Jim Grant's Tech Tips
Chevy Astro, Original Fuel Pump
Q: I own a ‘99 Chevy Astro van and one day it wouldn’t start. I’venoticed that the fuel pump sound was gone. I had the pump replaced with a genericpump,thenit started great. The next morning it wouldn’t. I checked everything, the fuelpump sounds ok. Someone told me that I need to install an original pump so Idid, but still the same thing... nothing!, What can I do now?
A: First, you have to find out if the vehicle has fuel pressure and enough of it. Check the fuel pressure at the test port of the fuel injection system, there should be 60 to 66 psi with the key on and the engine off. The injection system in your vehicle has 2 injectors for each cylinder. One injector is electronically controlled by the computer while the second injector responds to the fuel pressure received from the first. The electronically control injector is your basic electronically solenoid that opens a valve to allow fuel to flow. The second injector has what is called a poppet valve. Fuel pressure pushes a check ball back against spring pressure allowing the fuel to be sprayed into the intake port of the cylinder head. It takes a minimum of 40 psi of fuel pressure to push the check ball back. If you have less than 50 psi at the test port you’ll likely have starting problems. Original equipment or aftermarket they all have to do the same job.