DAP@EPL

Does the fuel rail hold system pressure overnight or does it drop off? Let me know the year and model along with your response, if you could.

Thanks.
-Dave Pramanik

Audi2ptzero

This happens because there is nothing to hold the pressure in the fuel system and it drains back to the tank. When you turn on your key the ecu sends a pulse of power to the fuel pump so that it builds up some pressure before you start it.

AggregatVier

"After 10 minutes the remaining pressure should be at least 2.5 bar."

DAP@EPL

I was told that it should hold pressure overnight, but mine wasn't... was concerned I had a leaking injector.

The fuel pressure seems to drop off gradually over a period of 2+ hours. Sound normal?

Cycling the ignition brings it right back up.

-Dave Pramanik

Brent V

Mine never held pressure overnight, it would bleed off slowly when the car wasn't running.

DAP@EPL

Thanks for the info. I feel much better about what I'm seeing.

Audi2ptzero

But on a return fuel system the pressure will leak off over time.

Yippers®

This is for the AEB but I suspect similar for the DBWs ...<ul><li><a href="http://1.8t.org/~quattroman/Audi%20B5%2097-2001/Fuel%20injection%20and%20ignition/AEB/MFI/24-1%20Motornic%20MFI%20&amp;%20Ignition%20system.pdf ">http://1.8t.org/~quattroman/Audi%20B5%2097-2001/Fuel%20injection%20and%20ignition/AEB/MF

xr4tic

mine will hold it for a couple hours at least. Sometimes it will be ~50psi, and sometimes it will be ~20psi when I shut the car off.

DAP@EPL

Takes a few hours before it drops down to zero. Just wanted to confirm that it was supposed to drop off and not maintain pressure over time.

Sounds like what I'm seeing is normal.

-Dave Pramanik