Can QCSC DAS electronically find a 'jumped' timing chain? YES

If the engine has cam and crank sensors we can measure the normal relationship between the ID or sync pulse and the reference pulse.

85 Riviera 3.8L/Distributorless/C3I-Type 1

All readings taken at the ignition module with the engine CRANKING.

All square waves are 0 volts when low and 7 volts when high.

ch0=crank signal, pin 'F', blu/wht ch1=cam signal, pin 'K', brn/wht ch2=reference, pin 'C', ppl/wht

The snapshot below shows that the offset between the rising edge of the cam signal and the rising edge of the next crank/reference pulse is 29 degrees (effectively 30 degrees). It also shows that the rising edge of the cam pulse is 91 cranksha ft degrees ( effectively 90) after the preceding crank-in pulse.

If we saw that this relationship had varied, we could suspect a timing chain problem.

Both ch0 (the crank sensor) and ch1 (the cam sensor) are 12 volt hall-effect sensors (switches), however, they both produce a wave that is either 0 volts or 7 volts. The crank sensor will average about 3.5 volts on a DVOM when the engine is running. Ch2 (the reference pulse) will also average about 3.5 volts when the engine is running. All these signals can be checked with a DVOM.

See same vehicle with engine running

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QCSC DAS Copyright 1997 -- Developed by; Daniel A. Buckley (NIASE GAM-CMAT-L1)

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