QuestionI have an 89 cadillac deville with a 4.5. I put a used motor and transmission in the car, it ran fine for about 5 miles and then just shut off like you had turn the key off. Messed with it for about two days and found a ground strap had came off by the starter. Repaired that, now it won't pump fuel to the carburator it just crancks over. Checked for voltage to the fuel pump and not getting anything. No juice to the pump nor from the pump. Parts house said it has a kill switch that when the ground strap came loose that it told the computer that the car had been in an accident. And it shut off power to the fuel pump, but I can't find the kill switch. And I can't find a manuel to tell me where the switch is.
AnswerThe 89 does NOT have a KILL SWITCH.
Fuel 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 ?.
7. If it does NOT run for the 2 seconds the fault is either the fuel pump or the fuel pump relay.
As soon as you turn ON the ignition switch to ON position, Just before you turn the key to the start position when the engine starts to crank over, A 2 second battery voltage signal is sent from the computer to the fuel pump relay and then 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.
Therefore if your POSITIVE you are hearing that 2 second pump run just when you turn the ignition switch to the ON position ONLY, just before you turn the ignition key to the start position, I would have to say you have a weak fuel pump upon initial start up.
If you are NOT hearing that 2 second fuel pump run, Then I would say that the fuel pump relay is defective.
I can e-mail you an electrical schematic of the fuel system. Contact me at: onlineautohelp@msn.com
