How much fuel pressure drop is acceptable?

Reply Subscribe

Thread Tools

Search this Thread

Dec 11, 2002 | 11:41 PM

MelloYellow

Thread Starter

TECH Fanatic

Joined: Nov 2001

Posts: 1,986

Likes: 1

From: Centrifugal City

How much fuel pressure drop is acceptable?

If you have a fuel pressure gauge that is normally 58-60psi and an upgraded in-tank Walbro 225lph pump. What dips on the fuel pressure gauge at WOT are acceptable/normal?

Dips to 56psi ok? 54psi?
At what pressure do you start to worry and address the fuel system/pump again?

Dec 12, 2002 | 09:13 AM

Black LS1 T/A

Moderator

Joined: Nov 2001

Posts: 3,048

Likes: 12

From: Raleigh, NC

Re: How much fuel pressure drop is acceptable?

Mine varies between 55 and 58 whether crusing or WOT. What ever I'm crusing at, when I kick it to WOT, it always matches that.

I guess my answer to your question would be: if the injectors are keeping the fuel to the motor it needs at whatever the fuel pressure is, you are ok.

Dec 12, 2002 | 09:42 AM

MelloYellow

Thread Starter

TECH Fanatic

Joined: Nov 2001

Posts: 1,986

Likes: 1

From: Centrifugal City

Re: How much fuel pressure drop is acceptable?

True about the injectors. Just trying to draw the line as to where I should be concerned.

I think one guy dipped to 52# and lost his motor.

Dec 12, 2002 | 09:55 AM

SS00Blue

TECH Fanatic

Joined: Mar 2002

Posts: 1,044

Likes: 0

Re: How much fuel pressure drop is acceptable?

<blockquote>quote:<hr />Originally posted by MelloYellow:
True about the injectors. Just trying to draw the line as to where I should be concerned.

I think one guy dipped to 52# and lost his motor.<hr /></blockquote>Pressure is always going to lower when the regulator is wide open. Not much pressure in a garden hose with no nozzle.

The guy lost his motor due to a whacked A/F, which is what you'd better be watching if you want to keep your engine alive.

Trying to determine whether or not your engine is safe by the fuel pressure is like determining if you need oil by watching the oil pressure gauge. <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

SC-

Dec 12, 2002 | 01:43 PM

MelloYellow

Thread Starter

TECH Fanatic

Joined: Nov 2001

Posts: 1,986

Likes: 1

From: Centrifugal City

Re: How much fuel pressure drop is acceptable?

SS00Blue:
Withya. But assuming the A/F is tuned correctly (I will babysit it) at what fuel pressure is the pump not keeping up and should be upgraded?

I assume fuel pressure of 40psi would be bad? <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" /> Where should you draw the line an defining when the pump isn't enough?

Dec 12, 2002 | 02:54 PM

AzzHauler

TECH Resident

iTrader: (3)

Joined: Nov 2001

Posts: 979

Likes: 0

From: Richmond, VA Where fast cars, well......are hard to come by.

Re: How much fuel pressure drop is acceptable?

Mine drops down to about 52 or so I'd say. But it's pig rich going by the o2's.

Dec 12, 2002 | 04:32 PM

NoGo

TECH Addict

iTrader: (2)

Joined: Jan 2002

Posts: 2,814

Likes: 110

From: Mass

Re: How much fuel pressure drop is acceptable?

I tuned one vehicle in which the fuel pressure dropped to 42 psi. I was still able to fuel the engine properly, but WOT a/f was inconsistant.....sometimes it would be rich, sometimes it would be lean. It varied nearly 1 point in a/f depending on how long it took for the fuel pump to finally catch the pressure.

Pressure drops down to ~50 weren't giving me any problems.

Good Luck,
Kevin