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This is from a flex fuel C/K, Gen4 engine. Stole these pictures from an older post but mine looks the same, and that OP ended up going with a surge tank.
There is a sock on the bottom, but also a plastic venturi that plugs into the pump but otherwise does not seem to be hooked up anywhere else. Is this going into another inlet on the pump, suction side? Trying to figure what I need to do for more fuel. Would like to keep the FSCM but also want to upgrade enough for flex fuel capacity, up to 650-700 crank hp. The metal can shown is under fuel pressure directly from the pump, which then exits out the top and to the fuel feed line. All of this sits inside the bucket. This venturi would not work with an aftermarket pump easily since that pump would only have one inlet. The pressurized bucket would act as a buffer for sudden demands and so is beneficial. Granted I am already at the max capacity of the stock FF pump at 194 lph on E10, running 93% duty cycle, but pressure does dip for an instant with a karate chop to the throttle.
It seems like there were so many design changes that we will never be able to piece together how all this stuff works. It looks like you have GMT-900 stuff or either stuff thats PWM driven, but I have a LQ9 escalade original pump that I just took out and it was so rusted I had to buy a new one. I had planned on putting a Walbro 450lph in but I am concerned I will lose the low fuel siphoning feature since all the aftermarket pumps like you said only have one hose outlet. If you look at the differences from my original stock bucket to the new delphi stock bucket I bought, you can see the new pump has an extra line that runs out of it into the side of the bucket:
I am with you on the thinking though, and I think there is some other way we can put the aftermarket higher flowing pumps in and still keep a working way to run the tank low. Either way with the differences in design changes through the years I guess they felt confident enough that they were backwards compatible.
Thanks for the pics. Do you have one of the venturi, and how that second hose is attached to it? This was my big question, as it appears the stock pump had a port at the bottom that the venturi plugged into, but I believe that port to be pressure OUT from the pump, even though it is right next to the pump inlet with the sock.
I would like to do something similar, but keeping the stock fuel outlet connection and going with a bigger pump without making a custom basket as he did, if there is the space inside the existing filter can.
Thanks for the pics. Do you have one of the venturi, and how that second hose is attached to it? This was my big question, as it appears the stock pump had a port at the bottom that the venturi plugged into, but I believe that port to be pressure OUT from the pump, even though it is right next to the pump inlet with the sock.
I would like to do something similar, but keeping the stock fuel outlet connection and going with a bigger pump without making a custom basket as he did, if there is the space inside the existing filter can.
So I messed up and forgot to take pictures before I put the new stock pump back in. I had to get the truck back together and running again, so I just put it back together like stock which is frustrating but trying to figure this stuff out is more frustrating. I can't understand how modifying the fuel system can be so complicated when everything else is so much easier.
If I remember the new stock pump did have this grey looking piece on the bottom but I didn't look like it had any holes to pull fuel in or anything. My stock original pump has these little red flap things on the bottom though, I assume they act like a one way valve I just don't know how they "suck" fuel into the bucket:
This is the best picture I have of the new stock bucket:
If I remember I am pretty sure the tunnel thing that the extra hose coming from the pump connects to goes all the way to the bottom of the bucket to this little grey pickup looking thing. Sorry I should have taken more pictures before I put it in, apparently this new Delphi part has OE improvements to the fuel level sensor but doesn't say anything about anything else. Either way I overpaid and spent $350 on it and I am still stock and the pump supposedly only flows 30 GPH which I am assuming is the same as the stock pump. At least I have a new good pump that hopefully won't go out though so my original one was probably due for a change, this one does seem a lot quieter than my old one.
So I noticed a few days ago the tank was hard to fill, you have to barely squeeze the pump or else the tank will overflow. At the same time I noticed it was hard to crank up but I didn't think much of it until it happened again. Then it started to get harder and eventually stopped cranking, I thought I was stranded until I found out cycling the key on and off got it to crank back up. It also started to cut out above about half throttle and 3000 rpms, I had to limp it back home and it started cutting out even at part throttle, you could also see the trims were trying to add fuel too.
Given these symptoms I figured the brand new $350 Delphi pump I just put in was bad maybe from sucking dirt in from when I contaminated it trying to pull it out. So I got a fuel pressure gauge and checked it and it was basically zero. After cycling the ignition (which supposedly turns the relay on for 2 seconds each time the key is turned to run) eventually would bring it up to about 35 psi and it would start up and idle at about 35 psi too.
So I knew something was wrong with the pump, so I decided to drop the tank. I pulled the bucket out and I think this is the problem:
So one of the tabs/clips is broken off. It broke off when I tried to take it apart since I was going to try to install a Walbro 450lph in it until I gave up since I didn't have a way to ensure the venturi pump thing would work.
So now this kind of proves this pickup has to be sealed from pressure, it does have o-rings in it. I am really hoping this is the problem, but I still can't think of a way to fix it. maybe I could try to tap the port and keep the o-ring for a good seal, I just don't think I have enough material to do that with.
That looks to be the fuel filter inlet from the pump? I took apart a delphi unit recently, dont recall that white “retaining bar” looking thing, will get pics tomorrow. In your pic it looks like the fitting could still snap back into the filter?
still shouldn’t have affected your tank filling. Was there a vent line connected at the top of the sender and the bottom(inside the tank)?
That looks to be the fuel filter inlet from the pump? I took apart a delphi unit recently, dont recall that white “retaining bar” looking thing, will get pics tomorrow. In your pic it looks like the fitting could still snap back into the filter?
Yes, one side of it can snap back in, but the tab that holds the other side is broken off (from when I tried to pull it out so I could put the Walbro in). I believe this retaining bar setup is part of the new design, I am just wondering that they had enough problems with the original design to spend the money and effort to completely redesign it. I was thinking some zip ties to try to hold it in place, but I know a stainless clamp would be better if I could figure out a way to get it around it to hold it in place.
On another thought, I was thinking of trying to go to the junkyard and pulling another bucket out. I know the L59 Flex Fuel Tahoes and Yukons had a different PN for the pump so I am wondering if there is any benefit to getting one of these or whether they would fit and flow better or not?
The pump I took apart was a Delphi FG1054. It is a flex fuel pump. Does not have that retainer bar. The hose barbs on the fuel filter are part of the molding. Don't know if that helps. I would like to try to 450 it if I can get one, TI Automotive production has been down due to covid, and you have to watch out for counterfeits.
The pump has a primary outlet that goes to the filter, and also a small one, guessing 3/16", that goes to what I think is a brass check valve pressed into the body of the pump. From there the passage travels down to the venturi, which pulls fuel from underneath the bucket and pushes it back up another tube to fill the bucket. You may also notice they also cheaped it up and only use one spring to push the bucket down to the bottom of the tank. It also only has 1 rubber check valve to let fuel into the bottom of the bucket.
I cannot find any cross-reference or specs on the pump itself. But it is for a flex fuel gen4 SUV (?? - 14) application, so good for maybe 500 crank, if on gas only.
07-27-2020, 01:20 PM
How does this style venturi work?
