My 1988 LFX F40 build. (Page 47/68)
Daryl M AUG 05, 08:06 PM
I recieved the Verano canister today. I checked and the vent solenoid is normally open, so I'm planning on wiring the vent solenoid to an ignition hot wire, so it is closed when the car is running and open when the car is not running. Does anyone see problems with this plan?

[This message has been edited by Daryl M (edited 08-05-2020).]

pmbrunelle AUG 05, 09:03 PM
You're sure the Impala doesn't have a vent solenoid, somewhere? What does the Impala do to vent its canister?

Modern cars/ECUs are control freaks; take away something from their grasp, and they may throw a check engine light back at you.
Daryl M AUG 05, 09:58 PM

quote
Originally posted by pmbrunelle:

You're sure the Impala doesn't have a vent solenoid, somewhere? What does the Impala do to vent its canister?

Modern cars/ECUs are control freaks; take away something from their grasp, and they may throw a check engine light back at you.



Yes it does, but the ecm I am using has been modified to delete that function. Many functions were deleted so the ecm could be used as a stand alone with a manual transmission.
pmbrunelle AUG 05, 10:16 PM
If your ECU doesn't do the leak test, then you never need to close the vent solenoid to test for leaks (by checking for pressure buildup). In that case, you don't need a vent solenoid at all.

I think that keeping the vent solenoid closed at all times during engine operation would cause a problem with purging. When you try to purge the canister, the engine won't be able to suck vapour from the canister if it's sucking from a dead-end. The vent would need to be open to get air to flow through the canister, pick up fuel vapours, and then be sucked into the engine.

[This message has been edited by pmbrunelle (edited 08-05-2020).]

Daryl M AUG 06, 01:35 AM

quote
Originally posted by pmbrunelle:

If your ECU doesn't do the leak test, then you never need to close the vent solenoid to test for leaks (by checking for pressure buildup). In that case, you don't need a vent solenoid at all.

I think that keeping the vent solenoid closed at all times during engine operation would cause a problem with purging. When you try to purge the canister, the engine won't be able to suck vapour from the canister if it's sucking from a dead-end. The vent would need to be open to get air to flow through the canister, pick up fuel vapours, and then be sucked into the engine.

In that case, couldn't I wire it in tandem with the purge valve solenoid?
Joseph Upson AUG 06, 07:53 AM

quote
Originally posted by Daryl M:


Yes it does, but the ecm I am using has been modified to delete that function. Many functions were deleted so the ecm could be used as a stand alone with a manual transmission.



You will not likely know the extent of the effectiveness of the changes to the programming until the system is up and running. Their are changes within changes to the modern PCMs in use, like the advent of global A which I understand has caused some tuning problems with swaps. More importantly, some functions are hard wired into the programming, particularly in the emissions department, where although a particular code has been turned off, it still reports in some way, for instance, disabling the EVAP code in some cases, may not ever set a code in the PCM, but I understand it will never show the test as having been completed also, which could set a red flag for someone needing it to register.

There's also the possibility that some other function may be disrupted as these systems are vast and it's very likely not many of the platform you are using have been used outside of their OE setting to know what problems may show up in a case like yours. The Fiero is probably the most transplanted car around so unknown problems may show up here. This info is from problems I've read about in more commonly modded platforms, particularly the Camaro. If the provider that made the changes to your PCM is applying a general approach used elsewhere, while at the same time having had little experience with your transplant vehicle due to low demand, you might be in for surprises. I'd set it up stock to minimize the potential for trouble.

This link can provide some insight;

https://forum.hptuners.com/...-pulled-when-scanned
pmbrunelle AUG 06, 08:38 AM
When the purge valve is on (either ECU-controlled or hot-in-run), the vent needs to be open.
When the purge valve is off (engine off), the vent needs to be open.

If you don't perform the leak test, the vent never needs to close, and as such a vent is not needed in this situation.

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Another more "hard-wired" idea would be to set the purge valve to be hot-in-run, if your computer doesn"t control the purge valve anymore (this is not clear from your posts).

Purging all the time (including at idle) may be contraindicated however.

In a stock Fiero, purging occurs any time when ported vacuum exists. So at idle, the vacuum leak (containing unknown amounts of fuel) from the charcoal canister is closed, preventing it from screwing around with the idle mixture.

At greater loads, I think the variability introduced from the charcoal canister is less of a problem.

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You could just try to get the Fiero canister working. It only needs two vacuum lines to work:
1 manifold vacuum line
1 ported vacuum line (may need to drill the throttle body for this)

It's a really simple non-computer setup.
Daryl M AUG 06, 03:45 PM

quote
Originally posted by pmbrunelle:

When the purge valve is on (either ECU-controlled or hot-in-run), the vent needs to be open.
When the purge valve is off (engine off), the vent needs to be open.

If you don't perform the leak test, the vent never needs to close, and as such a vent is not needed in this situation.

********************************************************************************

Another more "hard-wired" idea would be to set the purge valve to be hot-in-run, if your computer doesn"t control the purge valve anymore (this is not clear from your posts).

Purging all the time (including at idle) may be contraindicated however.

In a stock Fiero, purging occurs any time when ported vacuum exists. So at idle, the vacuum leak (containing unknown amounts of fuel) from the charcoal canister is closed, preventing it from screwing around with the idle mixture.

At greater loads, I think the variability introduced from the charcoal canister is less of a problem.

********************************************************************************

You could just try to get the Fiero canister working. It only needs two vacuum lines to work:
1 manifold vacuum line
1 ported vacuum line (may need to drill the throttle body for this)

It's a really simple non-computer setup.



The purge valve is still controlled by the ecm, according to the documentation I was given by the tuner. I may have not been clear about planning to wire the vent solenoid to the purge valve control circuit. I plan on using a relay in order to de-energise the vent solenoid when the purge valve is opened, and vice versa. Shouldn't that accomplish the goal of opening the vent when the purge valve is open and closing the vent when the purge valve is closed, while leaving the vent open when the ignition is off? Shouldn't that work?
pmbrunelle AUG 06, 06:55 PM
Your plan was not clear to me before. I get it now... it sounds OK.

Information of this nature is normally best communicated with plumbing diagrams, as we see on stickers under the hood of cars.

[This message has been edited by pmbrunelle (edited 08-06-2020).]

Daryl M AUG 06, 07:22 PM

quote
Originally posted by pmbrunelle:

Your plan was not clear to me before. I get it now... it sounds OK.

Information of this nature is normally best communicated with plumbing diagrams, as we see on stickers under the hood of cars.




If you saw my drawings, you may reconsider.