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Chris (aka- Moose)
Chris (aka- Moose), Mercury Technician
Category: Mercury
Satisfied Customers: 47633
Experience:  16 years experience with Mercury
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Mercury Grand Marquis: Changed the fuel pump in my 1999 mercury

Customer Question

Changed the fuel pump in my 1999 mercury grand Marquis and the relay, and the fuel pump is stll not getting any power
Submitted: 5 years ago.
Category: Mercury
Expert:  Chris (aka- Moose) replied 5 years ago.

Hello, I'm Chris.
I will do my best to answer your question fast and accurate using the info you have provided. Thanks for visiting Just Answer.


Is the fuel pump relay clicking under your finger when you are turning the key to the run position?


Customer: replied 5 years ago.
Expert:  Chris (aka- Moose) replied 5 years ago.

Is there power coming in and going out at the inertia switch when testing within the first 5 seconds of the key being turned from off to the run position?


Customer: replied 5 years ago.
There is power but it seems to be a low voltage power .. Test light barley glows
Expert:  Chris (aka- Moose) replied 5 years ago.

If you unplug the inertia switch and do the test again on the dark green/ yellow wire do you get full voltage then?


Customer: replied 5 years ago.
I haven't check that but did jumper across to bypass and that made no difference
Expert:  Chris (aka- Moose) replied 5 years ago.

Your going to need a volt meter to accurately test this. A test light is not going to do it. You have power right before the fuel pump but the light is dim so we do not know if the pump is trying to use that power and the circuit is low on amps or the circuit is low on amps prior to even getting to the pump. So far its looking like a wire thats faulty and has resistance or the pump has a poor ground. Use the diagram below if needed



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Customer: replied 5 years ago.
Will you email me the diagram please. [email protected]
Expert:  Chris (aka- Moose) replied 5 years ago.
The website blocks your email and I am not allowed to email you anyways. You can open it above and save it or print it.
Customer: replied 5 years ago.
, i wish to continue to be able to ask questions. This is a new direction that we haven't headed in.. I do plan to accept
Expert:  Chris (aka- Moose) replied 5 years ago.
Glad I could help
Customer: replied 5 years ago.

ok so i mixed up my engines... its a 8 cylnder, and when we unplugged the inertia switch and tested the green wire with a volt meetr while turning the key on for 5 seconds we only got 7 volts

Expert:  Chris (aka- Moose) replied 5 years ago.

The engine does not matter, I knew what you meant since the 4.6 is the only option.


Okay check the fuse that powers the switch side of the relay before and during this same test with the inertia switch unplugged. We need to see where your losing 5 volts with nothing on the circuit even being used.

Chris (aka- Moose) and 8 other Mercury Specialists are ready to help you
Customer: replied 5 years ago.
thanks for you help with this.. you were able to get us going in the right direction.. we just recently were able to find a broken wire... from the fuse to the relay.. repaired the wire and now im off and running
Expert:  Chris (aka- Moose) replied 5 years ago.
Good job