What would cause the starter to NOT crank when the switch is turned on. I had this problem yesterday on my '90 auto. I did the common sense stuff, putting in nuetral rocking car while in park, prayed, cussed...all to no avail. I ended up calling AAA once the wrecker got to me I sat down hit the switch and she turns over and the motor say chibrooom. What could caused this? Might it be my VATS resistor key going bad? Is there a way to measure the resistance if it is going bad?

 

Try jumping the solenoid switch by running a heavy duty cable direct from the positive post of your battery to the large post on the starter. If the starter is working, it will spin and engage the flywheel. Your ignition should be set to the "on" position, if you want your vette to start.
If the starter spins and engages the flywheel, you have a faulty solenoid switch.


[Modified by Oldman, 3:45 PM 9/26/2002]

 

Makes since. This seams like a valid test on the starter. What about a test of the VATS and the resistor key?

 

Here is how the VATS works on the 90.

You place the key in the ignition switch. Two little pins in the cylinder lock contact the pellet and carries the pellet's resistance down two little wires, through the steering column over to the Central Control Module CCM. The CCM evaluates the resistance and if it likes what it sees, it provides a ground for the control side of the start enable relay. With a ground, relay's windings are energized and pull the relay's contacts together, sending 12 volts to the clutch switch (stick)/ neutral safety switch(auto), from there, current flows to the control side of the starter solenoid. Once again, coils are energized and the contacts join sending big power from the battery to the starter. We are not done. A SECOND circuit in the CCM provides a signal to the Electronic Control Module (ECM) telling the ECM it has received a good resistance from the key and it's ok to pulse the injectors. With a bad resistance value, turning on the key and jumping the starter will not start the car. Turn over, yes, pulse injectors, no. This was part of the theft prevention logic. You need both starter and fuel. Remeber, this is for the 90. I have not seen the schematics for previous or later years. There are differences.

Whew. Now that we know how the system works, it's test time.

If you want to test the system, take a multimeter and read the key pellets resistance value. Compare with the values published in tech section. 15 of em. Should be very close. I would be suspicious if greater than 1%. Not for sure on allowable range. Heard plus or minus 2%. Can't find this published. Now the fun starts. You may have to remove the hush panels and knee boltser on the drivers side gaining access to all the wires under the column. Look for two really small wires, white maybe, separate from other wire bundles. There will be a little square connector, pull it apart. Place the key in ignition, attach ohm meter across the connector under the dash, reading should be same as over the key, or real close. Now you are pretty sure the key/contacts work. Under a no start condition, the next place to check is the clutch/neutral safety switch. Does power make it to the switch (bad relay?)and through the switch when attempting start. This could arguably be the first step. If you have power here, the VATS is happy. No power here, probably the key lock assembly.

If you have the service manual, check section 8, electrical supplement on VATS, good schematic. Remember with the service manual supplement, the location reference in the back of the book will help locate components. Without this reference. it's hard.

Good luck.

dlmeyers 90 coupe zf6 3 speed shocks

 

Have had same problem on 90 ZR-1. I have done the following:
New key
new battery
by -passed clutch saftey switch
by- passed VATS with resisitance plug
Bench tested starter
Can the Vats still cause problems even with the resistance chip by-passing the key? :mad :cry

 

It could be the VATS circuits in the CCM but unlikely. Installing the resistor "bypass" means your CCM should see the correct resistance. You have removed the key/pins as possible problems.

Are you still having problems?

Remember, after the CCM sees the correct resistance, it provides the ground for the control side of the start enable relay. If the start enable relay does not close, no current through the clutch switch, or in your case, through the clutch bypass on the way to the solenoid. In replacing parts, you skipped part 1 (relay) bypassed part 2 (clutch) checked part 3 (starter). I am not suggesting go out and replace the relay.

Do you have the manual and a good multimeter? Light tester would also work good in this application. Just ground the clip and start testing, making sure you get the correct circuit. When this occurs is the best time to check. When this happens again, check the voltage at you clutch bypass. No voltage MAY mean start enable relay. It could also be an intermittent solenoid if there IS current past your clutch bypass. You need to find out where the current stops. Multimeter/light tester. Sometimes I just hate electrons.

dlmeyers 90 coupe zf6 3 speed shocks


[Modified by dlmeyers, 8:10 AM 9/30/2002]

 

EXCELLENT reply DL

:D