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homeslicej2 · 09-21-2017, 09:12 AM

You either have a blockage restricting fuel flow, or not enough voltage reaching pump. Replacement WIX fuel filter for 300zx states filters down to 10 microns (via Summit Racing website), so probably not your 40 micron filter (could be though). You replaced the FPR (what brand, is it factory?) IIRC, you should be running 43.5psi at FPR at idle with Vac hose disconnected, and about 37-40 psi with Vac hose connected. This pressure should rise 1:1 with boost. Healthy, stock SR20det should run ~20 mmHg of vacuum at idle speed of 750 RPM (+/- 50 RPM). Larger than stock cams will lower idle vacuum. My guess as of now, since you fixed vacuum leaks (what is it at idle now and what is idle speed?), is that you have weak fuel pump/voltage supply/blockage/bad FPR/etc. Double check your Fuel pressure at FPR and test that direct relay voltage at the pump at both idle and under load. Might need to take car to shop and put on dyno to check voltage at pump under full boost/load.

09-21-2017, 09:12 AM	#10
homeslicej2 Zilvia Member Join Date: Aug 2008 Location: Adairsville, GA Age: 41 Posts: 152 Trader Rating: (0)	You either have a blockage restricting fuel flow, or not enough voltage reaching pump. Replacement WIX fuel filter for 300zx states filters down to 10 microns (via Summit Racing website), so probably not your 40 micron filter (could be though). You replaced the FPR (what brand, is it factory?) IIRC, you should be running 43.5psi at FPR at idle with Vac hose disconnected, and about 37-40 psi with Vac hose connected. This pressure should rise 1:1 with boost. Healthy, stock SR20det should run ~20 mmHg of vacuum at idle speed of 750 RPM (+/- 50 RPM). Larger than stock cams will lower idle vacuum. My guess as of now, since you fixed vacuum leaks (what is it at idle now and what is idle speed?), is that you have weak fuel pump/voltage supply/blockage/bad FPR/etc. Double check your Fuel pressure at FPR and test that direct relay voltage at the pump at both idle and under load. Might need to take car to shop and put on dyno to check voltage at pump under full boost/load.