You have the right idea but 20 seconds is way too long. The automatic shutdown (ASD) relay turns on for just one second after turning the ignition switch on, then again during engine rotation, (cranking or running).
The ignition coil(s), injectors, alternator field, oxygen sensor heaters, and fuel pump or pump relay are powered from that relay. Often you can hear the fuel pump run for that one second but it can be easier to monitor the voltage at the ignition coil. Use a test light if you have one because most digital voltmeters don't respond fast enough.
What's important is if that voltage comes back during cranking. If it does, you have a spark or a fuel supply problem. Most commonly it doesn't come back. The usual cause is a missing signal from the crankshaft position sensor or the camshaft position sensor. You didn't say which engine you have but since you mentioned coil packs you don't have a camshaft position sensor in a distributor. Given the recent service I'd be looking at the wires and connector to the crank sensor. It's right behind the right head in the transmission bell housing.
Be aware too that if you have spark and fuel pressure, you can have a failure to start simply from disconnecting the battery. The Engine Computer has to relearn "minimum throttle" before it will know when to be in control of idle speed. Until then you may need to hold the accelerator down 1/4".
Sunday, September 1st, 2013 AT 9:01 PM