Pre-2003 fuel system balance
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Pre-2003 fuel system balance
I've been searching and researching this for awhile so sorry if I missed it.
I understand very clearly how the 2003-> fuel system uses the secondary jet pump etc. to balance the fuel tanks.
But I haven't been able to figure out how the earlier system worked. Is there a bottom transfer tube ? How does fuel get out of the passenger tank ?
I'm looking at a picture of a RH sender assembly that has a looped hose on it with a check valve and filter sock, and the mounting plate has an inlet and outlet. But I can't figure out if there is some kind of venturi effect bringing the fuel back over from the RH tank ? One guy I talked to thought that the return line circulates through this loop and uses some kind of ventuir effect to bring the fuel over to the main tank.
Can anyone explain how the earlier fuel system works ? Again, this is not for the returnless 2003+ system, I understand how that one works.
I'm trying to replicate this in my hot rod where I need to balance 2 tanks, and I want to get away from having a low level x-over hose and be able to better scavenge the non pump tank.
I dont think I can use the 2003+ system because using a return system I don't have pressurized fuel back at the tanks.
I understand very clearly how the 2003-> fuel system uses the secondary jet pump etc. to balance the fuel tanks.
But I haven't been able to figure out how the earlier system worked. Is there a bottom transfer tube ? How does fuel get out of the passenger tank ?
I'm looking at a picture of a RH sender assembly that has a looped hose on it with a check valve and filter sock, and the mounting plate has an inlet and outlet. But I can't figure out if there is some kind of venturi effect bringing the fuel back over from the RH tank ? One guy I talked to thought that the return line circulates through this loop and uses some kind of ventuir effect to bring the fuel over to the main tank.
Can anyone explain how the earlier fuel system works ? Again, this is not for the returnless 2003+ system, I understand how that one works.
I'm trying to replicate this in my hot rod where I need to balance 2 tanks, and I want to get away from having a low level x-over hose and be able to better scavenge the non pump tank.
I dont think I can use the 2003+ system because using a return system I don't have pressurized fuel back at the tanks.
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Joined: Aug 2000
Posts: 4,933
Likes: 30
From: San Rafael CA
preston,
Not sure what you're looking for ... but here's how my 2001 fuel system works (not sure where it differs from 2003+, or if it does) ....
The Right tank has (omitting EVAP lines) 3 lines attached to it.
1 Large line at the top allows fuel to feed into the tank when filling the car at a gas station.
2 smaller lines are located near the bottom of the tank.
One line has pressurized fuel coming from the fuel pump in the left tank. That fuel runs through a "siphon jet pump" and feeds fuel through the second line into the left tank, scavenging the right tank over time.
I'm not sure what you meant by "I dont think I can use the 2003+ system because using a return system I don't have pressurized fuel back at the tanks."
HTH
Not sure what you're looking for ... but here's how my 2001 fuel system works (not sure where it differs from 2003+, or if it does) ....
The Right tank has (omitting EVAP lines) 3 lines attached to it.
1 Large line at the top allows fuel to feed into the tank when filling the car at a gas station.
2 smaller lines are located near the bottom of the tank.
One line has pressurized fuel coming from the fuel pump in the left tank. That fuel runs through a "siphon jet pump" and feeds fuel through the second line into the left tank, scavenging the right tank over time.
I'm not sure what you meant by "I dont think I can use the 2003+ system because using a return system I don't have pressurized fuel back at the tanks."
HTH
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Thanks Black Z06, that's 90% of what I needed to know.
>I'm not sure what you meant by "I dont think I can use the 2003+ system because using a return system I don't have pressurized fuel back at the tanks."
You're right I was confusing myself. Since the 03+ regulator is back right next to the pump, I thought there was a difference in fuel pressure between that and a front mounted regulator (back at the tank) but I was mistaken - obviously in both systems the entire system from pump to regulator is pressurized.
So actually I think I now have 100% of what I needed to know, which is that I can just feed pressurized fuel to the 97-99 RH setup that I bought on ebay to siphon pump my RH tank. Just need to determine an orifice size to bleed off of the main fuel feed to drive the jet pump.
(Man, tons of info on the web and this site about the 2003+ setup, and nothing on the earlier cars)
Thanks again
>I'm not sure what you meant by "I dont think I can use the 2003+ system because using a return system I don't have pressurized fuel back at the tanks."
You're right I was confusing myself. Since the 03+ regulator is back right next to the pump, I thought there was a difference in fuel pressure between that and a front mounted regulator (back at the tank) but I was mistaken - obviously in both systems the entire system from pump to regulator is pressurized.
So actually I think I now have 100% of what I needed to know, which is that I can just feed pressurized fuel to the 97-99 RH setup that I bought on ebay to siphon pump my RH tank. Just need to determine an orifice size to bleed off of the main fuel feed to drive the jet pump.
(Man, tons of info on the web and this site about the 2003+ setup, and nothing on the earlier cars)
Thanks again
Supporting Vendor
Joined: Jul 2003
Posts: 6,486
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From: http://www.mphparts.com 800-364-1975
As far as I know, all year C5s used a venturi/jet pump in the passenger tank, fed by a small amount of fuel straight from the fuel pump, to balance the tanks. I know my 2002 certainly did.
Safety Car
Joined: Aug 2000
Posts: 4,933
Likes: 30
From: San Rafael CA
preston,
If it helps, the fuel fed to the right tank to "power" the siphon pump is fed from the main fuel line ....
The fuel line off the main fuel pump exits the left tank and feeds directly to the fuel filter/regulator. However, as the line leaves the tank there is a "T" fitting installed before it reaches the filter. Off that "T" is the feed for the right tank siphon pump.
I bet if you get the GM "T" fitting it will provide just what you're looking for in the way of the correct "orrifice".
HTH
If it helps, the fuel fed to the right tank to "power" the siphon pump is fed from the main fuel line ....
The fuel line off the main fuel pump exits the left tank and feeds directly to the fuel filter/regulator. However, as the line leaves the tank there is a "T" fitting installed before it reaches the filter. Off that "T" is the feed for the right tank siphon pump.
I bet if you get the GM "T" fitting it will provide just what you're looking for in the way of the correct "orrifice".
HTH
Le Mans Master
Joined: Oct 2005
Posts: 7,088
Likes: 1,829
From: Metro Detroit Michigan
You need this overflow connection, and be careful about venting the driver side tank. Unless your vent is quite a bit higher than the overflow tube, you could pump fuel out the vent. The Corvette is only vented on the passenger side (to the evap system).
A simpler option on your hot rod might be to install an electric fuel pump between the two tanks, and use a momentary switch to pump fuel to the main feed tank until the gas guage on that tank reads close to "full".
Last edited by Warp Factor; Jan 6, 2007 at 06:19 AM.
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Thanks guys that mention of the orifice size not being too important is helpful. I'm assuming that that extra piece in the line is some kind of little regulator or something that would keep flow down. I'll definitely experiment with it.
Warp factor, I appreciate the warnings as running dual fuel tanks is more complicated than most people realize, but yes I was planning on putting in a large diameter x-over tube and the vent will be above this level. Even with the check ***** and flaps, I noticed right away that my old system would still fill the vent line up to wherever the "full" level was.
As far as a simpler solution, one of the goals for this car was to be very streetable. I've had several versions of the car that had switches all over the place for this and that and I'm trying to go for a more "OEM" feel to the car where I can so I don't have to worry about running a lift pump etc.
PUmp plans are similar to vettes, two of the big in tank Bosch pumps with one turned on under power, and a BAP if I two aren't enough.
I still have concerns that one of those Bosch pumps is still pumping too much fuel for idle situations though, but I really don't want to complicate things by also having a step down on it !
Warp factor, I appreciate the warnings as running dual fuel tanks is more complicated than most people realize, but yes I was planning on putting in a large diameter x-over tube and the vent will be above this level. Even with the check ***** and flaps, I noticed right away that my old system would still fill the vent line up to wherever the "full" level was.
As far as a simpler solution, one of the goals for this car was to be very streetable. I've had several versions of the car that had switches all over the place for this and that and I'm trying to go for a more "OEM" feel to the car where I can so I don't have to worry about running a lift pump etc.
PUmp plans are similar to vettes, two of the big in tank Bosch pumps with one turned on under power, and a BAP if I two aren't enough.
I still have concerns that one of those Bosch pumps is still pumping too much fuel for idle situations though, but I really don't want to complicate things by also having a step down on it !
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