Low fuel pressure during acceleration?
Thread Starter
Teching In
Joined: Oct 2010
Posts: 31
Likes: 0
From: Mooresville, NC
Low fuel pressure during acceleration? I recently finished my engine swap and took it out the dragstrip for a few full throttle ecu learn passes last night. After checking the data log when I got home, I noticed I am losing fuel pressure under heavy acceleration. The pressure drops to 12psi and the the afr rose to around 18:1. At idle and light loads, it maintains a steady 58 psi. Here are the specs on my set up:
Car:
1969 Camaro
LY6 6.0
T56
223/230 .601 lift cam
LS3 intake
Holley HP EFI
Walbro 255lph fuel pump
Tanks Inc pick up module
-6 fuel lines
Corvette regulator/filter mounted by fuel tank
I contacted Tanks Inc and the tech guy there seems to think the regulator is mounted too far from the engine. I have never heard of this being a problem before? The voltage stayed at a constant 14V throughout the run.
I've attached a copy of the data log to this thread.
Any help/thoughts/insight on what may be causing this would be greatly appreciated.
Car:
1969 Camaro
LY6 6.0
T56
223/230 .601 lift cam
LS3 intake
Holley HP EFI
Walbro 255lph fuel pump
Tanks Inc pick up module
-6 fuel lines
Corvette regulator/filter mounted by fuel tank
I contacted Tanks Inc and the tech guy there seems to think the regulator is mounted too far from the engine. I have never heard of this being a problem before? The voltage stayed at a constant 14V throughout the run.
I've attached a copy of the data log to this thread.
Any help/thoughts/insight on what may be causing this would be greatly appreciated.
Last edited by Regal454; Apr 12, 2013 at 07:28 PM.
12 psi and 18:1?!?! Wow, you're lucky you have pistons left! And judging by your graph, looks like you were closer to 20:1. VERY dangerous territory to be in.
Sounds like your pump cant keep up. While not very common, its not unheard of to have a Walbro go bad. IIRC they had a not so good batch of pumps a while back. Out of curiosity, what injectors are you running? And yeah, how much fuel was in the tank? If it was very low, you could have been starving the pickup during accelleration.
Sounds like your pump cant keep up. While not very common, its not unheard of to have a Walbro go bad. IIRC they had a not so good batch of pumps a while back. Out of curiosity, what injectors are you running? And yeah, how much fuel was in the tank? If it was very low, you could have been starving the pickup during accelleration.
With the regulator mounted in the rear you have the fuel pressing back against the regulator under acceration. This can confuse the regulator causing it to drop the fuel pressure. It would see the proper PSI at the regulator but the PSI at the fuel rails would be low. Not sure if this would account for that much drop but it might be contributing to the problem.
Depending upon how much HP you are making -6 lines might be a bit small.
Depending upon how much HP you are making -6 lines might be a bit small.
Thread Starter
Teching In
Joined: Oct 2010
Posts: 31
Likes: 0
From: Mooresville, NC
With the regulator mounted in the rear you have the fuel pressing back against the regulator under acceration. This can confuse the regulator causing it to drop the fuel pressure. It would see the proper PSI at the regulator but the PSI at the fuel rails would be low. Not sure if this would account for that much drop but it might be contributing to the problem.
Depending upon how much HP you are making -6 lines might be a bit small.
Depending upon how much HP you are making -6 lines might be a bit small.
Thread Starter
Teching In
Joined: Oct 2010
Posts: 31
Likes: 0
From: Mooresville, NC
12 psi and 18:1?!?! Wow, you're lucky you have pistons left! And judging by your graph, looks like you were closer to 20:1. VERY dangerous territory to be in.
Sounds like your pump cant keep up. While not very common, its not unheard of to have a Walbro go bad. IIRC they had a not so good batch of pumps a while back. Out of curiosity, what injectors are you running? And yeah, how much fuel was in the tank? If it was very low, you could have been starving the pickup during accelleration.
Sounds like your pump cant keep up. While not very common, its not unheard of to have a Walbro go bad. IIRC they had a not so good batch of pumps a while back. Out of curiosity, what injectors are you running? And yeah, how much fuel was in the tank? If it was very low, you could have been starving the pickup during accelleration.
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Basicaly it can be one of about 4 problems;
1. Demanding more fuel than the fuel system can deliver.
Stock LY6 so that problem is unlikely.
2. Faulty fuel pump
3. Faulty fuel pressure regulator
4. Clogged fuel filter
Where the pump & regulator new when you installed them?
It's not uncommon for for dirt to get into the tank when installing a intank pump clogging the intank filter.
Did you install a hot wire kit? You can supply ample voltage but not enough current to the pump.
Good luck.
1. Demanding more fuel than the fuel system can deliver.
Stock LY6 so that problem is unlikely.
2. Faulty fuel pump
3. Faulty fuel pressure regulator
4. Clogged fuel filter
Where the pump & regulator new when you installed them?
It's not uncommon for for dirt to get into the tank when installing a intank pump clogging the intank filter.
Did you install a hot wire kit? You can supply ample voltage but not enough current to the pump.
Good luck.
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Verdad Gallardo Thread Starter
Teching In
Joined: Oct 2010
Posts: 31
Likes: 0
From: Mooresville, NC
Where the pump & regulator new when you installed them?
It's not uncommon for for dirt to get into the tank when installing a intank pump clogging the intank filter.
Did you install a hot wire kit? You can supply ample voltage but not enough current to the pump.
Good luck.
It's not uncommon for for dirt to get into the tank when installing a intank pump clogging the intank filter.
Did you install a hot wire kit? You can supply ample voltage but not enough current to the pump.
Good luck.
The pump has it's own relay wired into the battery with 10ga wire and ground.
I pulled the pump and there was a lot of dirt around the pump sock. I'm going to have the tank boiled out tomorrow to assure there is no further dirt/debris left in the tank. Hopefully that was it.
"With the regulator mounted in the rear you have the fuel pressing back against the regulator under acceration. This can confuse the regulator causing it to drop the fuel pressure."
Huh?? I suggest there are 1000's of Vettes running, that don't suffer from this malady....
Huh?? I suggest there are 1000's of Vettes running, that don't suffer from this malady....
Actually G-forces are a very real issue, but insignificant in an EFI application.
At approx .35lb/ft for Gas you would see an approx. 3.5lb drop in a 10ft line at 1g acceleration.
At approx .35lb/ft for Gas you would see an approx. 3.5lb drop in a 10ft line at 1g acceleration.
Actually G-forces are a very real issue, but insignificant in an EFI application.
At approx .35lb/ft for Gas you would see an approx. 3.5lb drop in a 10ft line at 1g acceleration.
At approx .35lb/ft for Gas you would see an approx. 3.5lb drop in a 10ft line at 1g acceleration.
