curious question: my fuel rail pressure grows after the engine has been shut off (at least the sensor says so). I've been sitting her for 5ish minutes and my Interceptor says 1850 PSI, and my Torque app says 1925 (shouldn't the be the same??). In any case, is this accurate or just a symptom of the car being off?

 

Mine spikes too. This is normal. When the car is running, the injectors are open so there is flow in the fuel line. When the car is off, fuel flow stops, and pressure builds up to a steady state value. I'm not sure if there's a drainback valve in the line that allows the pressure to be bled off.

The discrepancy between values could be due to a time delay in the torque app. They should in theory be monitoring the same OBD PID.

 

I'm just sitting here waiting until the fuel rail pressure tops off, lol. Thanks.

I was under the understanding that they would be monitoring the same PID, but that has come into question recently when my interceptor says I'm at 17.2in/Hg vacuum at idle, while Torque says 19.8. (I'm trying to diagnose an issue with terrible fuel mileage, like 22mpg at 70MPH, and I'm grasping at straws now..)
Thanks for the help!

 

For those that are curious, FRP stops increasing at about 2370PSI

 

its normal. it goes up for a bit then drops. id like to say cause of because of heat but who knows?

 

Who knows is right lol. Thanks guys

 

Well, I just told you why your fuel rail pressure increases at shut off so you do know why lol... and it's not due to heat.

Have you checked your equation for this PID in torque?

 

Some of your mileage has to do with rpm. The faster you are buzzing the motor but it still should be higher than that. I purposely drive highway at 60 verses interstate at 75. For me it's over 7 mpg just in that. I can get 35-37mpg at 60 if I'm lite on the throttle.

 

I have not. I'm not overly concerned with the difference, more that I wasn't sure it was supposed to be rising. I'm using a Droid from like 5 years ago and I can't update the app anymore so I'm kinda stuck there.. lol

Correct, yes. I used to be able to, until October. As soon as it warms up, I'll actually dig in there and see what I can or cannot find

 

I read a long time ago your not suppose to mess with the engine unless it's been sitting for awhile for this reason. The psi in the fule rail is high and it could fk u up lol

 

I've taken off the fuel pump like 10 minutes after turning the car off. Just need to pull the fuel pump relay and let the car die. Lol

 

These cars are different. They can still have about 100# of pressure after yanking the pump relay due to the way DI and the HPFP works.

The safest way to bleed off the pressure is to jump one of the injectors after the car is off. Obviously the fuel pump relay still needs to be yanked prior.

 

meh, hardly any fuel came out when i just pulled the relay