Need Fuel Pump/Tank Experts
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Joined: Sep 2007
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Need Fuel Pump/Tank Experts
I'm in the middle of replacing my stock C6 fuel pump with a Z06 pump as part of a supercharger upgrade and have a problem. Here are the symptoms. When I start the car I only see about 20psi at the rails. I put 5 gallons of fuel in the tank when I started and the right side tank was empty. Within a fuel minutes at idle fuel pressure drops off to zero. I pulled the tank back out to check all of my work and couldn't find anything wrong with my install. The other interesting thing is that the driver's side tank was pretty much empty and now the 5 gallons appears to be in the passenger side tank.
I added 5 gallons again after I put it back together and same thing...20psi at first tapering off to 0psi and I hear the pump starting to cavitate as the pressure drops...I'm assuming that second 5 gallons is now over in the passenger tank.
Do I have a bad pump or have I missed something in my install that is causing this?
Help!
I added 5 gallons again after I put it back together and same thing...20psi at first tapering off to 0psi and I hear the pump starting to cavitate as the pressure drops...I'm assuming that second 5 gallons is now over in the passenger tank.
Do I have a bad pump or have I missed something in my install that is causing this?
Help!
Racer
Joined: Jan 2009
Posts: 405
Likes: 1
From: SPRING CREEK NEVADA
I am going through the same thing still trying to figure it out, I will let you know what I find, only difference is I did the duel walbro,s.. I will try putting the pumps in a bucket with fuel and hook everything else up as normal so that I can see whats going on with the pumps. hopefully get time to check it out monday.
Thread Starter
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The only thing I've found is this link which talks to a C5 setup but I'm still at a loss to figure out why the pump is sending everything to the passenger side.
http://www.corvetteactioncenter.com/...el+Tank+System
http://www.corvetteactioncenter.com/...el+Tank+System
Thread Starter
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Joined: Sep 2007
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I also found this....
"When the fuel pressure drops below 54 psi, the transfer pump from the passenger side tank will no longer correctly function and will fail to transfer fuel. This situation will reduce the vehicle range and fuel system capacity. Since this transferred fuel also helps keep the canister full in the driver side tank, it may also cause the vehicle to loose fuel pressure under high power conditions."
"When the fuel pressure drops below 54 psi, the transfer pump from the passenger side tank will no longer correctly function and will fail to transfer fuel. This situation will reduce the vehicle range and fuel system capacity. Since this transferred fuel also helps keep the canister full in the driver side tank, it may also cause the vehicle to loose fuel pressure under high power conditions."
Racer
Joined: Jan 2009
Posts: 405
Likes: 1
From: SPRING CREEK NEVADA
I suspect I have a hose leaking by and that would explain lower pressure and why its not pumping back to the left tank, not sure why its pumping the left tank over to the right tank though. I am hoping I can see something obvious when I try it monday.
Racer
Joined: Aug 2007
Posts: 397
Likes: 0
From: East Longmeadow MA
probably x-over pipe
first do a search and find a diagram of the fuel system here on the forum, it will be worth 1,000 words like they say
.
ok, you have a leaky connection in the system on the supply (pressure) side. I'm guessing the x-over tube at the tank. Sometimes the clip holding the piece just inside the tank will break and get pushed in a bit then u get a pressure leak. Check the sub (right) side first. Or you simply have an o-ring cut.
BTW, the sub side has a jet pump that gets full pressure fuel in (20 liters/hr) and returns about 120 lph at low pressure back to the main (left) tank. There's a pressure regulator over in the rt tank too and 20 psi is not enough to open that up! So, i'm even more convinced of a leak on that side.
Did you have the sub tank out of the car? Module out of tank? If so the connection to the module can be suspect as well.
While you're investigating, the smaller diameter hose in the x-over is the high pressure & the bigger one is the low pressure return back to the main side tank.
Let me know if you need more info, i'll try to check back.
.ok, you have a leaky connection in the system on the supply (pressure) side. I'm guessing the x-over tube at the tank. Sometimes the clip holding the piece just inside the tank will break and get pushed in a bit then u get a pressure leak. Check the sub (right) side first. Or you simply have an o-ring cut.
BTW, the sub side has a jet pump that gets full pressure fuel in (20 liters/hr) and returns about 120 lph at low pressure back to the main (left) tank. There's a pressure regulator over in the rt tank too and 20 psi is not enough to open that up! So, i'm even more convinced of a leak on that side.
Did you have the sub tank out of the car? Module out of tank? If so the connection to the module can be suspect as well.
While you're investigating, the smaller diameter hose in the x-over is the high pressure & the bigger one is the low pressure return back to the main side tank.
Let me know if you need more info, i'll try to check back.
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Thread Starter
Safety Car
Joined: Sep 2007
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Likes: 82
first do a search and find a diagram of the fuel system here on the forum, it will be worth 1,000 words like they say.
ok, you have a leaky connection in the system on the supply (pressure) side. I'm guessing the x-over tube at the tank. Sometimes the clip holding the piece just inside the tank will break and get pushed in a bit then u get a pressure leak. Check the sub (right) side first. Or you simply have an o-ring cut.
BTW, the sub side has a jet pump that gets full pressure fuel in (20 liters/hr) and returns about 120 lph at low pressure back to the main (left) tank. There's a pressure regulator over in the rt tank too and 20 psi is not enough to open that up! So, i'm even more convinced of a leak on that side.
Did you have the sub tank out of the car? Module out of tank? If so the connection to the module can be suspect as well.
While you're investigating, the smaller diameter hose in the x-over is the high pressure & the bigger one is the low pressure return back to the main side tank.
Let me know if you need more info, i'll try to check back.
.ok, you have a leaky connection in the system on the supply (pressure) side. I'm guessing the x-over tube at the tank. Sometimes the clip holding the piece just inside the tank will break and get pushed in a bit then u get a pressure leak. Check the sub (right) side first. Or you simply have an o-ring cut.
BTW, the sub side has a jet pump that gets full pressure fuel in (20 liters/hr) and returns about 120 lph at low pressure back to the main (left) tank. There's a pressure regulator over in the rt tank too and 20 psi is not enough to open that up! So, i'm even more convinced of a leak on that side.
Did you have the sub tank out of the car? Module out of tank? If so the connection to the module can be suspect as well.
While you're investigating, the smaller diameter hose in the x-over is the high pressure & the bigger one is the low pressure return back to the main side tank.
Let me know if you need more info, i'll try to check back.
"The majority of the pressurized fuel is directed through the filter and on to the fuel feed pipe to the engine. Some of the pressurized fuel is directed through a feed pipe inside the crossover hose, to a siphon jet pump in the right tank. The jet pump relies on the venturi effect to use pressurized fuel to draw additional fuel from the tank."
This was a driver's side only tank drop.
Oh and I can use all of the help you are willing to give...gotta get this baby out of the garage and on the road!!!
Last edited by Motorhead-47; Apr 4, 2010 at 09:36 AM.
Safety Car
Joined: Feb 2008
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From: TEXOMA
St. Jude Donor '08-'09
anti syphon hole blocked?
p.s. i wonder if you can modify the in tank main fuel pressure regulator so its boost referenced, aka, run a vacuum line from the engine to the regulator?
p.s. i wonder if you can modify the in tank main fuel pressure regulator so its boost referenced, aka, run a vacuum line from the engine to the regulator?
Last edited by carlrx7; Apr 4, 2010 at 08:31 AM.
Thread Starter
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I don't think it's anti-siphon related. As I understand it the anti-siphon's job is to stop drain down after the car is shut off.
Racer
Joined: Jan 2009
Posts: 405
Likes: 1
From: SPRING CREEK NEVADA
thanks for the replies, I agree I believe it is a leak bleeding off pressure, now I just have to figure out where. I am working today so tomarrow I will try to get it figured out, I need to get mine out of the shop as well been working on mods all winter time to get it on the road.
Thread Starter
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update....pump checks good. I "engineered" up a test stand and although it's nearly impossible to use hose clamps to hold back 60psi I managed to connect a fuel pressure gauge on one fitting and with my thumb was able to modulate the other pressure line. I was able to see 60psi continuously at the gauge. I guess it's time to fire the "wrench" who did the install 
.
Looking to the next possible link it appears that I may have lost a very small plastic ferrule which sits just in front of the pressure line o-ring where the tank lines join the crossover tube. Here is a picture I took earlier with both ferrules in place. The upper one is now missing.
I probably knocked it off during the install and I'm guessing it is floating around in the other tank.
Guess I'll order up a complete replacement in tank fuel line set unless someone has a spare laying around they'd be willing to part with.
. Looking to the next possible link it appears that I may have lost a very small plastic ferrule which sits just in front of the pressure line o-ring where the tank lines join the crossover tube. Here is a picture I took earlier with both ferrules in place. The upper one is now missing.
I probably knocked it off during the install and I'm guessing it is floating around in the other tank. Guess I'll order up a complete replacement in tank fuel line set unless someone has a spare laying around they'd be willing to part with.
Racer
Joined: Jan 2009
Posts: 405
Likes: 1
From: SPRING CREEK NEVADA
I have both ferrules and O rings on mine but one O ring has a small chunk missing may be my problem, I noticed when I took the X pipe apart the the pump lines came apart with it so I may not of had them connected correctly. I will check it all out tomarrow.
Thread Starter
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I just went ahead and ordered a new set of lines...$55.00. I'm assuming it comes with the o-rings/ferrules etc.
#9... http://www.partstaxi.com/partlocator...layCatalogid=0
#9... http://www.partstaxi.com/partlocator...layCatalogid=0
Thread Starter
Safety Car
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Is the chunk missing out of the upper o-ring? That is the pressure side.
Racer
Joined: Aug 2007
Posts: 397
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From: East Longmeadow MA
ah... why the fuel pressure change? and no probably not too easily i'll tell ya that.
Racer
Joined: Aug 2007
Posts: 397
Likes: 0
From: East Longmeadow MA
doubt it
I just went ahead and ordered a new set of lines...$55.00. I'm assuming it comes with the o-rings/ferrules etc.
#9... http://www.partstaxi.com/partlocator...layCatalogid=0
#9... http://www.partstaxi.com/partlocator...layCatalogid=0
if all the fuel ends up in the RS tank that is the problem right there.
just to correct something mentioned earlier, ALL the fuel from the pump goes thru the filter then the quick connect off the bottom of the filter end cap connects on #9 mentioned above and then other end to the xover tube #6 tubes.
you can just get fuel resistant o-rings and a spacer if GM dealer doesn't have repair kit for that x-over tube. Don't get cheap crap from the HomeDepot or something cause that will last about 2 days then same problem!
