Final Steps To My 5.4 Swap, Please Help With Fuel System.

Scarreddragon

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Apr 11, 2015
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I have been working on and off for 4 years on a 5.4 swap. The car is a 1998 GT, and I have placed neatly a 2002 expedition 5.4. I had the engine running, and did a break in phase. I was loosing oil pressure, and had a clutch squeak issue. So I pulled the motor, upgraded the oil pump, and replaced all the clutch moving parts.

Dropped the motor back in last week, it is now 100% back together! No nuts or bolts left, lol.

Go to start it up today, and nothing. I am getting no fuel at the fuel lines on the rail.
- Pulled the fuel lines at the rail, and no fuel was present after trying to start it, however there was a very small amount of air pressure on the smaller line.
- Checked the interrupt button, and it is pressed in, tapped it till it popped up, then pushed it down.
- Checked the 20a fuse in the engine bay and it is good.
- Cut off the fuel filter (did not have ford connectors, instead it was a previous hack job). The lines were totally dry.
- With the lines disconnected, I had the key turned to the on position, and no fuel came out, nor did I hear the pump.
- Tried to turn it over, with the line held in a bucket and nothing.
- Unplugged the plug under the gas tank, and checked all the pins for power, while my GF cycled the key from off to on, while I was testing. I looked for full and micro voltage, and saw no fluctuation.
- I can feel the relay in the passenger side wheelwell clicking when the key is turned to on. (it clicks more than once per keyturn, it is not simply, on click, off click. It clicks maybe 3 times or 4 every cycle.)
- I can see voltage at the plug on the bottom of the emergency button.

I still do not have voltage at the plug under the bumper at the gas tank... To test the fuel pump, is there a way that I can hook the battery up to the plug harness and force the pump to come on, to check its operation? Will I break the pump with battery amps? Does anyone see anything above that stands out, including the clicking relay, I do not have another mustang around to compare it to?

Here are some vids just for show! I got a lot of help on these forums when I did the build, including a great seller that gave me some awesome parts! Perhaps this is the final challenge!!!

Pre-tune, first start,

View: https://www.youtube.com/watch?v=bIfNgtE94Jw

Post tune, Pre break in.

View: https://www.youtube.com/watch?v=91fnz0F3eXc


Help me make one more video when it's done!!!
 
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I'm going to assume this car is using the basic stock GT fuel system.

This is important. The BR/PK wire from the trunk IFS switch goes through connector C420 and then onto the tank hat. Therefore if there's voltage at the IFS BR/PK wire and there's no voltage at C420 BR/PK wire, then there has to be a fault in the wiring harness.

As for how to force the fuel pump to run, injecting +12 volt at the trunk IFS switch BR/PK wire should make the fuel pump run. IF the fuel pump does not run, Confirm ground G300.

The best way to confirm ground G300 is to measure the resistance from connector C420 black wire all the way back to the battery negative. Use a scrap piece of wire to extend the VOM leads. Should be low (less than 2 Ohms). I recommend using a new battery in the VOM meter and zeroing the meter before the test.

Please note. The 1998 GT has a two speed fuel pump that uses a relay with a ballast resister. So if there were NO VOLTAGE at the IFS switch, in addition to a possible CCRM issue, there's a possibility of a bad high/low speed fuel pump relay or ballast resister.

Your post stated there was voltage at the IFS switch. However, it did not state how much voltage. This might be important as it helps determine if the fuel pump speed relay is in high or low speed.

In summary. At connector C420, the BR/PK and BLACK wires go straight to the fuel pump. So injecting 12 volts directly towards the fuel pump doesn't make the fuel pump run, the pump has to be bad.

Once the fuel pump has been confirmed to work, I recommend confirming ground G300 is good. As a bad ground could keep the Fuel pump from working.

Finally need to trouble shoot the voltage on the BR/PK wire as this could be fuel pump speed relay, CCRM, fuse, ignition switch, or wiring fault.

Good luck.
 
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So I got to the bottom of one problem. It was the anti-theft, I found my other key today, and went out there and tried again. I actually heard the pump come on when I inserted the key!!! I used my SCT to clear the code for anti-theft. Let the pump cycle 3 times, and actually heard it, and then when I tried to turn it over, for 10 seconds, after it did that, the pump was not cycling again. l had a code p0232 on the scanner. I went back and checked my wiring again. This time when I tested the power at the plug by the gas tank I had no power again. I tested the voltage at the emergency shutoff switch like you said, and it is a fluxuating voltage between 5 and 2 volts, it hops all around, it is not a steady voltage at all.

After I pulled the plugs for testing, I went back to the scanner and cleared the 0232 code, and tried again. No fuel, but now I am throwing NO codes. I have a guy getting set up to come help me, I guess he is a good wiring guy! I hope he can find it, but in the meantime, this is VERY frustrating, that I could hear the pump, the anti-theft problem is gone... And now no power at the tank harness again...
 
There are some "issues" with your trouble shooting steps. The lack of fuel pressure is NOT related to the anti-theft system (PATS). For the 96+ model years PATS does NOT with hold power to the fuel pump. PATS works by with holding fuel injector pulse.

Therefore, if the fuel system does not develop pressure the problem is more basic.

Recommendation. Focus on WHY the voltage at the trunk IFS switch is not correct. As stated before the likely reasons are:
  • CCRM
  • CCRM ground
  • radiator core support grounds
  • for the 98 model year, the high/low speed fuel pump relay.
  • fuel pump ground
  • fuse
  • ignition switch
  • wiring
  • PCM