View Full Version : psi question

11-14-2005, 11:52 PM
I have a new adj. fpr set to 43psi vacuum off. I also recently attached a fuel pressure gauge at the rail. When rotating the throttle, the fuel pressure drops steadily as the engine revs. Is this normal? Also, since I installed the new fpr, I can hear the fuel pump humming louder and more inconsistent. Is this a problem, or should I go ahead and upgrade the fuel pump? BTW, I have the hotwire kit on the way and will install this week. I know these are newby questions. Any help is greatly appreciated.

11-15-2005, 01:19 AM
You normally set the fuel pressure with the vacuum line disconnected from the FPR ... that sets the BASE pressure.

When you hook the vacuum line back up at idle, you'll see about a 6-7psi drop, since the manifold vacuum will change the reference. This is probably what you are seeing if you are just upping the throttle at idle ... if the manifold vacuum changes, the fuel pressure will follow it. Best test is to watch the FP at WOT. it should equal the base pressure you set + 1 psi for each psi of boost.