Fuel Low fuel pressure under hard acceleration then pops

[Snomann]

I have a 2002 mustang gt 4.6. It is stock except a cold air intake. No cel on or stored codes. Under hard acceleration at about 3000-3500 rpm I'm getting low fuel pressure and it pops and sputters till you let off but doesn't stall. I have checked the fuel pressure with a manual gauge while driving as well as have a snap on Solus pro scanner that confirms the same readings. The fuel pressure stays at 38-44 psi at idle and as long as your not hard an the pedal but when under load or higher rpm it keeps dropping to almost nothing.

I have tried to clean the MAF sensor with no change. I replaced the MAF sensor with a know good one with no change. There is good vaccum at the Fuel pressure sensor. I have battery voltage at the inertia switch in the trunk. I dropped the tank to make sure there wasn't any debris in the tank so I replaced the fuel pump and filter while is was there. Tank was clean and the new fuel pump and filter didn't help at all.

I would like to test the Fuel pump driver module and CCRM but not sure how to test it while this is happening at 3500 rpm. If someone can let me know how to test them or have any other ideas would be much appreciated!

 

[wmburns]

If this were my car I would start by measuring charging system voltage during the problem. Then move onto the IFS switch during the problem. It will be necessary to do some work with long Volt-Ohm Meter (VOM) leads so that it can be monitored while driving.

Regarding IF the CCRM is working or not. IMO it is. Why? Because if it wasn't the fuel pump wouldn't run at all. The fuel pressure would go to zero.

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

 

[Snomann]

The lowest voltage I have seen on the scan tool was 13.7 volts when the problem was happening. Would you test differently, as in not just looking at the scan tool? I can set up some long wires to do a test at the ifs switch. What kind of voltage should i be seeing there when this is happening?

I wasn't sure how the ccrm works but that's good that i can rule that out.

 

[Snomann]

I set up the long leads and i hooked up my volt meter to the ifs switch. I never saw a voltage drop lower then 13 volts. I put the leads on both the wires on the ifs switch and there was no difference. Its battery voltage about 14.4 at idle but when you are accelerating it drops till it hits just above 13 volts when the fuel pressure drops right off and it pops. It fluctuates between 13-14.4 volt while normal driving. Would this rule out the FPDM?

What would be the symptoms of a bad fuel pressure sensor. Are fuel pressure sensors common to fail on the 99-04?

 

[wmburns]

Wild goose chase alert! Just want to make sure that no corners have been cut with regards to testing the alternator. Why? Because your symptom could be caused by a bad alternator diode (excessive AC ripple) or worn alternator slip rings (brush bounce).

If this were my car I would also test the trunk ground. Confirm that it's clean and tight and able to carry a large current. A voltage drop test between the trunk ground and battery negative.

As far as how to test the fuel rail pressure sensor (FRPS), the best way is to cross check the fuel pressure as reported by the PCM against an external fuel gauge.