fuel pressure is dropping at wot

if i go wot by the time i get to the top of 2nd gear my fuel pressure is dropping, its set at 50psi and it drops to at least 34 psi, but while cruising, ideling, and accelerating here and there its fine or it goes up a little bit,

for a fuel system i have a 255 walbro in tank pump 1year old, 30lb svo injectors 2years old, aeromotive afpr 2 yrs old

and according to the dyno its leaning out upstairs

checked fuel injectors and they are not leaking, checked regulator with engine running and vacum line on it reads 50, off it reads 56 psi

checked voltage at pump with engine running and its at 12.5 volts

i also notice that the fuel pressure drops when the key is on but engine is off. it graduatly drops from 50 to 0


im going to change my fuel filter and take it for a ride and see what happens now, could i have a faulty fuel pump, is it possible that i may have installed it wrong

ok i changed the fuel filter and when i go from 10mph to 100mph the fuel pressure drops to about 42 to 43 and then it holds there

I think your close to factory setting but obiviously you helped out the pressure with the fuel filter. Mine will drop to 0 after 30 minutes after you shut it off but it takes over 20 minutes to start. The pressure regultor bladder might be bad if it drops to fast. I have an FMU so mine rises with acceleration so i am not sure how yours should respond.

If you've got the pressure set to 56psi (no vacuum compensation) with the AFPR, its shouldn't let the fuel pressure drop to 43psi at WOT. If you sized the injectors for 56psi, and put the correct constant in the PCM, the reduced fuel pressure is reducing injector flow by more than 12%, compared to what the PCM thinks they are flowing. Not a good way to run an engine at WOT.

Hate to mention it, but a large number of people have had problems with the Aeromotive AFPR. Not finding fault with Aeromotive, just pointing out that their LT1 AFPR has been the source of many problems.

Hate to mention it, but a large number of people have had problems with the Aeromotive AFPR. Not finding fault with Aeromotive, just pointing out that their LT1 AFPR has been the source of many problems.

If you have the "LT1 " regulator that replaces the factory one...it is a pc. of junk. Never had a problem with anything else aeromotive but I know for a fact those have had problems from day 1

this problem has been noticed durring a dyno tune, so the tuner raised the fuel pressure and made changes accordingly, he said that as the fuel pressure was dropping on the gauge it was leaning out and he wanted to get it to a point where i can drive it without it running too lean.

is there a way i can check to see if my aero regulator is bad, should i put my stock one back on? what other regulators are out there for the lt1 fuel rail,

isent the pressure supposed to hold when the system is primed? could a bad check valve in the pump be the problem

put the stock one on and get him to adjust the tune

thanks for the replys, i will give this a try tommorow,

A leaking fuel pressure regulator, bad check valve in the pump, or leaking injectors will cause fuel pressure to drop rapidly on shutdown.

i took off the rail with injectors attached and turned the key on and did not see or feel any fuel from any of the injectors, but i can smell some fuel, maybe because i just had the engine running for a little bit prior to pulling the rail? im going to put my stock regulator back on and see if it holds pressure.

it shouldent drop at all right? or is it ok if pressure drops a little bit?

At WOT, the only reason pressure can drop is if the pump can not supply enough fuel. It has to supply enough to feed all the injectors, and have some left over for the fuel pressure reugulator to control the pressure by squeezing down on the flow returning to the tank.

Or, if the FPR is faulty......

thanks again i will change out to the stock regulator tonight or tommorow night and see if anything happens

ok stock regulator is back in and i turned the key to the on position let the fuel pump prime and it goes straight to 38 psi and holds maybe it will drop 1 psi within 2 minutes but it holds pressure now, i havent started it yet because it was too late out and i dont want to wake everyone

ok took the camaro out for a quick ride today and fuel pressure is at 37-38 psi and its staying there doesent drop when i lay into the gas in first second and third, so im gonna say its the regulator? what adjustable regulator do you guys reccomend, i dont wanna drive it unless i have the regulator set to what it was for the tune

thanks for all the help

At WOT, the only reason pressure can drop is if the pump can not supply enough fuel. It has to supply enough to feed all the injectors, and have some left over for the fuel pressure reugulator to control the pressure by squeezing down on the flow returning to the tank.

Or, if the FPR is faulty......

God, your quest is such horse****.

A "faulty" fuel pressure regulator would leak, not drop pressure at wot. You really aren't very strong technically when it comes to parts.

God, your quest is such horse****.

A "faulty" fuel pressure regulator would leak, not drop pressure at wot. You really aren't very strong technically when it comes to parts.

Thanks for the kind words.

Of course that fuel flowing through the diaphragm, out the vacuum compensation line, and into the intake manifold wouldn't cause any drop in fuel pressure - or would it? Or let's say the "fault" in the AFPR is that it can't close down all the way..... but hey... the fact it can't fully close off the return flow wouldn't drop pressure..... or would it?

You just can't accept the fact the Aeromotive AFPR is a POS. I made sure I didn't even mention the name because I knew you'd be trolling around at the mere mention of Aeromotive, but the thing is so bad, other people know it too.

Have a nice day in fairy-tale land :D

ok took the camaro out for a quick ride today and fuel pressure is at 37-38 psi and its staying there doesent drop when i lay into the gas in first second and third, so im gonna say its the regulator? what adjustable regulator do you guys reccomend, i dont wanna drive it unless i have the regulator set to what it was for the tune

thanks for all the help

I'm not sure about the different brands, I will comment on the few I have had experience with....I had a metco, I used it for 6 years worked great.

My buddy had an accel..he had problems
Now I use an aeromotive external regulator...works fine.
My other buddy uses an external Weldon.....its top of the line

One thing to consider is that you could hold only 43psi with the aftermarket regulator.

Now that you have the stock regulator, it holds steady, but at a lower pressure.

I would bet that your Aeromotive may hold the same lower pressure at a steady rate as well. This test would not prove a regulator at fault unless the stock regulator could hold pressure at 43psi or more for comparison.

this problem was first noticed when on the dyno and it was set at 42psi the tuner said that it was dropping 10 to 15 psi and running too lean as well (should of mentioned that) so im sure pressure was dropping lower then stock fuel pressure

I had a leaking Aeromotive FPR. Was a real problem and took a while to T_shoot. Don't like their design of the diaphram. Leaked alot of fuel thru the boost ref line to the intake manifold.