Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) Zetec EVAP system

There are some evap systems that carry out an integrity check to ensure that the fuel tank and evap system is capable of holding a vacuum. In the case of the zetec and 4/4 it doesn't run such a precheck, it just allows the vapor from the entrapment filter into the manifold when conditions are correct.

I just checked my ECU data sheet and the signal to the evap control valve is pulsed - conditions are engine under load and engine hot - the pulse is 10 volt at 10ms
not sure if that is 10ms cycle time, or duty time, as I can't find the shot from the scope. This is much the same as my +8 where you can hear the valve tapping away.

Looks like pin 22 of the ECU feeds 12 volt to the valve, and pin 11 grounds the valve. So pin 11 has 12 volts on it until the engine is hot and under load when the ECU turns the valve on, at which point it probably goes down to something like 2 volts, then up to 12, then back to 2 and so on. Hence a 10 volt pulse across the valve

I double checked and confirmed there are no sensors, so the ecu will not know if there are vapors in the filter, but just goes through the pulsing routine to purge any that are there

The filter is a ford part, I have ordered one from ebay so I can study the vent valve. I assume that the filter must allow positive pressure to escape but trap any vapor. As on a hot day with the car at rest the petrol will vaporize, and needs to be vented. Then once the car is running the trapped vapor needs to be sucked into the engine, while retaining a level of vacuum on the tank.

Its possible to overthink these things. Why not just disconnect the valve and see what happens? From what the OP and teknome have said, that should not be a problem.

It wil cause a problem because it's the only way the fuel tank vents to allow air in as fuel is used...

Simon @ Sifab.co.uk

In which case, disconnect the valve to tank hose, plug the end temporarily with a rag and then try it. Or extend the hose and re-route top below the car as always used to be the case.

All we're trying to do at this stage is make sure that the ECU doesnt react with an EML, and the fuelling isnt messed up. If as I suspect there is no problem then proper arrangements can be made long term to vent the tank in a safe way and to block up the feed from valve to manifold.

If the evap equipment is removed then you would need to revert to a vented tank. Could be achieved by changing the fuel cap.

The MOT testers manual section 7.2 doesn't appear to require the tester to confirm that the evaps system is operational. It does require the cap to be in good shape and that there are no leaks in the fuel system and as follows

'Check fuel tank cap /filler neck sealing device
for presence, positive fit and condition of sealing
washer and flange.'

So I don't know if an MOT examiner would have any grounds to fail a vehicle with a vented tank.

However the vehicle would no longer conform with construction and use regulations, and may be considered unsafe if the vehicle should overturn. That would be a golden opportunity for an insurance company to refuse to pay out. Also I guess there is a possibility of failing a roadside emissions check.

Best to start off with an old Morgan that predates all this emissions stuff, or ensure you can pass inspection if you have a more modern Morgan.

Sadly (or fortunately) we can't get away with what was done back in the 60's. A recovery garage I did some part time work for ran a fairly rotten zodiac for local taxi service on trade plates. Only picked up old ladies to take them to church on sundays, honest !

Mike

I think the tank vent used must have a sealing mechanism to prevent petrol leakage if the car rolls.
Almost certain this applies to race cars at least.
The IVA test for kitcars specifies a vent must be in place to prevent pressurising the tank whilst the car is being driven. No mention of a sealing valve for rollovers/steep slopes etc. though. I assume the same for any car.