I need help understanding why this is happening (fuel pressure)

[RRF985]

Ok so I have been watching my fuel pressure gauge since I installed it back in July. I've noticed that in a certain gear the pressure would always drop more than it does in others. Today I finally did some investigative work and this is what I found:

At idle the fuel pressure is 65-70psi. Upon spirited driving the pressure may drop to 60psi. Nothing to be alarmed about. Here is the interesting part. At WOT the pressure maintains a rock solid 60psi in gears 1, 2, and 3. Upon shifting into 5th, the pressure will begin drop rapidly. At around 3,000RPM it starts to drop to about 55psi and at 3,300RPM it is at 50psi. Anything beyond 3,500 and I'm well below 40psi. I actually saw the pressure drop to 20psi a few days ago with the engine running at ~3,800 RPM. I first noticed this when I installed my gauge back in July and found that I always had to feather the throttle in 5th to maintain atleast 50psi. Once it's in 6th gear and with the TC locked the fuel pressure problems go away.

So what I'm wondering, is there anyway to cure this without going to a full aftermarket fuel system? Before anyone says it, the fuel filters were replaced ~1,000 miles ago. I am just amazed that the pressure is ok in 1-3 and 6th but upon the selection of 5th is there really that much more demand for fuel?

Sorry for the long winded post. I'm just trying to figure out what is going on with my fuel system.

[frakchered]

Originally Posted by RRF985

Ok so I have been watching my fuel pressure gauge since I installed it back in July. I've noticed that in a certain gear the pressure would always drop more than it does in others. Today I finally did some investigative work and this is what I found:

At idle the fuel pressure is 65-70psi. Upon spirited driving the pressure may drop to 60psi. Nothing to be alarmed about. Here is the interesting part. At WOT the pressure maintains a rock solid 60psi in gears 1, 2, and 3. Upon shifting into 5th, the pressure will begin drop rapidly. At around 3,000RPM it starts to drop to about 55psi and at 3,300RPM it is at 50psi. Anything beyond 3,500 and I'm well below 40psi. I actually saw the pressure drop to 20psi a few days ago with the engine running at ~3,800 RPM. I first noticed this when I installed my gauge back in July and found that I always had to feather the throttle in 5th to maintain atleast 50psi. Once it's in 6th gear and with the TC locked the fuel pressure problems go away.



So what I'm wondering, is there anyway to cure this without going to a full aftermarket fuel system? Before anyone says it, the fuel filters were replaced ~1,000 miles ago. I am just amazed that the pressure is ok in 1-3 and 6th but upon the selection of 5th is there really that much more demand for fuel?

Sorry for the long winded post. I'm just trying to figure out what is going on with my fuel system.

I did not see in your post or the signature that you have completed teh Blue Spring upgrade for the fuel pressure.

[g2shuck]

this is very odd

[RRF985]

Originally Posted by frakchered

I did not see in your post or the signature that you have completed teh Blue Spring upgrade for the fuel pressure.

I should have mentioned it. Blue spring has been in for 2 years just about.

[southend]

My guess is coupled with your tune, your hfcm is failing. They dont last forever, nice you got a guage, low fuel pressure will kill injectors real quick.

Sent from my phone that somebody didn't help me get.

[harlo]

I'd bet your pump is tired too. mine was kinda like yours but not really. lol. Mine would be fine for a couple days then i'd randomly lose pressure when getting on it but fine under easy driving. Mine had around 130k when i replaced it.

[shawnb99]

i would say tuning.... your stock fuel system just isnt keeping up with the demands.

[RRF985]

Originally Posted by harlo

I'd bet your pump is tired too. mine was kinda like yours but not really. lol. Mine would be fine for a couple days then i'd randomly lose pressure when getting on it but fine under easy driving. Mine had around 130k when i replaced it.

Well mine has about 96.5k on it. Just seems premature on going out but I guess it could happen. Maybe I'll replace it next summer or so.

Originally Posted by shawnb99

i would say tuning.... your stock fuel system just isnt keeping up with the demands.

Could this be fixed with tuning? I think it would kind of ruin the tune.