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Walbro 400 primary pump acting strange, fake? 20b twin pump setup

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Walbro 400 primary pump acting strange, fake? 20b twin pump setup

Old 02-08-15, 03:42 PM
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Originally Posted by Monsterbox View Post
So would you consider the factory return to be too high in relation to the pickups for these pumps? Attach a hose to the return pipe inside the hanger to extend the length/depth?
I don't remember what the factory setup looks like, my tank is sumped. I'm using the factory feed on the sender as a return. I first ran a hose from my "return" to the sump well and had mild cavitation issues, I moved the return outlet from the sump well to the front of the tank floor- no issue since. It would be worth putting a hose on your return to the floor and see if that helps. The placement of your current return stream may be causing turbulence in the factory pump well, causing aeration.
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Old 02-08-15, 04:39 PM
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You can see the return pipe here.

Also, notice that the pumps sit about 1 inch higher than factory. It now starves when the gas light comes on, but I never run that low.

The pump (s) only make the noise after 30-1hr of running the motor. It does not matter the fuel level. Have had it malfunction after a freshly refilling the tank and sitting in stop and go for 45 mins. Tank was only 2 gallons down.



Thanks for everyone's help. Tune is in 3 weeks, have to fix this issue. Its driving me nuts.
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Old 02-08-15, 05:07 PM
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That's 1 or two feeds there? Looks like a y block.
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Old 02-08-15, 05:22 PM
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Originally Posted by IRPerformance View Post
That's 1 or two feeds there? Looks like a y block.
Yes sir a y block combining both pumps into a -8 bulk head, -8 to the engine y block, to -6 each rail, -6 to each side of regulator, factory return to tank
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Old 02-08-15, 07:24 PM
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Wonder if the y is causing a problem. Maybe bypass it temporarily?
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Old 02-08-15, 07:35 PM
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I'm also running 2 walbro 400 in a CJ hanger, drove 3-4 hours not a issue, 6an out of each pump to a 10an line. Like IRP just mentioned, maybe that Y block is to close to the pumps.

I also know someone that was having a similar issues with twin 044 and even bought a new pump and didn't fix the issue, turn out to be the inline fuel filter was dirty.

I would run only one pump straight to see if it changes anything.
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Old 02-08-15, 09:14 PM
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Hmm this is so strange.

Iv seen a number of guys using y blocks with no issues. I have the same block Mr.Gasket up at the engine bay branching off to each rail. The port holes are nice and fat and open. The pump is definitely flowing perfectly fine and the filter must have less than 1500 miles on it

Its only after coolant temps reach around 200f and im sitting in traffic w heat soaked engine bay that the pump starts cavitation. At this point, either pump will pump air so there def localized boiling in the tank.

The question is how is this heat getting into the tank.

My fuel rails seem pretty hot to touch and some of my lines rest along the block itself. Could this be a significant source of problem?

Should I try lowering the pump voltage as bumpstart suggested?

Tomorrow:

-remove and inspect the inline filter
-remove pumps, add a submergable fuel hose to the end of the return line, possibly w a brass elbow to move the return flow away from the socks
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Old 02-08-15, 09:43 PM
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Really there's probably a number of factors, contributing to your problem. Probably changing the fuel filter, and more importantly, moving the return away from to pickup will have some success.
The stock return line is not helping. Having that small return with such a high volume of fuel passing through it, raises head pressure at the pump, making it work harder increasing the heating on the fuel. Also by having such a high velocity flow can create turbulence and cavitation in the return line.
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Old 02-08-15, 10:00 PM
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Also you mention that your base pressure is 60psi?why so high? Small Injectors?
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Old 02-08-15, 10:08 PM
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Thanks,

Base pressure is not 60psi, its 43psi. Without adjusting the regulator it will go to 60psi if I were to engage both pumps simultaneously.

Also, I realize stock return may be too small, however, it must be noted that I never had an issue with stock lines and walbro 400 on last motor. Im likely incorrect, but it seems to me that the regulator is the source of head pressure for the pump. If the return is too small then this would be exhibited as an inability to reach a reasonable base pressure. If the regulator can maintain 43psi then the pressure against the pump is 43psi no?

I want to change one thing at a time as to not confuse what the issue may be.

-lower pumps
-relocate return
-check filter unit

Test for cavitation

-lower voltage

Test for cavitation

-Upgrade return line and add fuel cooler

In this order is what im thinking
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Old 02-08-15, 10:24 PM
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The most common failure of high flow fuel systems is cavitation, or “vapor-lock”. The combination of too much heat or too much inlet restriction can create this operating condition, where the liquid fuel literally vaporizes (boils) inside the pump assembly. Symptoms of this operating condition may include one or more of the following:
• Dramatic loss of flow rate
• “Gauge Bouncing”
• Ratchet or grinding sounds from pump
• Inconsistent or loss of fuel pressure
• Temperatures above 120F (50C)
As bad as the symptoms of this condition are, the results of this condition are often permanent, even if what caused the condition in the first place was fixed. Loss of fuel delivery pressure will also result in a lean-out condition as well that can result in engine damage. Typically, even with very short amounts of time of exposure to cavitation (depending on severity) will cause damage to the fuel pump. This damage results in a direct loss of capacity and efficiency. Often as noted when unchecked, this damage to the pump results in operating conditions that quickens cavitation exposure at each use. Eventually, the fuel system resorts to complete failure to build or maintain pressure. For all fuel systems of any manufacturer, this failure can be avoided as it is not a result of a manufacturing defect, but a result of a fuel system design failure.
Two operating conditions can create the cavitating condition:
• High operating temperatures
• High inlet plumbing restrictions
High operating conditions can exist for several reasons, such as high inefficiencies (such as a worn or damaged pump), overly high fuel pressures, high flow rate pumps for long durations with low fuel amounts, or secondary sources of heat such as fuel rail(s), engine or exhaust. Prodigy Fuel Pumps have the distinction of having speed control, inherent in its design. This allows a reduced speed during low engine demand conditions that can add excessive temperatures to the fuel system.
Some refer to pumps as “pushers” or “pullers”. The truth is that all pumps are both. This reference comes from the amount of resistance to cavitation a particular pump has versus another. Minimizing the amount of restriction feeding the pump’s inlet is a critical element to avoid cavitation. This is the main reason why typical OEM fuel systems have their pumps mounted inside the fuel tank. Use of straining filters is required for the inlet of the fuel pump, to have a fine enough filtering to protect the fuel pump, yet coarse enough not to inhibit flow, or capture enough particles to cause a building up of debris. Finer filtration, to protect the rest of the fuel system (such as fuel injectors and regulators) can be accomplished downstream of the fuel pump with a second filter. Typically, straining filters for fuel pumps elements have micron ratings from 25 to 150 micron rating. Fuelab recommends the use of 75 micron rating for Prodigy Series fuel pumps (75-150 micron required). Typically, modern OEM straining filters are at a lower micron rating and made of plastic weave cloth. While these types of filters are adequate and desirable for OEM applications, however typical aftermarket fuel systems have far too high of flow rate to accommodate this form of straining filter easily. The biggest mistake and almost certain doom for a high flow fuel system, is to use a 10 micron filter upstream of the fuel pump. Plumbing size and the types of hose (or tube) play a vital role in the effects of cavitation as well general performance. The larger the flow rate, the larger the line size must be. Always avoid the use of check valves, or cross-drilled fittings when plumbing upstream of the fuel pump.
The second aspect that can cause cavitation is allowing heat to build-up in the fuel system. Most high flow EFI and carbureted fuel pumps are rated as “not continuous duty”. This is due to the amount of heat build-up that occurs over time as the fuel system is operating. When the fuel system has a high enough temperature, then the fuel will start to vaporize at the pump assembly, even with low pressure drop plumbing at the pump’s inlet. To allow for continuous or “street” use, voltage controllers are employed to reduce the pump speed during low engine demand operation, to prevent heat build-up. Once fuel temperatures are above 120F (50C), then the fuel is prone to vaporizing. A rule of thumb is: if it’s hot enough not to be comfortable to the touch, then it is too hot.
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Old 02-08-15, 10:36 PM
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i think the best move with such a large fuel system is to try all the ideas

if the ecu can do a duty cycle then you may not need to use the changeover relay and resister trick
( but the option is there for others with simple fuel pump switching )


especially you need to run a new return that is at least as big as the supply line
( or the maximum lift in the reg .. whatever is smallest )

add a fuel cooler under the car in the hose section at the rear will get airflow and not add too many joins or points to leak

and you may be able to get away with modding the lid for a bulkhead fitting and placing a longer dipped return ( well away from the fuel pump well )

PS.. double check that all that stuff in the tank is submersible fuel hose

and be sure each pump has a decent earth to the lid,, and the lid has its own ( same sized ) earths to chassis

Last edited by bumpstart; 02-08-15 at 10:39 PM.
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Old 02-09-15, 02:14 AM
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Originally Posted by bumpstart View Post
i think the best move with such a large fuel system is to try all the ideas

if the ecu can do a duty cycle then you may not need to use the changeover relay and resister trick
( but the option is there for others with simple fuel pump switching )


especially you need to run a new return that is at least as big as the supply line
( or the maximum lift in the reg .. whatever is smallest )

add a fuel cooler under the car in the hose section at the rear will get airflow and not add too many joins or points to leak

and you may be able to get away with modding the lid for a bulkhead fitting and placing a longer dipped return ( well away from the fuel pump well )

PS.. double check that all that stuff in the tank is submersible fuel hose

and be sure each pump has a decent earth to the lid,, and the lid has its own ( same sized ) earths to chassis
Ordered 6an line for the return line upgrade

Ordered a 12" fin style heatsinked fuel cooler 3/8npt threads (6an sized)

6an bulk head fitting for fuel tank cover

Submersible line to connect to that bulkhead, and 90 degree fitting for the end of that line inside the tank to connect another submerisble hose and span to the corner

Hopefully this will work. Id rather not mess w voltage unless it continues to overheat.
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Old 03-19-15, 08:49 AM
  #39  
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I installed a heat sink type cooler on the return line before the tank and removed the socks on the pumps to eliminate restriction issues.

The car is now improved and makes it at least 2 hrs with no issues.

However, I had it tuned this past weekend and after a couple hours on the dyno the problem returned. Extreme cavitation to the point that 2 pumps yielded no more fuel than 1 pump. Loud rocks bouncing around in tank and bouncing fuel pressure gauge. Shut down for a few hrs and fuel pressure is back up 20psi and tons of fuel again.


Talked to Aeromotive about the issue and they suggest the fuel pump speed controller on the primary pump to slow down the impeller and lower the flow. They suggest that the 400lph circulation at 13.5 is just adding fuel into the tank from the bypass through the rails.

I want to strongly agree, but my objection is that I've had the same pump on the stock engine with no issues

Talking with Aftermarket Industries from Australia, these guys suggest that its not the speed or flow but rather the return line being to small and causing turbulence.....I'm still on the fence with this theory
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Old 03-25-15, 01:53 AM
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Originally Posted by Monsterbox View Post
I installed a heat sink type cooler on the return line before the tank and removed the socks on the pumps to eliminate restriction issues.

The car is now improved and makes it at least 2 hrs with no issues.

However, I had it tuned this past weekend and after a couple hours on the dyno the problem returned. Extreme cavitation to the point that 2 pumps yielded no more fuel than 1 pump. Loud rocks bouncing around in tank and bouncing fuel pressure gauge. Shut down for a few hrs and fuel pressure is back up 20psi and tons of fuel again.

Talked to Aeromotive about the issue and they suggest the fuel pump speed controller on the primary pump to slow down the impeller and lower the flow. They suggest that the 400lph circulation at 13.5 is just adding fuel into the tank from the bypass through the rails.

I want to strongly agree, but my objection is that I've had the same pump on the stock engine with no issues

Talking with Aftermarket Industries from Australia, these guys suggest that its not the speed or flow but rather the return line being to small and causing turbulence.....I'm still on the fence with this theory
Walbro e85 flows alot and draws lots of amps both heat fuel up, few mns ago took walbro 255 out and instaled the walbro e85 without touching the regulator fuel pressure jumped around 10psi more, I let the pump run with the engine off at around 14 volts and set it at 50 psi pressure with few galons fuel in the tank it didnt take long for the rails to warm up, with the big 20b running it should heat up even more, I will install bosch 044 as my primary pump in next couple days, as it draws and flows less at base pressure,* and will have the walbro e85 kick in at few psi boost
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Old 03-25-15, 02:51 PM
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Originally Posted by tony94s4 View Post
Walbro e85 flows alot and draws lots of amps both heat fuel up, few mns ago took walbro 255 out and instaled the walbro e85 without touching the regulator fuel pressure jumped around 10psi more, I let the pump run with the engine off at around 14 volts and set it at 50 psi pressure with few galons fuel in the tank it didnt take long for the rails to warm up, with the big 20b running it should heat up even more, I will install bosch 044 as my primary pump in next couple days, as it draws and flows less at base pressure,* and will have the walbro e85 kick in at few psi boost
DAMN GOOD INFO.

Probably will end up installing a fuel pump speed controller
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Old 03-31-15, 08:08 AM
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I wanted to update everyone in here and thank you guys for the support!


Turns out that the issue all along was the oem return line was either restricted or too small. Switched to a larger return line and all issues solved. Still not sure why this would cause heat to build up in the tank, and it may very well have just been aeration from high pressure coming through the return, who knows, but this fixed the problem. Lesson learned.

Car made 720rwhp @ 20psi spinning! (and on ONE walbro 400, 93 octane, and CM10 meth/water nozzle)

Thanks again
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Old 03-31-15, 05:59 PM
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May not be SUPER helpful but I think I will send my personal experience with my walbro and apexi pump. We race in Guyana where the average temps on the track and even just casual driving can and normally reach above 30 ambient temps.
I had a weird issue after a 20 min session on the track, the pump would get alarmingly loud and fuel pressure would jump from 35-40psi and cause my AFR's to fluctuate erratically and made my idle jump around and at some points, it would just fail to restart like what occurred the first three times.

Turns out, that the the first pump I used (walbro 400) would overheat and and loose pressure as actual bubbles started occurring in the tank as you you could see it if you pulled the pump right after the symptoms started.

Never ran low and had a brand new sock and sender unit. After a few cycles of this, the pump started "cavitation" till I put the apexi in and rewired my pump with larger gauge wires because and the internal temps of the fuel dropped by 15 degree's which was REALLY alarming. I just concluded that walbro's run warmer but it could also be due to using an average gauge of wire. But then again, I do not know if anyone as similar ambient temps to deal with.
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Old 03-31-15, 06:20 PM
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this could be of interest.
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Old 04-01-15, 08:33 AM
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Originally Posted by sctRota View Post
May not be SUPER helpful but I think I will send my personal experience with my walbro and apexi pump. We race in Guyana where the average temps on the track and even just casual driving can and normally reach above 30 ambient temps.
I had a weird issue after a 20 min session on the track, the pump would get alarmingly loud and fuel pressure would jump from 35-40psi and cause my AFR's to fluctuate erratically and made my idle jump around and at some points, it would just fail to restart like what occurred the first three times.

Turns out, that the the first pump I used (walbro 400) would overheat and and loose pressure as actual bubbles started occurring in the tank as you you could see it if you pulled the pump right after the symptoms started.

Never ran low and had a brand new sock and sender unit. After a few cycles of this, the pump started "cavitation" till I put the apexi in and rewired my pump with larger gauge wires because and the internal temps of the fuel dropped by 15 degree's which was REALLY alarming. I just concluded that walbro's run warmer but it could also be due to using an average gauge of wire. But then again, I do not know if anyone as similar ambient temps to deal with.
Sounds like the exact same issue I was having.

The walbro 400 does run at much higher amperage than most high-flow pumps, and this is probably the cause of the heat. I don't know why the larger return line fixed the issue, as the base fuel pressure was easily manageable. Interesting, thanks for sharing. Hopefully the 400 doesn't overheat again on very long trips.
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