DOES ANYONE HERE KNOW WHAT THE FUEL PRESSURE SHOULD BE ON A 94Z28 LT1....I TESTED BECAUSE I STARTED TO HAVE A SLIGHT IDLE MISS...THE GAUGE READS 43 KEY ON ONLY, DROPS TO 35 WHEN RUNNING, THIS SEEMS A LITTLE LOW TO ME. ANYONE HAVE ANY SPECS ON THIS OR AM I FINE? I INSTALLED A NEW FILTER LESS THAN 1K MILES AGO SO I KNOW THATS OK..

 

Should be around 38 PSI at idle. Make sure the vacuum hose is attached to the regulator. Pull off the vacuum hose and it should bounce up to somewhere around 45 PSI (???).

Could be a bad regulator or a weak fuel pump. Might also be an inaccurte fuel pressure gauge possibly. If the fuel filter is clogged that might have an effect on it as well.

 

That's perfectly normal fuel pressure.

 

The factory spec for fuel pressure, with no vacuum, is 43.5psi +/- 2.5psi, so with the vacuum line disconnected, any value from 41-46psi is within spec.

When you attach the vacuum hose, the fuel pressure MUST drop in direct relation to vacuum level in the engine. Since is isn't too hard to pull a 20"Hg vacuum at idle in a stock engine, and that is equal to about minus 10psi, it sounds like your pressure is fine.

The place you need to check is at WOT.... a system may have more than enough capacity to provide the required pressure at idle and low loads, but at WOT a failing fuel pump or clogged filter is going to kill the pressure. At wOT, since there is little or no vacuum, so fuel pressure should be equal to whatever reading you got at idle with no vacuum line connected.