why does my 96 tahoe turn over good but it will not start? on 1995 Chevrolet Tahoe

it is a 96 tahoe, 5.7 l v8. sometimes it starts great other times it wont start at all. i replaced the fuel pump module and the fuel filter. the first day it was great . the next back to having trouble.turns over hard but just wont start. i try cranking it until i finally drain the battery and have to jump start it. soon as i hook up the cables it instantly starts up. why does this happen and how can i fix it?

by in Texarkana, TX on December 09, 2012
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2 answers 6 comments
ANSWER by , December 09, 2012
When it dont start up need to check fuel press. and ignition fire. Bet you dont have one or the other or both. Can you hear the pump run when it is not starting? Crank, let off key but leave it on, does pump run a couple of seconds? Can repeat this as many times as needed to see if pump is working. If that is ok check ignition fire if that is ok injector pulse should be too, start engine and drive away. I assume you can do this as you said, "I replaced fuel pump module and filter".
COMMENT by , December 10, 2012
I agree with wetry
COMMENT by , December 10, 2012
thats why i replaced the pump to begin with because it wasn't coming on when i turned the key. prior to that it would come on every once in a while then just quit coming on. now that i replaced it the first day yes it was coming on and cranking just fine thought the problem was fixed. last night i turned the key, pump came on it tried to crank shook a little and died tried again but pump never would come back on no matter how many times i turned the key back and forth.
COMMENT by , December 10, 2012
Well you should know what to do then. If the pump aint working. Check for voltage at the pump if present replace it again! Good luck! and Good day.
COMMENT by , December 10, 2012
i checked the fuel pump relay and it is bad. there is a spot that has gotten hot and melted a little. if i replace it could there be something that caused that one to over heat that i might need to check. dont want to replace it and that happen to the new one.
COMMENT by , December 10, 2012
the old fuel pump could have shortsd out the relay
COMMENT by , December 10, 2012
thanks all
ANSWER by , December 10, 2012
have fuel pressure tested,it may be on the low side of spec's