I have an 89 chevy 1500 I inherited from my dad a few months ago. I started it this morningand drove a couple mile, stopped shut truck off went inside come out not even 5 minutes later and it wont start. Itll turn over, pour gas down the tbi and itll run till that runs out. Took fuel line of back of tbi turned key on but no gas. Undid lin off front of filter and gas flowed out, not sure if I can hear if fuel pump is running because I am hard of hearing. Could it be pupm or oil switch gone bad? which should I start with to see what problem might be?