Both tests failed. Provided voltage drop and ground at the pump are good, you need a new fuel pump. AC Delco or Delphi only, don't waste your time or money on aftermarket stuff. Don't forget to check Amazon & Ebay.

 

I would do amazon/rock auto over ebay, too easy for people to put an aftermarket pump in a delphi/delco box.

 

Good point Richard!

Also, 2 door and 4 door pumps are NOT interchangeable.

 

OK, thanks a lot. For my own personal knowledge what should the fuel pressure be at the filter?

 

From post #9:

If it fails one or both tests, [at the service port] pressure and leakdown must be tested at the fuel filter outlet to determine where the problem is. All pressure and fuel flow must end at the tester. While the pump is activated, pressure must be 73psi to 108psi and it must remain above 55psi for at least 10 minutes after the pump shuts off.

 

You loose 25-50 lbs of fuel pressure from the filter to the service port on the engine? That seems very excessive. That is what your personal Blazer reads for pressure at the filter?

 

The "deadheaded" pressure (at the filter) is what the pump can put out. At the engine, the pressure is regulated from that maximum pressure down to ~62 psi for the injectors. A regulated pressure is required so the computer knows what volume is being injected.

So the pressure loss is only due to the Regulator doing its job. The fuel pump puts out more pressure than needed to maintain an adequate flow rate for all conditions.

Hope that explains it.

 

so the regulated gas goes back to the tank via the return line?

 

Perfect explanation!

"All pressure and fuel flow must end at the tester."
Maximum pump output pressure=dead head pressure. (no fuel allowed to the engine)
The link in post #19 lists all of the parts that you will need to make the adapter, so you can check maximum pump output pressure, (dead head) and leakdown. After you do the tests explained in post #19, post all four readings.

 

Yes. When fuel pressure overcomes spring pressure, the valve plate opens, fuel pressure drops, and the excess fuel & pressure is sent back to the tank via the return line. When spring pressure overcomes fuel pressure, the valve plate closes, fuel pressure rises, and the cycle repeats.




The green arrow on the left is fuel entering the regulator after it leaves the fuel metering block, (the regulator is downstream of the injectors). The arrow on top is fuel returning to the tank. The vacuum connection is exposed to manifold vacuum inside the plenum, (no vacuum hose is necessary). When manifold vacuum is high, (idle & cruising) the spring is compressed and fuel pressure drops.