First thing you ALWAYS want to check. Set it to 13psi and you will be fine.
Help fuel pressure problem
Thread Starter
Instructor
Joined: Jun 2018
Posts: 111
Likes: 1
Help fuel pressure problem
Looking for some help. Just did a rebuild on my 84 crossfire. 2.02 heads 170cc intake 62cc compression, comp cam Dur 250/260 lift .432/.444. Renegade intake. Ive replaced fuel pump last year with an 85 and replaced the fuel filter. Car runs super lean. Yesterday i was showing 9.5 psi, today i was just under 8. Vacuum seems to be good. Anyone know whats going on? And/or how to fix? I have it timed in at 12 advanced. Im running out of ideas over here.
Safety Car
Joined: Nov 2005
Posts: 3,532
Likes: 1,185
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
If the pressure keeps going down, the pump could be going bad already, it happens. Did you replace the small rubber lines at the tank when you replaced the pump? They do crack.
Last edited by Buccaneer; May 17, 2020 at 06:07 PM.
Race Director
Joined: Apr 2003
Posts: 17,700
Likes: 1,667
From: moraga ca
Thread Starter
Instructor
Joined: Jun 2018
Posts: 111
Likes: 1
Safety Car
Joined: Nov 2005
Posts: 3,532
Likes: 1,185
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
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
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
If you go to the trouble of adjusting the pressure, and the hose is leaking, you won't solve the problem. If you rebuild the injectors, and the hose is leaking, you will have wasted your time and money, as that won't solve the problem, either. Is it a major problem, or a major expense to check that hose? When the pump was replaced, was that hose replaced with the proper fuel-proof hose?
If you have a good spray pattern from the injectors, and you know the fuel pressure is low, why would you rebuild the injectors?
If you have a good spray pattern from the injectors, and you know the fuel pressure is low, why would you rebuild the injectors?
Thread Starter
Instructor
Joined: Jun 2018
Posts: 111
Likes: 1
If you go to the trouble of adjusting the pressure, and the hose is leaking, you won't solve the problem. If you rebuild the injectors, and the hose is leaking, you will have wasted your time and money, as that won't solve the problem, either. Is it a major problem, or a major expense to check that hose? When the pump was replaced, was that hose replaced with the proper fuel-proof hose?
If you have a good spray pattern from the injectors, and you know the fuel pressure is low, why would you rebuild the injectors?
If you have a good spray pattern from the injectors, and you know the fuel pressure is low, why would you rebuild the injectors?
Safety Car
Joined: Nov 2005
Posts: 3,532
Likes: 1,185
From: Arizona - If you don’t know CFI, STOP proliferating the myths around it...
What ECM are you using since you did the mods, stock? I would go with 13psi and then "maybe" depending on AFR, bump it from there. Keep in mind that you CAN NOT go very high on the pressure using the stock regulator. First off, it may not get to the pressure you want and second, if it does you have to be careful of the bladders. If you were to blow one (either side) you will have a big fire on your hands on a hot motor. I always recommend a TB rebuild kit from (GP Sorensen) they are the best kits so that you know how old those bladders are before raising the FP. I honestly don't think that you will need to go more than 14psi. BTW...There are kits out there that are not the correct kits for the regulated side and you will have issues trying to increase the FP for sure. If you did not get the Sorenson kit, verify that the regulated bladder looks "EXACTLY" like the one you removed. The tiny swivel on the top of the bladder MUST look exactly the same (in height) or you WILL have issues.
Hot Rod has a point, but it's your car, you decide what you want to do and how much work you want to put into this I guess. I hope you get her fixed and running well.
Hot Rod has a point, but it's your car, you decide what you want to do and how much work you want to put into this I guess. I hope you get her fixed and running well.
Thread Starter
Instructor
Joined: Jun 2018
Posts: 111
Likes: 1
What ECM are you using since you did the mods, stock? I would go with 13psi and then "maybe" depending on AFR, bump it from there. Keep in mind that you CAN NOT go very high on the pressure using the stock regulator. First off, it may not get to the pressure you want and second, if it does you have to be careful of the bladders. If you were to blow one (either side) you will have a big fire on your hands on a hot motor. I always recommend a TB rebuild kit from (GP Sorensen) they are the best kits so that you know how old those bladders are before raising the FP. I honestly don't think that you will need to go more than 14psi. BTW...There are kits out there that are not the correct kits for the regulated side and you will have issues trying to increase the FP for sure. If you did not get the Sorenson kit, verify that the regulated bladder looks "EXACTLY" like the one you removed. The tiny swivel on the top of the bladder MUST look exactly the same (in height) or you WILL have issues.
Hot Rod has a point, but it's your car, you decide what you want to do and how much work you want to put into this I guess. I hope you get her fixed and running well.
Hot Rod has a point, but it's your car, you decide what you want to do and how much work you want to put into this I guess. I hope you get her fixed and running well.
Safety Car
Joined: Sep 2004
Posts: 3,953
Likes: 550
From: Mission Viejo CA
Theoretically, your fuel pump should be delivering more fuel than needed, and the pressure regulator should be flowing excess fuel back to the fuel tank to maintain the proper fuel pressure. So which is it: insufficient fuel being delivered, causing the pressure to be low, or excessive fuel being returned to the tank, causing the pressure to be low??
Try this: squeeze the rubber fuel return hose to close off the fuel flow, that's located after the LH injector. If the fuel pressure doesn't go up, you have a deficient fuel delivery problem, If the pressure goes above 15 psi, you have a fuel pressure regulator problem. If the pressure goes up, keep the test short so you don't blow the diaphragm in an injector.
Try this: squeeze the rubber fuel return hose to close off the fuel flow, that's located after the LH injector. If the fuel pressure doesn't go up, you have a deficient fuel delivery problem, If the pressure goes above 15 psi, you have a fuel pressure regulator problem. If the pressure goes up, keep the test short so you don't blow the diaphragm in an injector.
Thread Starter
Instructor
Joined: Jun 2018
Posts: 111
Likes: 1
Okay heres where im at. Adjusted the FPR spring almost all the way not getting any more than 11.5 psi. Also after it heats up to running temp it starts to slowly lose pressure. After driving for a few miles it drops to 8psi. Fuel filter and pump are both new