Question about 2000 Mercury Grand Marquis

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Fuel pump not always on

2000 mercury grand marquis 4.6 Intermittent problem. 35,000. miles. Problem engine died several times wile driving. Also after car is parked from a drive will not start. Found that the fuel pump is not turning on with the ignition key turned on after car was parked. Checked for fuel pressure pressure. Suspect that fuel pump is not on when cart dies when driving. #1 1st Tested car when car was working good and problem was not there. .Fuel pump fuse good. Fuel pressure good 35psi Tested Fuel pump relay according to the "Chilton Manual 26180" According to the fuel system test... installed a jumper wire into the fuel pump relay terminals that power the fuel pump (per foto). Listed for fuel pump to turn on (it did) says "if you now hear the whirring sound, the fuel pump relay or its control circuit is faulty." Switched PCM power relay, fuel pump relay and air conditioning relay . Drove car and started and stopped engine in driveway dozens of time to get it to fail. No failure. #2 Drove car. Started engine and stopped engine dozens of times in driveway and after some time starting engine and stopping engine got car to not start. Fuel pump not sound. Fuel pressure gauge pressure. Car wont start. Pulled fuel pump relay and installed a jumper wire into the fuel pump relay terminals that power the fuel pump according to book. This time fuel pump did not turn on. According to the book "If there is no whirring sound ,there is a problem in the fuel pump circuit from the relay panel to the fuel pump,defective power relay or a defective fuel pump". Replaced pulled fuel pump replay...turned key... fuel pump did not turn on. Turned key to try and start dozens of times and after lots of tries fuel pump now on ...pressure in fuel line starts. Got any ideas? .

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Not sure if Ford did this in 2000, but in my 1996 4.6L it seems they put an automatic shutoff sensor for the fuel pump. This kicks out the power to the fuel pump if the engine loses oil pressure. Why they didn't follow this thought through and realize that if the oil pressure drops suddenly you don't need the fuel pump quitting too. Failure on a highway leaves you at the mercy of the first driver who didn't know you were stopped.... Anyway hope this helps!

Posted on Jun 08, 2016

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Did you reset the inertia switch that shuts pump down in case of collision?

Posted on Feb 22, 2012

  • paul Feb 23, 2012

    Yes. Check it several times with a rubber mallet.Works and reset several times.

  • don-ohio Mar 03, 2012

    Well,I've been gone a while.......have you found the problem yet? What do you mean you reset with a rubber mallet? Heh,heh.....
    I've seen a lot of times where the problem was the chip in the ignition key or the computer that responds the that signal was bad.Working intermittently.
    Sometimes.....and I hate to admit it.....I have had to go to Ford to get a 60 dollar diagnosis. They have the sophisticated equipment to tell them a problem.
    I hope you find out what it is and PLEASE post the solution for everyone to benefit from? don-ohio (:^)



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2000 mercury grand marquis 4.6 Intermittent problem. 35,000. miles. Problem engine died several times wile driving. Also after car is parked from a drive will not start. Found that the fuel pump is not...

I'd have to test when problem is ongoing. When you first turn on key, no crank, you should hear the pump run for a few seconds then stop. For initial prime, the computer doesn't need rpm signal. Engine cranking, the computer needs to see rpm signal or it won't ground the fuel pump relay. W/o rpm signal, no spark at the plugs and no fuel injector pulse. I know your talking about fuel, but, when problem is ongoing, check spark and fuel injector pulse, engine cranking.
Intermittent problems are a pain, have to test when problem is ongoing.
mercury fuel pump-i4kx0gxqalhdz4ok10irisui-5-0.jpg

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