For those running intank pumps and after market fuel pressure regulators...

After you shut your car off, does the fuel system maintain the pressure in the lines?

Thanks,

Anthony

 

No.... it bleeds off slowly, back to the tank

 

Anthony posted this question for me. I was told by a friend who has basically the same setup that I have in my FD. Stock fuel lines, -6 lines in the engine bay with 1600 secondaries and 550/850 primarys and a walbro intake pump 255hp. When th car is idling I have 40psi without the vac hose connected to the regulator. Now once I shut off the car my fuel pressure begins to drop down to 25psi. This all happens within 10min of the car being shutoff. My friend with the same setup does'nt lose any pressure untill the car is left over night so Im just trying to figure out if its the regulator thats bad or a leak somewhere I can't see. Even though its a new regulator I can't tell ifits the reg thats bad or something else. I've check the pump and replaced the rubber hose and added 4clamps. So it's back to the drawing board for me. Any help is appreciated thanx....

Jay7

 

It's normal. Fuel returns to tank trough fuel pump valve.

 

do you both have the same in tank fuel pump??
if not his fuel flow back into the tank may be less than yours.

 

We both have walbro 255 pumps..

 

I called Aeromotive support on this when I installed mine. Spoke to a guy who sounded like he knew what he was talking about. His reply was that many performance regulators don't hold pressure on shutdown, and that it just fine as long as they regulate pressure fine when the car is running. Retaining fuel pressure after shutdown is an emissions requirement (helps reduce emissions on startup or something) and it has no effect on the regulators ability to regulate pressure.

That said, mine drops to 20 lbs in a few minutes and completely bleeds off after 5. Runs fine like this for several years.

Dave

 

Thanx for the good info NewbernD, rx794 chime in please....

 

It depends on the fuel pump. I know that some pumps have a 1-way valve that only allows for fuel to flow one way (to the motor) and not backwards. Aeromotive pumps don't have this valve; an optional part can be purchased. I'm pretty sure the walbro does not have an internal one-way valve, so after shutdown, fuel pressure will drop. It maybe that he is running a newer walbro or possibly another pump which he believes to be a walbro.

 

I have -6 lines from in-tank pump to stock rails to SX regulator back to stock return tube at top pf tank. Pressure bleeds back with both pumps I've used - hi-flow Nippendenso and Apexi.

Jack

 

I'm using Walbro pumps and I don't have this sudden pressure drop as soon as I shut off the vehicle like you do. I spoke with Boostn7 about this and he believes his to be the same since he's using a Walbro as well.

 

Some pumps may leak after shutdown so I wouldn't worry about it.

 

Hehehe....I'm still on the OEM regulator and Walbro 255hp:-)

I would not worry so much about pressure after shut down.....however, if you have a sudden drastic pressure loss you may have leaky injectors.

If the regulator performs the following well it should be OK :
-maintains set static pressure
-drops pressure with engine vacuum connected
-raises pressure @ 1:1 ratio over static under boost.

 

I'm gonna go over the injectors with Anthony this coming week. Thanx guys for the quick responce....

Jay7..