kelc31757

Im having a starting problem with my 87.I disabled vats 10 years ago with one of those under the dash bypass modules.Has anyone ever had a problem with one of those modules? Its been so long i can't remember if vats is screwing up nothing happens when you turn the key except dash light come on, or do you get click at starter?

vetteoz

Doesn't " disable" VATS; only fools the VATS module into thinking that the correct key is being used.
If the VATS module, it's other components or wiring develop faults then the "bypass" module will do zilch

First thing to check is the starter enable relay controlled by the module.
If that is faulty ( common with age ) you will get no power to the starter even if VATS is functioning correctly
Just jumper the two thick wires at the relay connector to bypass relay for test purposes

kelc31757

Would a bad relay allow the starter to just click once?

vetteoz

Possibly
Clicking generally indicates not enough juice to the starter;
low batt , bad cable / connections from batt to starter / block , worn contacts in the starter solenoid
or possibly not enough power on the circuit from the Ign switch ( through the relay ) that operates the solenoid

I would start by confirming the starter works before chasing other problems
If you disconnect the purple wire from the starter solenoid and run a wire up from that terminal to the batt ,
if you touch that wire on the batt Pos+ terminal then the starter should crank the engine over.
If it does then you know the problem is in the circuit from the Ign ( which also runs through the clutch or neutral safety switch.
A bad connection somewhere in the starter circuit could be giving voltage drop which could be your problem

Not sure what year this is from (85 ?) but typical early C4 starter circuit

Dans 85

Another way without taking anything apart is to find the thick purple wire is in the big loom running over the brake booster and using a meter check voltage here while turning key to start. If there is battery voltage there it is not VATS or a fault coming from inside the car.

MRPVette

Are you sure it is the starter clicking and not the relay? if the starter is clicking I would say it is a starter or battery problem.

kelc31757

I have replaced battery (had it tested)and the starter.So I think its something in between.Also my battery light has been coming on when i try and start.The only time that light has come on is when my alternator was going bad.