ok so i bought this 94 blazer the guy said it need s a new fuel pump when we get there we spray some starting fluid in it and it starts up i let it run for about 20 mins then drive it on to the trailer drive about 40 mins home get in it it starts up first try and i drive it off the trailer then the next day i go out start it up with starting fluid agian it starts then pull it in the barn and let it sit for a day or two then go out to work on it and it wont start at all so i replaced the fuel filter then the fuel pump and the sending unit and the spark plugs and still nothing at all still acts like it isnt getting gas

 

Start by running the standard fuel pressure test as described many times here and report back with the figures.

 

is that located on the back by the cap ??

 

94 so ill assume its the cpi version since tbi was extremely rare that year should be a shrader valve on the fuel line in the vicinity of the backside of the manifold hook the fuel pressure test gauge to that and let us know the numbers you get, engine off key on see what the pressure reads and how fast it drops when the pump turns off. (If you want more detail search for fuel pressure test on these forums or take a look at the related threads listed at the bottom of this page)

 

ok so i ran a test on it and the first time it read 20 psi then i redid it 3 times and each time it read 15 psi and would drop to 0 everytime with out the key on

 

you have an leak somewhere thats not even in the same ballpark as the pressure your engine requires to start. Id start by removing the vortec cover on top of the upper plenum (2 screws) and the round plug right below that (again, 2 screws) then take a look inside if the passenger side looks clean you have a bad fuel pressure regulator if the driver side looks clean the spider and/or nut kit is leaking.

 

ok where is the fuel pressure regulator?

 

inside the upper plenum on passenger side which is why I suggested removing the plastic cover and round plug so you can see inside to verify which side is clean.
(FPR is the round piece on the left half in this picture)

If you verify the fpr or spider is in fact leaking take a look at the link below my sig for more info on the repair.

 

well i just called the parts store and they sold me the wrong pump they sold me one for a onvortec but how much psi would a onvortec need

 

how much for that part u had to buy???