Fuel Pressure Questions

Cbussilver01es · Post by **Cbussilver01es** » Wed Sep 02, 2009 6:26 pm

OK guys. Another question. I finally got around to firing the car up, but Im having some fuel issues now. I have the vortech sfmu hooked up and the only way that it will build enough pressure to start is if I jump the fuel pump relay so that it is running all the time. Also when I jumped the relay, the highest psi that I could achieve was 20psi, now I know that with big injectors, the lower the fuel pressure, the better but I couldn't get the regulator higher than 20 psi. Is it because there isn't enough fuel in my tank or what. Also while it was running, my wideband was reading at about 12.9 and then kinda made its way to 14.7 eventually and the idle is really erratic, but I think that is due to random vac leaks everywhere. Any help with this would greatly greatly be appreciated.!

Jamie · Post by **Jamie** » Wed Sep 02, 2009 11:04 pm

I am not sure of your set up or how big your injectors are. So I have some questions.
1. How big are your injectors and they are still being controlled by the stock ECU?
2. Did you do the stock Fuel pressure regulator bypass mod to the fuel sending unit (canister with fuel pump in it in the tank)(spoolboy mod)?
3. Is the static pressure (pressure with the vacuum/Signal line unplugged) at 20, or do you have a one way check valve in there so It only sees positive pressure?

should be able to give you some hints after that. The computer is going to trim the injector opening times to a point to get the 14.7 at idle. If it has to really trim them down its gonna throw a code of too rich. as far as the initial AFR being 12.6 ish. that depends on where in the exhaust your O2 sensor is located. the farther away the slower the AFR;s are going to react... has to get the gasses flowing over the sensor. however you dont want the sensor too close or you will smoke it.

also a little rule of thumb that I obide by is I dont run my car down past 1/8th of a tank. when I am in boost it sucks gas like a slurpie and dont want to risk it fuel starving and getting lean.

peace
J

Cbussilver01es · Post by **Cbussilver01es** » Thu Sep 03, 2009 6:27 am

ok. My fuel system consists of 40/hr injectors with a spoolboy modded canister with a walbro 255 and a vortech sfmu. The highest that i could get my static pressure was 20psi but that was only when I jumped the pump relay. When I plugged the relay back in and turned the key I could hear the pump prime but it wouldn't build fuel pressure. There is no check valve that I have installed. My wideband sensor is actually plugged in where my downstream was located. I have a gutted cat.

hul kogan · Post by **hul kogan** » Thu Sep 03, 2009 10:38 am

Ah, the joys of the Vortech unit. I was forever fighting with mine when I had it on my first turbo setup.

Anyway, as I mentioned in one of your previous posts, have you made sure that the unit is put together correctly? One pinch or bump in the blue 'membrane' can cause you a variety of problems. It sounds like something is throttling back your fuel pressure in there, especially if you are adjusting and it doesn't move.

Cbussilver01es · Post by **Cbussilver01es** » Thu Sep 03, 2009 11:53 am

Yea chris its weird, I even took the whole thing apart. Well not the entire thing apart, but the whole top cover and put it all together too. When I jump the relay and have the static screw is all the way in, my gauge reads 0psi and when I start to loosen it up, it starts to build ressure but once it hits 20psi it wont go any higher than that. Honestly I am about fed up with this regulator. Its starting to get ridiculous. I have no clue why it wont build or maintain pressure with the relay plugged in.

Jamie · Post by **Jamie** » Thu Sep 03, 2009 6:34 pm

well its a return line regulator though. once the fuel pump kicks on, and then off, the pressure is going to flow back into the tank ultimately reading zero if you leave it long enough.

when you fire it up, the injectors are expecting stock injectors so its gonna throw a crapload of fuel in the cylinders. which is going to give you a really rich AFR during start like you describe. when the computer sees that its running crappy rich its going to close the injector times to bring it back to 14.7, like your seeing.

I would fire it up and spray some Throttle body cleaner in places all around the intake of the engine and find your vacuum leaks. I think thats where your problem may be with your idle. everything else is just virtue of having a turbo car.

Cbussilver01es · Post by **Cbussilver01es** » Fri Sep 04, 2009 9:34 am

see I kinda figured that having a return line would have the fuel dump back to the tank, but my question is that is it always really hard to start since I dont have any pressure in the rail? Or is it because I only have 1/8 of gas or less in the tank that I cant build enough pressure to start it or have it idle normally or even adjust the pressure past 20 psi? I appreciate the help guys I really do. Im just so lost on getting this thing to run right. And its really frustrating...

hul kogan · Post by **hul kogan** » Fri Sep 04, 2009 11:58 am

I mean unless you are pretty much running on fumes, you should surely be able to build more than 20PSI of fuel pressure. If the regulator is built correctly and you have it hooked up properly, I can't see the issue pointing to it. So, as Jamie mentioned, it could be an issue with the vacuum leaks.

If the regulator isn't getting the right vacuum reference, it isn't going to be able to regulate pressure correctly. I'm thinking if you have a number of leaks then it isn't seeing much vacuum at all...thus making it difficult to build any fuel pressure. Hmmm.

Cbussilver01es · Post by **Cbussilver01es** » Fri Sep 04, 2009 3:31 pm

Well Im hoping that I have it hooked up properly and that its not defective you know? The thing that is killing me is that I have no Idea on where a vac leak would be, since I have everything connected where it should be and clamped/tightened down correctly. Even when I was trying to set my static pressure the highest I could get was 20psi and that was without the engine even running or any vac line hooked up. Could it be the spring in the reg? Or could my car not be timed right either? Or could the thing just be defective?