Jeep Wrangler/YJ 1987-1995 Repair Guide

Single Board Engine Controller (SBEC II) System

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The 1991-92 2.5L and 4.0L Engines are equipped with multi-port fuel injection. The ignition system, which is operated by the Single Board Engine Controller (SBEC II), consists of:



Spark plugs
 
Secondary ignition cables
 
Ignition coil
 
Distributor (contains rotor and fuel sync sensor)
 
Single Board Engine Controller (SBEC II)
 
Crankshaft position sensor
 

DIAGNOSIS & TESTING



Testing for Spark at the Coil

See Figure 1



Click image to see an enlarged view

Fig. Fig. 1: When checking for spark only hold the wire using an insulated tool or you risk a BAD electrical shock

Remove coil secondary cable from distributor cap. Using a suitable tool, hold the end of the cable about 1 / 4 in. from good engine ground. Crank engine and look for good, constant spark at coil secondary wire. If spark is constant, have a helper continue to crank engine while moving coil secondary cable away from ground. Look for arcing at the coil tower. If arcing occurs, replace the coil. If no arcing occurs, ignition system is producing the necessary high secondary voltage. Make certain this voltage is getting to spark plugs by checking distributor rotor, cap, spark plug wires and spark plugs. If all check in good condition, ignition system is NOT cause of problem.

If spark is weak, not constant or not present, continue with Failure To Start test.

Testing Secondary Circuit
  1. Remove the center wire from the distributor cap.
  2.  
  3. Using insulated pliers, hold the terminal end about 1 / 2 in. (13mm) from the engine head and crank the engine.
  4.  
  5. If a spark jumps from the wire to the head, reconnect the wire and remove a wire from one of the spark plugs.
  6.  
  7. Make a metal extension to insert in the spark plug wire boot, and, holding the wire and extension about 1 / 2 in. (13mm) from the head, crank the engine.
  8.  
  9. If a spark occurs, check the engine control sensors using tester DRB II, or equivalent. If the sensors check out okay, the problem is probably in the fuel system.
  10.  
  11. If no spark occurs, The rotor, distributor cap or spark plug wires are defective.
  12.  

 
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