Engine/Transmission (1998.5 - 2002) Walbro Lift Pump Users

[ASimpson]

I just puchased the Walbro 392 pump and I have a couple questions. First do I need to run a different or bigger return line? Is this pump going to make that much pressure? I have read where some people did run a different return line back to the fuel neck. Does anyone have any pictures of their setup with the different return lines. I do plan on running the pre filter or strainer. Thanks Adam

 

[Gary - K7GLD]

Check out these threads:



https://www.turbodieselregister.com...mission-1998-5-2002/182134-carter-walbro.html



https://www.turbodieselregister.com/forums/general-diesel-topics/172940-latest-project.html

 

[ASimpson]

Gary that looks great. Did you run a different return line to handle the extra fuel that the Walbro supplies or has it not been an issue? Thanks

 

[Gary - K7GLD]

If you look closely at the pic in those threads of my homebrew regulator/bypass valve, you will see the 3/8 inch return line that runs excess fuel back to the tank - you'll see part of that return line running close to the Walbro pump, and it then "T's" into the line seen here running into the vapor line at the fuel filler where my in-bed tank fuel is pumped:



#ad

 

[RDyson]

You do need to run a fuel pressure regulator with a seperate line back to the tank. If your current return line is not big enough to handle the increased flow of the Walbro, it will continue to build pressure untill something pops. I think I have read on the Walbro site that these pumps will put up to 100+# of pressure if not regulated. Better safe than sorry... ... ... ...



Randy

 

[Gary - K7GLD]

You do need to run a fuel pressure regulator with a seperate line back to the tank. If your current return line is not big enough to handle the increased flow of the Walbro, it will continue to build pressure untill something pops. I think I have read on the Walbro site that these pumps will put up to 100+# of pressure if not regulated. Better safe than sorry... ... ... ...



Randy

Absolutely - there's no way an otherwise stock Dodge/Cummins fuel system can withstand the PSI and volume of a Walbro GSL-392 - some form of regulator and fuel return should be considered a must...

 

[wcoomes]

You should have enough hose in your kit from Glacier to install a return line. I have have mine for about 5 months now. I've been very impressed. I haul a 4000+ truck camper and last week I had its 60 gallon water tank full and was towing an 18' aluminum boat and the fuel pressure never fell below 15 psi. I was actually passing cars running 62 mph going up a long grade just north of Bloomington, IN on Indiana 37.

 

[Joe Mc]

I've had my 392 system for well over a year now and never upgraded the return line from the VP. The psi reg in the kit dumps excess psi back to the tank inlet, so there shouldn't be any problem/need to increase the VP return to the tank. You may wish to install a Vulcan draw straw though to make sure there's enough volume going to the walbro and just for insurance - I put one on mine because the stock metal supply at the tank module rusted and developed a pin hole which made system loose prime evertime it shut down = hard start. I also use the pre-screen/filter befor the walbro - keeps the chunks from gumming/clogging things up. FYI do yourself a favor since you'll be working in the area below the tank - install a small ball valve in the line from tank to the walbro - keeps you from getting a fuel shower ever time you have to change pre-filter also - cheap anti-theft device - no fuel = no go to far . . .

 

[JKinney]

Kudos to Gary for building his own sytem with a walbro pump.



for the rest of us theres eric at Glacier Diesel Power



The kit will come with everything you need.

 

[ASimpson]

I didn't buy the kit from glacier. I have everything I need except the reulator and the tee for the fill hose. What is the regulator you guys speak of is it just a certain pound check valve or what? Could a ball valve be used in the return line to regulate pressure? Other than these two items I have a fourth of the cost of the kit in parts and can get check valves fairly cheap. Thanks Adam

 

[rweis]

I do not have a Walbro, but I think the bypass check valve is like the RASP bypass valve. It is a mechanical spring against a cone seated sliding valve. The excess fuel comes into the nose of the valve and pushes on the spring to open the cone seated sliding valve. The higher the pressure the more the valve opens and bypasses fuel and vice versa.



I got my bypass valves from Kinsler and they are called Jet-Can bypass valves. You can tell Kinsler what pressure to set the valve for, or you can get an array of springs and shims and set whatever pressure you want.



The bypass valve that came from KO Engineering for the return bypass did not have an array of springs and shims is why I went to the Kinsler Jet-Can.



Bob Weis

 

[ASimpson]

Well guys the Walbro is in and with some advice from Rich at Glacier and a relief valve from Kinsler im holding steady at 21 pounds hopefully the last pump I will have to put under this thing.

 

[ERuhl]

Well guys the Walbro is in and with some advice from Rich at Glacier and a relief valve from Kinsler im holding steady at 21 pounds hopefully the last pump I will have to put under this thing.

21 lbs? Why so high?

 

[rweis]

I think it is supposed to be 13. 5# + - 3 #. The reason is the diaphram is allowed to flex . 5mm in it's seals without dammage. Above or below the diaphram starts getting stressed or the seals start getting stressed. If either the diaphram developes a crack or the seals do not seal then the high pressure side can not develop high pressure and the VP44 ceases to function. It may not be immediate, and is generally cumulative over time.



Bob Weis

 

[ASimpson]

That is as low as I could get it with the shims provided with the valve. I am going to see if kinsler will send me a smaller shim. According to Rich at Glacier it is 15 +/- 3.

 

[rweis]

I have some Kinsler shims left over from my JetCan bypass valves. Which shim(s) do you have / are using? I have a pretty good variety of left overs. I also have a variety of springs. Maybe a 1 step lighter spring with the same shim would do it? It took me weeks of changing springs and shims to finally get 14 + - 2. In cold weather until the fuel warms up to ~ 80* I'll get another 1# or so for that duration.



I would try a spring, let it run for a couple of days to see how it acts and that it was properly seated, then work the shims one at a time. Each time letting it run for a couple of days. Takes a while, but it resulted in a really stable psi.



I got the 13. 5 form what the VP44 test stand calibration pressure is. I got the +-3 from Brady at II as to what psi is tolerable with the diaphram flex of +- . 5mm which is allowable and is a included in the design of the diaphram and the seals that are holding the diaphram.



Bob Weis

 

[ASimpson]

I changed some shims in the valve and now its setting right on 16 pounds and thats good enough for me.

 

[rweis]

ASimpson,



Those Kinsler JetCans are really nice. Try it, adjust it, Try it, adjust it, until you are satisfied with the psi you have. They bypass a full AN-6 and are really well made.



16 psi should do just fine. I would be interested this winter if you see +1 psi when the fuel is thick / cold. Next summer when the fuel is thin / hot I would bet it goes -1 psi from what you are seeing now when the fuel is a moderate temperature.



Excellent bypass valve though.



Bob Weis