Hi, I have a 98 Blazer 4.3 It won't start but will "run" on sprays of ether. Fuel pressure at rail is 45 psi and drops instantly when fuel pump is disengaged. I checked the pressure at the filter and it reads 60-70 lbs and once again instantly drops pressure when pump stops. I did a continuous crank and the pressure maintained while cranking. Then it drops when the ignition is shut off. From what I gather it points to a bad fuel pump check valve. What I don't understand is a bad check valve causes hard starts not a no start, is that mostly correct? If it was "running" with the sprays of ether shouldn't the pump be engaged thus pressurizing the system and it should start at that point. Remember pressure held when pump engaged at 45lbs at schrader valve and 60+ at fuel filter.The gas in the tank is a) 3 gals 5 years old b) 4 gals 2 years old c) 5 gals of 91 octane just added. So I believe I definitely have a bad check valve but is the reason it won't start bad gas? What do you all think?

 

I would suggest to dump the old gas (known to cause issues) taking the appropriate precautions.
Also change the filter.

Not sure about the 98's where the check valve sits. Usually it's a component of the fuel pump itself at the outlet.
In addition not sure if the pressure regulator can cause the dropping fuel pressure as soon as power is removed.
Would need a proper diagnosis of the fuel system.

Maybe somebody savvy on the 2nd gen can enlighten us.

 

Fuel pressures are way low. should read 60+PSI key on prime and hold for 10 minutes key off above 60. Check fuel pump voltage at the pump connector with the prime terminal jumped/the fuel pump energized somehow using the trucks existing electronics. there is a thread somewhere showing how to do it and i can get pictures off my rig if needed. if you have system voltage at the pump atleast 11.9 volts or higher, swap the gas, flush the fuel lines thoroughly with an evaporative solvent (brake/carb cleaner) and if all that fails, replace the pump, and try it again, also check that you have a good regulator, and if you replace the pump,replace the regulator as well, its under the upper intake manifold and its rather easy to get to. if you have low voltage at the fuel pump but normal system voltage between body grounds and frame grounds (check both connector and frame grounds, or else we cant isolate the hot wire as being an issue)