Help please: 95 Northstar no start problem

joe graham velocity150 at hotmail.com
Thu Mar 21 19:48:30 GMT 2002


>My first incling is that the ecu is loosing, not getting, or getting the
wrong synk pulse, the  ecu and dis unit both get signals from the cam and
crank sensors.<

ECM gets 4x, 24x,and cam signal from DIS module.

>the ecu uses the crank signal as a referance untill it sees a
cam signal to ''''phase" itself. both sensors go through the dis module
(there are actually 2 crank sensors) they plug into the dis with a  4
wire-crank signal- connector and a 2 wire-cam sensor-connector.<


>i would check
all three with a waveform vewer to make sure you are getting a signal. if 
you
dont have access to a wave form vewer, you can use a dvom set on ac volts, a
good sensor will make about 1 volt ac. if the ecu doesnt see a cam signal in
2 crank revolutions it will shut down the injectors.<

No it won't.  If the ECM does not see a cam signal in 5.3 seconds it turns 
on the SES light(code 41).  The engine will run without the cam sensor. The 
ECM will likely be wrong about the correct injector synching but this will 
not cause the engine to stop.  If there are not 8 4X pulses between cam 
pulses then a code 81 is set if it is wrong twice in a row (4 revolutions.) 
Other than setting a code the ECM does nothing.  The instructions are do not 
diagnose without drivability symptoms.  You can find more about this in 
section 6d and 6e of the factory service manual for 1993, 1994, or 1995.

FWIW his problem was the lack of a VATS signal.  It was cured by building a 
pulse generator.

JG

good luck. joe



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