Fuel pressure woes!
Thread Starter
Safety Car
Joined: Mar 1999
Posts: 3,613
Likes: 182
From: Toronto, Canada
Fuel pressure woes!
Guys I need your help trouble shooting a problem I'm having with my fuel pressure. What's happening is after I go wot and then just settle back to cruising my fuel pressure drops to about 22psi and the car runs rough. If I shut the motor off and restart everything goes back to normal and my fuel pressure is back at 50psi. During a wot pass my fuel pressure is 60+ so no worries there.
Here are some details of my set up.
The car is an 04 and I have a walbro 255 intank with LPE regulator block off plugs. Up front at the rails I have an adjustable fuel regulator(boost refrenced) to set the pressure. This uses the stock feed line and runs just like oem.
I also have the ECS fuel system which uses an in line pump activated by a hobbs switch come on when in boost. This pump has its own dedicated -8an line which is run to the back of the passenger side rail. In combination to everything there is also a -6an return line.
So under normal driving everything works fine, but when hitting boost and activating the second pump pressure rises to over 60psi and then drops to 22psi when getting off the throttle. If fuel pressure was bleeding off somewhere I would think it would be all the time? Does this sound like an electrical problem?
I'm stumped and need your help!
Here are some details of my set up.
The car is an 04 and I have a walbro 255 intank with LPE regulator block off plugs. Up front at the rails I have an adjustable fuel regulator(boost refrenced) to set the pressure. This uses the stock feed line and runs just like oem.
I also have the ECS fuel system which uses an in line pump activated by a hobbs switch come on when in boost. This pump has its own dedicated -8an line which is run to the back of the passenger side rail. In combination to everything there is also a -6an return line.
So under normal driving everything works fine, but when hitting boost and activating the second pump pressure rises to over 60psi and then drops to 22psi when getting off the throttle. If fuel pressure was bleeding off somewhere I would think it would be all the time? Does this sound like an electrical problem?
I'm stumped and need your help!
Safety Car
Joined: Jun 2004
Posts: 4,353
Likes: 22
From: Bella Vista Ca
Could the high pressure under boost be back feeding into the fuel tank screwing up the stock in tank regulator? When you turn the car off the regulator could reseat proper....
I run a check valve to isolate the stock pump/ regulator when my boost activated ECS pump kicks on (basically a check valve between the stock pump and were the ECS pressure line ties into the fuel system.
Good luck tracking the issue down
I run a check valve to isolate the stock pump/ regulator when my boost activated ECS pump kicks on (basically a check valve between the stock pump and were the ECS pressure line ties into the fuel system.
Good luck tracking the issue down
Le Mans Master
Joined: Feb 2009
Posts: 5,177
Likes: 201
From: Your Sister's Bedroom
I guess I have a question first, why is your base fuel pressure set so low? 50psi?
As far as the problem itself, this kind of gremlin is exactly why I am not a fan of piggybacking off the factory style pump setup. Instead of running two seperate fuel systems why not simplify it and run one feed setup instead of two. You already have the return done so your halfway there! Run Dual in tank 255 or larger pumps, a -8 Feed and never worry about stuff like this again.
Sorry im no help with your actual problem!
As far as the problem itself, this kind of gremlin is exactly why I am not a fan of piggybacking off the factory style pump setup. Instead of running two seperate fuel systems why not simplify it and run one feed setup instead of two. You already have the return done so your halfway there! Run Dual in tank 255 or larger pumps, a -8 Feed and never worry about stuff like this again.
Sorry im no help with your actual problem!
Melting Slicks
Joined: Feb 2006
Posts: 2,184
Likes: 2
I guess I have a question first, why is your base fuel pressure set so low? 50psi?
As far as the problem itself, this kind of gremlin is exactly why I am not a fan of piggybacking off the factory style pump setup. Instead of running two seperate fuel systems why not simplify it and run one feed setup instead of two. You already have the return done so your halfway there! Run Dual in tank 255 or larger pumps, a -8 Feed and never worry about stuff like this again.
Sorry im no help with your actual problem!
As far as the problem itself, this kind of gremlin is exactly why I am not a fan of piggybacking off the factory style pump setup. Instead of running two seperate fuel systems why not simplify it and run one feed setup instead of two. You already have the return done so your halfway there! Run Dual in tank 255 or larger pumps, a -8 Feed and never worry about stuff like this again.
Sorry im no help with your actual problem!
Thread Starter
Safety Car
Joined: Mar 1999
Posts: 3,613
Likes: 182
From: Toronto, Canada
If I'm not mistaken the walbro 255 pump has a built in check valve, so I don't think its back flowing. Plus many people use this pump for intank set ups.
My set up is boost refrenced and at full boost I see 75psi if I recall correctly. If I up the base pressure to say 55-58psi then I would be over 80psi at the rail and my injectors can go static. What would you suggest is the ideal fuel pressure?
The problem is I have a late model fuel system C6 style and its very labour intensive to put in pumps in as you need to drop the rear drivetrain. The secondary fuel systems developed by vendors such as ECS, A&A, Dallas Performance have been proven to work well as many forum members can confirm. My problem could be unique to me and might be something as simple as a bad ground or a short somewhere. What puzzles me is when I restart the car fuel pressure returns back to normal. Maybe the walbro pump is bad?
As far as the problem itself, this kind of gremlin is exactly why I am not a fan of piggybacking off the factory style pump setup. Instead of running two seperate fuel systems why not simplify it and run one feed setup instead of two. You already have the return done so your halfway there! Run Dual in tank 255 or larger pumps, a -8 Feed and never worry about stuff like this again.
Sorry im no help with your actual problem!
Sorry im no help with your actual problem!
Safety Car
Joined: Jun 2004
Posts: 4,353
Likes: 22
From: Bella Vista Ca
For trouble shooting, disconnect the pump located in the stock location electrically. Wire the ECS pump to always on. Give the car a drive and see if it duplicates. That could give you a direction to go.....
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Le Mans Master
Joined: Feb 2009
Posts: 5,177
Likes: 201
From: Your Sister's Bedroom
As far as the fuel system being a pain in the *** to get at, consider that part of owning a corvette, nothing on the cars are easy! Fact is, the less complicated your fuel system is, the less chance there is for problems with it. I am not a fan of redundant fuel systems such as this, nor am I a fan of using pressure switches to activate extra pumps. Put two in the tank, run them constant, and forget about your problems.
Melting Slicks
Joined: Jul 2007
Posts: 2,939
Likes: 7
From: Simpsonville SC
St. Jude Donor '09-'10
So, I need to chime in to get some clarification on the BEST fuel pressure setup. Tell me if this is correct:
1. Set the boost-referenced regulator to 50 PSI with the vacuum line DISCONNECTED.
2. When the hose is reconnected, the vacuum will lower the pressure to around 45
3. Under boost, the pressure will go up to around 65
Sound right?
1. Set the boost-referenced regulator to 50 PSI with the vacuum line DISCONNECTED.
2. When the hose is reconnected, the vacuum will lower the pressure to around 45
3. Under boost, the pressure will go up to around 65
Sound right?
Le Mans Master
Joined: Feb 2009
Posts: 5,177
Likes: 201
From: Your Sister's Bedroom
So, I need to chime in to get some clarification on the BEST fuel pressure setup. Tell me if this is correct:
1. Set the boost-referenced regulator to 50 PSI with the vacuum line DISCONNECTED.
2. When the hose is reconnected, the vacuum will lower the pressure to around 45
3. Under boost, the pressure will go up to around 65
Sound right?
1. Set the boost-referenced regulator to 50 PSI with the vacuum line DISCONNECTED.
2. When the hose is reconnected, the vacuum will lower the pressure to around 45
3. Under boost, the pressure will go up to around 65
Sound right?
Set the fuel pressure at the regulator at 58-60psi with the vaccum disconnected. When you reconnect the vacuum hose the pressure will drop, exactly how far depends on your engine. Under boost the fuel pressure will rise 1psi of fuel pressure to every 1psi of boost.
Le Mans Master
Joined: Feb 2009
Posts: 5,177
Likes: 201
From: Your Sister's Bedroom
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To test that theory, just do a heavy decell and see what the pressure goes to. The pressure will not exceed 60lbs because of the factory regulator in the tank, but the second regulator can allow it to drop if not set correctly. For the late C5's and C6's that get our stage 2 fuel system, need to have the factory regulator blocked off so the Aeromotive regulator can boost reference correctly.
Melting Slicks
Joined: Jul 2007
Posts: 2,939
Likes: 7
From: Simpsonville SC
St. Jude Donor '09-'10
I had my pressure set at 60 WITH the vacuum line attached... that was the wrong thing! My pressure under boost was norht ov 75, so, I set it at 50 WITHOUT the vacuum line, and it runs around 40-45 at idle and decel. It jumps to 65 under boost!
I still think I will bump it up to 55 without the vacuum line.
Le Mans Master
Joined: Feb 2009
Posts: 5,177
Likes: 201
From: Your Sister's Bedroom
I had my pressure set at 60 WITH the vacuum line attached... that was the wrong thing! My pressure under boost was norht ov 75, so, I set it at 50 WITHOUT the vacuum line, and it runs around 40-45 at idle and decel. It jumps to 65 under boost!
I still think I will bump it up to 55 without the vacuum line.
I still think I will bump it up to 55 without the vacuum line.
We are using the same fuel system, RSI hanger, -8 Feed, -6 return off a boost referenced magnafuel regulator. Ive always set them up at about 58-60psi without vacuum.