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Fuel No Fuel Pressure At Fuel Rail

  • Thread starter Thread starter xking_conquerx
  • Start date Start date Apr 20, 2017
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xking_conquerx

New Member
May 25, 2014
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fort bragg
Apr 20, 2017
#1
  • Apr 20, 2017
  • #1
Disconnected the main line to the fuel rail, cranked, and no fuel came out. Cranked for a good 30-40 seconds. Checked inertia switch, not tripped. Have ~11v going to the switch. Unplugged it and tested continuity, and that was good. Tried testing what i think is the fuel pump harness (middle of the tank in the rear, 6 pin connector?) But wasnt getting power at the pins. Read that i was only supposed to have power at the inertia switch for 2-3 seconds but it was constant, stayed constant until i turned key off. Is that an issue? Also, to the left of the gas tank (drivers side) what is the cylinder thing with a 2 wire harness hidden in the frame? Car in question is an 04 gt 5spd, 63k miles and has been sitting for a year. Had 1/4 tank, filled with new fuel amd octane booster and replaced filter. Was parked cause intake manifold disintigrated at the crossover. Im leaning towards the pump being bad, but id like to test and be sure. Also dont hear pump with key forward.
 

TechnicallyMasterful

Member
Oct 16, 2016
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Apr 20, 2017
#2
  • Apr 20, 2017
  • #2
Fuel pumps fail on those cars a bit. I say get a dead blow and hit the hell out of the gas tank while someone else cranks it over. If it fires up it's a bad pump. Is the car cranking and not starting or no crank no start. 11v seems weak for a battery.
 
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xking_conquerx

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May 25, 2014
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fort bragg
Apr 20, 2017
#3
  • Apr 20, 2017
  • #3
Even at 63k miles? Im sure lettin it sit for a year didnt do any good. And yes it cranks but no start. Seems low cause i was constantly cranking it every minute or so. Probably took a good year off the starter with how much ive been cranking it. I could just replace the pump part, and not the whole assembly right?
 

wmburns

SN Certified Technician
Aug 14, 2009
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Houston Texas
Apr 20, 2017
#4
  • Apr 20, 2017
  • #4
Just wondering.......What model year Mustang are we dealing with?

Why is this important? Because it makes a difference in what is "normal" at the trunk IFS switch. But in general for the 1996+ model year there should be voltage at the IFS switch anytime the key is on.
 
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xking_conquerx

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May 25, 2014
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fort bragg
Apr 20, 2017
#5
  • Apr 20, 2017
  • #5
2004. The posts i had looked at were for 2001, and they were saying power would only be there for 3 seconds. Personally i dont see it being a problem if it stays powered longer.
 
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xking_conquerx

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May 25, 2014
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fort bragg
Apr 20, 2017
#6
  • Apr 20, 2017
  • #6
2004. The posts i had looked at were for 2001, and they were saying power would only be there for 3 seconds. Personally i dont see it being a problem if it stays powered longer.
 

TechnicallyMasterful

Member
Oct 16, 2016
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Apr 20, 2017
#7
  • Apr 20, 2017
  • #7
I'm not sure about the electrical part as I have no wiring diagrams. Could just give the pump a generic power and ground with a 9v and some extra wires. As for vehicle mileage. Parts can fail at any time so I wouldn't dwell on mileage. I'm not sure about the pump parts. It's been a while since I replaced it on my old gt. I think I just bought the entire unit from pep boys.
 

wmburns

SN Certified Technician
Aug 14, 2009
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Houston Texas
Apr 20, 2017
#8
  • Apr 20, 2017
  • #8
xking_conquerx said:
2004. The posts i had looked at were for 2001, and they were saying power would only be there for 3 seconds. Personally i dont see it being a problem if it stays powered longer.
Click to expand...
For the 1999-2004 Model year the fuel pump on runs for 3-4 seconds at initial key on but there's MUST be +12 volts (battery voltage) at the trunk IFS switch anytime the key is on.
 
Last edited: Apr 21, 2017
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xking_conquerx

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May 25, 2014
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fort bragg
Apr 21, 2017
#9
  • Apr 21, 2017
  • #9
So anything less than 12v is not going to turn the pump on at all. Ill recharge the battery and retest then.
 

wmburns

SN Certified Technician
Aug 14, 2009
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Houston Texas
Apr 21, 2017
#10
  • Apr 21, 2017
  • #10
xking_conquerx said:
So anything less than 12v is not going to turn the pump on at all. Ill recharge the battery and retest then.
Click to expand...
Didn't say that. IF the voltage at the trunk IFS is 11 volts likely it will will work. Use your head and factor in what is going on with the car at the time. IF the battery voltage is 12 volts AND the trunk IFS is 9 volts, THEN likely there's a problem. On the other hand if the battery voltage is 11 volts and the trunk IFS is 10.5 volts then the wiring isn't likely a problem.

Finally if the voltage is 6 volts THEN likely there is a problem.

Here's where the model year is important as for example for the 98 model year with a two speed fuel pump relay, 6 volts at the IFS switch is likely OK.

Again. Use your head.
 
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xking_conquerx

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May 25, 2014
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Apr 21, 2017
#11
  • Apr 21, 2017
  • #11
Alright just clarifying. Im not familiar with electric pumps, so wasnt sure if it needed 12v to kick on or if itd kick on with lower but not work as intended (ie. My truck needs 11.5v for the pcm to fire the injectors, anything lower and itll crank but never fire) ill double check my readings this afternoon and give the gas tank some persuasion and see if it starts. Like i said, just trying to get a without a doubt reasoning that the fuel pump is the issue and not something else, not a fan of part swapping to fix the issue.
 
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xking_conquerx

New Member
May 25, 2014
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fort bragg
Apr 22, 2017
#12
  • Apr 22, 2017
  • #12
So i get 11.8v to the harness at the tank, and beating on the tank while trying to start did nothing. Safe to say the pump went out. Time to drop the tank. Thank you guys.
 
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