ZR-1 Net Registry Forums - View Single Post - 1990 fuel pressure & vac readings good/bad?

Marc Haibeck · 11-14-2017

The fuel pressure drop off that you are describing is typical for a secondary fuel pump that is not working. The fuel pressure is normally 48 to 51 PSI from 3000 to 7000 rpm at wide open throttle. When driving the car you should see the fuel pressure spike up a few PSI when the secondary pump turns on at 4000 rpm.

An easy way to test the pumps is to open the electrical connector to the pumps at the fuel tank. Remove the fuel door panel to access it. Apply 12 volts through a 5 amp fuse between the black and grey wires. This should run the primary pump. Connect the 12 volts between the black and the green wire. This will run the secondary pump. Never connect to the purple wire. Doing so will damage the fuel level sensor. If the secondary pump runs, check the fuse under the right hush panel.

We use the Airtex E3240 as a replacement pump.

A .035" gap is good for Rapid Fire spark plugs.

11-14-2017	#3
Marc Haibeck Join Date: May 2007 Location: Addison IL Posts: 250	Re: 1990 fuel pressure & vac readings good/bad? The fuel pressure drop off that you are describing is typical for a secondary fuel pump that is not working. The fuel pressure is normally 48 to 51 PSI from 3000 to 7000 rpm at wide open throttle. When driving the car you should see the fuel pressure spike up a few PSI when the secondary pump turns on at 4000 rpm. An easy way to test the pumps is to open the electrical connector to the pumps at the fuel tank. Remove the fuel door panel to access it. Apply 12 volts through a 5 amp fuse between the black and grey wires. This should run the primary pump. Connect the 12 volts between the black and the green wire. This will run the secondary pump. Never connect to the purple wire. Doing so will damage the fuel level sensor. If the secondary pump runs, check the fuse under the right hush panel. We use the Airtex E3240 as a replacement pump. A .035" gap is good for Rapid Fire spark plugs.