98 Blazer, 4.3L CSEFI engine VIN "W"

vehicle cranks but no longer turns over, previously died during idle, and about a month ago it put out a CEL that had something to do with O2 sensor, bank 2 i believe (not sure if it's related)

car had no start in 01, the mechanics replaced the pump, still didn't fix the problem and it ended up being the FPR, the FPR was also replaced again in 04. got a complete tune up within the last year (plugs, wires, distributor, etc.)

starts on starting fluid, but dies. starts if gas tank is hit with hammer during crank and dies shortly after. fuel pump whines when key is turned, no start. recently the fuel pump no longer whines, and i can hear a click from the under hood fuse box at the times when the pump would normally turn on and off. I know a fuel pressure check/diagnostic is in order but im having difficulty getting a pressure gauge, the only one available at checker was $80+

could the issues with the relay and intermittent whining noise be something other than the fuel pump for sure or does that indicate the fuel pump itself would be the replacement? also im concerned about the FPR since it seems to be a continuous trend in my blazer causing no starts before, do my symptoms give any indication that it would really be the fuel pump and not the FPR instead? I've been told that if it starts from hitting the tank with a rubber mallet that its the fuel pump, is this a for sure thing or is it just kind of a usually means the fuel pump?

Thanks in advance for any help

 

If banging on the pump causes it to start, the cause is definitely back at the tank. I would start by checking the wiring harness, making sure that you have a good ground and power circuit. If that checks out and the harness looks normal (ie. not burnt or deformed), then I would get yourself prepared to drop the tank.

 

Alright i'll have to check those out tomorrow, i tried again to start it up by hitting the tank and this time got nothing, although now the pump kicks on and whines like it normally should.

went out and got a pressure gauge this morning, went and hooked up it, with key on the pump whined and the gauge stayed at zero, same result the next couple tries. banged on the fuel tank some more, this time no fuel pump whine and only the clicking noise again, gauge showed 0. is this even possible or would it mean just a dead fuel pump and/or sending unit?

Ive heard about the fuel pump test wire under the hood, im not exactly sure it exists on my engine but if it does would that make any difference in the readings if it was hooked up and where exactly would it be located?

 

Updated ^^

also when i went to relieve pressure from the system there was very little fuel that came out of the schraeder valve, is this typical or should there be more if things were working properly?

update again... pressure reaches 51psi at key on, then drops off, at about 41 during crank. this only happens when the pump actually runs, the pump wont activate sometimes so the gas tank it hit and it seems to start it up again, meaning electrical problems?

 

Sounds like a weak pump. That is not enough pressure to start the vehicle. You could start by making sure that the electrical connection to the pump is clean (no corrosion) and not burnt/distorted.

 

in effort to try some things before going through all the work of dropping the tank and looking at the fuel pump / FP electrical stuff, i changed out the fuel filter (which had been replaced last year) only to find that it sure looked more than a year old. pressure tests after that bring the key on pressure up to 57psi, enough to start the vehicle first try and sets it to idle at 1000 rpm the pressure quickly drops down to about 43psi and the idle drops off 1000rpm and the engine dies. is FPR still a possibility, along with possible electrical problems that may be causing the intermittent action of the pump coming on?

also in trying to follow the fuel system diagnostic thread in the beginning step it asks if the pressure is between 60-66psi, but in the forums and haynes manual it says normal pressure is 54-61psi, is this correct and the diagnostic one is just high or is that intentional?

 

GM has revised their key on, engine off fuel pressure requirement. Who knows why. 52 is the minimum pressure to actuate the poppet nozzles. 55-60 is the generally accepted as the proper range, but it cannot drop below 52psi while cranking.

To test the FPR, watch the pressure drop once the key is turned off. If the pressure bleeds off to zero, then there is a leak in the fuel system. If it bleeds off quickly, then the FPR is the likely cause.

 

on key on and off the pressure was at about 57 and after 15 minutes following key off it dropped to around 49-50 and remained there.

Good news is though if it does end up actually being the fuel pump, the dealership that replaced it in 01 has a lifetime warranty on parts and labor.

now all that's left is to figure out if it's worth it to replace the FPR by ourselves to see if it fixes the problem or to just bring it to the dealer to have them redo the fuel pump now... or eventually for free when it does go out.

Final update

after getting sick of trying to deal with it in the cold weather, we finally towed it over to the dealership, they found that the problem after all was a faulty fuel pump, which was replaced and installed for no cost. replacing the fuel filter before anything else definitely helped but didn't fully solve the problem. anyone with fuel related no start problems should definitely check out the minor things like that first, mine had been replaced within the last year but it wasn't even close to being in a like new condition. i guess you never know...

thanks for all the help, glad to have my blazer up and running again