hey i am new here. i dont have a blazer but my friend dose. it is a 1999 blazer v6 (4.6L i think)
anyways he has been having a problem starting it. if he turns it off and leaves it for 20min it wont start. it will act like it's out of gas or it will start and die a second latter. then if he comes back 5min after that it starts up just fine. when it is running the fule pump wines a little so it might be the fule pump. is there a relay that can go bad or could the spark plugs be gaped wrong? he had them changed 9k ago, along with the fule filter, and it fixed the problem for a little. the aif filter is also really dirty so i blew it out with my compressor. but that shouldent cause it not to start.
some help would be nice. i owe him for bulding me a sweet a$$ computer.

 

no one knows?
is there a link on how to replace the fule pump.
is there anything special to it or do i just unbolt the 2 straps dissconect the filler neck and drop it down?

 

Get a pressure gauge and check but from your description could be a weak or leaking fuel pressure regulator or fuel pump.

The gauge would tell you if it is the fuel pump, because they are supposed to go to 60psi if they are working. There is a valve near the firewall on the drivers side (looks like a tire valve with a black cap [called the shrader valve]), this is where you hook the gauge into. If you get between 55-60 psi then then the truck will start right up, anything less than that and the injectors in that vehicle won't work.

As far as the pressure leaking down after 20 min of not running that could be a bad injector,fuel pressure regulator, or bad evaporative pressure relief valve in the tank...

 

Steve, The Whinning noise you hear comming from the fuel pump is NORMAL......

 

so it is ok for it to wine all the time?
i know it is ok for it to wine before start up but once it's running?
as for checking the pressure i don't have a guage.
but it will run fine once it gets started so that just sounded wierd to me.
wouldent it run strange all the time if the pump was going out?
but the pump sounds like it is working even when it won't start.
any thing else it could be? that is easyer to check?

 

Yes, it is normal for the pump to have a high pitch whine when running.

The fuel pressure needed to run the truck is lower than what is needed to start it. So it is possible for the truck to run fine but have difficulty starting if your fuel pump is going bad. You can try turning the key to the on position (but not starting) for 5 seconds to let the fuel pump prime the system, then turn the key to the off position. Repeat this about 5 times and see if it helps to start the truck easier. If it does, then maybe the fuel pump is not able to pressurize the system properly and may need replacing.

The only accurate way (at least that I know off) to check is to hook up a fuel pressure gauge. There are numerous links this the forum on how to do this and what the pressure readings should be.