Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Fuel vapour emissions container V8 engine

Hi everyone, I thought I had put a question on the forum, but I cannot see where it has gone!!. Never mind I'll do it again, sorry if you see it twice!!
I have a 1997 Plus 8 4.6ltr
I have been looking with interest at the big black plastic container in the engine compartment situated on the passenger side rear in the engine compartment.
This has something to do with fuel vapour capture from the fuel tank and I believe helps with fuel emissions and reduces fuel smells from the excess vapour.
This device is connected to the vacuum side of the air box and connects to the vent on the fuel tank.
There is an electrically controlled valve that I imagine opens at some time to allow the excess fuel vapour into the airbox.
Does anyone know much about this device?
What triggeres the valve to open, is it something to do with the ECU?
I cannot see much info on the internet about this!
Thanks all.
Martin

Sounds like an charcoal filter or canister. The charcoal absorbs the petrol vapours . The solenoid valve opens to allow the vapours to burn once the engine is warm & over a set RPM.
The ECU controls that.
http://blog.widiyanata.com/en/autom...ter-functions-pictures-and-how-it-works/

The valve is triggered at cold start or when at full throttle when a rich mixture is needed

Have a look in gomog in the Plus8 specific section. There are details in there of the efi systems used.

Simon,
I was quoting from the Haynes manual I have for my Ti6 +4. See point 7. I guess it varies by ECU engine etc
John

Evaporative emissions control
6 To minimise the escape into the
atmosphere of unburned hydrocarbons, an
evaporative emissions control system is fitted
to models equipped with a catalytic converter.
The fuel tank filler cap and vents are sealed
and a charcoal canister is mounted in the
engine compartment to collect the petrol
vapours generated in the tank when the car is
parked. It stores them until they can be
cleared from the canister via the purge valve
into the inlet tract, to be burned by the engine
during normal combustion.
7 To ensure that the engine runs correctly
when it is cold and/or idling, and to protect
the catalytic converter from the effects of an
over-rich mixture, the purge valve is not
allowed to open until the engine has warmedup, and is under load; the valve is then
opened to allow the stored vapour to pass
into the inlet tract.
8 On 4-cylinder engines the vacuum supply
to operate the purge valve is regulated by a
purge control valve solenoid which itself is
under the control of the ECU. The solenoid is
mounted either separately within the engine
compartment or, on later models, directly on
top of the charcoal canister.
9 On V6 engines the vacuum supply to the
purge valve is regulated by the constant
vacuum control valve (under ECU control) and
by a thermostatic valve which is opened or
closed depending on coolant temperature

That all sounds logical and comprehensive despite coming from a Haynes manual John

John
That’s exactly how the Advanced EVAP worked on my 2002 +8. After enthusiastic overfilling by a petrol attendant in France and a morning of splutter and cut outs (plus me in panic mode) I managed to clear it but wanted to analyse how and when it worked.

The GEMS system supplied an Earth to the constantly (ignition on) fed purge valve, I lashed in an LED test lamp and can confirm it did not operate on cold start up and had nothing to do with enrichment as that was done by widening the injection pulse width as seen on an O’scope engine analyser.

The purge valve was energised when the coolant temperature reached 80-82 degrees AND the throttle signal was more than 15% above idle. I fed this data back to David Ashley-Poole who I knew well at that time and I believe he included it in his magnificent GEMS manual.

I learnt not to overfill the car as the carbon EVAP canister was in the rear alongside the fuel tank and very difficult to bypass the ECU and manually purge!

BR
Colin

I had an idle issue with my t16 which is why I know. The purge valve had failed I thought. Turns out it was the ecu.

Ah, now that makes a lot of sence, I thought it must have been related to a combnation of engine temp and throttle position, as it is shut off when I first run the engine. But as this is a very early model injection system, it seems pretty basic, so I wanted to understand what sensors trigger the purge valve device.
I will also fit an LED to see what happens with the purges valve, as I have a feeling that the valve occassionally does not shut off correctly, as sometimes (rarely now!) I have a stalling issue which annoys me.
When I bought the MOG in 2016, I had all kinds of issues which I repaired one by one (as we all do).
The most annoying issue was an occassional stalling at idle, I tried all the usual things to try to resolve the stalling issue, IE checked for (and found) vacuum leaks, checked vacuum advance, cleaned and later replaced the idle control valve, replaced the throttle potentiometer (TPS), replaced the mass air flow meter and set up the idle speed on the throttle body. I also fitted new injectors and rechipped the ECU.
After all this work the idle stall problem improved greatly and no problems for 3k miles. But returning from the NC500 last year it stalled again!!! AAAAHHHHH.
So either the idle control valve needs a clean again or maybe its the EVAC purge valve.
Any ideas?

Have you checked the earth on the road speed sensor? I had a similar issue on my 94 +8, it started by on occasion stalling when coming to a halt and progressively got worse over time. On locating the road speed sensor I found it had become loose from the bulkhead and not giving a good earth, cleaned up the bolt tightened and never had the problem since. If the road speed sensor is not functioning correctly when the car is coming to a stop the ECU does not react quickly enough to the slowing of the vehicle which the sensor would tell the ECU and hence it can stall.