My friend has a 1991 Camaro z28 5.0L, we just intalled a walbro 255 lp fuel pump and the car fires up and runs very rough, the throttle not responsive at all, and it seems as if its running really rich. When i floor it the car shuts off, and sometimes it pops really loud. The only thing in my mind is that the fuel pressure regulator is bad, which is making it run rich. What i really wanna know is if there is any other reason his car could be running rich, such as CTS even though there is no check engine codes. I also want know if the higher fuel pump is making it run rich, shoudl he buy a adjustable fpr? thanx

 

Why was the pump replaced? Was the new pump the proper replacement for your car?? Did you remove the in-tank pump and replaced it with another in-tank pump, or did you use an external pump. The reason I am asking is that the Walbro pumps come in many different types. Some people add an external pump and leave the old pump in the tank, this does not wok out to well.

If everything is correct, take a fuel pressure reading & see if the pressure is in spec. Also check that the cold start valve closes once the engine is running. A higher fule pump pressure can make the mixture rich if the pressure regulator in not designed to handle the higher pressure.

 

Well the reason the owner thought the pump was bad, was because everytime his tank got below 1/4 the car would run horribly. From previus experience on my car, i was pretty sure it need it a fuel pump and so was the owner, so we went ahead and changed. But the pump he put on is a walbro 255 which flows more than stock, I am thinking htat maybe the regulator cant take adjust to new fuel pump making it run rich. Also we changed the in-tank fuel pump we didnt put a external. Well I told him to have to towed to get it diagnosed and then i can fix watever is wrong with it, because without any tools or anything I cant diagnose and replacing random stuff wont get me far. So i ll keep u guys posted on wat the shop will say.