My father recently bought a 93 auto lt1 that is quite a project car. The previous owner sold it cheap because he didn't know how to fix it or what was wrong with it. He said the water pump started leaking and then it just quit running all together. He just got frustrated and decided to sell it. That of course was good news for my father, as he bought it and just replaced the water pump and distributer and it ran fine except for the occassional not wanting to start because of VATS. We then ordered the VATS bypass and I hooked it up for him, and it had been starting and running perfectly for a few months until about a week ago. It will turn over with no problem, and it will sometimes start, but it will only run for 2 or 3 seconds then quickly die. Other times it will start on the first try and run perfectly, so I know it can't be anything such as a bad fuel pump, etc., b/c when it runs it runs perfectly. He took it to a repair shop and they replaced the fuel pump and filter, and didn't know what else to do after that didn't fix it, so they just gave it back to him with a hefty bill. (needless to say, my dad was not a happy camper...) Anyway, I noticed when I would try to start it and it wouldn't start the security light is coming on and staying on, doesn't that mean that there's a problem with the vats again? I know the security light means different things whether blinking or constant or whatever. The one thing that makes me question vats is everytime I had a problem with vats on either my 92 or 87 model it wouldn't turn over at all. Have any of you seen vats let the car turn over but not start? If any of you have any ideas I would greatly appreciate any input! Thanks in advance!

 

Co-worked has a similar problem with his '87.

If it were a VATS problem with either the key or the igntion lock cylinder, then the starter will not turn over. This could also be a bad starter relay..but still..the starter would not turn over.

When it starts and runs for a few seconds and then stops...sure sounds like a fuel problem. Could be the fuel pump relay, or the oil pressure switch is shutting off power to the fuel pump. You would need to monitor the voltage going to the fuel pump and see if its there or not. Or monitor fuel pressure and if it drops out..then the injectors will not pulse.

Other things...could be an intermittent ignition module, or ignition coil. losse connection at either or at the fuel pump. Could also be loose connection at the Opti...in other words...alot of things to check out.
Just have to eliminate them one by one.

Good luck

 

When it won't start, or quits after several seconds, that is the time to do some testing. First, use your timing light to see if you have spark and spark at the correct time. Pull a plug wire and bring a grounded wire near the plug wire, the spark should easily jump 1/2 inch while cranking. Connect a fuel pressure gauge on the shrader valve on the end of the fuel rail and see if it drops rapidly with the ign cycled. Leaky injectors cause this and cause a too rich condition to start. The CCM turns on the fuel pump for only 2 seconds when starting and if the engine runs, an oil pressure switch that closes at 4 psi supplies 12v to the fuel pump. Engines that start and quit likely have a defective oil pressure switch. You can unplug the oil pressure switch and jump the connector and see if it will start and continue to run, and also check the oil pressure switch with an ohmeter when the engine is running. Connect a noid light (available at parts stores), or a low power 12v lamp like a side marker lamp across an unplugged injector socket and while cranking, observe if the lamp pulses. No pulsing, could be defective opti.

 

The flashing sys light could also mean LOSS OF SERIAL DATA. Check for codes, CCM & ECM. If the loss of serial data is present at start up the injectors will not pulse.