High Pressure FP vs. Regular Pressure?

[XVeloX]

Well there is obviously a difference between the two...

http://www.prostreetonline.com/buy/walbro_high_volume_fuel_pumps/mitsubishi/

I would imagine people have had experiences with both, i'm in the market for one and just want to make sure i get the right one... i get that feeling i will be asked my current/upcoming mod list for this one... anyways let me know what you guys think about the difference...

[Matz]

I recall a recent post by Tam that indicated that he had both, and now has the lower pressure fuel pump. He had a problem with exhaust fumes in the cabin, and the LP version possibly helped make the problem go away. I don't know why it would necessarily matter, as there's a fuel pressure regulator downstream anyway, right? And if there's excess pressure, doesn't the fuel get rerouted? I remember reading somewhere that DSMs don't have this feature, so you have to be careful which FP you use, but on the Evo, it doesn't matter. Of course, if you run into the situation where you actually do need extra fuel, then I would guess that the HP version is the way to go. :?:

[Dr. Evo]

H probably screwed up his oring installing the thing :lol:

[vtluu]

Yeah, it's hard to say if the couple of problems I was trying to fix--exhaust smell and partial-throttle misfires--were due to the high-pressure pump or just the fact that my timing was off by a tooth and making the car sensitive to all kinds of issues. Those two problems seemed to go away after installing the low-pressure pump but again I don't really know if they were related to the fuel pump or not. I've heard some people say the high-pressure pump can overwhelm the stock fuel pressure regulator, I've heard some people say the high-pressure pump will fail earlier, but I've heard a lot of things... some people say the high-pressure pump will work just fine.

If you want a high-pressure pump, you can have mine--barely used!--for $45. :lol:

[XVeloX]

ahh o jeez, do you have an install kit with it? as in the new filter, o-rings etc.? you know what, screw it im shootin you a pm... i get a feeling the timing being off by a tooth had oh i dunno a HUGE part to do with the misfires :shock: :P I'll take it!

[evo_dadi]

dont worry about the install kit and just re-use everything ;) and buy tam's fuel pump :D

[turbotiger]

The high pressure pump flows more at high pressure, which is what we run when we're under boost.

I'm pretty sure that switching out the fuel pump from HP to LP didn't help, but if a o ring was nicked or installed incorrectly, reinstallation probably helped.

As for the DSM's, you're referring to the stock fuel pressure regulator. Stock fuel pressure regulator's weren't big enough after installing a walbro to return the fuel back to the tank causing high fuel pressure at idle.

Evo's have a different, larger fuel pressure regulator, and should be able to handle the walbro without excessive fuel pressure at idle.

[vtluu]

I re-used the stock O-ring since it's a lot beefier than the one that comes with the kit. I re-used it again on the LP pump so it's unlikely it was bad. But as I said, it's possible, likely even that my problems were due to something totally unrelated to the fuel pump.