Walbro Fuel Filter sock - how often do you change it?
Thread Starter
Melting Slicks
Joined: Jul 2004
Posts: 3,277
Likes: 32
From: Mission Viejo California
Walbro Fuel Filter sock - how often do you change it?
Hi guys. How often do you guys change the sock on the walbro pump? I've heard of guys doing it super often yet for the most part, I haven't heard of anyone doing it at all. Have you guys inspected the part after 5000 or 10000 miles? if so, how'd it look?
Race Director
Joined: Jan 2008
Posts: 16,028
Likes: 170
From: oregon
inspected the one on my stock pump at 100k, looked totally fine. pulled one out of a 240k honda a few weeks ago, it also looked fine. the darn socks won't fit the big bosch 255lph pumps ! now my car cuts out when it's low on gas and i rail corners 
Burning Brakes
Joined: Jun 2005
Posts: 1,191
Likes: 15
From: Wallingford Vermont
FWIW My truck (diesel K5 Jimmy) was having a problem surging at road speed. Eventually I was having a problem with fuel gelling (common with diesel at cold temps), or so I thought...
Long story short; I finally dropped the fuel tank to look at the fuel sock (expecting to see a ball of "black gew" fuel pariffin). I saw nothing initially. I looked closer and found black/silver metal particles imbedded in the sock. A good back flush in the parts washer and the sock was good as new.
It's a heck of alot easier to pull the fuel sender/pickup in the our Vettes than most (I had to drop the tank in the truck PITA). Check it. It won't hurt. Clean it if need be (socks are cheap and re-usable). Most are replaced only when the pump goes
Long story short; I finally dropped the fuel tank to look at the fuel sock (expecting to see a ball of "black gew" fuel pariffin). I saw nothing initially. I looked closer and found black/silver metal particles imbedded in the sock. A good back flush in the parts washer and the sock was good as new.
It's a heck of alot easier to pull the fuel sender/pickup in the our Vettes than most (I had to drop the tank in the truck PITA). Check it. It won't hurt. Clean it if need be (socks are cheap and re-usable). Most are replaced only when the pump goes
Last edited by DanZ51; May 1, 2008 at 09:08 PM.
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Thread Starter
Melting Slicks
Joined: Jul 2004
Posts: 3,277
Likes: 32
From: Mission Viejo California
My problem is that it doesn't seem like I'm getting enough fuel at higher rpm.
On paper it looks like I should have enough fuel according the the flow charts on the blowerworks website. However, even with the p/e maxed from 3800, the car won't go rich.
My setup is 255 high pressure in tank to t rex inline to 60's to an fmu with a 1.66 to 1 stepup ratio. Base fuel pressure is 45. Boost is only 10 lbs. The t rex is boosted by a magnavolt which raises the voltage to 16.5 volts while in boost.
I've read that when using inline pumps, the flow is limited to the lessor of the two's "free flow" rating. The walbro flows about 304 at free flow so it shouldn't be cavitating. The t rex being the smaller of the two is boosted. Supposedly, the t rex flows about 190 lph at 70 psi. I'm only seeing about 60 psi currently. The increase in voltage is supposed to add about 30% to the flow rating (right around 250 lph at 70psi).
I do have a new sock sitting around so I'll try pulling it tonight and see what it looks like. I'll also assess how easy it'll be to install the 2nd pump. There's a great thread on ls1 tech on how to do it using stuff from home depot.
On paper it looks like I should have enough fuel according the the flow charts on the blowerworks website. However, even with the p/e maxed from 3800, the car won't go rich.
My setup is 255 high pressure in tank to t rex inline to 60's to an fmu with a 1.66 to 1 stepup ratio. Base fuel pressure is 45. Boost is only 10 lbs. The t rex is boosted by a magnavolt which raises the voltage to 16.5 volts while in boost.
I've read that when using inline pumps, the flow is limited to the lessor of the two's "free flow" rating. The walbro flows about 304 at free flow so it shouldn't be cavitating. The t rex being the smaller of the two is boosted. Supposedly, the t rex flows about 190 lph at 70 psi. I'm only seeing about 60 psi currently. The increase in voltage is supposed to add about 30% to the flow rating (right around 250 lph at 70psi).
I do have a new sock sitting around so I'll try pulling it tonight and see what it looks like. I'll also assess how easy it'll be to install the 2nd pump. There's a great thread on ls1 tech on how to do it using stuff from home depot.
Thread Starter
Melting Slicks
Joined: Jul 2004
Posts: 3,277
Likes: 32
From: Mission Viejo California
I'll check the voltage, but I didn't think it was an issue previously. My fuel pump sees 14.1 volts(the in line). If I knew it, I'd toss a boost a pump on that one too. I have one in my car sitting brand new in the box. But, from a price stand point, it's almost easier to just add a second pump (about $250). As for 61 psi, yeah, that's at what pressure I need to see enough fuel for 750 hp. I thought this would be enough but I'm having second thoughts. I'm also having second thoughts about my 60lb injectors as well. I think they may be too small.
Last edited by qwiketz; May 3, 2008 at 02:52 PM.
Safety Car
Joined: Nov 2004
Posts: 4,991
Likes: 5
From: The Pines South Jersey
Pro
Joined: Oct 2004
Posts: 628
Likes: 6
So if I understand correctly, the fuel pressure is reaching 60psi at full boost but it doesnt matter how far you take the PE tables the car never goes rich (are you using a wideband to measure it?).
So logically there seems to be some kind of delivery restriction; either the injectors are too small (what does the duty cycle look like?), the fuel rail isnt up to the task; maybe you have a restriction in the return that is holding the pressure 'up' artificially; is the car going into open loop (maybe the TPS isnt detecting 100%, which is a problem I had on mine after I removed the throttle body. Easily checked and fixed).
I would suggest increasing the FMU ratio to 2:1 (if that's possible) and see if the pressure rises to about 66 at full boost. I often get confused with the complex relationship between pressure and flow, but I believe that if flow is a problem then pressure will not rise (someone kick me if I am wrong).
Good luck in solving your problem, I am very curious to what the eventual solution is because I am considering upgrading to Y trim next year.
So logically there seems to be some kind of delivery restriction; either the injectors are too small (what does the duty cycle look like?), the fuel rail isnt up to the task; maybe you have a restriction in the return that is holding the pressure 'up' artificially; is the car going into open loop (maybe the TPS isnt detecting 100%, which is a problem I had on mine after I removed the throttle body. Easily checked and fixed).
I would suggest increasing the FMU ratio to 2:1 (if that's possible) and see if the pressure rises to about 66 at full boost. I often get confused with the complex relationship between pressure and flow, but I believe that if flow is a problem then pressure will not rise (someone kick me if I am wrong).
Good luck in solving your problem, I am very curious to what the eventual solution is because I am considering upgrading to Y trim next year.
Thread Starter
Melting Slicks
Joined: Jul 2004
Posts: 3,277
Likes: 32
From: Mission Viejo California
That's correct. No matter what we do the p/e tables (they're maxed out above 3800, the car doesn't run rich. With them maxed out, you would imagine that it would run pig rich at 3800, but it just isn't the case.
I'm probably leaning toward going to dual walbros with the second operated via hobbs switch. With that setup, I shouldn't have to ever worry about pump volume or pressure. I can also sell my boost a pump to recoup the cost for the 2nd pump.
I'm not totally sure what is causing my fueling issues, but I guess I'll go one piece at a time and modify what I have. Perhaps after I do the fuel pump upgrade, if flow is still an issue, I'll run a 2nd line to the front of the car. Maybe a -6 or something easy to run.
The 60's are a little too small, hence the fmu. So, I'm going to need a pump setup that can handle the fuel volume with the higher pressure.
I wonder if my car being batch fire has anything to do with it.
I'm probably leaning toward going to dual walbros with the second operated via hobbs switch. With that setup, I shouldn't have to ever worry about pump volume or pressure. I can also sell my boost a pump to recoup the cost for the 2nd pump.
I'm not totally sure what is causing my fueling issues, but I guess I'll go one piece at a time and modify what I have. Perhaps after I do the fuel pump upgrade, if flow is still an issue, I'll run a 2nd line to the front of the car. Maybe a -6 or something easy to run.
The 60's are a little too small, hence the fmu. So, I'm going to need a pump setup that can handle the fuel volume with the higher pressure.
I wonder if my car being batch fire has anything to do with it.
Racer
Joined: Apr 2003
Posts: 426
Likes: 0
From: Detroit MI
I replaced the pump and sock with a 255 lph unit that was a kit at the local speed shop for a mustang.
Fit was fine with the normal modifications expected with this repair/upgrade and the fuel starving is gone in the turns.
Pro
Joined: Oct 2004
Posts: 628
Likes: 6
That's correct. No matter what we do the p/e tables (they're maxed out above 3800, the car doesn't run rich. With them maxed out, you would imagine that it would run pig rich at 3800, but it just isn't the case.
I'm probably leaning toward going to dual walbros with the second operated via hobbs switch. With that setup, I shouldn't have to ever worry about pump volume or pressure. I can also sell my boost a pump to recoup the cost for the 2nd pump.
I'm not totally sure what is causing my fueling issues, but I guess I'll go one piece at a time and modify what I have. Perhaps after I do the fuel pump upgrade, if flow is still an issue, I'll run a 2nd line to the front of the car. Maybe a -6 or something easy to run.
The 60's are a little too small, hence the fmu. So, I'm going to need a pump setup that can handle the fuel volume with the higher pressure.
I wonder if my car being batch fire has anything to do with it.
I'm probably leaning toward going to dual walbros with the second operated via hobbs switch. With that setup, I shouldn't have to ever worry about pump volume or pressure. I can also sell my boost a pump to recoup the cost for the 2nd pump.
I'm not totally sure what is causing my fueling issues, but I guess I'll go one piece at a time and modify what I have. Perhaps after I do the fuel pump upgrade, if flow is still an issue, I'll run a 2nd line to the front of the car. Maybe a -6 or something easy to run.
The 60's are a little too small, hence the fmu. So, I'm going to need a pump setup that can handle the fuel volume with the higher pressure.
I wonder if my car being batch fire has anything to do with it.