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Help with fuel issue

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10 replies to this topic

#1
doctorspeed1

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Hi all. I'm trying to figure out what is going on with my fuel system. I seem to be running lean.

Background.

Built motor/trans, newer SiR stage 3 turbos 33psi max boost. Fuel system is a dual 485 Visconti Basket with secondary pump hardwired. Stock fuel lines, upgraded fuel rails, SiR 2000cc injectors, flex fuel, Aeromotive FPR set to 45 psi base pressure. About 8 months on this setup. I was having cold and warm start issues 4 months ago and found my EFI connector was not tight in the post filter so I fixed that and while the basket was out also removed the cone filter before the venturi siphon system. Before, my my idc was around 70 percent at 35psi. Now its around 60 at 22 psi.

So far, it seems the feed side is not leaking based on the fact that my FPR holds 45 psi for over an hour after shutdown before it starts do decrease. Using the EcuTek fuel pump tool, you can hear the pumps activate and cycle through low med high and secondary. I removed the fuel hat to make sure the feed and return lines were not kinked and checked the feed fittings to make sure they were snug. Out of curiosity, I wanted to see how much restriction was left in the venturi siphon system so i tried to blow into the return fitting on the fuel hat. It actually took a moderate amount of effort to get air to pass and felt very restrictive. If you had to exhale through this to survive you would probably die. So does anyone know if this is normal? Are there check valves somewhere in the system between the hat fitting and the siphon system?

Any suggestions appreciated.

Logs attached.

Attached Files


Edited by doctorspeed1, 12 July 2017 - 08:01 PM.

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#2
Doug@WGP

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What did the filters look like when you removed the setup?  Did you clean the post filter?  Are they first or second gen 485s?


Doug Ross
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#3
doctorspeed1

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What did the filters look like when you removed the setup? Did you clean the post filter? Are they first or second gen 485s?

pre and post filters were clean a few months ago. I haven't checked again. My tank was still 2/3 full so I'm running it down. the pumps were pre installed with the unit sometime last summer.

#4
Doug@WGP

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485s can lose efficiency over time, especially first gen ones as their pressure relief spring weakens and can crack open, reducing their output... Why did you only hardwire the second pump?

Doug Ross
Owner of Weapons Grade Performance
-Northeast/Pacific Northwest Shops where we ONLY work on GT-Rs
-Owner/Builder of the 1st Ever Home Garage GT-R Drivetrain Removal
Cobb Protuner / EcuTek Tuner
-All Wheel Drive Mustang Dyno in House
doug@weaponsgradeperformance.com
Our Online Store
East Coast Location 226 N. Plains Industrial Rd, Wallingford CT 06492 203-668-4765


#5
doctorspeed1

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485s can lose efficiency over time, especially first gen ones as their pressure relief spring weakens and can crack open, reducing their output... Why did you only hardwire the second pump?

I knew someone would bring that up. it was running fine before that way and to keep things simple and use the stock control for the primary.

I'll have to look next week at the pumps when I run my tank down

#6
Doug@WGP

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485s do not like being run at less than 12v and that will also reduce their lifespan.

Doug Ross
Owner of Weapons Grade Performance
-Northeast/Pacific Northwest Shops where we ONLY work on GT-Rs
-Owner/Builder of the 1st Ever Home Garage GT-R Drivetrain Removal
Cobb Protuner / EcuTek Tuner
-All Wheel Drive Mustang Dyno in House
doug@weaponsgradeperformance.com
Our Online Store
East Coast Location 226 N. Plains Industrial Rd, Wallingford CT 06492 203-668-4765


#7
LTHL VNM

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I've got a JMS Fuel Pump Voltage Booster for sale if you're interested

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#8
240Z TwinTurbo

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To check pump performance you just need to log pump pressure under boost.  If you run 22psi and the pressure is not holding at (45+22) 67psi then the pump is not keeping up with the flow of the injectors.  For 35psi you need to see a steady (45+35) 80psi.  If pressure holds then it should not be a pump issue and perhaps injector pre-filters are dirty.  Keep in mind that pump flow is a function of voltage and pressure so most pumps, including 485s, will have performance loss as pressure is increased.

 

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#9
doctorspeed1

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If I only had a fuel pressure sensor. Thanks, I've been looking for a graph like that. What I'm really wondering though is of I have a back pressure issue on the return side that's restricting flow

#10
earico

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A restriction in the return line would just make higher fuel pressure at WOT and make the car rich not lean.

 

There is a little coned shaped screen inside the return line where it mounts to the OEM fuel boat. We've seen those get debris in them and cause back pressure in the return. This can lead to decreased life of the primary pump too if it's bad enough. You can remove this screen or back flow the return line to clean the debris out.

 

Like Doug asked. Do you have the old 485s or the new high pressure ones? You are right at the psi the old ones start to fall off.

 

It could also just be due to the fact that it takes more fuel flow when it's warm out. Increased fuel temps reduce the density of the fuel which increases flow demand. You are right on the edge of what's possible with a dual 485 setup to begin with on e85. I assume you are on e85.


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#11
doctorspeed1

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I removed the cone filter in April and it was clean. I'm not sure what pumps I have but they came with the basket last summer when it first came out. any way I can tell?

Edited by doctorspeed1, 13 July 2017 - 12:09 PM.





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