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Need Help With Locating Fuel Pressure Regulator Vacuum Line On 98 Eclipse RS

Wicket_Eclipse

Probationary Member
6
0
May 31, 2012
Wisconsin Rapid, Wisconsin
I swapped the engine from a 1996 RS into my 1998 RS but can't seen to find the hose to connect the FPR which is back by the tank in my car on the firewall. I know all three connections on the 3 way were hooked up before i swapped the engines have the Cruise Control and EGR all working but I've learned that there is a bracket to bring this line forward on the engine from the 96 and there wasn't on my 98. The vacuum box was in the passengers fender on the 96 where as mine is in the fuel tank. I'm a little confused right now I have the line plugged off but it feels like I should be accelerating faster. Can anyone help my track down this lonely hose? Photos of where it should come through would be greatly appreciated.
 

jayson427

Proven Member
1,515
3
Dec 20, 2011
Mesa, Arizona
if its the one im thinking about then it is on the left side of the head where the cam gear cover is. if its what im thinking there is a metal tube the connects it from the canistar in front of the passengers tire and runs up by the power stearing pump and ac compressor and to the head. then that comes around the intake to the three way valve. not 100% if thats what your looking for.
 
Last edited by a moderator:

Doug99RS

DSM N/T Wiseman
DSM Wiseman
2,020
18
Nov 10, 2002
Raleigh, North_Carolina
The 96 and newer year models should have all used a return-less fuel system. The fuel pressure regulator on those models is back at the tank. Fuel is fed from the pump to the regulator, then excess pressure is fed back to the tank and the balance is sent to the filter then to the rail. All the fuel that enters the fuel rank on those models is to be consumed in the combustion process.

The 95 year model had a vacuum operated fuel pressure regulator on the fuel rail. Fuel is sent from the pump to the filter and then to the engine bay. Excess fuel pressure is bled off and sent back to the tank and re-used later.

The 95 system was made obsolete because the fuel that goes back in to the tank has been heated by engine bay temps. Hot fuel can cause fuel vapor locking, changes the pressure (as temp increases, pressure increases), and emissions are higher. Doing away with the fuel return line meant that the fuel in the rail is cooler, won't vaporize in the rail or prematurely during the injection process and the fuel in the tank stays cooler as well.

Many fuel rails that do NOT have a FPR on the rail actually have a DAMPER instead. This is used to maintain an even pressure and it does so by absorbing pressure changes created by pressure changes from the pump and pressure changes created by the operation of the injectors. The damper smooths out the pressure in the rail.

Things don't seem to make sense based on the year model of the car vs what you're trying to do with it. If you had a returnless fuel rail then your "FPR" could be a damper and as a damper, there would be no vacuum fitting. But if you had a fuel rail for a car that uses a return line then your chassis shouldn't be able to accomodate the line.

Can you take pictures of your fuel rail in the car? Can you simply swap fuel rails around or did you only get a donor engine and no fuel rail/intake manifold?
 

jayson427

Proven Member
1,515
3
Dec 20, 2011
Mesa, Arizona
i think he is just missing the third vacuum line behind the intake. which is for the fumes which recycle to the canistar right? i know that little line always falls down between the cruise control and the head. thats what i got from reading his thread.
 

Doug99RS

DSM N/T Wiseman
DSM Wiseman
2,020
18
Nov 10, 2002
Raleigh, North_Carolina
Click on the link I posted. Post 6, item 36 is the PCV valve. It is the only vacuum line on the front of the intake manifold.

Item 37 is for the brake booster.

Post 8, just to the right of the yellow box is the vacuum tree on the manifold. The small vacuum port on the driver's side is for the EGR vacuum solenoid. The larger vacuum hose off the back goes to the Evaporative Emissions Leak Detection pump.

Post 12 shows a cap on the vacuum port on the top of the throttle body. That originally had a medium size U-Shaped vacuum elbow that connected to a plastic tube that runs along the back of the intake manifold and then on the passenger side it changed back in to rubber. It lead to item 50 in post number 11. This picture is taken looking upward from under the car, behind the bumper and headlamp area.

On the later year models, the third small vacuum fitting is capped off for non-cruise cars. For cruise cars, this hose went to a vacuum reservoir mounted under the intake manifold that's part of the cruise control vacuum system.
 

Doug99RS

DSM N/T Wiseman
DSM Wiseman
2,020
18
Nov 10, 2002
Raleigh, North_Carolina
Also, just for clarity, the Evaporative emission system isn't recycling, it's drawing gas vapor from the fuel tank. The PCV system again is drawing vapor though there is a fresh air inlet allowing fresh air to be mixed with the crank case fumes which are then drawn in to the intake through the PCV valve.

The only thing that is recycled is the exhaust gas under very specific conditions. Even at that it's only a few percentage points worth of exhaust.
 

jayson427

Proven Member
1,515
3
Dec 20, 2011
Mesa, Arizona
i know what your talking about, sorry i have an aftermarket im LOL i have not looked at a stock manifold for a while now. now i got it after reading it twice. i guess that line does run to the tb but doesnt it go down to the canistar under the bumper?
 

Doug99RS

DSM N/T Wiseman
DSM Wiseman
2,020
18
Nov 10, 2002
Raleigh, North_Carolina
Not directly. From the TB it goes to the evap purge solenoid, the second hose on the purge solenoid goes to the canister. Yes but it's not a straight shot.
 
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