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4.2L MPI Installation Instructions

Contributed By: Tom Anhalt

JEEP 4.2 LITER (258 CID)

P5249610 For Manual Transmission Vehicles
P5249686 For Automatic Transmission Vehicles




This product is intended for use on STOCK, UNMODIFIED, WELL MAINTAINED 1981-1990 4.2 LITER (258 cid.) ENGINES. Installation on engines with MODIFIED CAMSHAFTS, INCREASED COMPRESSION RATIO or engines that are in POOR MECHANICAL CONDITION, such as LOW CRANKING COMPRESSION or EXCESSIVE OIL CONSUMPTION is not recommended.

NOTE: If spark knock (detonation) occurs, it is recommended that 92 octane or better premium fuel be used. The use of Mopar combustion chamber cleaner will reduce carbon deposits and help reduce spark knock.


1. Disconnect the ground cable from the battery and drain the coolant from the radiator.

2. Loosen the power steering pump and the alternator and remove the drive belts. Remove the two bolts that hold the power steering pump to the water pump. Remove the two nuts from the rear power steering pump bracket, then slide the pump forward to disengage it from the rear bracket. Remove the rear bracket from the intake manifold.

3. Remove the air cleaner assembly as a unit and discard it.

4. Remove all of the production emissions controls from the engine, including the three (3) solenoids located on top of the valve cover, the vacuum switch assembly and any lines and delay valves connected to the carburetor.

NOTE: Refer to the Production Emissions Schematic or to a proper shop manual for your particular year vehicle.

5. Remove the pulse air valves, which inject fresh air upstream and downstream of the catalytic converter, and all associated fittings.

6. Disconnect the heater hose from the fitting on the intake manifold. Remove the throttle linkage and throttle cable. Remove the carburetor/intake manifold assembly. This will require removing the tube that connects the exhaust manifold to the EGR valve mounted on the intake manifold.

NOTE: It is not necessary to remove the exhaust manifold.

7. Remove the stock mechanical fuel pump and fuel lines from the engine. Make sure to mark the lines PRESSURE and RETURN where you disconnect them at the fender well.

CAUTION: GASOLINE IS HAZARDOUS!! Wear eye protection and never work on a HOT engine or around FIRE OR FLAME!

8. Disconnect the upper and lower radiator hoses and remove the radiator, fan shroud, engine fan, thermostat housing and crankshaft pulley.

9. Remove the plug wires and distributor cap. Remove the #1 spark plug and rotate the engine in its normal direction until the #1 piston is on the compression stroke. The timing mark on the dampener should line up with the "O" mark on the timing tab. Looking through the stock fuel pump mounting boss, rotate the engine backwards until the camshaft moves and note the amount of slack in the timing chain as degrees on the timing tab. If the slack is more than 10 degrees, replace the timing chain. Rotate the engine in the direction of rotation to the "O" of the timing tab. Note the clocked position of the distributor rotor. Loosen the hold down clamp and remove the distributor. Remove the ignition coil and bracket and discard them.

10. Using a suitable puller, remove the crankshaft dampener. You will need a new dampener, P5249688 for serpentine belt, or P5249687 for V-belt driven pulleys.

11. Remove the brake booster fitting from the old manifold and install it in the new manifold.

12. Remove the windshield washer bottle and the charcoal fuel cannister. Be sure to mark the vacuum lines that go from the fuel cannister to the intake manifold and the fuel tank.

13. Remove the front three (3) driver's side oil pan bolts.

14. Remove the oxygen sensor from the exhaust manifold.

15. If the vehicle has a catalytic converter, it will be necessary to seal the air injection tubes at the CAT and header pipe. Seal by bending the end of the tube and crimping.


1. Install the new oxygen sensor in the exhaust manifold.

2. Cut off one end of the tube that went from the exhaust manifold to the EGR valve and remove the tube nut from it. Install the saucer shaped freeze plug into the hole in the exhaust manifold where you removed the EGR tube. Secure the freeze plug by tightening the now free tube where nut down against the freeze plug.

3. Install the new distributor (The distributor is shipped with an indexing lock pin and will not rotate. DO NOT REMOVE THE PIN UNTIL THE DISTRIBUTOR IS INSTALLED).

NOTE: If you think the engine may have moved from TDC, make sure the engine is at TDC on the crankshaft balancer. Install the hold-down clamp and remove the white locking pin.

4. Install teh conbination fuel pump block-off plate/ignition coil bracket where you removed the original fuel pump. Install the coil with the plug wire terminal toward teh distributor.

5. Install the new crankshaft dampener. (Torque the bolt to 120 ft. lb.)

6. Install the pickup sensor bracket. The bracket bolts to the oil pan where you removed the three (3) bolts in step #13 of the disassembly instructions. Install the pickup sensor on the bracket with the bolt provided. NOTE: There should be between .020" and .060" clearance between the sensor and the crankshaft dampener. This clearance is the thickness of the paper button on the end of the sensor. You push the sensor up against the dampener, then tighten the mounting screw. This will set the initial clearance.

7. Install the crankshaft pulley, the fan, and the radiator. Install the new 195 degree thermostat. This is critical. Temperature level of 195 degrees is critical for fuel system operation. Install the coolant sensor supplied into the new thermostat housing in the 3/8" pipe hole, then reinstall this new assembly on the engine. Reinstall the radiator hoses and heater hoses; reroute the new heater hose supplied, as it no longer goes through the intake manifold.

8. Install the new intake manifold. You will only be able to reinstall one of the power steering pump bracket bolts and You may have to trim the top lip off of the power steering pump bracket to make it fit the new manifold. DO NOT over tighten the bolts! Bolt torque is 23 ft. lb.

9. Install the throttle cable and bracket.

10. On automatic transmission vehicles: the kickdown linkage must be installed Once these parts are assembled, you should set the adjustment. Rotate the throttle body to wide open throttle. This will cause the cable to ratchet to the proper zero clearance. At this time, verify that the throttle linkage works smoothly and returns to IDLE (closed throttle).

11. Reinstall power steering pump bracket and belts. Tension the belts. The hole in the bracket may need to be enlarged slightly.

12. Connect the new fuel lines to the fuel rails and attach to the mounting bracket on the new intake manifold. Find the fuel inlet line where it was connected to the stock mechanical fuel pump (NOTE: Some CJ models have the fuel supply line routed down the right passenger side of the vehicle.) Trace this line back across the engine bay to the driver's side frame rail. Cut this line and the fuel return line a few inches behind the front leaf spring eye. Bend them up slightly to align with the new fuel lines that come from the MPI fuel rail. Connect the lines with the 5/16" fuel hose and clamps provided. NOTE: The new fuel lines look almost identical. You will note that one has an orange dust cap over the quick connect. This is the return line, or fuel out, and has the smaller 0-rings inside. It connects to the new fuel rail on the forward end of the line coming out of the fuel pressure regulator. The pressure line has a yellow dust cap over the quick connect which has the larger 0-rings inside and connects to the second connection on the fuel rail. IT IS IMPERATIVE THAT THESE LINES ARE CONNECTED PROPERLY. Improper connection can cause damage to the fuel pump. THE RETURN FUEL LINE GOES FROM THE FUEL REGULATOR (on the fuel rail) BACK TO THE FUEL TANK.

NOTE: On models with the fuel supply line on the right side, carefully route the line around to the fuel rail similar to the O.E. setup.

CAUTION: If you buy any fuel line to hook up the fuel pump, make sure it is rated to handle EFI pressures!


13A. Jack up the rear of the vehicle and place on jack stands. From under the vehicle looking to the rear you will notice a cross member in the frame above and behind the axle housing. On the driver's side of this cross member you will notice a rubber block with three (3) flexible fuel lines emerging from it. The lines turn 90 degrees toward the frame and are connected to hard lines with clamps. On the flange of the cross member are three (3) bolts that attach the fuel tank skid pan to the cross member.

13B. Remove the center bolt.

13C. Disconnect the center fuel line from its hard line at the clamp. Reconnect this flexible line to the inlet of the new fuel pump assembly using the same clamp.

13D. Mount the fuel pump assembly to the cross member flange using the nut and lock washer.

13E. Connect the 5/16" flexible line coming off the new fuel pump assembly to the fuel filter inlet line, with the clamp provided, and the fuel filter outlet to the center hard line of the original fuel line.

14. Install the new charcoal cannister in the stock location and hook up the new vacuum lines. Some engines will not use the plastic valve cover fittings. The many different valve covers have different PCV and fresh air fittings. Make sure to use the stock 258 PCV valve or orifice at one end of the valve cover and provide fresh air at the other end of the cover. It is important that the engine is ventilated properly to meet emissions and reduce oil leaks caused by crankcase pressure.

15. Install the new Powertrain Control Module (PCM) right above the charcoal cannister on the bulkhead with the supplied hardware.

16. Plug in the wiring harness to the PCM using the 60-pin connector. DO NOT OVER TIGHTEN THE CONNECTOR! Drape the harness over the top of the master cylinder, then around the back side of the engine.


17. Find the two relays on the harness a short distance from the PCM. Mount them to the bulkhead with the screws provided. NOTE: Mount the relays with the wires pointed down. This is to prevent water build-up within the relays. The PCM may be mounted at any angle, however, do NOT mount it with the wire connector facing up. This would allow water to pool in the connector! The PCM is waterproof. The 60-pin connector is splash proof, but will not work when immersed in water.

18. Mount the MAP sensor to the bulkhead right behind the engine with the screws provided. Plug the green three (3) prong plug from the harness into the MAP sensor.

19. Route the harness down along the valve cover toward the front of the engine. Connect the fuel injectors. Each one is marked where it goes.

20. In the center of the harness between injector plugs #3 and #4 is a group of four plugs. Connect three (3) of these to the throttle body in their respective receptacles, and the fourth one to the Manifold Air Temperature (MAT) sensor.

21. In the harness at the front of the engine is another group of three (3) plugs. One of them is very long; this is the Oxygen Sensor plug. The three (3) prong plug in this group is the pickup sensor plug. The other (two prong) plug is the coolant sensor plug. These will only plug in to the correct sensors. Secure the cables with tie wraps provided. Make sure the pick up sensor connector is tied away from the exhaust manifold.

22. Bend the harness toward the passenger side of the Jeep and down along the spark plug side of the head. The next plug is the ignition coil connection. Then comes the harness ground with the distributor plug. Connect the harness ground under the bolt that holds the dipstick tube to the engine block. (it has other ground wires on it. Do not remove any.) Connect the distributor.

23. Route the rest of the harness along the top of the transmission. The next plug will be the vehicle speed sensor. Route the remaining harness along the frame rail to the rear of the Jeep' to connect the fuel pump power (+) to the green wire with the black stripe. The ground wire is black with an orange stripe. Secure the harness all along its length in strategic locations with the tie wraps provided. Make sure that there is clearance between any moving parts or areas of high temperature, such as the vehicle exhaust. You may want to use dielectric grease on the connections to prevent corrosion (Mopar part number J8126688).

24. To supply a switched 12 volt power supply to the two bulkhead mounted relays, locate the old positive (+) side coil wire (usually a yellow color). Connect this wire to the relay wire. Now connect the red relay wire to the starter relay, battery plus(+). The starter relay is usually located under the battery box or mounted on the fender panel. Mount the system fuse.

NOTE: Make sure that the switched 12 volt wire is not routed thru a ballast resistor or resistance wire. Also make sure that 12 volts are present on this wire during cranking!

25. Install the 7.5 amp diode (supplied) in the field wire of the alternator. This is the smaller of the two wires, usually brown in color, that plugs into the alternator. Cut the wire and install the diode with the pink crimp-on connector facing toward the alternator. It is imperative that this diode be in the field circuit to protect the new electronics.

26. You may wish to install a new windshield washer bottle and bracket. These can be obtained through your local Jeep/Eagle dealer. Washer bottle part number is 55154744; bracket is 55026288.

27. Install the new air filter and bracket. It attaches to the driver's side body support rod. Connect the two 1/2" hoses, from the aluminum connectors, to the valve cover vent and the fuel cannister vent line.

28. OPTIONAL: If you wish to install a tachometer or an engine light, the wires for these are already in the harness, located close to the relays. They will be hanging out of the harness. The tachometer wire is light gray with a yellow stripe. This is the tachometer trigger wire. The O.E. 81-90 Jeep tachometer WILL NOT work with this system. The tach wire switches a 5V signal two times per engine revolution. Set your aftermarket tach on the 4-cylinder scale to achieve a true RPM reading. Some tachs will not work with this 5V signal, or they may have needle flutter at low RPM. If this is the case, you will have to splice into the coil negative side to operate your tach. If you hook up to the coil, use the 6-cylinder setting on your tach. The coil negative side wire is gray. (Hook up the tach last, after the engine is running, because some tachs have a low impedance and will short the coil to ground. This will not harm anything, but will prevent the engine from running.)

29. The "check engine light" wire runs directly to the PCM. The PCM grounds this wire to turn on a light to display fault codes. The light bulb holders are available at any local electronics supply.

30. On automatic transmission Jeeps, the brown wire that is coiled near the PCM connector must be connected to the neutral safety switch. This wire can be connected to the bottom of the starter relay, or to the center terminal on the neutral safety switch. On Chrysler automatics, this is the center terminal. If you choose to connect it to the starter relay, make sure that the terminal is for the neutral start switch. It should be grounded in park and neutral. This wire is for improved idle quality when in "Drive"

31. Reconnect the battery and turn on the ignition key. You should hear the electric fuel pump run for a few seconds and then shut off. Start the engine and IMMEDIATELY CHECK FOR FUEL LEAKS. Depending on the ambient temperature, the idle RPM may be high initially, and decrease as the engine warms up. This is normal!! Do not try to adjust the RPM by changing the opening of the throttle blade. Test Drive! Recheck all connectors and fuel lines!

32. Be sure to apply the CARB E.O. decal supplied in the kit in a visible location under the hood.

Hints we have found useful

1. This system is the same as used on the 1994 4.OL Wrangler. If you need service parts, or are checking fault codes, refer to the 1994 Jeep Wrangler Service Manual. The wiring is also the same as a 1994 Wrangler in function and color. You may call 1-800-626-1523 to order a service manual.

2. The crankshaft sensor is very sensitive. Make sure it is solidly mounted. Make sure that your engine does not have too much crankshaft end play. The paper button on the sensor will wear off with use of the engine.

3. The distributor should not be turned to change timing. It will not. The distributor is set to have the rotor tip .020' past #1 spark plug terminal with the engine at TDC.

4. The fuel return line to the tank must be unrestricted. Check this carefully before you hook up the return hose.

5. You may see fault codes for charging system too high or too low. This is normal and should be ignored.

6. The PCM does take some time (15 - 30 minutes) after first use to "learn" the best settings for your engine. You will notice better idle quality and acceleration after this learning period. For this reason, the battery should be left connected if this vehicle is to be driven daily. If you use a kill switch, do not interrupt the B+ circuit or the PCM will need to "re-learn" every time you start the engine.


1) WIRING HARNESS P4532698 1 51) THROTTLE BODY 04856107* 1
3) COOLANT SENSOR 33004281 1 53) 3/16' VACUUM CAP 9400049 * 1
4) INTAKE MANIFOLD 9400045* 1 54) FUEL LINE CLIP 34202997* 1
5) FUEL INJECTOR CLIPS 04418257* 6 55) VACUUM PORT 53004523* 1
6) FUEL INJECTOR 53030343* 6 56) SPEED SENSOR 56027015* 1
7) FUEL INJ LINE-INLET 52018416 1 57) MAP SENSOR BRACKET 56027080 1
8) FUEL INJ LINE-RETURN 52018417 1 58) 5/8"X7/8" SPEEDO ADAPT 9400012* 1
9) FUEL PRESSURE REG 53030001* 1 59) 1/2" PCV HOSE 9400048 2
10) FUEL RAIL ASSEMBLY 53030435 1 60) 1/2" PLASTIC HOSE SPLC 9400016 2
11) THROTTLE CABLE 52079382 1 61) 3/16" TUBE X 1/4" NPT 9400018* 1
12) THROTTLE CABLE BRCKT 53007486* 1 62) #10 X 1/2" SHEET METAL SCREW 9400020
13) COIL BRKT & FUEL PMP PLATE P4532710 1 63) 1/4" TUBE X 1/4" NPT 9400019* 2
14) IGNITION COIL 04797293 1 64) M5 X 20MM CAP SCREW 9400021* 1
15) SPARKPLUG WIRE SET 83507178 1 65) 1/4" NC X 1-1/4" CAP SCREW 9400025 2
16) OXYGEN SENSOR 56028301 1 67) 1/4" NC X 1 l/2" CAP SCREW 9400022* 1
17) CRANK SENSOR 56026884* 1 68) M6 X 20MM CAP SCREW 9400023* 4
18) THROTTLE BODY ELBOW 53006289 1 69) M8 X 20MM CAP SCREW 9400024* 1
19) THROTTLE BODY CLAMP 53008274 2 70) 5/16" X 1" CAP SCREW 9400030* 1
20) FUEL PUMP-ELECTRIC P4532709 1 71) M5 FLAT WASHERS 9400027* 3
21) FUEL FILTER 33000076 1 72) M6 FLAT WASHERS 9400028* 11
22) FUEL HOSE-18"X5/16" 9400047 1 73) 5/16" FENDER WASHER 9400029* 1
23) FUEL PUMP CLAMP MNT 9400009 1 74) 5/16"X1-1/4" CAP SCREW 9400030* 1
24) HOSE CLAMPS 5/16" 9400002 9 75) M8 LOCK WASHER 9400031* 1
25) INTAKE HOSE-CAT 18" X 2-3/4" 9400008 1 76) M5 HEX NUTS 9400032* 2
26) AIR FILTER ADAPTER 9400007* 1 77) 1/4" NC NYLOC NUTS 9400034* 2
27) K&N AIR FILTER 9400003 1 78) 5/16" NC NYLOC NUTS 9400035*
28) CLAMP 2-3/4" WORM 9400013 2 79) 3/16" VACUUM HOSE 9400036* 1
29) ADAPTER HOLDDOWN CLAMP 9400006 1 80) 2.5" ADEL CLMP (FUEL FILTER) 9400037 1
30) INTAKE HOSE ADAPTER 9400005 1 81) 1/4" NC X 1" CAP SCREW 9400039 2
31) VENT TUBE 1/2" X 3/8" X 90' 9400010 2 82) 3/16" FLAT WASHER 9400040 2
32) CRANK SENSOR BRACKET 9400004* 1 83) 1/4" FLAT WASHER 9400041 3
33) MAT SENSOR 33004280* 1 84) CONCAVE EXPANSION CUP 9400042 1
34) MAP SENSOR 33000153 1 85) INSTALLATION INSTRUCTS 9400043 1
35) FUEL CANNISTER 53030500 1 86) DIODE SPLICE 9400044 1
36) TIE WRAPS 4" 9400014 1 87) #10 X 2" SHEETMETAL SCREWS 9400015 3
37) THERMOSTAT 4494469 1 88) VACUUM TUBE 53006237 1
39) M6 X 14M CAP SCREW 9400052 7 90) 3/8" MOUNTING CLAMP 9400054
42) VACUUM TUBING 53030728 1
44) VACUUM TUBE 53006226 1
45) VACUUM TUBE 53030473 1
46) VACUUM TUBE 53030474 1
48) M5 X 30M CAP SCREW 9400011* 2
49) FUEL PRESS. REG. CLAMP 04418897* 1


The author wishes to extend his appreciation to Terry Morris and Robert Flowers from the Jeep-L mailing list

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