Hope all is well. Jumped in the car the other day and turned the key and it didn't crank. Ran perfect earlier in the day, but now I've got nothing. All the lights work fine, but not getting anything when I turn the key. Put it up on jacks today and did the standard checks. First I checked for corrosion at all the connections and cleaned all of them up even if they didn't need it. Battery is good. Ground from the battery checks out. Connections at the battery and the starter are good. I also ran jumper cables right from the battery to the starter and crossed fat stud to smallest one to engage the starter. It did engage the starter. I also tested out the solenoid and it did engage the bendix. So I'm not sure if I can count out the starter because both of those tests came out positive. Sort of lost on what to do now. Any help would be much appreciated.

 

Just to add to what I already have...Fuel pump primes and fuel pressure at the rail is on point. I've got no idea what I should try next.

 

Starter circuit from the Ign switch to starter solenoid would be the obvious choice.
Checking for 12V in / out the NSS would be 1st item
if so ,12V on purple wire at solenoid in START position?
if not ,12V on yellow starter wire out of Ign switch ?

 

There's a few things.

The '88 GTA has VATS and could be causing the problem, this is common. After a while the pellet in the key can lose contact with the contacts in the tumbler and cause difficult starting or no start conditions. What does the VATS or SECURITY light in the gauge cluster do when you attempt to start?

Another common issue is the neutral safety switch ("NSS") going out of adjustment. Sometimes pushing the gear shift forward when in park and turning the key to start will allow for a connection to be made. If you have a manual there is still an NSS, but will be located either above the pedal and attached to it, or mounted on the firewall where the pedal will push a large plunger. I have found that the ones mounted above the pedal sometimes go out of adjustment, and need to have the sliding collar moved down the shaft and reset. The firewall mounted ones I don't recall ever really having an issue with them other than having a floor mat not allow the pedal to move through it's full motion and not allowing the NSS to fully close.

There is also the possibility of worn out relays, or a broken wire somewhere in the circuit, these are more difficult to find, but using a DMM, you can trace there the flow of current stops in the circuit, starting at the ignition switch to ensure it is good, and following the circuit through it's full path. Sometimes you can skip many of the test points by going to a known area of the circuit downstream, where you suspect there might be a problem, such as the VATS starter enable relay, and testing for voltage at that point, where the signal is fed into the relay from the ignition switch. Don't be fooled though, if you have removed the relay to test for voltage, and you get a voltage signal there, this does not automatically mean everything upstream is good, because there could be a corroded point that will allow low current to pass, but once a load is applied, the current capability drops to near 0 and will not engage the the device that should be turning on. You need to test under no load and loaded conditions.