QuestionI have a 1985 Cadillac Fleetwood and my fuel pump keeps going out. So we think the relay needs to be changed but don't know where to find it, could you tell me where I can find it?
AnswerFuel pump test:
1. Get yourself a helper.
2. remove the gas cap.
3. have one person listen in the gas tank at the gas cap opening.
4. have the other person turn the ignition switch to the ON position ONLY so as the dash lights come on. Do NOT attempt to start the engine.
5. As soon as the ignition key is turned to the ON position, The person at the gas tank should hear the fuel pump run for TWO SECONDS and then it should STOP.
6. Does it ?.
If you do NOT hear it run, in most cases the fault is the fuel pump.
As soon as you turn ON the ignition switch to start the engine a 2 second ONLY battery voltage signal is sent from the computer to the fuel pump relay and from the relay back to the fuel pump in the fuel tank. This runs the fuel pump for ONLY 2 seconds of which pressurizes the fuel system in preparation to start the engine.
Once the engine starts, The computer BYPASSES the fuel pump relay and sends constant contionous battery voltage from the computer to the oil pressure switch of which is now CLOSED because the oil pressure is UP because the engine is running. Therefore the battery voltage flows thru the oil pressure switch back to the fuel pump to run the fuel pump constantly until you turn OFF the engine.
