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Chris (aka- Moose)
Chris (aka- Moose), Mercury Technician
Category: Mercury
Satisfied Customers: 43885
Experience:  16 years experience with Mercury
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Mercury Mountaineer: I have a 2003 mountaineer 4.6litre , just

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I have a 2003 mountaineer 4.6litre , just replaced fuel pump and fuel filter, still wont start from fuel. Itll start off the bottle though , so I know I have spark. Please help

Hi, I’m Chris. Welcome and thanks for asking your question!


Have you checked the fuel pressure?

Have you verified the pump is getting power and ground and is running?

Have you checked injector pulse?

Is the theft light on solid or flashing fast after the key has been in the run position longer than 5 seconds?


Customer: replied 3 years ago.

Wasnt getting fuel pressure, so changed pump and filter, 26 lbs of pressure.


Climbed under with test light getting power to pump , had the wife crank it while I tested it .


no flashing theft light when I turn the key


whats injector pulse

Did you install a Motorcraft pump, because 26psi is not enough.

Injector pulse is the ground signal to each injector from the computer. You plug up a noid light in place of a injector to see if there is a flashing light while cranking.


Customer: replied 3 years ago.

Airtek fuel pump


Could it be bad injectors even thow it starts off the bottle

It can be injectors, computer, wiring, sensors. We first of have to get the fuel pressure to the minimum 60 psi.


Is 26 psi tested at the injector rail the highest pressure you can get when turning the key from off to run?


Customer: replied 3 years ago.

That was before I changed the pump and filter, I will run back to the store and rent a pressure tester again

Unplug an injector and turn the key on, is one wire showing power?


Customer: replied 3 years ago.

Yes power to one side of injector

Great, now clip your test light on the battery positive post and check the other wire while cranking. It should flash the test light very dim. Check this.
Customer: replied 3 years ago.

Sure did , test light was flashing

Okay it runs off spray, its has spark obviously, one injector is working, we do not know the current fuel pressure, and the theft system is not activated.


This leaves checking at least 3 more injectors since the engine can run on 4 cylinders. Then checking your new pumps fuel pressure. It has to be fuel pressure based on what results I am getting now.


Other possible causes are clogged air intake, faulty idle air control valve, clogged injectors.


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