502 mpi Fuel Pressure- need help
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2000 model 502 mpi's: (Naturally aspirated) I rebuilt the top ends last yr. to make approx. 500 h.p. The guy that reprogrammed the ECU's suggested I buy the kits from CP Performance to make the fuel pressure reg's adjustable for fine tuning. The pressure always seemed squirrley- every time I checked them they'd be different and adjusting them was a nightmare due to the location of the reg. so I just installed Aeromotive regulators plumed into the same place as the old regulators but mounted where I can easily get to them. One motor set up easy as pie and is running around 39-40 lbs. as a starting point. The port motor however seems as erratic as ever- I set it to around 40 lbs. and the next time I put the gauge back on it was around 30 lbs. When I turn the adjusting stud it take a while to react- sometimes a minute or so, unlike the Stbd. eng. which reacts immediately. The pump is only a couple of yrs. old and has never failed to work or given any signs of failing so I'm skeptical that it's the problem. The system holds pressure normally after shut-down and takes several hrs. to bleed off any pressure. Anyone have any idea what else could be causing the pressure to be erratic??
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if its erratic low, then its almost certainly a pump or pickup issue. if its erratic high than it could easily be a partially blocked or occluded return line issue ... especially if the return is done as stock back to the filter housing.