new fuel pump/has power but doesnt turn on

ackard2 · #1 02-18-2011, 04:11 PM

2004 Grand prix GT2 :Ive changed the relays/fuses, changed the fuel pump, its getting the required 5volts but it doesnt kick on. Ive tried looking to see if theres a switch that kills the pump in case of an accident(no accident but maybe went bad) but havent been able to find out if it has it. Im lost, any advice

inafogg · #2 02-18-2011, 04:33 PM

inertia switch should be in trunk side panel behind carpet.
are you sure you have a good ground connection for pump??

ackard2 · #3 02-18-2011, 04:50 PM

theres 5v going to the purple wire on the four prong harness but only .03v going to the grey wire, it is my understanding that the four prong is associated with providing power to the pump itself. I am unsure if the grey wire should have 5v as well.

olopezm · #4 02-18-2011, 08:00 PM

The purple wire is the Fuel level sending unit and with the connector unplugged you'll get constant 5v as the resistor in the level unit is not present (voltage divisor in electrical terms). If you connect it and backprobe the connector you'll see the voltage increase and drop depending on the fuel level.

YOUR PROBLEM is with the gray wire, that's the VCC signal for the pump and that's where 12v should be constant with key on, check the fuse panel for any blown fuses.

Best regards,

Oscar.

olopezm · #5 02-18-2011, 08:07 PM

By the way

Welcome to the forum!

I forgot to mention the electric diagram does NOT shows any inertia switch, the power runs straight from the fuel pump relay to the fuse box and to the pump. The highlighted wire corresponds to the gray wire in the first diagram.

BNaylor · #6 02-18-2011, 08:21 PM

Is the FUEL PP (fuel pump) relay energizing? Once energized by the ECM/PCM module the contacts of the relay passes B+ which is 12 volts to the fuel pump on the gray wire as olopezm pointed out.

ackard2 · #7 02-23-2011, 03:49 PM

The grey wire has 8-10v during the first few seconds when i turn the key on but then drops to 0 . I have checked all the fuses and replaced them just for kicks. Im lost on how to cure the problem.

olopezm · #8 02-23-2011, 07:53 PM

The system primes the pump during the first seconds and turns off when you turn the key to the ON position; after that when you turn the key to the START position it will run the pump continuously.

Ask an assistant to hold the key at the START position while you measure the voltage, if you see it raise then it will be very likely you have a bad pump, there is a small chance you got a bad one right out of he box.

Best regards,

Oscar.

tblake · #9 02-24-2011, 09:16 AM

Quote:

Originally Posted by olopezm

I forgot to mention the electric diagram does NOT shows any inertia switch, the power runs straight from the fuel pump relay to the fuse box and to the pump. The highlighted wire corresponds to the gray wire in the first diagram.

Hey Oscar, I'm not suprized. I think the inertia switch is just a ford thing. I know my 2000 GP doesn't have one but I've never worked on 2004+ so I didn't want to chime in and be wrong.

tblake · #10 02-24-2011, 09:18 AM

ackard2, before you remove the pump again, check the your ground wire (black), measure resistance between it and an unpainted metal part on the car. Should have 0 ohms or very very close to.

brcidd · #11 02-24-2011, 09:23 AM

This happened to me once- put it all back together and went to prime system with primer lead--and nothing-- Got upset and beat the bottom of the fuel tank, and the pump started running. From then on, I always test new pump prior to install- don't want a bad one out of the box! Seems the new one was just stuck, from a long shelf life....as far as I know. Worked for several years there after....

olopezm · #12 02-24-2011, 11:08 AM

Quote:

Originally Posted by tblake

ackard2, before you remove the pump again, check the your ground wire (black), measure resistance between it and an unpainted metal part on the car. Should have 0 ohms or very very close to.

Good one Tim, I guess I'm a little pessimist and like to go after the worst case scenario first LOL.

Quote:

Originally Posted by tblake

Hey Oscar, I'm not suprized. I think the inertia switch is just a ford thing. I know my 2000 GP doesn't have one but I've never worked on 2004+ so I didn't want to chime in and be wrong.

I know what you're talking about, even after I saw the wiring diagrams I was hesitant to reply saying there was no inertia switch, my 1997 GP doesn't have one either, but the windstar and the all-mighty TC both have the switch which is know to cause problems even when the car hasn't been in an accident

.

Best regards,

Oscar.

danielsatur · #13 02-24-2011, 12:26 PM

Some newer Auto's have a pretection circuit for the electric fuel pump, if the fuel is too low, it will disable pump so you don't burn it up.

You can measure a volatge accross any open circuit!
If you bench test your new electric fuel pump, try to pump some fuel in a spare gas can for lubriication.

BNaylor · #14 02-25-2011, 11:50 PM

And who gave the suggestion on an inertia switch?

Speak up and please explain.

FORD - Found On Road Dead.

BTW - The problem is we have people giving their two cents worth on models (i.e. Grand Prix) they know nothing about or probably never owned let alone ever worked on one.

I'd say the 5 letter word starting with a "T" but I'll save that for a PM.

inafogg · #15 02-26-2011, 10:23 AM

And who gave the suggestion on an inertia switch?

Speak up and please explain.

that would be me,after OP asked... my bad
also suggested the ground being checked
so PM me if you wish

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