FormulaIntegra

I removed almost all of the Evap Purge system. The charcoal canister is gone, all the vent lines, and the 2-way valve back at the tank have been removed. The purge soleniod is still mounted on the intake manifold and hooked up to the ECU, but I put a vacuum cap on the valve control port (the one that runs to the top of the charcoal canister and actuates the diaphram valve), so I'm expecting the solenoid to still actuate and the the ecu shouldn't throw a code for that.

My actual question/concern revolves around the 2-way valve back at the tank that is inline between the charcoal canister and the gas tank. In it's place, I installed a small inline fuel filter, and some tubing running up the fill pipe, so it can vent to atmosphere, but not get any dirt or water into the tank. The manual says the 2-way valve opens to allow fumes to travel to the canister and then closes again (when and for why, I don't know), and I know that if you leave the gas cap off, sometimes you'll get a Check Engine light for this, so I'm wondering, now with the setup I have, am I going to get any cel codes for the tank being able to freely breathe, or should I put the valve back in, but still run the vent line to open air?

I rely on my check engine light while racing to know if there's a serious problem, and I don't want to throw a race by having to come into the pits just because the ECU didn't feel there was enough vacuum/pressure in the tank. From a racing standpoint, would it be better to have that valve in place anyways? I'm not sure what the system wants to see regarding pressure/vacuum in the fuel tank.

sander

If the ecu runs a fuel tank leak test, the fuel tank shut off valve is closed and the purge valve is pulsed to develop a vacuum in the tank to determine if there is a minor or major evap system leak (or no leak obviously). if the fuel tank pressure sensor does not register a vacuum, it will determine that there is a major leak in the evap system and set a CEL.

and also depending on the year of the car CEL's don't generally mean anything important to a race. you will feel or see a problem on a gauge before a CEL will tell you something is wrong in most cases. (e.g. oil press, fuel press, misfires, etc)

ErrDizzle

on a 05 hell yeah

FormulaIntegra

It's a 1995 EJ1. #05 is the car race number.

Relic1

OBD1 = doesn't know if any of the EVAP system or solinoid is there or not = no CEL even if you strip it all out of the car. Also OBD1 does not have a fuel tank pressure sensor.

OBD2 = integrated all over the place = yes CEL


95 EJ1 = OBD1

FormulaIntegra

So, rather than let the tank vent and maintain atmospheric pressure, should I just cap the vent line and allow it to build it's own vacuum? Any downside to this? There are no wires to the 2-way valve that was back at the tank, so it worked strictly mechanically, but I'm not sure what criteria was involved in causing it to open, unless it was a vacuum coming from the evap solenoid via the charcoal canister.

Could I get away with putting the 2-way valve back inline, and then my filter and tube to the atmosphere? Does it even need to vent, or is that just an emissions thing (which isn't a concern here)?

TIA

FormulaIntegra

Good info, Relic. Thank you.

So I could even remove the evap purge solenoid, and the ecu wouldn't even notice it? Awesome.

On that note, even if the ecu doesn't have a fuel tank pressure sensor, mechanically/hydraulically, does the tank want to have a vacuum to work best, or is atmospheric pressure okay, or does it really even matter?

sander

OBD1 doesn't matter. None of what I said basically applies to you.

You're set.

prkiller

Don't cap it, just leave it open to atmospheric pressure.

Relic1

I've been driving mine for several years now with no evap at all.

vented is fine, all though you want to prevent slopping out of the tank under really hard braking so an inline filter (pointed up) is a good idea on the vent line.