99 sierra new pumps no power?
 

i have replaced both tank fuel pumps the fuel filter, spark plugs, wires and still have no power over 1/2 throttle! it has good power to 1/2 throttle then drops of and backfires through airbox! was told checkfuel pressure regulator and remove catalytic converter! anyone had this problem and know what to do? i know both replaced pumps cant be defective! :waah: need some help please!!!

Re: 99 sierra new pumps no power?
 

Have you checked for codes? TPS voltage? Whats the fuel pressure under full load? did you use quality parts(AC Delco)? need more input

Re: 99 sierra new pumps no power?
 

have not read codes , did not replace pumps with oem parts! my dad took truck to garage when this started they told him fuel pumps were gone he paid out 1200.00, 2 fuel pumps later not fixed! the fuel pumps are not the problem nobody can tell me 4 pumps all fail in no time and problem still exists! so i replaced fuel filter which garage neglected ran a bit better but not fixed? runs fine with lots of power untill 1/2 throttle then just craps right out if you continue to hold in wide open throttle vehicle slows down to a crawl and motor wont run good for awhile! sometimes motor starts running poor even when your not forcing it but if you add fuel additive motor runs good again! it doesn,t matter what tank your on and both had new pumps! i dont have a code reader! but i have seen other people post on various sites this exact same problem!rtunately there were no answers given other than replace fuel pumps! this is not a fuel pump problem it strarts right up which requires 50+ psi once running it only requires 40psi wondering if regulator is gone or catalytic is plugged or some stupid sensor is gone but garage should have read codes too. check engine light only goes on when it runs like crap for atleast 5 minutes or more!

Re: 99 sierra new pumps no power?
 

Get it scaned and tell me what the codes are. autozone will do it for free around here,but dont listen to them on what they think your truck needs.

Re: 99 sierra new pumps no power?
 

need to ceck the tps sensor

Re: 99 sierra new pumps no power?
 

My 99 was running some what like that....

I pulled the cats and put a flowmaster on it . Runs great.

But yes have it scanned, the computer remembers the problem.autozone does it free.

Did you check air filter and mass air flow???????

Re: 99 sierra new pumps no power?
 

if you have aces to a back pressure gauge that screws into the o2 sensor hole. this will tell you if you have a restriction in the exhaust system. i would start with the tps.