I seriously doubt that tapping on the filter caused it to start but here is the isolation procedure.
Every engine requires spark, fuel and compression to run. That's what we have to look for. You need to first test a few functions during the failure.
1) Test for spark at the plug end of the wire using a spark tester. If none found, check for power supply on the + terminal of the coil with the key on.
2) Test for injecter pulse using a small bulb called a noid light. If none found, check for power supply at one side of the injecter with the key on.
3) Use a fuel pressure gauge to test for correct fuel pressure, also noticing if the pressure holds when key is shut off.
Once you have determined which of these functions has dropped out, you will know which system is having the problem.
Here's what the noid light looks like.