The injectors, coils, and fuel pump or pump relay all get 12 volts from the Automatic Shutdown (ASD) relay for only two seconds when the ignition switch is turned on, then again when the engine computer sees engine rotation (cranking or running). It knows the engine is rotating by the pulses from the crankshaft position sensor.
There's a clinker though. This is an interference engine meaning if the timing belt breaks, the open valves will hit the pistons and become bent. To prevent this, the engine computer watches the relationship between the pulses from the crankshaft position sensor and the camshaft position sensor. If the timing belt jumps one tooth, the engine computer turns on the "Check Engine" light and sets a fault code in memory. If the belt jumps two teeth, the computer shuts the engine down. If it jumps three teeth, the pistons can hit the valves and damage them.
The computer shuts the engine down by turning off the ASD relay. That's why you have no spark. The first thing to do is check the camshaft timing to be sure the timing belt didn't skip a tooth or two. If the cam timing is ok, or if it's too hard to get to the crank sprocket, remove the camshaft sprocket and check for a sheared off locating pin. This has been a real common problem. Although the sprocket and timing belt are in perfect time, the camshaft is late because it slipped a little on the sprocket. Since the cam sensor is on the other end of the camshaft, its pulses are late too, and the engine computer interprets that as an out-of-time camshaft, ... Hence, ... Shutdown!
Replace that dowel pin, and it will probably start right up. There is a relearn procedure that involves the Chrysler DRB3 scanner, but that is often unnecessary.
Caradiodoc
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Saturday, March 21st, 2009 AT 12:34 AM
