Pressure build up in tank
Thread Starter
Staging Lane
Joined: Mar 2018
Posts: 52
Likes: 0
From: Texas
Pressure build up in tank 94 z28 LS swap. After diving to break in engine when I returned home I hear hissing sound like I heard a few weeks ago . Posted on ls1 forum determined I had a leak I found and repaired,. Now 3 weeks later I hear the sound again not its coming from gas cap. I opened cap and a load of pressure was released. My fuel rails were hot then I've ever felt them. What could cause this . My fuel System consists of 94 z28 stock fuel lines and 94 stock fuel pump. c5 fuel pressure regulator under hood at engine and JEGS LS1 fuel rails .
Just my 2 cents, but you may be over stressing the fuel pump because the 94 lt1 only required 43# of fuel pressure and the LS motors all require 58#, I would definitely change the fuel pump to a 255lph at least..
Pressure as in it was under vacuum, or it was under pressure and it blew air out of the filler neck? Might be as simple as needing a vented gas cap......could be a plugged vent line, canister etc....
T,
T,
Excessive pressure or vacuum in the tank is a result of a tank that is vented improperly. Don’t run it again until you’ve resolved. Under pressure you have a bomb; under vacuum (just from fuel leaving the tank with air unable to enter) the tank can collapse - either situation a big safety issue. Air should be able to enter the tank as fuel leaves - usually through a one-way vented gas cap; air can enter, but not exit. If the car has to pass emissions then pressure is vented through a charcoal canister and allowed to enter the intake manifold through the purge valve. Most folks who remove the VATS from ecu's for swaps also routinely disable the purge valve function. I simply routed the line from my charcoal canister into the air inlet pipe UPSTREAM of the maf sensor.
Figure out why your tank isn’t vented properly.
Figure out why your tank isn’t vented properly.
Last edited by Michael Yount; Mar 8, 2019 at 06:02 PM.
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On The Tree
Joined: Jan 2019
Posts: 103
Likes: 3
From: north-central Virginia
Question on this. On mine, the MAF sensor will be located in the stock truck air filter box. Can I run the canister vent tube upstream of the filter, or does it have to be between the filter and the MAF? In other words, is there a problem with gas vapors going through the filter?
Also, presumably while filling the tank, it's pushing a lot of gas vapors up into the canister and into the air intake. Is there any detrimental effect of these vapors? Flooding the engine, backfiring, etc?
I wouldn’t think it would be a problem. When filling the tank, the filler neck is open to atmosphere (at least with our gas oumps here) - don’t think you’ll be “pushing vapors” to canister. Worst case for tank vapor pressure is idle when the fuel pump is circulating most of the pumped fuel back to the tank.