Fuel pump constantly running!
11-14-2011, 09:48 PM
#1
Thread Starter
Join Date: Nov 2011
Location: Texas
Posts: 3
Fuel pump constantly running!
I hope this is a dumb question. This weekend I switched out the battery cable in my 2005 GT convertible. I used an OEM cable as my + terminal was corroded. No problems installing the cable, but when I attached it to the battery, the fuel pump kicked on, but no other power is to the car. Key in or out does not change anything. If I turn key to the ignition position, the fuel pump stops, but no juice. Did I screw something up?
11-15-2011, 10:47 AM
#2
6th Gear Member
Join Date: May 2006
Location: Nicely done
Posts: 11,881
if you pulled relays out, just double check they went back where they
were originally. it's possible they work when mixed around but i just can't
tell for sure at the moment.
hopefully it's something simle and not the PCM.
were originally. it's possible they work when mixed around but i just can't
tell for sure at the moment.
hopefully it's something simle and not the PCM.
11-16-2011, 01:31 AM
#4
5th Gear Member
Join Date: May 2007
Location: Central Texas
Posts: 2,388
Are you sure it's the fuel pump? Are you hearing the sound from under the hood, standing by the battery? Or sitting inside the car and know for sure it's behind you?
The shaker system's crappy cd changer will cycle and sound like something buzzing, and will stop when the ignition is turned on. If you're standing by the battery, it sounds like its coming from near the firewall in the engine compartment.
Make sure the radio is turned OFF before turning off the ignition to prevent it.
The shaker system's crappy cd changer will cycle and sound like something buzzing, and will stop when the ignition is turned on. If you're standing by the battery, it sounds like its coming from near the firewall in the engine compartment.
Make sure the radio is turned OFF before turning off the ignition to prevent it.
11-16-2011, 07:36 PM
#7
5th Gear Member
Join Date: May 2007
Location: Central Texas
Posts: 2,388
It'd be good to see what the fuel pressure is doing with key-on/engine-off, via diagnostic datalogging of the pressure.
It would stay running if it cant hold prime pressure, or if the PCM thinks it isnt building enough pressure due to a faulty FRPS.
Otherwise with adequate pressure, it should not be running once pressure is established.
Back to your first post. Replacing the battery cable wound not affect the fuel system, as the wiring and control to the pump is through the wiring harness running under the fender. Is it possible some battery acid or something made its way under the battery and shorted or melted some of the wiring harness underneath?
Some other things to try (summarizing what others also suggested)
- pull out the fuel pump relay, see if it pump still runs; if it does with key-off and no relay in place, you have a short to the fuel pump power wire (runs from the BEC underneath on passenger side into cabin and over to the inertia cut-off switch).
- if removing the relay kills the pump, either the relay is bad or it is being activated even with the key in the off position. If the relay clicks when you plug it in, it is being activated even with the key off, and that's a problem in a different circuit.
- check voltage at the switch or at the white wire going to the FPDM module in the trunk; if voltage is there with key-off, you have a short (this is just an extension of checking the above, but is after the inertia cutoff).
With pump running and key off, it shouldn't be too hard to isolate where the power is coming from, and determining if its due to the relay energizing or to some other issue after the relay.
Refer to your owner's manual to the location of the relay. It'll be one of the smaller rectangular ones in the center row of the BEC, and not one of the larger square ones.
It would stay running if it cant hold prime pressure, or if the PCM thinks it isnt building enough pressure due to a faulty FRPS.
Otherwise with adequate pressure, it should not be running once pressure is established.
Back to your first post. Replacing the battery cable wound not affect the fuel system, as the wiring and control to the pump is through the wiring harness running under the fender. Is it possible some battery acid or something made its way under the battery and shorted or melted some of the wiring harness underneath?
Some other things to try (summarizing what others also suggested)
- pull out the fuel pump relay, see if it pump still runs; if it does with key-off and no relay in place, you have a short to the fuel pump power wire (runs from the BEC underneath on passenger side into cabin and over to the inertia cut-off switch).
- if removing the relay kills the pump, either the relay is bad or it is being activated even with the key in the off position. If the relay clicks when you plug it in, it is being activated even with the key off, and that's a problem in a different circuit.
- check voltage at the switch or at the white wire going to the FPDM module in the trunk; if voltage is there with key-off, you have a short (this is just an extension of checking the above, but is after the inertia cutoff).
With pump running and key off, it shouldn't be too hard to isolate where the power is coming from, and determining if its due to the relay energizing or to some other issue after the relay.
Refer to your owner's manual to the location of the relay. It'll be one of the smaller rectangular ones in the center row of the BEC, and not one of the larger square ones.
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