Superduty

People need to understand a few things when comparing Walbros to other pumps, using pressure as the gauge.

When one puts a big line kit on a carburetor pump and the pressure increases, all that is happening is that they are removing a few psi of restriction so that a feeble pump can get the pressure up while supplying the injection pump with 20-30 GPH.

The result is that the injection pump see 15 PSI at idle (5 GPH) and 10 PSI at WOT (25 GPH.) As the filter plugs or the pump gets old the pressure drops. And the pump is operating at 100% of its capability.

When one installs a Walbro with an open bypass like Trik has, one is taking a pump that will make 100 PSI and installing a pressure relief (the bypass) to get the pressure down to 18 PSI at idle.

At 25 PSI total pressure (18 PSI at the lift pump and 7 PSI for filters and lines) the Walbro is moving 70 GPH past the inlet of the injection pump. That is 70 GPH at 18 PSI versus 5 GPH at 15 PSI for the carburetor pump. At WOT the Walbro is seeing 20 PSI for a flow rate of 75 GPH, versus 20-30 GPH with the carburetor pump.

The difference is night and day.

And all the while the Walbro is operating at 25% of its design pressure versus 100 or 150% for the carburetor pump.

And the only reason the pressure falls with the Walbro/open bypass is because there is absolutely no pressure regulation involved, only the backpressure of the return line. People are now installing Walbros with pressure regulators and oversized return lines. That should result in perfect pressure regulation at both idle and WOT.

Do you want your injection pump to have just enough flow or a surplus of flow ?

Do you want your lift pump operating at 100-150% of its design load or 25% of its design load ?

When a stock lift pump won't make 15 PSI it is because that is all the pump can put out volume wise at the lower pressure. If it could put out more volume the pressure would rise.

When a Walbro doesn't make 15 PSI it is because the bypass is allowing too much fuel through, thus lowering the pressure. Volume wise the Walbro is putting out tons and tons more fuel than the injection pump needs. Almost 3x more. (75GPH/25GPH = 3.) And unlike other pumps that return the excess fuel to the tank at the lift pump, all the Walbros fuel goes right by the lift pump inlet. What is the use of pumping fuel if it doesn't go to the injection pump ?

upersleder

some ?s superduty...... i have followed some of your threads and have considered the walbro pump, my truck is still under warranty and i figure they should be messing with it, not me, and i have been getting the 0216 code for some time and have been wanting a new injection pump. now with this low pressure lift pump, am i to assume it is flowing more volume because the pressure is lower? i would guess no, because when i step on the pedal the pressure drops like a rock.

when the walbro is hooked up with lets say 1/2" lines and fittings, your flowing all this fuel around in a loop, does thet in itself heat up the fuel?

what size lines do you think would be best?

would you say bigger with a pressure regulator or size it so you obtain the desired PSI without one?

and what would happen if one were to cut the voltage down to slow the walbro down? will it last? its just a DC motor, i would be curiouse

Superduty

"now with this low pressure lift pump, am i to assume it is flowing more volume because the pressure is lower? i would guess no, because when i step on the pedal the pressure drops like a rock."

It has less pressure because it is flowing less volume to the VP44. If it had more volume the pressure at the VP44 would be greater.

"when the walbro is hooked up with lets say 1/2" lines and fittings, your flowing all this fuel around in a loop, does thet in itself heat up the fuel?"

The heating is minimal. The power consumption of the Walbro is about 4 amps x 14V = 56 watts, so that isn't much heat for the fuel.

The 70 GPH I speak of is with stock lines except for a fitting to connect an non engine mounted pump to the stock hookup.

"what size lines do you think would be best?"

Stock lines are fine.

"would you say bigger with a pressure regulator or size it so you obtain the desired PSI without one?"

On the supply side it doesn't matter.

On the return side you have 2 choices.

a) stick with the stock return lines and run a plain hose bypass. (No regulator.) You should see 17 PSI at idle and 13 to 10 PSI at WOT, depending on your level of mod. In this situation the pressure regulation is coming from all the fuel running through the stock return line, which is restrictive. WIth the Walbro, even at WOT these is enough fuel returning through the stock return line to keep the pressure at 10-13 PSI.

b) replace the return line with something larger and run a regulator at the VP44.

The problem with running a regulator at the injection pump with the stock return line is that the Walbro flows so much that the backpressure is 17 PSI with the regulator set at 0 PSI.

So if you want to run a regulator, run a second return line from the injection pump (3/8 or 1/2") as the return for the regulator itself. And then run a good, high flow regulator, suitable for working with an EFI type pump.

"and what would happen if one were to cut the voltage down to slow the walbro down?"

Don't cut the voltage to the Walbro. There is nothing wrong with its stock flow. If you want less flow, select a smaller Walbro. The 70 GPH I speak of is with the GSL392. Walbro makes other pumps that flow less.

"its just a DC motor"

ANY DC motor will burn out if you stall it. The armature has to keep running. If you want less flow, select a smaller Walbro.

upersleder

thanks for your input superduty

ram23

With all these supplemental LP's, can you use them with the intank pump? I'm having this installed now under Wty. and need to add a secondary pump.

Superduty

You can't use a Walbro with the in tank lift pump. It flows more than the stock lift pumps and thus will be starved. It needs to go by itself. Besides, it has more than enough fuel for the VP44 all by itself.

ram23

Does anyone know of a pump that can be used with the intank pump to assist with fuel. I hate the thought of removing the intank pump.

Dr. Evil

You will have no choice when it dies.

01blkcloud

I am a tech at the local dodge dealership. From what DC's TECHConnect and Star have told me, on a un-modified Cummins, pressure is not as important as the amount of fuel the pump flows. In order for us to diag a bad lift pump we need to perform a fuel flow test (at least 50oz within three pre-pump cycles, turning key on a bumping and allowing pump to run for it's 25 sec cycle.) THEY DONT CARE ABOUT PRESSURE. People who modify fuel systems(injectors, pumps, programers, etc.) do not keep within the same fuel requirements as a stock Cummins, obviously. All of these parameters are pre-thought by Cummins engineers, and all they care about is FLOW. You guys are complaining about a component that is meant to be in an unmodified Cummins. For those under warranty, sorry to say but if you want your truck fixed free, thats the way we are PAID to do it. For a stock cummins, this intank system in my opinion, everyone I work with at the dealership, and everyone I have talked to at my training courses, they all agree this is an adequate and reliable system. Just keep in mind to keep your fuel tank at least 1/4 full to provide proper cooling for the pump (as you would with any in tank pump)

On the other hand, my truck is not stock, and I can see as a consumer and an enthusiast standpoint how you guys feel about the intank pump. Thats why I opted to go with a FASS II and engine mounted pre-pump.

Dr. Evil

That is, by far, the most important part of your post.

This is in no way a slam against you but why do you suppose DC went from measuring fuel pressure to the flow test? I would bet my last dollar it was because DC was replacing far too many lift pumps under warranty. When they changed to the flow test they saved big $ right? I do not put much stock/faith or trust in whatever DC does/says. They have been working on trying to improve lift pumps since 98.5 and STILL dont have anything thats really reliable. Im no expert on the third gens but to my knowledge they are still having LP trouble. Why hasnt DC come up with a fix that would be something like a FASS??

Even on a stock truck, the LP and VP-44 are barely adequate. Im sure others will feel the same.

2500CTD

My engine pump went dead, didnt have the time, or resources at the time to redo the fuel system so the intank got the nod. I got the "normal" pressures. No biggie. But I'm getting more into BOMBing and will need more flow. The Walbro is my next upgrade. I have a couple different ideas, but gotta a little more research yet. At the time the intank was ok for me. Hell I towed 24K from OR to FL with no problems. I knew the intank was not a permanent fix, especially if the modding continues

2500CTD

SuperDuty, you said the VP44 needs around 25GPH? Is that the most a "stock" truck would need at WOT? Needing a little help picking a different Walbro pump.

skinny_9

do you remove the stock lift pump for the fass II and walbro?
then it sound like you mount one of these by the motor?
what size or pump would be good for 275 injectors and a chip?, and could you use the same pump just stock in case factory blew?
does all this come in a kit pump, regulator, 2nd return line,fittings?
sorry for all the questions but you can look threads up all day and still be confused,also the only time i can play with you guys is a little bit each day when the boss isn't looking. again sorry for the repeat questions.

Dojman

I just ordered a FASS system for my wife's truck. Convinced to do so by the Dodge dealer mech. My truck's not under warranty, so it's not an issue with me, but he said that he wouldnt pursue a warranty revocation w/ a Fass installed. He's installed them there in the Dodge dealer shop. From old trucks to brand spanking new ones. He's telling everybody that runs a bed tank, they might as well just put one on, because if they dont now........they will later. I'm gonna put mine on myself, but ordered it through them. Same price as the website.

Superduty

Fuel(lbs) = HP X BSFC = 250HP x 0.380 = 95 pounds an hour. Diesel weighs 7 pounds per gallon, so 95/7 = 13.6 GPH. That is how much the engine will use. Add 30% extra to cool and lube the VP44 and you get 17.6 GPH. 25 GPH gives you a big cushion.

If you run a smaller Walbro, you will need to run a regulator in the bypass, because the lower flow won't give you backpressure from just the return line.

You have to remove the stock pump, or at least you can't draw fuel through it. (Some people have added a second pickup and left the stock pump in place.)

You can mount them wherever you want. A Walbro 392 flows way, way more fuel than any Cummins needs.

The Walbro pump is just the pump, the mount and maybe some fittings. You have to piece the second return line together yourself. Some of this is documented better on another website.

I suggest staying after work and doing some reading.