I was getting ready to fire up the 383 for the first time and when I turned on the ignition and the fuel pump primed the system, I hear a swishing/hissing noise coming from the engine compartment when the pump primes. It sounds as if one of the injectors is stuck open and shooting fuel into the chamber. I put a video scope into each one of the runners (I have a Super ram intake and took the top off) and do not see any injectors leaking which is good. I primed the fuel pump via the test connector and hear the hissing noise and it seems to be coming from the regulator. The fuel pressure goes up but then gradually goes back down to zero when pump is turned off. I have a Walbro 255lph in-tank pump. I pinched the return line and the pressure holds. I replaced the regulator diaphragm and it's still making a hissing noise when primed. Has anyone experience this before? How long is the pressure supposed to hold? Thanks in advance.

 

TTT

 

anybody?

 

sounds like what i got going on. what brand of afpr do you have?

 

It's a homemade afpr that Vader wrote an article on. It never made the noise with the stock pump. I'm assuming that since the Walbro pump flows more fuel that the noise is coming from the fuel rushing past the return opening under the regulator. Are you having any issues with yours or is your car running fine? Reason why I ask is because I haven't fired mine up yet.

 

as soon as i get done putting my new injectors in, i will let you know. should have them in by tomorrow morning. they are the last original part on the damn thing, so i figured if its anything, its them.

 

None of my fuel injectors are leaking and I verified that by viewing each nozzle through a color video scope. I'm almost convinced the swishing noise is fuel rushing into the return line port beneath the diaphragm.

 

well, i feel like a complete ***. the vacuum line to the afpr (specifically the 90deg. boot) had a pin hole in it. as soon as i replaced it, the hissing went away.