Fuel pump will not shut off

When you turn the key on the fuel pump should pump for about five to ten seconds. Do this a few times and it should start. Even with a full tank the pump will do this to pressurize the system. If the pump keeps running it's not picking up fuel. Have a friend listen at the gas cap with the cap removed for the pump to cycle. If it doesn't work there is a fitting on the fuel rail that looks like a valve on a tire. Take the cap off of it and use a small screwdriver to push the center in and see if there is pressure in the fuel rail. Have the key on and wear safety glasses.You should get a squirt of fuel out of it. If you have no pressure there the pump could be bad or the filter plugged. If there is pressure you have other problems. There is no shut off switch. Only fuses and a fuel pump relay. https://www.google.com/search?client=ms-android-samsung&source=android-browser&ei=_skGWP71NoOFmwGwvp-YCw&q=1998+buick+lesabre+fuel+pump+switch+location&oq=+1998+Buick+le+sabre+fuel+pump+switch+location&gs_l=mobile-gws-serp.1.0.30i10k1.20246.66235.0.71699.52.41.2.0.0.0.354.6560.4j26j8j2.40.0....0...1.1.64.mobile-gws-serp..17.35.5853...0i10k1j0i7i10i30k1j0i13k1j33i21k1j33i160k1.pAvwOOuWlKU#imgrc=99du9RTFFGCYhM%3A&scso=uid_WAbKSQAIdFcKJtQCGQCAqw_8:0

If the Oil Sending Unit becomes defective, it often keeps the fuel pump running even after the car's engine is shut off. Replacing the Oil Sending Unit should correct the problem. Believe it or not Pontiac uses the oil sending unit as a back up to power the fuel pump.

the fuel pump relay contacts may have fused together, remove the relay and see if it stops, if it nuns for10 minutes then stops points to fuel fault, replace the filter then check pressure and flow. if the pressure is low check the fuel regulator and pump.

IT IS LOOKS LIKE A FUEL PRESSURE LEAKING INSIDE THE ENGINE OR DEFECTIVE FUEL INJECTOR LEAKING . TRY DISCONNECTING THE FUEL PUMP RELAY. AND CRANK THE ENGINE IF ALWAYS CRANK WITH OUT OF FUEL (CRANK WITHOUT START) YOU HAVE FUEL LEAK INSIDE THE ENGINE
REMOVE THE INJECTORS RAIL UP EVERYTHING CONNECTED,PUT BACK THE FUEL PUMP RELAY TURN THE SWITCH ON AND FIND WICH ONE IS LEAKING. (GASOLINE IS FLAMMABLE TAKE CARE)

There is an oil pressure switch in parallel with fuel pump relay, if that switch is closed, the fuel pump will run all the time. Click on the link. At the fuel injectors, top wire is voltage, bottom wire is ground. If there is no ground, both wires will have voltage. Make sure battery has a full charge.

https://s17.postimg.org/vijjimikf/fuel_injectors.jpg

Generally speaking, its supposed to do that.
The fuel pump(s) is powered by a relay that turns on for 3 seconds when you turn the key on. If the engine does not start and produce oil pressure, thats all the power the pump gets. If you were in a wreck the pump would shut off when the engine dies even with the key on to prevent a fire.
You would need to jumper the relay to make the pump run beyond the 3 second time.

Kent, That sounds like normal operation.....see this link (https://www.justanswer.com/chevy/0z9bu-fuel-pump-relay-located-1987-chevy-silverado.html) The ECM shuts the pump down if the engine doesn't begin running in two seconds. I would bleed out the fuel line up to the TBI...crack the line at the TBI then cycle the key a couple of times until you see gas coming out of the line at the TBI. That will ensure you have fuel at the TBI, then try to start the engine. See the link for additional info.

no but if the security system is activated it will disable the fuel pump is security light on

relay can do that

First I would check the fuel shut off switch, push down on the red button, switch is located in trunk. Make sure you are getting fuel and fuel pump fuse is ok. You can remove fuel line from fuel filter and turn key on to see if fuel comes out of hose and also get a glass jar and take a fuel sample to see if anything is in fuel. Sounds like you may be having a fuel problem.