Fero313

iTrader: (1)

S5 TII with a Sprint RE
stock s5 turbo
550cc/750cc injectors
FD fuel pump

Car originally had a Rtek 2.0 and ran great. Fuel pressure was 32psi at idle and 89-40 at 0psi or with engine off. Switched to the Sprint RE this week and when we started tuning I noticed that the fuel pressure was around 50 psi at idle. The fuel pressure doesn't change with vacuum and when revving the gauge sways a 1-2 psi either way. No changes to the fuel components were made and I didn't make any changes to the vac/boost reference for the FPR. I am getting voltage for the pump from haltech fuse block so it is getting full voltage when running as it is no longer going through the fuel resistor box.

Is the FPR damaged?
Is the full voltage causing the FD pump to overwhelm the regulator?
What else could cause this?

*** Subquestion: Is the stock TII fuel pressure regulator rising rate?

arghx

iTrader: (3)

So you are in fact using the stock FPR? It is a 1:1 fuel pressure regulator and base pressure on a 100% stock car should be around 2.5bar (36psi). With a higher flowing fuel pump and increased voltage it doesn't surprise me that the pressure is higher at idle. You will have to put up with a richer mixture or get an adjustable FPR.

Fero313

iTrader: (1)

Line pressure at engine off or 0 psi should be 34-40 psi

At idle it should be 27-33 psi


So what you are saying is that with a FD pump and batt voltage (about 13.5V) I'm going to see 50psi at idle.... I could understand a few psi but 15 more? The FPR is that weak at regulating pressure? Is this the norm for people who have kept the stock rails??

Jobro

iTrader: (2)

One of my mates uses a stock s5 tii fuel rail with a bosch 044 and does not have any problems with the pressure rising above stock.

Fero313

iTrader: (1)

Hey thanks. I've got a line on another rail and just going to swap it out and see what happens.

arghx

iTrader: (3)

swap out the rail and report back.

Fleemer

i have a walbro 255 in my s5 and pressure holds around 40psi

Fero313

iTrader: (1)

Got home to the fuel rail in my mailbox. Installed it and now I have 41-42 psi priming the system. Much better than 50+ psi! Looks like somewhere between removing the old harness and installing the Haltech the regulator failed. Weird. Oh well. I Pulled a little vac with my mouth and the pressure went down. Everything looks good. I'll be reinstalling the mani and firing it up tomorrow as today is the girlfriend's birthday.

Fero313

iTrader: (1)

ok. Everything is NOT OK. I bolted everything back down and started the car. Fuel pressure stayed at 40psi until revved and went to 50psi. Seems to still coorelate with the battery voltage as I was getting 12.5V at startup and 13.5V volts AFTER i revved. Engine vacuum is at 17inHg and is definitely what the fpr is seeing. After the car warmed up I revved a little more aggresively. It even got a little boost, about 3-4 psi, and the pressure actually started falling!! It fell to just under 40psi as the rpms rose and entered boost. It seems to be doing the OPPOSITE of what it should be! I'm so confused. Ideas anyone?

** With the gauge on the return, I saw NO pressure at all, so I have no restriction in my return line.

With the new (used) secondary rail:

Car off 12V: 40-42psi
13.5V: 50psi
pressure falls with revs

arghx

iTrader: (3)

Get a hand pump that can do vacuum and pressure (Mityvac). Jumper the fuek pump check connector with key ON, engine OFF. Apply vacuum to FPR and observe whether pressure changes. Apply pressure to FPR and observe whether pressure changes. Report back.

Fero313

iTrader: (1)

I tried to take a gopro video but no luck... too low of light. anyway.... I have a mityvac but it only does vacuum. So thats what I can do tonight...

Key ON, engine OFF:
no vac: 41psi
25inHG: 40psi

Something odd I noticed. With the key OFF after priming the system... with 40psi holding in the lines I used the mityvac. With 15inHg I saw 30 psi holding in the system. Now, this is leaning toward proper FPR function.... BUT, I turned the key (still 15inHg on FPR) and the pressure went back up to 42psi...

Arghx, that leans toward your idea of the FD pump overwhelming the stock FPR. But, others have refuted that.

Jobro, does your friends system follow the stock fuel pressures at idle and boost?

Fleemer, does your system hold around 40psi all the time or does the FPR provide proper pressure in all scenarios?

C. Ludwig

iTrader: (27)

Do you still have the vacuum source for the regulator plumbed through the regulator solenoid? If so, disconnect it and run a line directly from the regulator to a manifold vacuum source.

Fero313

iTrader: (1)

No emissions, no solenoids on the engine. FPR is (and has been) connected to the manifold source at the single nipple on the inside part of the LIM. I'll take pictures tomorrow showing my setup and configuration.

arghx

iTrader: (3)

Here is somewhat relevant anecdotal input. Many many moons ago (2005) I had my nonturbo GTU which was heavily modified for what it was. It was consistently running lean up top... 14's maybe despite messing with an SAFC. Of course it didn't really knock because non turbos rarely knock.

I still had the stock non turbo fuel pump. I ended up swapping in an FD fuel pump that I got for free from a friend who had swapped a Cosmo pump into his FD. My knowledge of AFR's, fuel pressure, etc was pretty limited at the time but I eventually got a wideband and it was idling at 11.5:1 with that pump (engine had no smog pump). The pump wasn't rewired or anything but the s4 non-turbos never had a fuel pump resistor anyway. Weird thing was, when I installed an MSD 6A box on the leading coilpack the idle leaned out to about 12:1 immediately. I guess a stronger spark was helping ignite the high pressure fuel.

I never measured fuel pressure or anything but looking back at it I think there's a good chance I was running richer due to the FD fuel pump. Here is what the FC training manual has to say about the stock FC FPR:

Fero313

iTrader: (1)

Took a few pics to show my setup and to give context to this whole issue. I also tested the "dead-head" pressure this morning. 95-97 psi when I clamp off the hose right after the gauge.

Arghx, I understand that the FPRs job is to maintain the pressure difference between the rail and the manifold. When the manifold pressure goes down (idle), the fuel pressure lowers. As the pressure increases (WOT and eventual boost), the fuel pressure rises to maintain that pressure difference. This ensures a that for a given injector open time that there is a consistent quantity of fuel leaving the injector regardless of the engine's state. You know this of course.... just letting you know i'm on the same page. Maybe the fuel pump IS overwhelming the regulator and it is just now presenting itself because I am giving it full voltage. This just seems like a problem that would have been addressed already as the mods I'm doing aren't new by any means.

RotaryRocket88

iTrader: (7)

I don't think I've seen anyone use that spot on the inside of the LIM for a vac source. Does it go through into a runner? I thought it came out at the ACV on the other side. How about that metal 3-way splitter? I remember someone having problems with their pressure signal to the MAP sensor because the splitter they were using on the line was creating problems.

An FD fuel pump does not overwhelm a stock FC FPR. I've tested fuel pressure with both an FD pump and a walbro back when I was troubleshooting a mixture issue, and these were the results:

Walbro GSS-341
Idle: 46 psi
Atm: 48 psi
10 lbs. "boost": 54 psi

FD pump
Idle: 34 psi
Atm: 41 psi
10 lbs. "boost": 51 psi

Boost pressure was simulated with a hand pump, and atmospheric pressure was with the vac line removed. Factory idle spec is right at about 30 psi, but it will vary with vacuum level. I don't know what it was during this test, but my car idles around -15 inHg. The key was 'ON' with the test connector jumpered at all times.

arghx

iTrader: (3)

iirc that runner goes right into that primary runner. It's been a while since I polished the runners on my s5 manifold. The previous owner of my car had used that port for the FPR a long time ago but the car had some fueling issues at the time so I can't say how well it worked really.

RotaryRocket, what kind of pump voltage did you have for your test? I wonder if the OP has some kind of weird mechanical problem going on.

Fero313

iTrader: (1)

http://www.youtube.com/watch?v=oFVqUztjdCY

http://www.youtube.com/watch?v=PnkrvxwfAdc

Took a few vids to show some of the symptoms... Pardon the person talking in this vid... He's "special".

First is with the fuel pump running. It starts at 41-42psi and when vacuum is put on it, about 20inHg, the pressure barely moves to 40psi or so.

In the second vid, I have turned off the pump. It is still holding about 38-39psi, and when I put vac on the FPR, about 15inHg, pressure drops to 30psi!

RotaryRocket88

iTrader: (7)

Was the vacuum pump actually hooked to the FPR nipple in those videos, or was it connected to the black vacuum lines w/ the splitter?

The symptoms just don't add up. Pressure decreased with boost pressure applied while driving, which could suggest the pump can't keep up. Yet when vacuum is applied by the engine or a hand pump it wants to just sit at 40 psi, which would suggest too much flow.

Deadheading and getting 95-97 psi says the pump is delivering fuel just fine, so how could fuel pressure drop with positive pressure on the FPR diaphragm? It would be nice to apply pressure with a pump (got a bike pump?), and see if fuel pressure drops again.

Are you sure it's an FD pump and not some other denso pump? They all kind of look the same. You said you tested fuel pressure before the Haltech swap, and it was fine?

Alright, I went and found a J-spec S4 LIM & that nipple does in fact go into the runner. There are 3 ports where the ACV mounts that also go into the 2 center runners in the same area.

I remember testing pump voltage at about that same time, and I think it was around 13v at idle. The pump is powered through the stock wiring, which does not have a resistor/relay combo (S4 NA never had it).

Fero313

iTrader: (1)

http://www.youtube.com/watch?v=NrtLSPM-T-0

http://www.youtube.com/watch?v=wDreWZWF1HE

Fero313

iTrader: (1)

The fuel pump is a FD pump but was purchased new. It is an aftermarket Denso pump (950-0014) and is the same pump that Denso sells for FDs AND TT Supras. The only difference in their aftermarket kits is that they require different strainers.

jacobcartmill

iTrader: (6)

what we're thinking now is that the stock regulator is designed to regulate pressure with the stock fuel pump with the stock s5 voltage switching resistor circuit.

this stock system will run the pump @ ~7 volts at low load, and ~10.5 volts at higher load (maybe higher if you have good stock wiring). what this means is we've nearly doubled the fuel pump voltage at idle and low load. this mixed with the fact that we have a slightly upgraded pump makes me think it's possible for the regulator to not handle the extra flow at low load.

just some food for thought.

Frostycrowd

iTrader: (9)

I wish I had a pressure gauge when I was on stock regulator. I am curious if this is a common problem.

None of these test rule out a return line restriction such as blockage, I know you mentioned it, but has this been ruled out?


btw nice wiring!

Fero313

iTrader: (1)

I put the pressure gauge on the return line earlier. It read 0 psi until I physically pinched the hose

RotaryRocket88

iTrader: (7)

This would assume it's an issue with any stock FPR used in conjunction with a fuel pump resistor/relay. S4 TIIs and all S5s would fall into this category, but I'm not sure I buy the idea that their FPRs would be different from those on an S4 NA. My car used to be an S4 NA, but now has an S4 TII engine in it. There is no resistor/relay because the wiring is still S4 NA, but the FPR is from an engine that would have used a resistor/relay in stock form. There seems to be no issue at all in my case (or a very minimal one); even with ~13v at idle.

And this still wouldn't address the pressure falling off under boost, so I'm not sure where that leaves it.