auto. Trans. |
|---|
| 2.5L (VIN E) | 8 @ Idle | 8 @ Idle |
| 2.8L (VIN R) | 10 @ Idle | 10 @ Idle |
| 3.1L (VIN D) | 10 @ Idle | 10 @ Idle |
| 3.8L (VIN L) | (3) | (3) |
| 4.3L (VIN W & Z) | 0 @ Idle | 0 @ Idle |
| 5.0L (VIN H) | 0 @ Idle | 0 @ Idle |
| 5.7L (VIN K) | 0 @ Idle | 0 @ Idle |
| 7.4L (VIN N) | 4 @ Idle | 4 @ Idle |
| (1) With transmission in Neutral. (2) With transmission in Neutral or Park. (3) Timing is not adjustable. |
| (1) | With transmission in Neutral. |
| (2) | With transmission in Neutral or Park. |
| (3) | Timing is not adjustable. |
IGNITION TIMING (Degrees BTDC @ RPM)
FUEL PUMP
| Application | Psi (kg/cm 2 ) |
|---|
| 3.8L (VIN L) | 41-47 (2.9-3.3) |
| 4.3L (VIN W) | 54-64 (3.8-4.5) |
| 4.3L (VIN Z Turbo) | 9-13 (.63-.91) |
| 6.2L Diesel (VIN C & J) | 5.5-6.5 (.38-.45) |
| 6.5L Turbo Diesel (VIN F) | (1) |
| All Others | 9-13 (.63-.91) |
| (1) Information not available from manufacturer. |
| (1) | Information not available from manufacturer. |
INJECTOR RESISTANCE
| Application | (1) Resistance (Ohms) |
|---|
| 3.1L (VIN D) | 1.2 |
| 4.3L (VIN Z Turbo) | 2.0 |
| All Others | 1.3 |
| (1) Injector resistance specification is at 140°F (60°C). |
| (1) | Injector resistance specification is at 140°F (60°C). |
INJECTOR RESISTANCE SPECIFICATIONS
IDLE SPEED & MIXTURE
Note. Idle mixture on fuel injected models is controlled by the Electronic Control Module (ECM) and is not adjustable. Controlled idle speed and IAC count can be checked using scan tester. See CONTROLLED IDLE SPEED & IAC COUNT table.
| Application | Idle RPM | (1) IAC Counts |
|---|
| 2.5L TBI "S" Series |
| Auto. Trans. (2) | 800 | 15-40 |
| Man. Trans. (3) | 900 | 5-20 |
| 2.8L TBI "S" Series |
| Auto. Trans. (2) | 800 | 5-20 |
| 3.1L TBI "U" Series |
| Auto. Trans. (2) | 600-700 | 5-15 |
| 3.8L PFI "U" Series |
| Auto. Trans. (2) | 650-750 | 16-20 |
| 4.3L CPI |
| "L" Series Auto. Trans. (2) | 625 | 5-50 |
| "M", "S" & "T" Series Auto. Trans. (2) | 550 | 5-40 |
| 4.3L PFI Turbo "S" & "T" Series |
| Auto. Trans. (2) | (4) | 1-50 |
| 4.3L TBI |
| "C" & "K" Series |
| Auto. Trans. (2) (5) | 537 | 5-30 |
| Auto. Trans. (2) (5) | 650 | 20-35 |
| Man. Trans. (3) | 550 | 2-20 |
| "G" Series |
| Auto. Trans. (2) | 538 | 5-30 |
| Man. Trans. (3) | 650 | 5-30 |
| "L" Series |
| Auto. Trans. (2) | 625 | 5-50 |
| Man. Trans. (3) | 600 | 3-30 |
| "M" Series |
| Auto. Trans. (2) | 538 | 5-30 |
| "P" Series |
| Auto. Trans. (2) | 650 | 20-35 |
| 5.0L TBI "C" & "K" Series |
| Auto. Trans. (2) | 500 | 5-30 |
| Man. Trans. (3) | 600 | 5-30 |
| 5.7L TBI |
| "C", "G", "K" & "P" Series |
| Under 8500 GVW |
| Auto. Trans. (2) | 525 | 5-30 |
| Man. Trans. (3) | 600 | 5-30 |
| Over 8500 GVW |
| Auto. Trans. (2) | 550 | 5-30 |
| Man. Trans. (3) | 600 | 5-30 |
| 7.4L TBI |
| "C", "G", "K" & "P" Series |
| Auto. Trans. (2) | 750 | 5-30 |
| Man. Trans. (3) | 800 | 5-30 |
| (1) Add 2 counts for engines with less than 500 miles. On 4.3L V8 engines, add 2 counts for every 1000 ft. above sea level. On 2.5L & 2.8L engines, add 1 count for every 1000 ft. above sea level. (2) Automatic transmission in Drive. (3) Manual transmission in Neutral. (4) Set to +/-50 RPM from desired idle speed in Drive. (5) Calibration identification not given by manufacturer. IAC count and actual RPM should correspond to one of these calibrations. |
| (1) | Add 2 counts for engines with less than 500 miles. On 4.3L V8 engines, add 2 counts for every 1000 ft. above sea level. On 2.5L & 2.8L engines, add 1 count for every 1000 ft. above sea level. |
| (2) | Automatic transmission in Drive. |
| (3) | Manual transmission in Neutral. |
| (4) | Set to +/-50 RPM from desired idle speed in Drive. |
| (5) | Calibration identification not given by manufacturer. IAC count and actual RPM should correspond to one of these calibrations. |
CONTROLLED IDLE SPEED & IAC COUNT
MINIMUM IDLE SPEED
Note. Minimum idle speed adjustment can only be performed on the 7.4L engines. For minimum idle speed adjustment procedures, see ADJUSTMENTS article in the ENGINE PERFORMANCE Section.
| Application | RPM |
|---|
| Auto. Trans. (2) | 600-650 |
| Man. Trans. (3) | 675-725 |
| (1) Idle speed with seated IAC is lower than specified, if engine has less than 500 miles or when checked at altitudes above 1500 feet. (2) Automatic transmission in Drive. (3) Manual transmission in Neutral. |
| (1) | Idle speed with seated IAC is lower than specified, if engine has less than 500 miles or when checked at altitudes above 1500 feet. |
| (2) | Automatic transmission in Drive. |
| (3) | Manual transmission in Neutral. |
MINIMUM IDLE SPEED - 7.4L (1)
THROTTLE POSITION SENSOR
Note. Throttle Position Sensor (TPS) is adjustable only on 2.8L (VIN R) and 6.2L Diesel engines. For further testing, see TESTS W/CODES article in the ENGINE PERFORMANCE Section.
| Application | (1) Voltage |
|---|
| 2.8L (VIN R) | .42-.45 |
| 6.2L Diesel (VIN C & J) | (2) .63 |
| (1) At idle RPM or closed throttle. (2) This is a TPS voltage ratio. For adjustment procedure, see ADJUSTMENTS article in the ENGINE PERFORMANCE Section. |
| (1) | At idle RPM or closed throttle. |
| (2) | This is a TPS voltage ratio. For adjustment procedure, see ADJUSTMENTS article in the ENGINE PERFORMANCE Section. |
