slopefunk55

iTrader: (3)

Figured I would post up and see if anyone has anymore ideas.
Car - 2005 base 350z stock vortech kit

The problem is I am loosing fuel pressure when going into boost. I am almost sure it’s a messed up FMU. I have verified the stock aux pump operates. I have pressure tested the system. I electronic gauge starts to show a drop in fuel pressure as soon as I show positive manifold pressure.

So I then disconnected the FMU vacuum line and capped off the manifold line. I started the car and applied 10 psi from my compressor to the FMU line. My fuel pressure then dropped 10 psi. So for some reason my FMU is working the opposite way it is supposed to. I contacted vortech and they said that no one has ever reported having this issue and thought I had installed the lines backwards. The car had been working properly and raising fuel pressure prior to sitting for a month in the cold. So with all that said I would like to know if anyone has any more ideas for trouble shooting before I send this FMU in to be checked. As always any help is appreciated

qqqqball

iTrader: (10)

get a walbro and 440cc injectors with uprev and save your self the trouble, they fail all the time, you can clean them but its hit or miss

slopefunk55

iTrader: (3)

I plan on upgrading this summer. However I was looking for some more insight on trouble shooting. If they fail all the time why is vortech reporting that they have never heard of this issue

OldManZ350

iTrader: (23)

1. You can't test it that way, because the aux pump will not come on without pressure to the MAP senser in the SS Box.

2. if you have an 8 to 1 FMU and 10psi, Fuel pressure should be over 100 psi. What was your FP before.

3. are you sure the gauge is work correctly?

4. are you sure aux pump is working correctly?

I had a similar problem pressure would start to fall off in high boost, installed a Walbro, disconnected the Aux Pump, Works Great.

A Walbro and larger injectors is the way to go

OldManZ350

iTrader: (23)

Hay Slope,

Did you mess with you're SS Box?

Their are Setting in there for the AUX Pump. If you UpLoaded your SS Map to your Laptop it will not save some of the setting in the software.

PM me if you want

TimRod

slopefunk55

iTrader: (3)

Hey Tim, I am not 100% on weather it was 10 psi. Thats as low as my compressor gauge reads but I have the compressor pushing very little air as I did not want to mess up the FMU. My thoughts were that the FMU should still raise fuel pressure without the aux pump turned on. Right? I did pick up some 440cc injectors and 6:1 disc after talking with you awhile back. I still need to order a walboro pump, but I do not plan on upgrading until it warms up a little. I did end up pulling the map off the box and taking out some fuel at idle then I wrote it back to the box. What setting are you talking about?

OldManZ350

iTrader: (23)

And then You Lost Fuel Pressure....

You ***** it Up.......

YA, On UPLOAD some setting are in default.

Check your PM

georgek350z

iTrader: (1)

exactly what this guy said ! And get osiris tune !!! external fuel pumps are garbage !

slopefunk55

iTrader: (3)

Ok ok. First off external pumps are not garbage. I have ran plenty of inline pumps along with an in tank walboros in different cars. I understand everyone is against the whole vortech stock kit, but come on. I am just asking incite on trouble shooting. I did not ask if I should ditch the stock FMU and external pump. Running an inline pump is a very effective cheap alternative to the dual in tank pump solution for high horse power vehicles.

Vash350Z

iTrader: (9)

The newb tools need to stop drinking the koolaid and doing what the "experts" tell them to do. Stock Vortech fuel system is perfect for a stock block. I hope you get your issue worked out!

slopefunk55

iTrader: (3)

Me too I did pull my map off the car after his post about the fuel pump settings. I have it set up for over -1 hg and 1250rpms. talked to mark today and he said the 350z box should be set up for -4 and 1550rpms. Either way it should be kicking on once it sees manifold pressure. I am going to set it for idle rpm tomorrow and apply some pressure to the FMU and SS box.

slopefunk55

iTrader: (3)

Ok update, for future split second users. Im going to start with thanking TIm again THanks. I talked to him and checked my pump settings for a third time. I still had no luck. I ended up changing the fuel pump setting to kick on at idle and the FMU rises. Heres another issue I could only get it to raise my fuel pressure by changing the aux pump to come on during rpm condition.

So Recap - for some reason the rpm and pressure condition was not kicking on my pump. Everything seems to be working fine with the pump set to rpm. The split second box is also logging pressure fine.

slopefunk55

iTrader: (3)

Ok newer update. Hooked everything back up and drove to work. 2 psi on boost gauge = no raise in fuel pressure.

Soooo, this has to be a vac leak to the fmu and ss box. My issue is compressed air pumps up the fmu but manifold is not. Im going to replace the vac lines tomorrow.

If phunk gets back to me I am going to order my pump and fitting and pull my aux pump.

anyone have any input post away

jpc350

When I switched to a Walbro and eleminated the FMU/Inline Voretch pump my fuel pressure went high (even at idle) under boost it went to 90 + psi...The walbro needs some modifications to bring its pressure down to around 53 psi (idle)...Phunk has a write-up on what needs to be done to the walbro..

OldManZ350

iTrader: (23)

So, what do you have "Output B Mode" set to?

Over RPM
Over Pressure
Over RPM or Pressure
Over RPM and Pressure

OldManZ350

iTrader: (23)

The Fuel Pressure Rise is not linear to Boost pressure. I don't think you will see any rise @ 2psi. I think the FMU starts raising FP at about 3-5 psi.

zerosec

iTrader: (3)

+1

slopefunk55

iTrader: (3)

Took the car out today after talking with Tim. I was thinking that I should have been seeing more fuel pressure at 2 psi. Did a few WOT pulls and fuel pressure is building like it should be. I think from the very beginning I wasnt writing the fuel pump settings like I was supposed to.

Thanks again Tim for all the help.

I am going to start contributing to this community by randomly jumping in threads and saying get an uprev toon. Look for me soon in a thread near you.