Low Fuel PSI
Thread Starter
On The Tree
Joined: Feb 2015
Posts: 136
Likes: 0
From: columbus ohio
Low Fuel PSI I have the Chirs1313 dual 450's which just got the car tuned and for some reason I'm only seeing 39 PSI on the first pump. Anyone have any problems with these pumps? Or have any ideas what i need to look for to fix the problem?
Thread Starter
On The Tree
Joined: Feb 2015
Posts: 136
Likes: 0
From: columbus ohio
Thread Starter
On The Tree
Joined: Feb 2015
Posts: 136
Likes: 0
From: columbus ohio
Trending Topics
Thread Starter
On The Tree
Joined: Feb 2015
Posts: 136
Likes: 0
From: columbus ohio
This might help you understand why...... Fuel Pressure Explained
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
Thread Starter
On The Tree
Joined: Feb 2015
Posts: 136
Likes: 0
From: columbus ohio
Yesterday driving it ..Base at 43.5 getting into it it would drop as low as 39 psi. Come up to a light it would stall but start right back up.
Take the line off a vac. source, and hook it to an area before the TB. then you will
know if it is pump related or vac related-idle and cruise you have high vac, low fuel pressure,
I never use vac. to a reg. Nascar did, so during a caution, they could keep the plugs cleaner
for the restart.
know if it is pump related or vac related-idle and cruise you have high vac, low fuel pressure,
I never use vac. to a reg. Nascar did, so during a caution, they could keep the plugs cleaner
for the restart.
Take the line off a vac. source, and hook it to an area before the TB. then you will
know if it is pump related or vac related-idle and cruise you have high vac, low fuel pressure,
I never use vac. to a reg. Nascar did, so during a caution, they could keep the plugs cleaner
for the restart.
know if it is pump related or vac related-idle and cruise you have high vac, low fuel pressure,
I never use vac. to a reg. Nascar did, so during a caution, they could keep the plugs cleaner
for the restart.
If he has a vacuum referenced regulator it will lower the pressure when the manifold in under vacuum and raise the pressure when the manifold in under boost.
With your regulator hooked up to vaccum u should see a 1psi rise per 1pound of boost. So if your base psi is 43psi thin with 15 psi of boost u should see 58psi of fuel pressure.
Thread Starter
On The Tree
Joined: Feb 2015
Posts: 136
Likes: 0
From: columbus ohio
Thanks that helps! I did find out that i wasn't getting vacuum from where i was hooked into but now i have vacuum.
Thread Starter
On The Tree
Joined: Feb 2015
Posts: 136
Likes: 0
From: columbus ohio
Took car out and got into it a little and seen as much as 56 fuel PSI and thats okay because I'm only running 7.5 ILBS of boost right now but I'm a little confused about fuel PSI dealing with EFI! Why wouldn't i crank the base PSI say up to 60 PSI? I''m heading toward higher boost once I get the bugs worked out of the car which I'll need a heck a lot more fuel PSI than i have now which to me means ill need to crank up the base to get that higher fuel PSI. Someone explain to me what I'm not understanding? Thanks Bill
U can set the base to what ever u choose for it to be. U just have to make sure u have enough pump to support the higher pressure for when in boost. Some pumps dont like tht much pressure and loose flow. U will also gain more injector by going to a higher base pressure.
Most injectors are rated at 43psi so thts were most start off from for base pressure.
Most injectors are rated at 43psi so thts were most start off from for base pressure.
but I'm a little confused about fuel PSI dealing with EFI! Why wouldn't i crank the base PSI say up to 60 PSI? I''m heading toward higher boost once I get the bugs worked out of the car which I'll need a heck a lot more fuel PSI than i have now which to me means ill need to crank up the base to get that higher fuel PSI. Someone explain to me what I'm not understanding? Thanks Bill
So fuel pressure is set without the car running but fuel pump on = base pressure, We'll use 43lbs as an example base pressure.
So with neither vacuum or boost the fuel pressure is 43lbs.
Now you start the car you'll see the fuel pressure drop because you have a vacuum in the intake pulling on a vacuum diaphragm on the regulator that in turn lowers fuel pressure.
Now you step on the throttle and for every pound of boost in the manifold you'll see fuel pressure increase the same amount.
So with a 43lb base pressure setting and 7lbs of boost your fuel pressure should read 50lbs.
Now if you crank up the boost to 15lbs you have the 43lb base pressure and 15lbs of boost so you should have 58lbs of fuel pressure without actually adjusting the pressure yourself.
I hope that makes sense lol.
The only issue you need to worry about is if the fuel pump can keep up with the fuel demands as pressure increases. Fuel pumps are rated at flow x amount at x pressure. Raise the pressure and pump efficiency falls off.
Last edited by LLLosingit; Jun 3, 2018 at 09:47 PM.
Thread Starter
On The Tree
Joined: Feb 2015
Posts: 136
Likes: 0
From: columbus ohio
I'll try to explain it this way. With a boost referenced regulator fuel pressure will rise and drop at an equal rate as the manifold pressure changes. 1lb of negative pressure "vacuum" in the manifold will pull one pound of fuel pressure and 1lb of positive pressure "Boost Pressure" The fuel pressure will rise 1lb.
So fuel pressure is set without the car running but fuel pump on = base pressure, We'll use 43lbs as an example base pressure.
So with neither vacuum or boost the fuel pressure is 43lbs.
Now you start the car you'll see the fuel pressure drop because you have a vacuum in the intake pulling on a vacuum diaphragm on the regulator that in turn lowers fuel pressure.
Now you step on the throttle and for every pound of boost in the manifold you'll see fuel pressure increase the same amount.
So with a 43lb base pressure setting and 7lbs of boost your fuel pressure should read 50lbs.
Now if you crank up the boost to 15lbs you have the 43lb base pressure and 15lbs of boost so you should have 58lbs of fuel pressure without actually adjusting the pressure yourself.
I hope that makes sense lol.
The only issue you need to worry about is if the fuel pump can keep up with the fuel demands as pressure increases. Fuel pumps are rated at flow x amount at x pressure. Raise the pressure and pump efficiency falls off.
So fuel pressure is set without the car running but fuel pump on = base pressure, We'll use 43lbs as an example base pressure.
So with neither vacuum or boost the fuel pressure is 43lbs.
Now you start the car you'll see the fuel pressure drop because you have a vacuum in the intake pulling on a vacuum diaphragm on the regulator that in turn lowers fuel pressure.
Now you step on the throttle and for every pound of boost in the manifold you'll see fuel pressure increase the same amount.
So with a 43lb base pressure setting and 7lbs of boost your fuel pressure should read 50lbs.
Now if you crank up the boost to 15lbs you have the 43lb base pressure and 15lbs of boost so you should have 58lbs of fuel pressure without actually adjusting the pressure yourself.
I hope that makes sense lol.
The only issue you need to worry about is if the fuel pump can keep up with the fuel demands as pressure increases. Fuel pumps are rated at flow x amount at x pressure. Raise the pressure and pump efficiency falls off.