Question about Mercury Grand Marquis

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1994 mercury marquis, the fuel pump is on even with the key off. removed the relay and disconnected the PCM but the pump still runs. any ideas for a fix?

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  • Mercury Master
  • 5,252 Answers

I don't know about yours, but some cars are wired to run the pump off the oil pressure switch, after the car is running. You probably need to consult a wiring diagram to see how the pump is wired to power, and then try to solve it. Most unusual!

Posted on Dec 04, 2012

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Posted on Jan 02, 2017

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SOURCE: 2001 Mercury Grand Marquis hesitation and jolting from 35-45 mph

Sure, the more the throttle and the longer its open the more gas is being injected so if the spark is not there it will spotter. I think you have nothing to loose with an ignition tune-up. It'll be more economical than taking it to a mechanic and still ending up with the same problem. You should change the fuel filter also it could be clogged and there is'nt enough fuel delivered at these speeds. You can also try a fuel injector cleaning solution the kind you pour in the gas tank. This might work for you.

Posted on May 19, 2009

  • 30 Answers

SOURCE: 1994 toyota fuel pump relay

Fuel pump relay is in the engine compartment left side fuse block

Posted on Jul 08, 2009

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1 Answer

Where is the fuse for the fuel pump on a 94 grand marquis


There appear to be 2 fuses that can affect the fuel pump. #8 which provides power for the fuel pump, and #4 which provides power for the fuel pump relay. Both of these fuses are in the High Current fuse panel, which is located in the engine compartment near the battery.

The warning in the owners manual states: Always disconnect the battery before servicing high current fuses.Ford recommends that high current fuses be replaced by a qualified technician.

Jun 17, 2012 | 1994 Mercury Grand Marquis

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Fuel pump not always on


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

Feb 18, 2012 | 2000 Mercury Grand Marquis

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2000 mercury grand marquis 4.6 fuel


Voltage drop test the electrical circuit , do know how to do automotive electrical testing . Lose connection , resistance in the circuit , lose ground Mastering Voltage Drop Testing with Pete Meier and Jerry Truglia Testing Electric Fuel Pump Problems with Voltage Drop Test

Feb 27, 2017 | 2000 Mercury Grand Marquis

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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.
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Feb 27, 2017 | 2006 Mercury Grand Marquis

1 Answer

How to test your fuel pump on a 1994 GMC safari. Listening more often than not will not determine if the fuel pump is working, some are just too quiet even when inserting a hose in your tank and putting...


You hook up a fuel pressure gauge . No pressure does not mean the fuel pump is bad , could be a electrical problem . Fuel pump relay , A bad crankshaft postion sensor , if the PCM doesn't see an input from the crank sensor it will not energize the fuel pump relay . And Turning on the key to run for 2 seconds will energizes the fuel pump relay to prime the fuel system . An It will prime the system just that quick . Knowing how it works is key to fixing the problem . Testing at the relay . Fuel pump electrical circuit diagnosis no fuel pressure testing GM

Mar 14, 2017 | 1994 GMC Safari

1 Answer

97 grand marquis only getting 6 volts to fuel pump when key is on. through the ecm. replaced with a new ecm and still reads the same thing. why?


The PCM does not supply voltage directly to the fuel pump. It controls the fuel pump relay that dupplie the power to the fuel pump. The first thing you need to do is make sure there is 12 volts at the fuel pump fuse. If there is make sure there is 12volts at two of the pins at the fuel pump relay. If that checks out than you need to start looking for corroded wiring between the relay and the fuel pump. Corrosion = resistane which = voltage drop. Let me know what you find and i'll be happy to help you further.

Jun 09, 2011 | 1997 Mercury Grand Marquis

1 Answer

Can not find witch harness fuel pump fuse is in


fuel pump is protected by a relay. see owner manual for location.

PCM power relay powers up PCM. PCM then powers up fuel pump through fuel pump relay.

Also, check to be sure inertia switch is not tripped. In trunk. look for label or look in owner manual for info.

Jan 08, 2011 | 1989 Mercury Grand Marquis

2 Answers

Will not start. Won't even turn over. I can hear power going to the fuel pump. Checked all relays, fuses and diodes all ok.


Make sure you have juice on the single small wire at the starter when the key is in the start position. If you do then it is probably the starter.

Sep 21, 2010 | 1994 Mercury Grand Marquis

1 Answer

99 Grand Marquis Fuel Pump problem


Lets try a new keyswitch and a fuel filter. The key activates the starter side of the ignition. This terminal should power both the starter solenoid and the fuel pump. Although the fuelpump runs on the ignition side continuously, you should be primed when the key is in the "on" position. I would wonder if the pump is cutting off too early meeting the resistance of a dirty fuel filter.

Jun 09, 2009 | 1994 Mercury Grand Marquis

1 Answer

My 1994 mercury grand marquis wont start


Check your owners manual for a fuse &/or relay that may be faulty. If no luck , get back to us.

May 31, 2009 | 1994 Mercury Grand Marquis

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