Fuel Pressure Regulator

Adding PSI To Your Fuel

If you have installed the Mopar MPI fuel injection conversion to your motor, or added a 4.0 Head to your engine, and you are still having an occasional pinging problems, this project may be one of the simplest ways to resolve the problem.  Unfortunately, this solution isn't inexpensive but the savings down the road will make it well worth the cost.  The solution is to add an adjustable fuel pressure regulator to the fuel rail on the intake manifold.  Hesco, the creators of the Mopar MPI conversion kits for CJs, sells the regulators from their website.  This will increase the fuel flow to each of the injectors, which will richen the fuel/air mixture and hopefully solve your pinging problem.  Best of all, the installation is easy!

FPR-removing-old.jpg (38199 bytes) Remove the old fuel pressure regulator by removing the small bolt on top of the unit.  Then the regulator can be pulled out.  There may be some resistance as the moist O-rings may be holding it firmly.  A slight twist will help.
FPR-new-old.jpg (20405 bytes) The kit comes with the new regulator, a new bracket, new O-rings (large and small), and some shims (small washers) to go between the bracket and the mount on the rail.  You can see the new regulator (right) is slightly longer than the stock unit.  The new regulator comes pre-adjusted to 44 psi, but the unit is adjustable if needed.
FPR-new-o-ring.jpg (42222 bytes) Next, install the new large O-ring into the mount on the fuel rail.  The smaller new O-ring will be placed directly on the new regulator just as it was on the old stock unit.  Be sure to lubricate the new O-rings before reassembling.
FPR-install-with-bracket.jpg (38697 bytes) Before inserting the new regulator into the mount on the rail, set the new bracket over the vacuum hose bib.  As the regulator is beginning to go inside the mount on the fuel rail, insert the hook tab on the bottom of the new bracket into the hole below the regulator.
FPR-setting-shims.jpg (41929 bytes) After you press the new regulator in place (requires a small bit of pressure), insert the small bolt and original washer through the new bracket, THEN add the two new washers (as a spacer) to the bolt before threading it back into the holding bracket on the fuel rail.  Now the bolt can be tightened.  The spacer is very important as it keeps the fuel rail from becoming distorted, which will cause the regulator to bleed off fuel.


The unit comes pre-set, but you may need to check it later or make adjustments to fine-tune your pressure based on your particular engine's needs.  To adjust the regulator you will need a fuel pressure gauge.  Attach the fuel pressure gauge to the Schrader valve on the fuel rail.  Loosen the jam nut on the front of the unit.  Start the engine.  With the vacuum line OFF the fuel pressure regulator, screw the adjustment screw in until the gauge reads 44 psi.  Then tighten the jam nut being careful not to turn the adjusting screw.  Reattach the vacuum line making sure both ends are completely on (regulator and manifold).