092eg6

ok, turn the key on and my fuel pump sends fuel to my rail and injectors with about 60psi on the gage and as soon as the fuel pumps shuts off, the psi gage goes back down to zero, check all lines, injector seals, no leak anywhere...... it's a walbro 255 internal fuel pump im using. what could be the cause if theres no leak to be found?

092eg6

found out that it was the walbro fuel pump

7rrivera7

iTrader: (1)

Please elaborate...

092eg6

simple as this:
put on a stock one- it holds the pressure
switch to walbro 255- pressure drops

00Red_SiR

my stock pump drops pressure when I shut it off. I have removed the pulse absorber/dampner from the fuel rail inlet, not sure if that has an effect on pressure dropping after I shut the car off.

Scott_Tucker

Fuel pumps normally have a check valve in them so fuel pressure does not bleed off after the key is turned off. I don't know if a Walbro pump has one though.

7rrivera7

iTrader: (1)

Ok, since I have a Walbro, I decided to check it.

1) Battery disconnected
2) Connected the battery - no change in pressure
3) Put the key in the position right before cranking - pressure goes to 40 for a second then back to zero
4) Put key in the off position - pressure still at zero

So in my case after activating the pump's 12v line, it primes the fuel rail for a second, then shuts off sending the pressure goes back to zero.

Is there something 'wrong' with this behavior on the Walbro?

092eg6

yes im sure. because i had to use one of my friends walbro 255 yesterday for a dyno session, prime the pump, pressure goes to 60psi and drops to around 55psi and holds the pressure there and does not drop down to Zero.