Tune-Up - 6-cyl Dodge Ram Van II

ENGINE IDENTIFICATION

Engine can be identified by a number stamped on a pad on right side of block (below No. 6 spark plug). Engine can also be identified by 8th character of Vehicle Identification Number (VIN). VIN is located on a Gray plate attached to left corner of instrument panel and is visible through windshield.

Note. When ordering engine replacement parts, refer to engine serial number located on right side of block, below No. 1 spark plug.

ENGINE CODES

TUNE-UP NOTES

Note. When performing tune-up procedures, the following notes and precautions must be followed

1. Due to late changes and corrections, always refer to Emission Control Label in engine compartment before attempting tune-up. If manual and label differ, always use decal specifications.
2. For tune-up purposes, "Light Duty" refers to vehicles 8500 lbs. GVW or less which must conform to light duty emission standards and "Heavy Duty" refers to vehicles over 8500 lbs. GVW which must conform to heavy duty emission standards.
3. When performing tune-up on vehicles equipped with catalytic converters, do not allow or create a condition of engine misfire in more than one cylinder for an extended period of time. Total test time must not exceed 10 minutes or damage to converter may occur due to loading converter with unburned air/fuel mixture.
4. When inspecting distributor rotor, a Black silicone varnish will be noticed covering .20-.30" (.50-.80 mm) of rotor electrode tip. This replaces earlier silicone grease used to suppress electro magnetic radiation. Grease will darken with age, has an ash-like appearance and should not be removed. Ash formation (on both types of coverage) is normal and does not affect engine performance.
5. If it becomes necessary to replace the Spark Control Computer (SCC), do not disassemble computer for any reason. It is not serviceable and must be replaced as an assembly.

ENGINE COMPRESSION

Before performing compression test or cranking engine using remote starting switch, disconnect coil wire from distributor and secure to good ground. Check compression with engine warm, spark plugs removed and throttle wide open.

COMPRESSION SPECIFICATIONS

SPARK PLUGS

SPARK PLUG TYPE

SPARK PLUG SPECIFICATIONS

HIGH TENSION WIRE RESISTANCE

Note. Resistance type spark plug wires are identified by the words "Electronic Suppression" printed on cable jacket. Use an ohmmeter to check for open circuits, loose terminals and/or high resistance.

1. Carefully remove each spark plug wire from spark plugs. Detach coil wire from coil. Remove distributor cap without removing coil and spark plug wires.
2. Connect one ohmmeter lead to the coil or spark plug end of wire. Connect other ohmmeter lead to electrode inside distributor cap. Repeat procedure for the coil wire.
3. If resistance is not within specification, replace spark plug wire assembly and/or coil cable. Be sure to check ignition coil tower for carbon tracking, cracks and oil leaks.

HIGH TENSION WIRE RESISTANCE (OHMS)

Vacuum Test

Disconnect inlet and outlet fuel lines from fuel pump. Connect vacuum gauge to fuel pump inlet fitting. Using starter motor, turn engine over several times and observe vacuum gauge. Fuel pump should develop a minimum of 11 in. Hg. vacuum If not, replace pump.

Pressure Test

Connect a pressure gauge to fuel pump outlet fitting. Using starter motor, turn engine over several times and observe pressure gauge. If pump does not develop specified pressure, replace pump.

FUEL PUMP SPECIFICATIONS

VALVE ARRANGEMENT

E-I-E-I-E-I-I-E-I-E-I-E (Front-to-rear).

VALVE CLEARANCE

The 3.7L engine is equipped with hydraulic lifters and valve adjustment is not necessary. Valve clearance is at zero lash with engine at operating temperature.

DISTRIBUTOR

All 3.7L engine models use Chrysler Electronic Spark Advance (ESA) ignition system. Automatic transmission models have dual pick-up coil distributors. Manual transmission models have single pick-up coil distributors. Unless a pick-up coil has loosened or been replaced, no adjustments (other than basic timing) are necessary.

PICK-UP COIL AIR GAP ADJUSTMENT

If pick-up coil air gap is not to specification, turn adjusting screw to set proper air gap. Using a non-magnetic feeler gauge, set air gap (start pick-up to reluctor) to .006" (.15 mm). After adjustment, ensure a .008" (.20 mm) feeler gauge will not pass through gap.

On dual pick-up coil distributor, set run pick-up to reluctor air gap to .012" (.30 mm). After adjustment, ensure a .014" (.36 mm) feeler gauge will not pass through gap.

3.7L Timing Marks & Firing Order. Scheme 1

IGNITION TIMING

1. If a magnetic probe timing light is used, refer to equipment manufacturer's instruction for proper hookup. Use a 10° offset when required.
2. Turn off all lights and accessories. Disconnect and plug vacuum line at Spark Control Computer (if equipped), or at distributor. Connect a jumper wire between carburetor switch and ground (if equipped).
3. Connect tachometer to engine. Connect power timing light to No. 1 cylinder. Start engine and run in Neutral on second step of fast idle cam until normal operating temperature is reached. Ensure engine is running at or below curb idle RPM. If not, adjust curb idle. See HOT (SLOW) IDLE RPM in this article.
4. Quickly open and release throttle to ensure linkage does not bind and that idle speed screw is against its stop. Aim power timing light at timing marks or read magnetic timing unit. IGNITION TIMING SPECIFICATIONS (DEGREES BTDC @ RPM (1) ) Application Man. Trans. Auto. Trans. Calif. 12 @ 775 16 @ 775 Federal (2) 12 @ 725 (2) 16 @ 750 (1) Actual idle speed shown. Timing may be set between 500-900 RPM on Calif. models or 500-800 RPM on Federal and High Altitude models. (2) Idle speed on High Altitude models is 750 RPM for man. trans. and 775 RPM for auto. trans. CAUTION: Do not use distributor vacuum advance chamber as a turning handle when rotating distributor.
5. If timing is not within plus or minus 2° of specification, loosen distributor hold-down arm screw and rotate distributor housing to obtain correct timing. Tighten distributor hold-down screw when timing is correct.
6. Recheck idle speed and timing. If curb idle is not within plus or minus 50 RPM of specification, readjust idle and recheck timing. Repeat procedure until both idle speed and timing are correct. Turn engine off, reconnect vacuum lines and remove jumper wire and tachometer.

ELECTRONIC SPARK ADVANCE (ESA) CHECK

Note. Due to unique cold engine spark advance schedules (which change during engine warm-up), ensure spark advance testing is done with fully warmed engine and properly connected and operating temperature sensor.

1. Set ignition basic timing. Place thin insulating material (such as a piece of paper) between curb idle adjusting screw and carburetor switch. Remove and plug vacuum line at vacuum transducer.
2. Connect auxiliary vacuum source to transducer and set vacuum at 10 in. Hg. With engine warm, run engine at 2000 RPM for one minute (or accumulator clock up time), then check spark advance. See ELECTRONIC SPARK ADVANCE SPECIFICATIONS.
3. Advance specifications are in addition to basic advance. On some accumulator equipped systems, clock up time must be reached with carburetor switch ungrounded before checking specified spark advance schedule. Replace computer if advance is incorrect.

Note. On certain systems with an accumulator, specified time must be reached with carburetor switch ungrounded before checking specified spark advance schedule.

ELECTRONIC SPARK ADVANCE SPECIFICATIONS (1) (DEGREES BTDC @ 2000 RPM (2) )

Solenoid Idle Stop RPM

1. Ensure that ignition timing is properly adjusted. Disconnect and plug vacuum hose at EGR valve. Connect a jumper wire between carburetor switch and ground. Disconnect and plug 3/16" diameter control hose at canister.
2. Do not remove air cleaner. Prop up for access to carburetor. Remove PCV valve from cylinder head cover and allow valve to draw underhood air. Install tachometer. Start and warm engine to normal operating temperature.
3. Turn A/C on and set blower on "LOW". Disconnect A/C clutch wire. On non-A/C models, connect a jumper wire between battery positive post and solenoid idle stop lead wire. Be sure to jump proper wire or harness damage could result.
4. On feedback carburetor equipped models, disconnect and ground wire from oxygen sensor. Let engine run for 4 minutes before proceeding.
5. Open throttle slightly to allow solenoid plunger to extend. Remove adjusting screw and spring from solenoid. Insert a 1/8" Allen wrench into solenoid and adjust to correct RPM. See SOLENOID IDLE STOP RPM table. (Scheme 2)
6. Turn off A/C and replace A/C clutch wire (or remove jumper wire). Perform CURB IDLE SPEED adjustment. If no curb idle speed is to be made, see step 7) of CURB IDLE SPEED adjusting procedure in this section.

SOLENOID IDLE STOP (RPM) (1)

Adjusting Curb Idle Speed & Solenoid Idle Stop RPM (Shown With Idle Adjusting Screw & Spring Removed). Scheme 2

Curb Idle Speed

1. Ensure that ignition timing is properly adjusted. Disconnect and plug vacuum hose at EGR valve. Disconnect and plug 3/16" diameter control hose at canister.
2. Remove PCV valve from cylinder head cover and allow valve to draw underhood air. If necessary, prop up air cleaner for access to carburetor. Ground carburetor switch (if equipped) with jumper wire.
3. On California models, disconnect vacuum hose from heated air temperature sensor and plug hose. Remove air cleaner. Disconnect and plug vacuum hose at distributor. NOTE: DO NOT pull on wire attached to oxygen sensor. Disconnect "bullet" connector (located about 4" from oxygen sensor).
4. Disconnect engine harness lead from oxygen sensor connector, then ground engine harness lead. Remove and plug vacuum hose at vacuum transducer on Spark Control Computer (SCC). Connect auxiliary vacuum supply to vacuum transducer and apply 16 in. Hg vacuum.
5. On all models, install tachometer. Start and warm engine to normal operating temperature. On California vehicles, allow engine to idle for 2 minutes to allow effect of disconnecting oxygen sensor to take place. On Federal and High altitude vehicles, allow engine to run at idle for one minute to stabilize idle.
6. On all models, check idle speed. Adjust idle speed screw on solenoid to obtain correct idle RPM. See CURB IDLE SPEED table. (Scheme 2)
7. Turn off engine and remove tachometer. Reconnect oxygen sensor. Remove auxiliary vacuum supply and reconnect all vacuum lines and hoses. Remove jumper wire from carburetor switch. Reinstall PCV valve.

Note. After adjustment, idle speeds may vary from specifications. This is normal and no readjustment is necessary.

CURB IDLE SPEED (RPM)

IDLE MIXTURE

Note. Idle mixture adjustment is not part of a regular tune-up. DO NOT adjust mixture unless carburetor has been disassembled or vehicle fails emissions testing.

Mixture Screw Plug Removal

1. Remove air cleaner. Disconnect and mark (for reassembly) all vacuum hoses from front of carburetor. Center punch idle mixture screw housing 1/4" from end of housing. (Scheme 3)
2. Drill through outer section of housing at punch mark with 3/16" drill. Pry plug out of housing and save for reassembly. Reconnect vacuum hoses and install air cleaner.

Removing Mixture Screw Concealment Plug (Drill Through Outer Section Of Housing And Pry Out Plug). Scheme 3

Propane Enrichment Procedure

1. Remove concealment plug. Set parking brake and place transmission in Neutral. Turn all lights and accessories off. Connect tachometer to engine. Start engine and allow to warm up on 2nd highest step of fast idle cam until normal operating temperature is reached. Return to idle.
2. Disconnect and plug vacuum line at Spark Control Computer (if equipped), or at distributor. Disconnect and plug vacuum hose at EGR valve. If necessary, prop up air cleaner for access to carburetor. Ground carburetor switch with jumper wire.
3. Disconnect vacuum supply hose from choke diaphragm at the "Tee" fitting and install propane supply hose. Other connections at "Tee" fitting must remain in place.
4. With propane bottle held upright and in a safe location, remove PCV valve from rocker cover and allow valve to draw underhood air. Disconnect and plug 3/16" diameter control hose from canister. NOTE: DO NOT pull on wire attached to oxygen sensor. Disconnect "bullet" connector (located about 4" from oxygen sensor).
5. On California models, disconnect engine harness lead from oxygen sensor connector and ground. Remove and plug vacuum hose at vacuum transducer on computer. Using auxiliary vacuum supply, apply 16 in. Hg to vacuum transducer.
6. On all models, allow engine to run for 2 minutes to stabilize idle. Open propane main valve. Slowly open propane metering valve until maximum RPM is reached (too much propane will decrease RPM). "Fine tune" metering valve to obtain highest engine RPM. With propane still flowing, adjust idle speed screw on solenoid to reach specified RPM.
7. Adjust metering valve again to reach maximum RPM. If there has been a change in maximum RPM, readjust idle speed screw to specified RPM. Turn off propane main valve and allow engine speed to stabilize. Slowly adjust idle mixture screw (1/16 turn at a time), waiting 30 seconds between adjustments, until smoothest idle at specified RPM is reached.
8. Turn on propane main valve and "fine tune" metering valve to obtain highest engine RPM. If maximum RPM is more than 25 RPM different from specified RPM, repeat steps 6) and 7).
9. Turn off propane main valve and metering valve. Remove propane supply hose and carburetor switch ground wire. Reconnect oxygen sensor lead and all vacuum hoses. Remove test equipment. Install concealment plug. Perform all idle speed adjustments.

Note. After adjustment, specified RPM may vary. This is normal and does not require readjustment.

PROPANE MIXTURE ADJUSTMENT (RPM)

COLD (FAST) IDLE RPM

1. Ensure that ignition timing is properly adjusted. Turn off all lights and accessories. Disconnect and plug vacuum line at Spark Control Computer (if equipped), or at distributor. Disconnect and plug vacuum hose at EGR valve. Disconnect and plug 3/16" diameter control hose at canister.
2. Remove PCV valve from cylinder head cover and allow valve to draw underhood air. Install a tachometer. On Federal vehicles, prop up air cleaner for access to carburetor. Ground carburetor switch with jumper wire. NOTE: DO NOT pull on wire attached to oxygen sensor. Disconnect "bullet" connector (located about 4" from oxygen sensor).
3. On California models, disconnect engine harness lead from oxygen sensor connector and ground harness lead. Start engine and run at idle for 4 minutes to allow effect of disconnecting oxygen sensor to take place. On all other vehicles, start and warm engine to normal operating temperature.
4. On all models, open throttle slightly and place fast idle adjustment screw on second highest step of fast idle cam. With choke fully open, turn fast idle adjustment screw to obtain proper fast idle RPM. See FAST IDLE SPEED (RPM) table. (Scheme 4)
5. Return to idle speed, then reposition fast idle adjustment screw on second highest step of fast idle cam. Check fast idle RPM and readjust if required. Return to idle speed and turn off engine. Remove test equipment and reconnect all components.

Note. After adjustment, fast idle speed may vary from set speed under normal operating conditions (all wires and hoses connected). This is normal and does not require re-adjustment.

FAST IDLE SPEED (RPM) (1)

Fast Idle Adjustment Screw Location (Holley Model 1945 Shown. Holley Model 6145 Is Similar). Scheme 4

AUTOMATIC CHOKE

All models are equipped with non-adjustable choke covers. However, choke linkage and shaft must move freely hot or cold. Choke rods must be examined carefully for damage or bending. Use caution when installing carburetor to prevent damaging of choke rod. Do not force rod if it becomes trapped, release it by removal only.

Choke Valve Shaft

1. To prevent choke from sticking due to gum deposits on shaft, spray Mopar Combustion Chamber Conditioner (4318001) onto choke shaft where it passes through air horn. NOTE: Service choke valve shaft, fast idle cam and pivot pin every 12,000 miles for heavy duty models and every 30,000 miles on light duty models or every 12 months, whichever comes first.
2. Move choke blade back and forth to distribute solvent. Apply solvent to fast idle cam and pivot pin to remove dirt, oil and other deposits that may have collected which could cause sticking or erratic motion.

All 3.7L engine models use Chrysler Electronic Spark Advance (ESA) ignition system. Automatic transmission models have dual pick-up coil distributors. Manual transmission models have single pick-up coil distributors. Unless a pick-up coil has loosened or been replaced, no adjustments (other than basic timing) are necessary.

DISTRIBUTOR PICK-UP COIL RESISTANCE

DISTRIBUTOR PICK-UP COIL AIR GAP (1)

IGNITION COIL & BALLAST RESISTOR

IGNITION COIL RESISTANCE (OHMS) (1)

BALLAST RESISTOR RESISTANCE (OHMS) (1)

ALTERNATOR REGULATOR

All models use Chrysler Corp. Electronic Voltage Regulator. Unit is nonadjustable. Ensure battery specific gravity is above 1.200 when checking regulated voltage.

REGULATOR OPERATING VOLTAGE @ 80°F (27°C)

EMISSION CONTROL

For information on emission control systems, see EMISSION CONTROL section.

FUEL SYSTEM

CARBURETORS

BATTERY

BATTERY SPECIFICATIONS

STARTER

All models use Chrysler Corp. reduction gear type starter.

STARTER TEST SPECIFICATIONS (1)

ALTERNATOR

ALTERNATOR SPECIFICATIONS

DRIVE BELT ADJUSTMENT

SERVICE INTERVALS

REPLACEMENT INTERVALS

CAPACITIES

COOLING SYSTEM CAPACITIES

ENGINE OIL & FUEL CAPACITIES

TRANSMISSION, TRANSFER CASE & DIFFERENTIAL CAPACITIES

A/C SYSTEM REFRIGERANT CAPACITIES