- Installing the Holley Adjustable Fuel Pressure Regulator – The reason I got the Holley APFR, p/n 512-501, is because I have the TPIS AFPR and the vacuum stem on it is loose after 5 years of daily operation. I heard great praise from a lot of people so I decided to get it.. This all the parts you get in it. As you can see there are 6 pieces to the kit and the housing is made from Aluminum and is kind of heavy compared to TPIS’s housing. The TPIS kit only gives you a housing and a solid washer to put over the top of the spring. The Holley kit gives you a new washer / diaphragm, new spring, and a screw in brass vacuum tube! Basically you rebuild the fuel pressure regulator, very nice. Below is a comparison between the Holley housing and adjustment knob and my old TPIS regulators. The Holley housing is on top. So that is a slight comparison of two types of manufactures of AFPRs. Installation The directions by Holley are good and you could follow them but I like pictures so this is my install. First you need to either remove the fuse to the fuel pump and start the engine and let it die out. But all I did was the night before I loosen the gas cap. This was enough to release the pressure in the gas tank. Then you need to disconnect the battery and I took both positive and negative terminals off. First the air intake from the filters with the MAF need to be disconnected and then unscrew it from the throttle body. Now you are ready to remove the plenum, throttle body and the cables attached to drivers side of the plenum. I have the throttle body coolant by pass done on my system so I didn’t have to remove the coolant hoses from the throttle body but if you have the stock setup you need to remove them from the throttle body. In addition to that there are 2 hoses on the throttle body’s passenger side and connector for the IAC that need to be disconnected. Next I would remove the bracket that holds the throttle and tranny cables to the plenum on the drivers side, 3 bolts. At this point you could leave the throttle body connected to the plenum or remove the 4 bolts on the throttle body to the plenum or just remove the 8 (4 on each side) #40 Torx screws from the runners to the plenum and leave the throttle body connected to plenum, it is up to you So this is what it should look like.. The shiny little thing right before the distributor is the fuel pressure regulator, that was the old TPIS AFPR I had. The BIGGEST problem a weekend mechanic will have is removing the torx screws from the feul pressure regulator. The reason is there are 2 types of torx screws. The regular ones and the “Security” ones. The “Security” ones have a little tit post in the middle of the hole. Look at the above picture and white square under the word “Torx”. This is a picture of the bit and you can see this white circle in the middle of it and that indicates that center of these bits have a hole there for the post on the trox screw. If you try to use the solid torx bits you will bend that post and may not get the screws out unless you drill them out. A word to the wise! BE CAREFUL!!!! And use the correct #10 torx bit!! Once you get the screws out keep a rag handy to get any gas, as slight as it may be, when you remove the housing. I then used some CARB Cleaner and sprayed the area around it. Also spray in the screw holes to clean them out too. The above the picture is with the new Holley AFPR in but I found a problem on my setup. I don’t know if others had this problem but I did. Where I’m pointing to is a bolt to the hold the fuel line on the injectors but the AFPR housing would hit it and not allow the torx screws to line up correctly. I messed up on one of the hole to the AFPR and ended up cross threading the hole. I have to tap it to undo my mistake. So if you feel the screw getting tight too soon then double check everything. I had to grind down a little of housing so it would line up correctly as shown below. If you look above you can see how I ground out a little notch for that bolt and everything lined up good. Ok now the housing is on you can screw on the BIG knob for the adjustment. It says to not screw it on to far but if you just screw it on till it catches it is too low of a fuel pressure and the car will not idle. So I would screw it on like till you have 3 complete turns on it. This way it should have at least a 35psi and the car will idle. Other wise it is only going to give you about 22psi and the car won’t idle there. Now isn’t that a great big knob to adjust and just using your fingers!! Now that is about it and just do the reverse to assemble everthing back on the engine. Now did I notice anything?? Yeap, my idle improved more and even became alittle higher too. So I would say reset your IAC and TPS Voltage too and then your set. In addition to my idle getting better the car feels like it pulls better too but I have to get to the track to see if anything is that much better. Enjoy and Good Luck! Mike Ski (Ski89Z28) If you would like to contribute your articles to IROCZone.com, e-mail us at email@example.com!