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Gman7007
02-17-2009, 07:07 PM
Need a little help understanding how the NB fuel system operates without the return line at the FPR. The FPR is mounted on the fender well correct?

The system does have a return line at the tank access panel but where does that come from?

Where is the best place to plumb in a mech fuel press gauge? (On my NA I have a fluid filled press gauge mounted on the outlet side of the adj JR FRP)
Tom @ Fast Forward
02-17-2009, 07:44 PM
There is a return but I believe it is back at the tank at or part of the pressure regulator which, I believe is also back at the tank.

The hose going to the fuel rail is probably the best place for the pressure gauge. Actually, the fuel line coming up to the passenger fender (Intake manifold side) is at pressure so anyplace you see fuel in the engine compartment is at pressure.
Satisaii
02-17-2009, 07:54 PM
The return on the NB is from the filter back to the tank. The FPR is in the tank.
Gman7007
02-18-2009, 05:43 AM
IIRC the filter only has an in and out so how could "filtered" gas make it to the engine if it returns directly to the tank?
Satisaii
02-18-2009, 09:39 AM
There is a split plastic tube right before the filter. I should have said that it is in the filter area.
Gman7007
02-18-2009, 10:56 AM
That makes sense, only required fuel gets past the filter. The rest is dumped right back in the tank via the regulator mounted next to the fuel pump.

Any clues on the "regulator" mounted on the fender well? Is it more of a pulse regulator limiting fluctuations at the rail?
Tom @ Fast Forward
02-18-2009, 11:09 AM
There are two of those. One on the fender and one on the fuel rail. They are both dampers/snubbers.
Gman7007
02-18-2009, 09:00 PM
Thanks for your help fellas, I now have a full mental schematic. A wee bit different than the NA.
Gman7007
03-09-2009, 07:14 AM
Finally got around to plumbing in a mech pressure gauge at the fuel supply of the engine. Did a couple of 7000 RPM runs in third gear. Results:

65 psi @ idle
61 psi @ ~7000 RPM
50 psi 30 minutes after shut down.

Are these results typical?

Jose
Tom @ Fast Forward
03-09-2009, 08:00 AM
You really need a new fuel pump. Find a Walbro or call AZTPI. They have them in stock for $130 for the 99+ cars.
Gman7007
03-09-2009, 12:13 PM
These readings are with the new Walbro from AZTPI....

Fuel filter was replaced 15K miles ago.

What should the fuel pressure read on a 99?
Satisaii
03-09-2009, 12:29 PM
62 PSI stock
Tom @ Fast Forward
03-09-2009, 12:42 PM
Yep. 62 PSI but it shouldn't drop below about 58 worst case.

You have a flow restriction someplace?
Satisaii
03-09-2009, 12:51 PM
He is good. It is only dropping to 61 at WOT. The 50 psi is 30 minutes after shutdown. Does better than my external regulator.
Tom @ Fast Forward
03-09-2009, 01:12 PM
Mea culpa. I was multi-tasking. I missed that. Glad you caught me.
Gman7007
03-09-2009, 02:18 PM
You had me :sweatdrop: for a minute!

So I am good to go in the fuel area. Next up is the boost connection to the PC Pro. Looked over the rubber connector that adapts the 1/8 vacuum line to the nipple in the engine bay and it is dry rotted. Could be leaking under boost. Off to Napa....