Topic: Fuel Pressure
in Forum: C3 Fuel, Emission Control, and Exhaust Systems
Lifetime MemberDoes it also have anything to do with ruff idle?
I changed the fuel filter and it was really dirty. I guess I need to pull the fuel pump and fuel gauge system out of the fuel tank. Does any one have suggestions on what to look out for and what to replace or hints on how to do it other than what is in the Shop Manual (I have one of those).
Also I have heard that I should adjust the fuel pressure to somewhere between 12 and 14 pounds. I was also told that 82 fuel pumps may not put out that much pressure and I should replace it with a 85 fuel pump.
Does anyone have any objections to doing that?
I have not read about getting access to the fuel pressure adjustment on the crossfire so I do not know what I should ask about that but will start reading up on it tomorrow. I just wanted to give you guys a chance to provide some feed back before I start working tomorrow.
Thanks in advance
Gil
First suggestion is to pull the fuel pump and replace it with a new pump either 82 or 85. The short rubber fuel hose to the pump that is inside the tank is notorious fo deteriorating. The pump comes out the top after removing the fuel door and associated hardware around the door. It will come out, it just takes the appropriate amount of twisting and turning accompanied by a little blue language to get it out. When the pump finally starts out, make a note of which way everything was pointing so you wont have to go through the experimenting process again. You can replace it with an 82 pump that will put out about 11 pounds of pressure or with an 85 pump which will put out much more. If you do put in an 85 pump you will have to modify your drivers side throttle body so that you can adjust the pressure regulator to notice any difference. If you arent comfortable with modifying the throttle bodies then install the 82 pump as the 85 pump will make absolutely no difference. If you do install the 85 pump you dont want to go much over 14 psi on the pressure or you will blow the diaphram in the throttle body. If you are only getting 5 psi at the throttle bodies then YES that will cause idle problems as well as acceleration problems. The factory settings are for 9-11 pounds at the throttle body but my car runs better with the 85 pump and a setting of 14 psi. If you decide to install the 85 pump I can give you directions on how to modify the throttle body so you can adjust the factory sealed fuel pressure regulator which includes removnig the anti-tamper plate in the regulator. You will also need a tool, either bought from Dynamic Crossfire Solutions or home built so that you can get to the regulator screw one the plate is removed, it cannot be done with standard tools. I build my own from a flexible carburator adjustment tool from pep boys and a piece of copper tubing....just call me bubba. You may also want to balance the throttle bodies to make sure they are in sync. This involves drilling out an access hole in the TBs and knocking out more anti tamper plugs and breaking a factory weld on the TB linkage. A water manometer is needed to do the balance but one can be bubba built for less than $10 which works well. I am on the road at present and dont have the links to the balancing procedures but can provide them the first of the week if you are interested. What fuel pressure gauge did you install? DCS?
Lifetime Member #116
Dave's '82 
Lifetime MemberQuestion if I put in a 85 fuel pump do I need to do anything with the fuel regulator prior to starting it up the first time. Or will the regulator setting be such that it will not blow anything?
Also I know that I can order a fuel pump from one of the many Corvette suppliers but I would like to pick one up locally at O'rielly, Carquest, Autozone or Napa will all or any of these work just fine. Or does someone have a recommendation which one to stay away from.
First off, you will NOT need to remove the throttle body bases from the intake. You will need to remove the injector "pods" or "towers" from the bases. This can easily be done with the bases on the car. You will need to remove the 5 screws that hold the top of the tower to the tower itself. Once the 5 screws are out, you may need to tap the top the cover with a screwdriver or small hammer to jar it loose from the tower. After it is loose, remove the top and attached fuel fuel pressure regulator. Removing the injector itself is easy, just use a screwdriver to pry it out, here you see me using ahandle of a pair of pliers as a fulcrum for the lever. Pay PARTICULAR attention to the "O" rings and metal ring. These MUST be installed exactly right when you disassemble. Getting the injector back into its place with the spacer and "O" rings will be a difficult chore. It MAY be possible to leave the injector in place but scraping off the old gasket will be difficult but there are "O" rings and a screen filter on the injector itself that you will probably want to replace. You will next need to remove the the fuel pressure reguator from the lid. This will be done by removing the 4 screws that hold it in place. There is a STRONG spring in the regulator that mut be contained as you unscrew the 4 screws. This can be done either by mechanical clamps or with your hand . The spring is strong but not to the point that you cant hold it. Release all the parts that are inside and day attention to how the parts are arranged. When taking the screw mechanism out of the regulator try not to rotate the screw as this will either increase or decrease the regulated pressure, you will do this later when it is all reassembled and you can watch the pressure gauge. You dont want to inintentionally adjust it up too high and start blowing gaskets and diaphrams. There is a "plug" in the bottom of the regulator that blocks the adjustment of the fuel pressure. This plug must be removed by using a punch to drive it off, it will not give much resistance. Once the plug is removed, the regulator can be reassembled just as it was before. With the plug removed, you will be able to get to the adjustment stud. You now should be able to see how the tool works. By turning the stud, it moves the washer inside of the regulator and increases or decreases the spring tension inside of the regulator. Once the tower is reassembled onto the base and the injector is reinstalled, the tool is used to reach under the throttle body, engage the stud and adjust the pressure. The pressure you are looking for is 14 - 14.5.
Lifetime MemberThanks for the information. I just got back from purchasing an 85 fuel pump and about to start taking the old one out of the car. So sometime tonight or tomorrow after church I will have a chance to see where the fuel pressure will be with the new pump. hopefully it will be up to at least the 11 psi the GM manual says is the required pressure. I guess if I'm lucky enough to get that close we should see an improvement in drivability and I can then decide when and if I want to rebuild the FP regulator.
Do you recommend just adjusting the regulator and not rebuilding it. I have seen a couple of article on how to remove the plate to get access. Seem like rebuilding is not a requirement.
I think you are on the right track, install the pump and if that does the trick, leave well enough alone. If by rebuilding you mean bushings, that wont be required. You will absolutely have to replace some gaskets if you take the tower apart and if the regulator is apart it would be a shame to put the same 29 year old diaphram back inside. When you change the pump be sure and change the "sock" striner that attaches to the pump, they usually do not come with the pump and must be purchased separately. In addition, be sure all clamps are in good condition and hoses securely attached to the fuel pump, you will be dealing with considerably more pressure than with the original pump. Its a good idea to number or mark the two fuel lines that attach on the passenger side of the pipes at the filler neck to make sure these are reattached to the proper pipes. To keep from marring your paint, I would use old towels or similar to cover the rear deck around the filler hole kinda like a surgical site, there will be alot of twisting and turning trying to get the pump out and it would be easy to scratch paint.
Lifetime MemberWhat I was talking about is an article I read where they showed how to take the fuel pressure adjuster cover plate off and just doing the adjustments. Only reason I'm thinking about that instead of rebuilding at this time is I leave 9 July to Japan for a couple of weeks and ordering parts would mean I would not be getting anything done before I got back.