Tuan Le

What's your fuel PSI when you spray? On a 100-shot and on 150-shot?

On mine, I mounted the fuel pressure sending unit right after the fuel rail. And the PSI on the gauge drops as low as 40PSI when I spray (100-shot).

Just want to make sure that my fuel pressure is OK.

Thanks
-Tuan

Bad Habit Bird

iTrader: (12)

Your pressure shouldnt be dropping down that low. what mods do you have on the car and what year is it?

Tuan Le

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Bad Habit Bird:
<strong>Your pressure shouldnt be dropping down that low. what mods do you have on the car and what year is it?</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">My car is a 2000 6spd C5. I have Donaldson Blackwing Intake, Corsa Indys Exhausts, TPIS LT headers, MTI T1 cam, and ASP Pulley. The car dynoed around ~374rwhp/355tq on the motor.

Can it be the fuel pressure sending unit is not working correctly? Or how I have it mounted? I mounted right after the fuel rail, on the same 4AN line as the FPSS and fuel solenoid.

-Tuan

<small>[ May 28, 2002, 05:04 PM: Message edited by: Tuan Le ]</small>

akw408

It should be pretty easy to tell if the gauge is working properly. What is your pressure at idle or WOT all motor? It should be around 55psi+.

Bad Habit Bird

iTrader: (12)

You definatly might want to consider a new fuel pump for your setup, either an in-line pump or a new in tank pump

Tuan Le

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by akw408:
<strong>It should be pretty easy to tell if the gauge is working properly. What is your pressure at idle or WOT all motor? It should be around 55psi+.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">The fuel pressure is from 59PSI to 63PSI during normal driving and idling. Even at WOT (on motor only) it only changes 1 or 2 PSI. So I guess that rules out the fuel pressure sending unit being not working.

Chuck

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Bad Habit Bird:
<strong>You definatly might want to consider a new fuel pump for your setup, either an in-line pump or a new in tank pump</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">DITTO!
Some have been very lucky using the stock fuel system. IMO don't take the chance. Upgrade your fuel pump!
Chuck

Tuan Le

This is how I have mine hooked up. Is it pretty much the same with you guys?

<img src="http://pages.sbcglobal.net/badassc5/_images/sendingunit.jpg" alt=" - " />

Chuck

There have been alot of problems with that fuel pressure shut off...hmmm...perhaps thats your problem with the fuel pressure.
Get rid of it and watch the fuel pressure gauge and/or get yourself an exhaust temp gauge..better indication than the air/fuel ratio crap.

Just my opinion.

Chuck

Tuan Le

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Chuck:
<strong>There have been alot of problems with that fuel pressure shut off...hmmm...perhaps thats your problem with the fuel pressure.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">So far, the FPSS has been working really well for me. I have the ground cable of the fuel pressure sending unit wired off the FPSS switch too. So if the FPSS shuts off, it would have cut off the ground to the sending unit, which in turn should give me a 0PSI reading on my fuel gauge.

I will try and manually trigger the fuel solenoid while the car is running (of course, with the nozzle in a container <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> ) and see.

-Tuan

akw408

I don't think it is the actual FPSS that is causing the problem. The FPSS does not actually draw any fuel, it's just a spring.

I think a 4AN line is good enough for a 100 shot, I'm not sure what I'm using, probably also a 4AN. Maybe you could try a smaller shot and see if your fuel pressure improves (close your bottle while testing so you won't be running lean). I have a H/C C5 with stock fuel pumps and 125shot, and it's fine for me.

Another question is why would your nitrous engage when your fuel pressure is 40psi and you have a FPSS? What do you have your FPSS set at?

Tuan Le

I have found the culprit. It is the damn ground wire from the sending unit that causing false readings from the gauge.

I had the sending unit's ground wire together with the solenoids (fuel, nitrous and purge). So when the solenoids kick in, they cause a surge in the current which in turn makes the fuel pressure gauge giving out false reading.

I confirmed it. I tried the purge solenoid and as soon as I purge, the fuel pressure gauge PSI drops immediate.

Rfg

Tuan
I run constantly between 58.5 and 60. It never goes below 58 even on the squeeze.
Randy

Tuan Le

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by Rfg:
<strong>Tuan
I run constantly between 58.5 and 60. It never goes below 58 even on the squeeze.
Randy</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">I got the gauge fixed by having the ground cable wired directly to the battery (-) negative terminal. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

Cheers
-Tuan