Car sometimes won't start - lights come on and no click when turn key - I thought it was battery terminals (it had done this in past and cleaning terminals had done trick)(I sometimes heard solonid click back then) - cleaned and noticed heli-coil on one post was bad - replaced battery. Now car performs so much better than before - hard to believe that battery can have that much effect. But still get the no start sometimes - I'm wondering if its the pellet in key - or automatic park start switch or starter (solonid) going bad - I guess that I have to replace both. Any thoughts appreciated - did search but couldn't find anything definitive.
Car is a 90 L98, Automatic, Vert with no mods. New plugs, wires, injectors, plugs, fuel pump, egr, coil, cap, fuel filter, etc.
Thanks
Ernie

 

Next time it doesn't start, check for power at small terminal on solenoid, with key in crank position. From there, you will be able to rule out at least one possible choice.

 

When it won't crank, unplug the gear selector safety switch (at the base of the shift lever) and jump the socket. Measure the voltage on the jumper with ign sw in crank. It should measure 12v. You can jump 12v to the jumper and the starter should crank proving the starter and solenoid are ok. If no 12v, then remove the kick panel above the drivers feet and find the two wires from above the steering column that go to a 2 pin connector and unplug. Insert the ign key and measure the resistance across the two wires from the steering column. It should measure within 4% of the key pellet resistance. If more than 4%, you need a new ign lock which comes with new contacts that make connection to the pellet. You can temporarily bypass VATS by connecting a resistor the same value as the pellet across the two wires from the wiring harness (goes to the VATS module). I believe in the 90, you cannot leave the resistor connected like earlier C4's, and each time you want to start the engine you have to disconnect the resistor and reconnect it. Also there is a start enable relay that VATS closes if the resistance is correct and if the relay is defective, no 12v will be measured at the gear safety sw jumper in crank position. There are ways to eliminate VATS, but if you do, keep in mind that 99% of thefts are done by bashing the column and jumping the ignition.