Fuel Flow Problem

297 Views 14 Replies 6 Participants Last post by kjb302ho, 10 d ago

BigDumbRedneck

Discussion Starter · 13 d ago

I had an issue where the fuel pressure would not get above 51 psi. The filter and sock were clogged, the fuel pump was sitting on the floor of the tank, and there was a kink in the hose between the pump and filter. I've fixed all of that and now it's rising 1:1 with boost like it should. The problem now is that I may be running out of pump. Somewhere between 400 lbs/hr and 450 lbs/hr, it starts dropping fuel pressure. I run 45 psi base pressure and at 12 psi of boost, the fuel pressure is 57. At 15 psi, fuel pressure varies from 53-56. Duty cycle uniformly increases until you get the fuel pressure drop. It picks up the pace when the fuel pressure doesn't keep up and ends up at almost 80% DC.

The combo: 8.2:1 CR 363, .6xx/.6xx 23x/22x @ .050" custom cam, old school AFR 185s, On3 with 76mm turbo.
Fuel system: Walbro 450 lph intank, Magnafuel 7010 filter, Pro-M hanger, -8 feed -6 return, Aeromotive rails & regulator, 72# injectors, 93 octane pump gas.

Voltage to the pump is > 14 volts at all times. The vacuum line to the regulator is a dedicated line directly to the intake. I've swapped the fuel pressure sensor with the oil pressure sensor and both read the same PSI. The pump appears to be a genuine Walbro pump with all of the correct markings. I've applied 20 psi of shop air to the fuel pump regulator and it hits 65 psi like it should.

Am I running out of pump? If so, will the Walbro 525 lph pump make up the difference I need? Or should this 450 be able to keep up and there is there something else going on that I'm missing?

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KEVIN$

· #2 · 13 d ago

I think if you read the detailed print on the 525 that flow rate is measured at a higher voltage than the 450 rated pumps but at the same voltage they flow the same. Finding this info is a task and is not located in one area on the website..

I spent a lot of time this year researching the pumps and, boy-o-boy, it can get confusing b/c there are several different 450 pumps and choosing the wrong one for your combo may not fix your issues.

I have a thread on my scattered findings somewhere on this site and I would highly recommend reading through my trials.

In a nutshell the TI Automotive (Walbro) p/n I ended up with was F90000285.

F90000285 - TI Automotive

High output, in-tank pump fits most popular EFI applications

aftermarket.tiautomotive.com

ks

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Nitrous SSC

· #3 · 13 d ago

450lph will support up to 700lb per hour looking at the conversion math. I'm running the same 450 on my setup and it's roughly at around 450lb/hr without any issues at all.

Is the pump getting enough amperage via the wiring?

Michael Plummer

· #4 · 13 d ago

BigDumbRedneck said:
Voltage to the pump is > 14 volts at all times. The vacuum line to the regulator is a dedicated line directly to the intake. I've swapped the fuel pressure sensor with the oil pressure sensor and both read the same PSI. The pump appears to be a genuine Walbro pump with all of the correct markings. I've applied 20 psi of shop air to the fuel pump regulator and it hits 65 psi like it should.

Where did you buy the fuel pump?

Thanks
Michael Plummer

BigDumbRedneck

Discussion Starter · #5 · 13 d ago

KEVIN$ said:
I think if you read the detailed print on the 525 that flow rate is measured at a higher voltage than the 450 rated pumps but at the same voltage they flow the same. Finding this info is a task and is not located in one area on the website..

I spent a lot of time this year researching the pumps and, boy-o-boy, it can get confusing b/c there are several different 450 pumps and choosing the wrong one for your combo may not fix your issues.

I have a thread on my scattered findings somewhere on this site and I would highly recommend reading through my trials.

In a nutshell the TI Automotive (Walbro) p/n I ended up with was F90000285.

F90000285 - TI Automotive

High output, in-tank pump fits most popular EFI applications

aftermarket.tiautomotive.com

ks

Thanks for the part #. Helps with the search on this site. Originally searched "Walbro" and a thousand 255 lph for sale posts came up.

Nitrous SSC said:
450lph will support up to 700lb per hour looking at the conversion math. I'm running the same 450 on my setup and it's roughly at around 450lb/hr without any issues at all.

Is the pump getting enough amperage via the wiring?

I thought it should be able to keep up too but everything is pointing to it not. I'm not seeing a voltage drop but I'll get some readings today.

Michael Plummer said:
Where did you buy the fuel pump?

Thanks
Michael Plummer

Was in the car when I bought it. I've considered that it may be a knock off but it appears to be real.

Michael Plummer

· #6 · 13 d ago

BigDumbRedneck said:
Was in the car when I bought it. I've considered that it may be a knock off but it appears to be real.

Fakes are getting tougher to identify. Buying from a reputable reseller like Jegs or Summit Racing is the best way to ensure you're getting what you pay for.

Good luck
Michael Plummer

BigDumbRedneck

Discussion Starter · #7 · 13 d ago

I'm seeing 12 amps at peak fuel pressure. Seems a little low compared to what is published.

BigDumbRedneck

Discussion Starter · #8 · 13 d ago

Here's a screen shot of a log with fuel pressure and MAP. It's 8.5 psi in 1st gear, 12 in 2nd, and 15 in 3rd. Hits a max of 59 psi and then drops. This is around 430 lb/hr of fuel.

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Reactions: 1

kjb302ho

· #9 · 13 d ago

stay away from walbro. get a dw400 and be happy.

9-401-1044

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kjb302ho

· #10 · 13 d ago

Layzie

· #11 · 12 d ago

TI Automotive Walbro 450LPH / F90000267 internal E85 HP RACING fuel pump
Designed for E85 or Gasoline applications for high performance engines exceeding 750hp.

+

Caution: Extremely High Counterfeit Rate - Buy from an Authorized Dealer Only

kjb302ho

· #12 · 12 d ago

DW400 has 0 counterfeit problems.

Layzie

· #13 · 11 d ago

Dw400's are for the coyote crowds.

DW400 Doesnt fit into an sn95 division X or fore fuel hat. Since the pump is 7mm larger than the walbro, im not so sure its a real "drop in" for any fox hat either.

The DW400 also does not have a check valve

Nitrous SSC

· #14 · 11 d ago

BigDumbRedneck said:
Here's a screen shot of a log with fuel pressure and MAP. It's 8.5 psi in 1st gear, 12 in 2nd, and 15 in 3rd. Hits a max of 59 psi and then drops. This is around 430 lb/hr of fuel.
View attachment 1098994

Love the boost per gear.

I had an AEM320 pump that slowly died off. Usually pumps either work or don't but that one kept getting worse and worse. It's weird to see the fluctuation in pressure like that vs a smooth curve on it's way down.

If it were me I'd swap to a new pump.

kjb302ho

· #15 · 10 d ago

Layzie said:
Dw400's are for the coyote crowds.

DW400 Doesnt fit into an sn95 division X or fore fuel hat. Since the pump is 7mm larger than the walbro, im not so sure its a real "drop in" for any fox hat either.

The DW400 also does not have a check valve

it will on the pro m hanger that he has. and its a single pump setup.

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