MAIN HOME PAGE > Technical T O C > General Engine Specs > Ignition Conversion Page 1 > Lean Burn/Spark Control Computer (used from mid’70’s to the late 80’s)
Special thanks to John B. at: johnb66@aol.com for submitting the following infoREPLACING LEAN BURN/SPARK CONTROL COMPUTER IGNITION
Additional Tools Required
Electric drill
Wire cutter/stripper
12 volt test light
Roll of 14-gauge electrical wire
Two 14-gauge Scotchlok electrical connectors
One 14-gauge rounds eyelet electrical connector
Electrical tape
- Choose a suitable location for the Electrical control Unit (ECU). The ECU must be bolted down make sure the mounting location selected is a flat surface and can be drilled through. The ECU should be located away from the exhaust system, in the coolest place possible. Recommended locations are: the corner of the firewall; the inner fender well the radiator support panel/grill area; or under the dashboard, inside the car.
- Using the new wiring harness provided with the ignition kit, connect the two wire distributor wiring plug into the similar plug on the distributor. Place the five-wire ECU plug at the location chosen for mounting the ECU. Make sure the new wiring harness can be routed from the distributor to the ECU while avoiding exhaust parts and sharp edges. Try to follow the cars existing wiring harness.
- Once it is confirmed that the wiring harness will reach the location, use the ECU as a guide and mark the bolt holes on each side of the ECU.
- The attaching hardware to mount the ECU must be provided. It is not included in the kit. Either nuts and bolts or sheet metal screws can be used. If using sheet metal screws, make sure the sharp points will not damage or contact anything on the opposite side of the mounting location. If using nuts and bolts, make sure the nuts can be reached on the opposite side of the mounting location to tighten them. Drill holes to mount the ECU, making sure they are the correct size for the bolts or screws being used. Mount the ECU and tighten securely.
- connect the five-way plug to the ECU and route the distributor wires so they will be protected from harm. If possible, run them through existing looms and/or use plastic ties to secure them to the existing wiring harness.
- Remove all the wires connected to the ignition coil. If one of the existing wires is a tachometer feed wire, it may by reconnected. All other wired are to be left off. They should be covered with electrical tape and secured to prevent grounding out. They will not be used.
- Identify the three loose wires of the wiring harness. There will be a black wire (with a yellow tracer or line), a blue wire (with a yellow tracer) and a green wire (with a red tracer).
- The green wire is not used and should be cut off at the point where it comes out of the wiring harness’s protective wrapping.
- The black wire should be routed to the negative side of the ignition coil. Avoid the exhaust manifolds and sharp edges. Follow the cars existing wiring harness, if possible. Once suitably routed to the coil, cut the black wire to remove any excess. Strip the insulation off the last 1/4 inch of the wire. Crimp the round eyelet provided in the ignition kit to the exposed wire. Attach the black wire to the negative side of the ignition coil.
- Choose a location to mount the ballast resister. Do not remove the old ballast resister. Although the MP Ignition Kit will use the new ballast resister, other components of the vehicle may need the old resister.
- The attaching hardware to mount the new ballast resister must be provided. It is not included in the kit. Either a nut and bolt or a sheet metal screw can be used. If using a sheet metal screw, make sure the sharp point will not damage or contact anything on the other side of the mounting location. If using a nut and bolt, make sure the nut can be reached on the opposite side of the mounting location to tighten it. Drill a hole to mount the ballast resister. Make sure the hole is the correct size for the bolt or screw being used. Mount the ballast resistor and tighten. Do not over tighten the resister or the porcelain may crack.
- Route the blue wire to the new ballast resistor. Avoid the exhaust manifolds and sharp edges, follow existing wiring harnesses if possible. Do not cut the blue wire at this time.
- Locate the main ignition feed, or MIF, as it comes through the firewall at the master disconnect connector. Refer to the chart on page 8 and the connectors shown on page 9 to determine the style of master disconnect connector and the location of the MIF on the vehicles being modified.
- Temporarily, Turn the ignition key to the "on" position. Do not turn to the "start" position. Use a 12 volt tester to verify that the MIF found in step #31 has power when the key is in the "on" position and has no power when the key is in the "off" position.
- Turn the ignition key off and disconnect the negative battery cable.
- use 14-gauge wire and splice into the MIF. Do not cut the MIF. A splice must be made, the MIF must still power many other under hood functions. An electrical connector with the trademarked name Scotchloc is very useful. Slice or ScotchLoc the 14-gauge wire to the MIF, then securely wrap the splice with electrical tape to and prevent grounding.
- Route the spliced 14-gauge wire to the new ballast resister, where the blue wire of the new harness was routed in step #12.
- Allow 3 inches of extra wire for engine movement then cut off both the blue wire and the new wire spliced into the MIF. Strip 1/4 inch of the insulation from both wires. Place BOTH of the stripped wires into ONE of the 12-gauge female spade connectors and crimp securely. Wrap the connection with electrical tape to seal out moisture.
- Route a 14-gauge wire from the positive side of the ignition coil to the ballast resister. Avoid the exhaust manifolds and sharp edges. Follow existing wiring harnesses, if possible. Leave plenty of extra wire and cut off the new wire by the ballast resister. On the end of the new wire by the ignition coil, strip the insulation from 1/4 inch of the new wire. Crimp the 14-gauge wire from the positive side of the ignition coil to the ballast resistor.
- Locate the starter relay. It is usually located on the left (drivers) side shock housing or on the left side of the main bulkhead (firewall). A multiple wire connector will be connected to the starter relay. Carefully unplug the multiple-wire connector. Refer to Figure #2 on page 8 to determine the style of starter relay. Follow the instructions according to your style of starter relay.
Note: 1988 and newer cars/full size trucks/cans and 1990 and newer Dakotas do not have an under-hood starter relay. Refer to "Style B or No Relay")Style "A" Relay:
At the angles connector indicated by "BAL" in Figure #2 the vehicle may or may not have a corresponding 14-gauge wire in the multiple wire connector.
- If the multiple-wire connector has a corresponding wire for the "BAL" terminal, this is the Resistor By pass Wire (RBW). Plug the multiple-wire connector back onto the starter relay. Cut the RBW approximately 2 1/2 to 3 inches away from the starter relay. Make a new RBW by attaching a new wire to the old RBW coming from the starter relay connector so the new RBW connects to the starter relay. Crimp 14-gauge wire to the old RBW with the 14-gauge butt connector. Tape the connection to seal out moisture. Securely tape the end of the old RVW to prevent it from grounding to the vehicle.
- If the multiple-wire connector does not have a corresponding wire for the "BAL" terminal, create a Resistor Bypass Wire (RBW) from 14-gauge wire. On one end of the wire, strip 1/4 inch of insulation and crimp the 14-gauge female spade connector onto the new wire. Strip any insulation from the spade connector and plug the new connector and wire onto the unused "BAL" terminal. Thread the opposite end of the new wire through the previously unused hole of the connector and re-install the connector onto the starter relay.
Style "B" Relay or No Relay:
No additional wiring is required. On the new positive coil wire you created in step #19, strip 1/4 inch of insulation and crimp or solder a 14-gauge female spade connector to the end of the wire you ran from the coil to the ballast resistor. Wrap the connection with electrical tape to seal out moisture. Proceed to step #24.
- Route the new RBW to the new ballast resistor, where you previously routed a new wire form the positive side of the coil.
- Leaving 3 inches of extra wire for engine movement, cut off the new coil wire and the new RBW. Strip 1/4 inch of the insulation from both wires. Place both of the stripped wires into one of the twelve gauge female spade connectors and crimp securely. Wrap the connection with electrical tape.
- Plug the terminal containing the blue wire from the new harness and the MIF splice wire onto one end of the new ballast resister.
- Plug other new terminal (containing either the new positive coil wire and the new RBW wire or just the new coil wire) into the opposite end of the ballast resister.
Proceed to Logic Computer Controlled (used w/all TBI fuel injected cars)
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