Okay I'm sure this has been posted before , but I did not take the time to look it up. Just bought a 1979 Dodge Magnum. Over all very nice car. wants to run, but I'm thinking after sitting since 1993 it's gonna need a minute. So! What do you have to do to do a Lean burn delete? My understanding that " everything " runs through it. Your help is vastly needed.
1979 actually had a revised Electronic Lean Burn called Electronic Spark Control. It does not use the extreme lean running of Lean Burn and has better computer control, but operates similarly otherwise.
The following is conversion information from my document about converting the Electronic Spark Control system. Conversion details vary between the versions and what is being used.
For more conversion information, see the complete document at:
Replacing Chrysler Electronic Lean Burn, Electronic Spark Control, or Electronic Spark Advance with Earlier Electronic Ignition
For more information about Chrysler electronic ignition, including part numbers for ECUs, etc., see:
Chrysler Electronic Ignition
Conversion Items
New Items Required for Conversion
- Electronic distributor with pickup coil and vacuum advance unit (if vacuum advance is to be used)
- Electronic Control Unit (ECU). Note that early units were 5-pin and require a dual ballast resistor. Later and current units are 4-pin and use a single ballast resistor.
- ECU wiring - used from another vehicle, or new. Some sources include the following:
- Chrysler 3588421
- Mopar Performance/Direct Connection P3690152
- Mancini Racing MREP3690152
- Standard Motor Products S516
- Ballast resistor, to match the ECU. ELB has a dual ballast resistor. ESC has a single ballast resistor. These can be used or replaced.
- Carburetor: although earlier ELB and ESC carburetors can be retained and modified, replacing with an earlier,simpler, version to match the engine usually works better. ESA included electronic feedback carburetion, and the carburetor should be replaced. Without ESA, the carburetor will run full rich, and can be used, but tuning will be troublesome.
- Spade, and ring terminals, slices, electrical tape, and possible extra wire.
Existing Items that can be Retained
- Ignition coil.
- Distributor cap and rotor.
- Spark plug wires.
- Dual ballast resistor from ELB or single ballast resistor from ESC, but replacement might be needed.
- Carburetor, possibly, with modification.
- Air cleaner with computer removed. A block off plate can be added to cover the openings.
- Dual pickup start/run relay and associated wiring.
Items that can be Removed or Disabled
- Sensors:
- Carburetor idle stop/ground switch (retain if using for idle speed setting)
- Throttle position sensor
- Coolant switch
- Thermal Ignition Control (TIC) Coolant Switch, if equipped
- Detonation sensor
- Oxygen sensor
- NOTE: Additional switches, etc. might be present associated with EGR, etc, These are not associated with the system.
- Distributor
- Computer
- Computer wiring harness
Component and Wiring Removal
- Disconnect the battery.
- Unplug the two connectors from the computer and remove the air cleaner. NOTE: later 1980s M-body police vehicles have the computer inside the car.
- Remove coil secondary wire from the coil.
- Remove distributor cap and rotor, and set aside. Note the position of the rotor and the direction in which it points.
- Remove the wires connected to the ignition coil. If a wire is a tachometer feed wire, set aside to reconnect. The remaining wires will not be re-used and can be taped off and secured, or removed from the harness with the other computer wiring.
- Remove the distributor hold down bolt and clamp. Disconnect the wiring pickup connector.A dual pickup distributor has two connections.
- Remove the distributor. If the distributor has a vacuum advance canister, remove the hose and not the position of the canister in relation to the engine.
- Existing ballast resistor wiring and other wiring cuts to make:
- Cut the dark blue wire that connects to the resistor. Cut the wire on the computer side of the splice, leaving enough to splice later.
- Cut the black/yellow wire that connected to the coil to splice and keep the original terminal, if desired.
- NOTE: If the vehicle has the disconnect plug in the coil wiring, this can be retained.
- The computer wiring harness can be left and dressed out of the way, or can be separated from the engine and other ignition items wiring and removed from the vehicle. Specific wires for the original ballast resistor connections, if equipped, can be cut and retained to splice into the ECU wiring harness.
Distributor and ECU Installation
- Inspect the replacement distributor and check the air gap between the pickup coil and reluctor teeth. The air gap specification is .008". Check and set the gap with a brass, non-magnetic, feeler gauge at all eight reluctor teeth. If equipped with a vacuum advance canister, apply vacuum and re-check.
- Install the distributor with the rotor pointing in the same direction as the one removed, and with the vacuum advance canister positioned as with the old distributor, or positioned about in the middle of distributor rotation before it hits something.
- Install the distributor hold down bolt and clamp and lightly tighten for setting the ignition timing later.
- Re-install the original cap and rotor or new cap and rotor if replacing. Reconnect the coil secondary wire to the coil.
- Find a suitable location to mount the ECU on the firewall, fender apron, or other desired location, clear of other items. Position the ECU so that the wiring harness distributor lead will reach the distributor. This lead, and other wires can be lengthened as required.
- Mount the ECU solidly to the vehicle. The ECU is grounded through its case and the mounting screws. Use Chrysler number 6029513 toothed washer screws or equivalent to mount the ECU with a good ground.
- Connect the ECU molded plug on the wiring harness to the ECU.
- Route and connect the distributor twin lead molded connector to the distributor.
- Reconnect the vacuum hose if the original distributor had vacuum advance. Otherwise, the Carburetor Considerations section.
Wiring Installation
Single ballast resistor and 4-pin ECU:
Use the following diagram for the new ECU wiring harness connections as described in the following:
- Mount a single, two terminal, ballast resistor in a position to allow the wiring connections.
- Splice the blue/yellow wire with the dark blue wire previously cut, or add a new terminal to connect to the ballast resistor.
- Cut back the new green/red wire as it will not be used.
- Splice the new black/yellow wire with the black/yellow wire previously cut, or add a new terminal to connect to the negative terminal on the coil.
- Re-connect the tachometer lead to the negative side of the coil, if used.
- Connect the original dark blue wire from the ballast resistor to the positive terminal of the coil or connect new wiring as shown if used.
NOTE: If the vehicle has the disconnect plug in the coil wiring, this can be retained.
Other Electrical Considerations
1978 and later carburetors may have an electric solenoid bowl vent valve. This is wired into the Ignition RUN circuit. Be aware of its related wiring.
1976 - 1989 carburetors have an electric assist choke, except some trucks. This is wired into the Ignition RUN circuit. Be aware of its related wiring.
Start/Run Relay: Dual pickup distributors used a start/run relay to switch between the pickups when in start or run mode. After conversion to electronic ignition, the single pickup distributor is in place and connected directly to the ECU. The start/run relay has no effect at this point and can be left in place, unplugged, or removed.
Carburetor Considerations
Vacuum Advance
For a 1976 - 1979 ELB or ESC conversion, replacement with an earlier, simpler carburetor is preferred, but the original carburetor can be used. If used, it may not have a vacuum advance port or other desired features. An advance port can be added in some cases. For the Thermo-Quad carburetor, the following procedure can be used:
NOTE: The vacuum advance port is somewhat tricky and is best performed by comparison to an earlier throttle base that has the factory port to ensure proper placement of the transfer slot. Misplacing the vacuum idle transfer slot can cause an off-idle stumble and will necessitate additional tuning or replacement. To add the port, do the following:
1. Using a 5/32" drill bit, drill the throttle base where the vacuum port existed
on previous units. Drill into the open, roughly square, opening between the
outside and the throttle bore. This will accommodate the vacuum fitting.
2. Using a ~1/16" drill bit, drill two holes just above the throttle plate into the
same square opening from the throttle bore side, one hole adjacent to the other
and both parallel to the throttle plate.
3. Using a knife or small screwdriver, blend the holes together into a slot. This
slot serves as the off-idle transfer slot to feed the vacuum port.
4. Deburr and clean the drilled areas.
5. Press a short length of 5/32" pipe or an old fitting into the outside hole.
Idle Setting
Some carburetors will not have a conventional curb idle screw. ELB/ESC/ESA carburetor idle speed is controlled with the curb idle adjustment screw that contacts the "throttle closed switch contact". This contact signals the Spark Control Computer that the engine is at idle, or not. The contact is mounted on a bracket on the passenger side of the carburetor. There is also a transducer, but it is to sense throttle position and opening rate. Some had the conventional idle screw based on application. There are two approaches to the idle adjustment:
1) Retain the "throttle closed switch contact" bracket and adjust the idle there. This was the factory curb idle adjustment.
2) On Thermo-Quad carburetors, drill and tap the boss for the conventional idle screw. Drill the boss perpendicular and near the center, but align the hole with the throttle bracket extension. The factory screw size is 10-32. This approach yields an idle adjustment screw like earlier Thermo-Quads.
1980 and Later Electronic Feedback
The carburetors used with ESA had electronic feedback control in the carburetor. If the carburetor is operated without the ESA control, it will run full rich and basically be untunable. Some carburetors had sealed mixture screws and other tuning unfriendly features. In these cases, it is best overall to replace the carburetor with an earlier,simpler unit.
Completing the Conversion
- Double check all wiring routing and connections.
- Double check ECU mounting and ballast resistor mounting.
- Set the static timing of the engine, or try starting as is.
- After the engine is running, set the timing as shown in the service manual for a car with vacuum advance. The original model settings will no longer be correct, but initial settings for an earlier, similar engine can be used as a start for further tuning.
- If the carburetor was replaced, start by setting the idle speed and maximizing it with the mixture screws and peak engine vacuum. Further tune as an earlier, similar engine.
Excerpted and adapted from "Replacing Chrysler Electronic Lean Burn, Electronic Spark Control, or Electronic Spark Advance with Earlier Electronic Ignition", by Gary Lewallen, aka Vaanth
