I have a re-wired walboro 255. 95% of the time i can't hear it at all. and when i do it's very faint. im also getting alot of knock in the higher rshared_pm range. logger shows 0 until about 4k then it will rapidly start climbing from 7 counts and up. this is on a 14b with only 14psi. is it possible my fuel pump is faulty? and just to eliminate most comments about what it could be: the car is religiously maintained, boost leak tested to 25psi, ignition is tiptop.

 

i dont know if there is a way to check the actual pressure on the pump it's self, but you could do a fuel pressure test on the injector rail or fuel system.

 

i have a 255 as well,but when you turn the key on you hear it loud and clear.

 

Some people have problems with Walbro 255s blowing out their stock FPRs. It's possible your FPR is trashed and you're not making enough fuel pressure. You can get a pressure tester from any auto parts store...might even be able to "rent" one.

 

Ok i'll look into that. appreciate the good responses

 

Whoa whoa whoa. Back it up here: what are you at for AFRs? EGTs? Just because you are getting knock does not necessarily mean your fuel pump is dropping out. What is your fuel pressure? Are you using a 1:1 FPR? Rising rate?

Knock can come from a number of sources. Troubleshooting a boosted motor is a waste of time and money if done by replacing parts one by one.