Hey I was just wondering, I have a fuel gauge on my motor and I wasnt sure what is the normal psi for the fuel pres. on a lt4 motor, thanks In advance guys :) Jasin

 

ttt anyone know?

 

Should be the same as the LT1...right around 43.5 psi.

 

According to my manual, the LT1 and LT4 are 41 pounds... of course you disconnect the vacuum hose to take the reading...

mo

 

:confused:

Never heard of disconnecting vacuum hose to take reading. Why would that be. Is that for 1996? What manual did you find that in?
Thought you could just connect the fuel pressure gauge to the fuel rail and take the reading?
Thanks

 

To determine the true setting of the pressure regulator, you have to remove the vacuum line or check when the car is not running, but the fuel pump is (first 3 seconds after turning the key to "on"). Otherwise the readnig will be low because of the vacuum changing the regulated pressure. The more vacuum, the less pressure.

Chris

 

correct me if i'm wrong, but i believe if everything is working ok the pressure should hold steady for longer than 3 seconds, right??... it should hold for a while... otherwise the pressure relief valve is messed up, or something like that... been a while since i read that section in the manual.

do you want to set the pressure with the vacuum on or off??

 

It will hold the pressure for longer than 3 seconds, however, when the pump shuts off after 3 seconds, the pressure dips down 2-3 psi immediately. You want to set an adjustable fuel pressure regulator with the vacuum disconnected and the car running, or connected and watching the gauge for the first three seconds after turning the key to the run position. Either will acheive the same results.

Chris

 

Chris,

Thanks for clarifying for me... even if you shut the car off after the 3 seconds the system can hold pressure for quite some time, be aware of that disconnecting the fuel pressure gauge HEH.

I have always set my fuel pressure with the engine running and the vaccuum disconnected. If you leave the vacuum line connected you will end up misadjusting as the vacuum really is there to compensate for when you go partial to WOT to make sure there is enough fuel for the demand. The LT1's normally aspirated can be a bit finicky about how much pressure you are running...

ConeKLR, The information is in the 1996 Service manual book2 pg 6-314 step 8

Kinda look at it like in the old days setting timing on a car, you had to disconnect the vacuum advance to be sure that the mechanical timing was set properly ...

As an example: Since I'm running 30 pound injectors, my fuel pressure is set at 38 lbs to allow ofr a smoother idle under full boost ~8 pounds I'm pushing about 75 lbs to compensate for the demand and besure that the AFR is correct. :rolleyes:

Jasin if your just "checking" it out... it should be in the neighbor hood of 40 pounds and with an abrupt throttle mash it may bump up to say 45 the manual say 41 -47 lbs and return once the engine has caught up to you..

mo


[Modified by Mo_Bandy, 3:10 PM 7/17/2002]

 

ttt
My manual says 41 - 47. I assume that's at idle with vacuum disconnected and plugged. Not when you rev the engine a little. I've adjusted my to about 42. Sound right to you folks?
:)

 

Yes adjust the pressure, vacuum disconnected, engine idling. 42's fine... you can pretty much tell by the car idle if you go too high it will start to rough...

the book "Corvette Fuel injection and electronic engine management -Charles Probst" is an excellent resourse for L98 through LS6's

mo