Returnless to return issues - HELP
03-15-2009, 05:45 PM
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Returnless to return issues - HELP I really hope I could get some help over here, this is exactly what I faced.
I came to install an A&A fuel system and 95lbs injectors on my 08 C6 Z06, I guess other build details are unnecessary.
Those are the scenarios I came across:
1- Stock everything (fuel system wise), fuel pressure (hooked up to a mechanical gauge) at the end of the rail reads a steady 58-60PSI at idle - which is great
2- Stock fuel feed line and rails, yet this time with the exception of a regulator and return line were also added to the equation. Now upon priming the pump pressure goes up to ~55 PSI (great), however as I start the car it immediately drops to ~20-30ish PSI.
No matter what I have done to adjust the fuel regulator does absolutely NOTHING to the fuel pressure, whether fully screwed in or whether completely loose, fuel pressure was maintained at 20-30PSI!
The A&A kit that I have was designed to run with the stock pump feeding the motor at cruise and idle and anything below 2PSI, which through a boost switch activates the big "EXTERNAL" pump to furthermore feed the fuel thirsty engine, however bBecause of this issue, I can no longer run the big pump on standby while having the small pump do the work under cruise (because i can't get the idle/cruise FP correct to begin with.
I Ended up running the big pump continously, heating the fuel, getting annoyed with the Bosch pump's whine, and a transfer case that doesnt work (fuel is not transferring from the pass-side tank). For those who dont know, in our vettes, FP has to be maintained at a MINImum of 58PSI to transfer fuel from the pass. to drivers side tank.
What I ended up doing is I blocked off the stock fuel feed line with a (dead-end pipe) and measured the pressure to be 58PSI, which should get the tank-to-tank transfer system working while continously running the big pump. Just when I thought everything was okay, I discovered that under acceleration the FP fell to 40'PSI instantly and vehicle was down on power and thats when I discarded the whole idea.
Did anyone else over here EVER face an issue hooking up a fuel regulator to the stock feed line and not able to maintain nor increase/decrease pressure.
I was told by some mechanic that on the newer vehicles the fuel system has a module and its more digital vs is being more mechanical in the past, and thus harder to fool.
I mean how the hell will evap sense and work if someone is running an external pump to feed the motor. If evap is not working, sounds to me like someone trying to suck water out of a bottle that has no opening for the air to fill up instead of the water that resides there?
While I get some answers ill propose to you what I am thinking of, in another thread.
PS. I hope no one suggests a bad regulator because ive been able to maintain any pressure I wish with the big pump running.
I came to install an A&A fuel system and 95lbs injectors on my 08 C6 Z06, I guess other build details are unnecessary.
Those are the scenarios I came across:
1- Stock everything (fuel system wise), fuel pressure (hooked up to a mechanical gauge) at the end of the rail reads a steady 58-60PSI at idle - which is great
2- Stock fuel feed line and rails, yet this time with the exception of a regulator and return line were also added to the equation. Now upon priming the pump pressure goes up to ~55 PSI (great), however as I start the car it immediately drops to ~20-30ish PSI.
No matter what I have done to adjust the fuel regulator does absolutely NOTHING to the fuel pressure, whether fully screwed in or whether completely loose, fuel pressure was maintained at 20-30PSI!
The A&A kit that I have was designed to run with the stock pump feeding the motor at cruise and idle and anything below 2PSI, which through a boost switch activates the big "EXTERNAL" pump to furthermore feed the fuel thirsty engine, however bBecause of this issue, I can no longer run the big pump on standby while having the small pump do the work under cruise (because i can't get the idle/cruise FP correct to begin with.
I Ended up running the big pump continously, heating the fuel, getting annoyed with the Bosch pump's whine, and a transfer case that doesnt work (fuel is not transferring from the pass-side tank). For those who dont know, in our vettes, FP has to be maintained at a MINImum of 58PSI to transfer fuel from the pass. to drivers side tank.
What I ended up doing is I blocked off the stock fuel feed line with a (dead-end pipe) and measured the pressure to be 58PSI, which should get the tank-to-tank transfer system working while continously running the big pump. Just when I thought everything was okay, I discovered that under acceleration the FP fell to 40'PSI instantly and vehicle was down on power and thats when I discarded the whole idea.
Did anyone else over here EVER face an issue hooking up a fuel regulator to the stock feed line and not able to maintain nor increase/decrease pressure.
I was told by some mechanic that on the newer vehicles the fuel system has a module and its more digital vs is being more mechanical in the past, and thus harder to fool.
I mean how the hell will evap sense and work if someone is running an external pump to feed the motor. If evap is not working, sounds to me like someone trying to suck water out of a bottle that has no opening for the air to fill up instead of the water that resides there?
While I get some answers ill propose to you what I am thinking of, in another thread.
PS. I hope no one suggests a bad regulator because ive been able to maintain any pressure I wish with the big pump running.
03-15-2009, 08:30 PM
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I don't entirely understand your fuel system, but I don't believe the regulator has anything to do with your issue at all. If it will hold 55psi when the pumps prime, then it should hold it while you're running the car.
One possible scenario that comes to mind is this... Now, I don't know much about inline pumps, but here's what I'm thinking. If the external pump isn't running, perhaps it is a restriction in the fuel line. When you prime the system, the pressure behind the pump will slowly bleed through and make 55 on the engine side (where your fuel pressure gauge is). However, when you start the car, and the engine starts consuming that pressure, then you might end up with 60+psi behind the external pump, but 20-30 in front of it. So, the pressure is bleeding through the external pump, but the engine is consuming it faster than the pressure is able to get through.
I'm assuming this is an unlikely possibility since I'm pretty sure I've read about people using inline pumps in series. If so, then they would have run into the same issue. But, since this was the only idea that came to mind, I thought I would throw it out there for you.
One possible scenario that comes to mind is this... Now, I don't know much about inline pumps, but here's what I'm thinking. If the external pump isn't running, perhaps it is a restriction in the fuel line. When you prime the system, the pressure behind the pump will slowly bleed through and make 55 on the engine side (where your fuel pressure gauge is). However, when you start the car, and the engine starts consuming that pressure, then you might end up with 60+psi behind the external pump, but 20-30 in front of it. So, the pressure is bleeding through the external pump, but the engine is consuming it faster than the pressure is able to get through.
I'm assuming this is an unlikely possibility since I'm pretty sure I've read about people using inline pumps in series. If so, then they would have run into the same issue. But, since this was the only idea that came to mind, I thought I would throw it out there for you.
