Engine/Transmission (1998.5 - 2002) Dual Walbros...

[wlowe]

I've been running a carter pusher fuel pump w/bypass on the frame for about a year with no problems. Recently I installed a fuel pressure regulator to drop my idle fuel pressure from 23 psi to 14 psi. My only concern with this setup is the hassle of changing the OEM fuel pump with it mounted on the engine, especially if I'm on the road. My solution was going to be to move the OEM pump to the frame, in series with the pusher, but recently I've been thinking about going to a Walbro 392, which seems to be getting quite a bit of positive feedback. To meet my requirements of reliability, performance, cost of replacement and ease of maintenance I've decided to go with dual walbros in parallel on the frame. Here is how I plan to do it:



Line from tank to pre-filter/screener.

Line from pre-filter to tee.

Two lines from tee to input of walbos in parallel.

Output line from each walbro to parallel check valves.

Output from check valves to another tee.

Single line from tee to OEM filter housing, (with another tee installed in this line for input to the pressure regulator).

I will also plumb in a check valve/bypass around the pumps to make sure the VP44 can pull fuel if a walbro failure occurs.



The idea is to only supply power to one walbro at a time, if it fails all that is required is to swap the power wire from one walbro to the other. Another alternative is to wire a power switch in the cab to switch from one to the other. The check valves isolate each walbro to stop fuel from feeding back through the system no matter which walbro is being used.



The advantages of this system are:



Ease of maintenance.

Uninterrupted fuel flow to VP44 at all times.

Low replacement cost/availability, walbros go for about a hundred bucks on Ebay.

Proven pump reliability.

Guaranteed, easy backup for pump failure, (no bath in diesel fuel trying to change a pump on the side of the road).

Common mounting point, mount one walbro above the other using the same frame holes.



The only problem I have with this system is trying to source some quality, high flow check valves for a reasonable price. Summit Racing has some aeromotive -6 AN high flow check valves but they're kind of spendy, sixty bucks each, (item number AEI-15106), and I'm not sure if they're diesel compatible.



So what do you guys think of my idea, any comments/suggestions?



Also, I forgot to mention, for any of you that might be considering going this route, the Walbro is a high pressure pump which requires a pressure regulator to control fuel pressure, otherwise fuel system damage will occur.

 

[rweis]

GARY builds his own bypass valves. He has done it for some time. A good source of knowledge I think.



Bob Weis

 

[wlowe]

Yes, in the past I've used many of Garys ideas. Originally I was going to build a check valve for the bypass in my current setup but I found a Carter check valve for twenty bucks at Summit. The problem I have with the Carter check valve and Gary's check valve is that I'm not sure if the flow through these is sufficent enough to be used in the main feed line to the VP44. For use in the bypass I'm sure they are adequate because the bypass is a temporary, short term method of allowing the VP44 to get fuel if the supply pump fails. For full time fuel delivery I want to make sure the flow is adequate. This is why I am considering the aeromotive check valve, it is listed as a high flow valve for use in dual pump configurations.

 

[rweis]

If you are going to buy a check valve, Kinsler JetCan works well. Full 3/8 flow and when you order you tell them what psi to set it to. You can also get a sets of springs and shims so you can make it anything you want.



I'm thinking the check valve to be set with the very least spring they have and install it backward so RASP psi does not go toward the tank, but if Walbro fails there is a little resistance as possible. The lightest spring in the spring kit is not much resistance. The wire is really thin.



I think the Walbro, being a gerator should not pass fuel backward if the walbro pump is no trunning. Therefore the bypass will be parallel to the Walbro, not in series with it as is the carter. Basically like Gary does.



I have to experiment with it to be really sure what happens.



Bob Weis

 

[Allnew2Me]

The check valves would work but if I understand them they only come into play if you know the pump failed and have switched over to the other one. The advantage I guess is that if you have a switch in the cab you can just flip it and off you go. I used a similar system but with ball valves. If my main pump goes out I flip two valves and connect the power to my backup and I'm off in 30 seconds. The ball valves are a full 3/8 flow. I would have to get out and climb under the truck to make the change, but it is a fairly simple system. I've switched back and forth to exercise the pumps and it works great, Here is the original posting,



https://www.turbodieselregister.com...002/190424-no-more-lift-pump-troubles-me.html

 

[wlowe]

If you are going to buy a check valve, Kinsler JetCan works well. Full 3/8 flow and when you order you tell them what psi to set it to. You can also get a sets of springs and shims so you can make it anything you want.



I'm thinking the check valve to be set with the very least spring they have and install it backward so RASP psi does not go toward the tank, but if Walbro fails there is a little resistance as possible. The lightest spring in the spring kit is not much resistance. The wire is really thin.



I think the Walbro, being a gerator should not pass fuel backward if the walbro pump is no trunning. Therefore the bypass will be parallel to the Walbro, not in series with it as is the carter. Basically like Gary does.



I have to experiment with it to be really sure what happens.



Bob Weis

Thanks for the info on the Kinsler check valves Bob, I'll look into those.



If you are planning on using the Walbro as the backup for your RASP then it is a good idea to plumb a bypass, and yes it will need to be run in parallel with the walbro. This will allow fuel to flow around the Walbro if the Walbro fails. On my current setup I'm using a bypass around the Carter pusher pump utilizing a Carter check valve. It only has 1/4 NPT fittings but I think it has sufficent flow for a bypass.



Carter Check Valves: CRT-169-1002 - summitracing.com





Bill

 

[wlowe]

The check valves would work but if I understand them they only come into play if you know the pump failed and have switched over to the other one. The advantage I guess is that if you have a switch in the cab you can just flip it and off you go. I used a similar system but with ball valves. If my main pump goes out I flip two valves and connect the power to my backup and I'm off in 30 seconds. The ball valves are a full 3/8 flow. I would have to get out and climb under the truck to make the change, but it is a fairly simple system. I've switched back and forth to exercise the pumps and it works great, Here is the original posting,



https://www.turbodieselregister.com...002/190424-no-more-lift-pump-troubles-me.html

You are correct, our systems are very similar. The main difference is that on your system you have to manually isolate the working pump by opening/closing shut off valves, whereas on my system the check valves automatically isolate the working pump depending on which pump is receiving power. And yes, the main advantage is that this allows you to choose which pump you want to use by flipping a switch in the cab.



Here is how I plan to plumb it:

 

[rweis]

Will the Walbro need a check valve since it is a gerator pump?



Will the gears in effect act as a check valve themselves and prevent backflow?



Bob Weis

 

[wlowe]

Will the Walbro need a check valve since it is a gerator pump?



Will the gears in effect act as a check valve themselves and prevent backflow?



Bob Weis

That is a good point. The question is will the failed Walbro totally block the flow or only partially block the flow. If it totally blocks flow then the check valves may not be needed. If flow is partially blocked there may be pressure backflow. I think I'll be on the safe side and use the check valves.

 

[Gary - K7GLD]

That is a good point. The question is will the failed Walbro totally block the flow or only partially block the flow. If it totally blocks flow then the check valves may not be needed. If flow is partially blocked there may be pressure backflow. I think I'll be on the safe side and use the check valves.

On my own "blow test", I was unable to get any flow thru a stopped Walbro 392, and would assume it to be unsafe to expect any such flow under stopped or failed Walbro situations - that was why I wouldn't even consider installing one without some form of bypass. USUALLY, the Carters will pass at least SOME fuel flow thru them when not running - but that too is a gamble - and the reason I originally started installing automatic fuel flow bypasses around my pumps.



For those who are not familiar with my current setup:



#ad




I have now obtained another new Walbro 392, and will replace the old OEM Carter seen above that is installed in it's relocated position in my fuel flow after the Walbro I now have installed, where my Carter pusher pump used to be.



My own Carter pumps, the OEM, and the Carter pusher I had installed, both operated flawlessly for over 50K miles, but the Walbro so far has functioned well enough, long enough, that I feel comfortable with it, and instead of just leaving the other recently acquired Walbro on the shelf as an offline backup, I'll pull the remaining OEM Carter, and install the second Walbro there where it will be quickly accessible and available for operational backup - I paid for it, so might as well install it and have it ready to go if needed!



In my case, the pumps are in series, and switching from one to the other is a simple matter of connecting the power lead from one to the other as desired - normally the Walbro is engaged, and simply pumps fuel both thru and around the inactive Carter further down the line. It is well evident that a SINGLE Walbro, installed and functioning properly, is fully capable of providing FAR more than enough fuel flow for all but the most extreme power mods that we see installed in our trucks - they have been tested on seriously modded trucks as high as about 800 HP as I recall, with NO fuel flow issues.



SO, in my own opinion and usage, flow from seriesed pumps, normally only activating one at a time should be sufficient. But what I *will* do, is install additional wiring and a switch that will instantly allow selection from one Walbro to the other from the driver's seat - or BOTH simultaneously.



WHY?



Because the primary remaining threat to proper fuel flow is a clogged fuel filter or other obstruction that one pump alone can't overcome - in that case, the ADDITIVE flow and PSI of the 2 pumps combined may very well keep me moving on down the road until such obstruction can be corrected.



In my case, I have an added Frantz sub-micron fuel filter in my system - it provides added restriction to fuel flow even under the best of conditions - and a bad tank of fuel or gelling fuel could potentially benefit from increasing fuel flow and PSI on demand - that can more easily happen with seriesed pumps than paralleled ones.



Much of the above occasionally come under fire from guys who criticise the 24 valve engine - and resent the need or recommendation of add-on "fixes" to the OEM fuel system. Yeah, if you aren't comfortable with the use of tools, and crawling around under a vehicle (it's my HOBBY, and I actually ENJOY these sort of activities - but that's just me! :-laf), it can be a pain - but actually, guys like me and Bob - and many others have already done the testing and research - and now relativel inexpensive complete kits are readily available to do what we have already tested and done.



The actual cost of providing the increased protection with setups like ours is little more than that of a spare tire - and provides the same sort of emergency protection - it's really not that big a deal, and CERTAINLY not reason to scratch the 24 valve engines of as consideration for purchase. I have used my own in RV towing situations all over this USA even BEFORE many of the current mods were done - and I'd start out across the USA again heavily loaded in a heartbeat - with absolutely NO concerns!

 

[wlowe]

SO, in my own opinion and usage, flow from seriesed pumps, normally only activating one at a time should be sufficient. But what I *will* do, is install additional wiring and a switch that will instantly allow selection from one Walbro to the other from the driver's seat - or BOTH simultaneously.

I'm curious to see how this turns out. It will be interesting to see if the fuel return to the tank will be adequate to safely regulate the pressure/volume of two walbros running simultaneously. Oo.

Keep us posted.

Thanks,

Bill

 

[Gary - K7GLD]

I'm curious to see how this turns out. It will be interesting to see if the fuel return to the tank will be adequate to safely regulate the pressure/volume of two walbros running simultaneously. Oo.

Keep us posted.

Thanks,

Bill

Yeah - I'm curious about that as well - I *do* use a 3/8 return line...

 

[rweis]

More information on Kinsler JetCan bypass valves



IF you use Kinsler JetCan check valves -



I emailed Kinsler and asked what was the lowest possible psi setting they can do on a JetCan bypass valve. Their reply is 0. 5 psi.



The reason I wanted to know is in the diagram above where the check valves are you would want the lowest possible opening pressure where the check valves are after the pumps.



Where the valve is in the bypass around the pumps if both pumps should fail, and the VP44 has to use suction to draw fuel by itself, you would want the absolute lowest possible opening suction. This is not a good condition, but the VP44 would at least have fuel available without trying to draw it through a (internal gear pump) gearotor pump which I think is not possible anyway. If you have a RASP (Fuel Boss, MITUSA, etc) it is a external gear pump and you can not draw fuel through a non rotating external pump either.



The Kinsler's will flow a full 3/8" through the valve body.



Bob Weis