Cascade Crew

fiveoformula · Posted: Wed Mar 25, 2009 3:06 pm Post subject: Wideband!

Got a new toy...
Unfortunetly my car is still running really lean (16.0-17.0 @ WOT) Shocked

even after I resealed the intake...
Im looking for ideas why. fuel pressure at the pump is 10 psi.

Dewey316 · Posted: Wed Mar 25, 2009 3:18 pm Post subject:

10 PSI is a bit low. It should be in the 13-16psi range.

--John

fiveoformula · Posted: Wed Mar 25, 2009 4:43 pm Post subject:

Think that low pressure is enough to justify the lean AFR?

Twilightoptics · Posted: Wed Mar 25, 2009 4:45 pm Post subject:

fiveoformula · Posted: Wed Mar 25, 2009 5:42 pm Post subject:

Which pump do the cool kids run? Wink

91RSVert · Posted: Wed Mar 25, 2009 6:10 pm Post subject:

TBI? 10PSI at idle?

Yep, thats not good.

fiveoformula · Posted: Wed Mar 25, 2009 7:24 pm Post subject:

91RSVert · Posted: Thu Mar 26, 2009 4:02 am Post subject:

Still seems a bit on the weak side.

I dont know your car, any major modifications that may cause this problem?.

Can you drive and leave your fuel gauge attached and have someone watch it while you go wot to see what your psi is then?

fiveoformula · Posted: Thu Mar 26, 2009 11:34 am Post subject:

No major mods, just headers, and a cat-back, and a TB spacer and open lid.
The pressure gauge, I probably couldn't go drive around with it unless I got a lot more fuel line, I was using it in place of the fuel filter...

Twilightoptics · Posted: Thu Mar 26, 2009 5:16 pm Post subject:

TBI is a low pressure design. You can splice the 3/8 rubber feedline and Tee a pressure gauge there. Then just couple the two rubber pieces back together when you're done.

91RSVert · Posted: Thu Mar 26, 2009 6:18 pm Post subject:

With no major mods, I would suspect a bad part.

Check and make sure both injectors are spraying thru the whole rpm range. Good spray too, not a drip.

Other then tthat, dirty line or bad pump. Maybe the pressure diaphram.

fiveoformula · Posted: Thu Mar 26, 2009 11:41 pm Post subject:

It had 10psi at idle, and now that I recall the pressure slightly went down when I blipped the throttle, maybe to 9ish psi. I think I need a pump.

Twilightoptics · Posted: Fri Mar 27, 2009 6:39 am Post subject:

or regulator.

fiveoformula · Posted: Fri Mar 27, 2009 10:43 am Post subject:

Theres a regulator inline before the TB?

Dewey316 · Posted: Fri Mar 27, 2009 10:54 am Post subject:

The regulator is on the return side. It actually sits centered on the back side of the throttle-body. Basically right between where the two fuel lines go into the back of the throttle body.

fiveoformula · Posted: Fri Mar 27, 2009 11:21 am Post subject:

Right, but when I tested fuel pressure, I tee'd the line in place of the fuel filter, wouldn't that indicate a bad pump since pressure is low even before the regulator?

blue89 · Posted: Fri Mar 27, 2009 11:26 am Post subject:

Correct. Assuming the filter is on the high pressure feed side. The regulated pressure effects the fuel from the regulator to the pump. Neglecting line losses due to flow.

Twilightoptics · Posted: Fri Mar 27, 2009 11:27 am Post subject:

Think of the regulator as a dam. Anywhere between the pump and regulator will read your pressure. The dam holds the desired pressure and let's what it doesn't need flow down the river or return line.

fiveoformula · Posted: Fri Mar 27, 2009 11:40 am Post subject:

Ok that makes sense, I appriciate all the help. I have rebuilt the whole
Throttle body with a new reg. and a couple re-man stock injectors,
they spray a nice cone shape both at idle and when you give it some revs.

Under light and hard throttle its showing some high numbers on the wideband, idle is about right most of the time though.

blue89 · Posted: Fri Mar 27, 2009 12:07 pm Post subject:

Since you have a fuel gauge you can check it. If you feel comfortable that the lines will handle some major pressure, jumper the fuel pump relay with the engine OFF so that the pump will stay on. Then use some vice grips and squeeze the rubber fuel line just down stream of the gauge (called "dead-heading" the fuel pump). A good pump on an multiport engine will pump the pressure towards 80psi. Not sure what you should reach on your lower pressure pump, but if it can't build up pressure then you for sure have a bad pump. Or maybe this experiment will be the final blow Laughing

Be prepared for FAIL.