fuel pressure dropping??
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 949
Likes: 0
From: smithtown ny
fuel pressure dropping??
on my 91 i have a fuel gauge in the car and noticed that at almost wot the pressure will start to fall from 45psi down to 40psi give or take a few. new injectors, filter fuel pump, regulator. wtf ?????????
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
I too notice that with my '88; since I was running very lean on the dyno I installed a new fuel pump & injectors.
But I have been wondering about the FP drop issue. I remember that when you go to WOT manifold vacuum goes to nearly zero, so fuel pressure will climb to the max (no vaccuum) value. However, since manifold vacuum begins to climb as RPM come up, that may be the reason for the fuel pressure drop off.
What are your fuel pressure readings at idle with vacuum connected and with it disconnected??
But I have been wondering about the FP drop issue. I remember that when you go to WOT manifold vacuum goes to nearly zero, so fuel pressure will climb to the max (no vaccuum) value. However, since manifold vacuum begins to climb as RPM come up, that may be the reason for the fuel pressure drop off.
What are your fuel pressure readings at idle with vacuum connected and with it disconnected??
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
The pressure should jump as soon as you go WOT, because the vacuum drops, instantly. If the fuel pressure starts to fall off at higher rpms, it's good sign that the fuel system can't handle the volume. The first thing to check, is the filter, if that's OK chances are the fuel pump can't supply the demand, particularly if it only happens at the top of the rpm range.
RACE ON!!!
RACE ON!!!
Melting Slicks
Joined: Oct 2000
Posts: 3,010
Likes: 1
From: Sweden/Stockholm
Originally Posted by CFI-EFI
The pressure should jump as soon as you go WOT, because the vacuum drops, instantly. If the fuel pressure starts to fall off at higher rpms, it's good sign that the fuel system can't handle the volume. The first thing to check, is the filter, if that's OK chances are the fuel pump can't supply the demand, particularly if it only happens at the top of the rpm range.
RACE ON!!!
RACE ON!!!
Le Mans Master
Joined: Jul 1999
Posts: 8,683
Likes: 6
From: Phoenix AZ
Originally Posted by 6spd
on my 91 i have a fuel gauge in the car and noticed that at almost wot the pressure will start to fall from 45psi down to 40psi give or take a few. new injectors, filter fuel pump, regulator. wtf ?????????
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 949
Likes: 0
From: smithtown ny
can my stock pump be weak? it is new and i was told from members that the stock pump should hold up to 400hp. i have lots of bolt ons. still that should have nothing to do with it. i did notice that when i shut my car off the fuel pressure drops faster now but would a leaky injector cause wot pressure drop? i don't think so?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
