Dropping fuel pressure

[Blk04MM]

Via scangauge my fuel pressure drops from 38/39 PSI normal driving to as low as 31 PSI at WOT. basically the longer I stay in it the lower it goes. Is that because the alternator shuts off at WOT and don't feed the pump? Or do I have another issue here?

Car has 170k with OE pump & injectors

[lji372]

Alternator does not drive the fuel pump. (Control the pressure geeez)

When's the last time you changed the fuel filer?

[Blk04MM]

Alternator does not drive the fuel pump.

When's the last time you changed the fuel filer?

It's the new MM I just got. I have no clue. I'll change it though.

Could you explain how the filter would cause it to drop so that I know.

[lji372]

Hmm...imagine if you strangled somebody.
They would be okay at the first breath, as your grip tightened it would be harder for them to breath with every breath thereafter.

[Blk04MM]

Hmm...imagine if you strangled somebody.
They would be okay at the first breath, as your grip tightened it would be harder for them to breath with every breath thereafter.

That sum'd it up lol. Thanks. Is it worth doing the "upgraded" filter for an NA nitrous car or the OE stock is fine?

[Blk04MM]

And Me mentioning the alternator shuts off was in reference to my volts dropping at WOT as well down to 10volts but soon as I let out they go back up. Had the battery and alt checked was told they both are good. So is it the pump not getting proper amount of volts?

I'm just trying to eliminate things. I will do fuel filter regardless due to it being the original one

[RacerX]

Are you measuring fuel rail pressure or Fuel injector pressure drop?

[martyo]

Alternator does not drive the fuel pump.

Orly?

...............

[Blk04MM]

Are you measuring fuel rail pressure or Fuel injector pressure drop?

Whatever the scangauge tells me under FP. Don't know if it's rail or injector

[Blk04MM]

Alternator does not drive the fuel pump. (Control the pressure geeez)

When's the last time you changed the fuel filer?


Orly?

...............

I know it does not control pressure but if it's not getting enough volts it'll cause it to not work as efficient under WOT right? By all means correct me if I'm wrong. I'm just trying to get the situation fixed so I know it's getting fuel for spray

[RacerX]

I have Alt on at wot in my tune. Just my personal preference. The fuel injector just changes it's pulse width based on voltage. You can't go by rail pressure. There's so many variables and calcs done and you need to know injector pressure drop.

[Vortech347]

Orly?

...............

:lol:

I thought the same thing.

If the Pump is demanding more voltage than what is being logged, yes you will run out of pressure. Its a common occurrence on 03/04 Cobras because their alternators are over spun from the factory and will electronically cavitate after 4000rpm so they loose voltage like a MOFO and the car goes lean if its needing that upper scale.

If my Marauder was supercharged there's no way in hell I would allow the alternator to shut off in the tune. NA? I wouldn't worry to much about it. Unless your log says you need to.

[martyo]

I have Alt on at wot in my tune. Just my personal preference. The fuel injector just changes it's pulse width based on voltage. You can't go by rail pressure. There's so many variables and calcs done and you need to know injector pressure drop.


:lol:

I thought the same thing.

If the Pump is demanding more voltage than what is being logged, yes you will run out of pressure. Its a common occurrence on 03/04 Cobras because their alternators are over spun from the factory and will electronically cavitate after 4000rpm so they loose voltage like a MOFO and the car goes lean if its needing that upper scale.

If my Marauder was supercharged there's no way in hell I would allow the alternator to shut off in the tune. NA? I wouldn't worry to much about it. Unless your log says you need to.


What they said!

[LANDY]

You should dattalog the FPDC. Also is this happening on the gun?

[Blk04MM]

I have Alt on at wot in my tune. Just my personal preference. The fuel injector just changes it's pulse width based on voltage. You can't go by rail pressure. There's so many variables and calcs done and you need to know injector pressure drop.

I'll get readings on the injectors if the scangauge isn't reading them.


:lol:

I thought the same thing.

If the Pump is demanding more voltage than what is being logged, yes you will run out of pressure. Its a common occurrence on 03/04 Cobras because their alternators are over spun from the factory and will electronically cavitate after 4000rpm so they loose voltage like a MOFO and the car goes lean if its needing that upper scale.

If my Marauder was supercharged there's no way in hell I would allow the alternator to shut off in the tune. NA? I wouldn't worry to much about it. Unless your log says you need to.

Car is NA but will be on the bottle so I definitely need to have the Alt on if it's causing my FP to drop.


What they said!

Thank you


You should dattalog the FPDC. Also is this happening on the gun?

Haven't fired the gun. Making sure all parameters are set before I blow something up. Most likely the car will be taken to tony to be fixed. I like the tune I have in it now (zack) so I hope he can just alter the parameters that need to be altered for the gun