Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Breather valve?

I had an issue on the B58 engine on my Plus Six last year where it would often stall during warmup, accompanied by the drivetrain warning light. If it was started immediately it would run on 3 or 4 cylinders. If it was left for a few minutes it would start perfectly and continue to run well for the rest of the journey.

MMC had a look at the fuel system, which was fine, and re-did all the earthing points. This was in March 2025. Nothing obvious was found, but the Mog then ran perfectly for the rest of the year until ...

I put the Mog into storage for the winter at the beginning of November. A fresh tank of E5, together with fuel stabiliser. CTEK charger on the battery.

I ran the car up to temperature at the beginning of December, no issues.

Same at the end of December, and it started well, ran well for perhaps 5 - 10 minutes then stalled without warning. It started perfectly and ran for a minute or so and stalled again, and would continue like that irrespective of throttle setting. It's been the same since then, the battery is ok, the fuel pressure is good, and when running she seems to run well, perhaps a little lumpy just before stalling. There are no error codes shown on the OBD reader, and no warning lights on the dashboard. The car just goes into neutral and the engine stops.

The Mog was due in at MMC for a service / MOT later in February in any event, but will now be transported down there at the beginning of February specifically for this issue because it's essentially undriveable.

My money is currently on a breather valve malfunction, this based on a long (several minutes) first run followed by short runs (less than 1 minute) before stalling, that and a ticking noise from the engine bay. I've considered whether to get it done locally, or even do it myself (it's an easy DIY job), but if it's not that then I'm wasting time and money.

I'll let you know what the outcome is!

Maybe too simple, but have you tried running it with the fuel filler cap released?

The ticking noise from the engine bay is normal on the B58. I asked Krazy Horse to look at mine and they confirmed it was fine. It's the injectors.

I know the fuel has a stabiliser in it but did you circulate it before laying up the car.
Could it be damp in the wiring? My Roadster S1 was terrible for damp on the coils / igniton

Thanks for the thoughts. Appreciated

I'll give her a run with the filler cap released, it may help with elimination, doubt it can harm. Good to know a ticking noise is normal, one of the symptoms of a failing solenoid valve is a loud frequent ticking noise so I was a little concerned. Yes, I gave her a run to circulate the stabiliser before laying up the car. Damp is unlikely as the garage is heated and there's a dehumidifier in there. I'm not sure how fuel contamination or electrical issues could reveal in these symptoms, which are repeatable - long run from cold or if a period of time is left before restarting, shorter runs if restarted immediately after the first stall - but I'll keep an open mind.

I,m not sure it would have any effect on your problem but in any case I would fit a B58 PVC delete kit. This effectively routes crankcase gases to atmosphere (with or without a catch tank) which prevents the dreaded GDI gunge and carbon build-up on the backs of inlet valves, inlet manifolds and turbo internals. Best to run the vent pipe into a wheel well low pressure area to prevent any smells in the cockpit. I do this on all GDI engines from new and it works well in the B58 in my BMW.

I go with a cleanable in line filter between the crankcase out and the inlet vacuum connection as the crankcase is designed to have a slight negative pressure and on a good/new engine there will not be much combustable gasses leaking by the piston rings so not much draw is needed. Most of us won't drive the car as a race car and this should suffice the requirement of catching the oil contamination entering the inlet manifold and coating the backs of the valves and fir Gdi engines of any make it's a good idea'
Just to clarify for those who have the earlier engine which has indirect injection engines, the fuel is directed at or before the intake valves and therefore a fuel air mix enters the combustion chamber pre mixed. This has the effect of washing the back of the valves keeping them clean so unless you have a serious engine problem you should be fine. Racing and thrashing engines however does cause issues that normal driving however spritely won't cause and racing rules generally require the fitting of closed catch cans which need emptying,

DaveW has recently fitted a cleaning system `as a trial to his Gdi engine so it will be interesting to see haw he fairs with the system. If this works well it may prove a real asset to the Gdi owners cars.

Happy Birthday Sewin

Any info on how you fitted a filter or catch tank please?

I ran the Mog with the fuel cap released today, exactly the same as before, longish run then stalled, short runs after re-starting. The car is essentially still under warranty, and some warranty issues will be looked at when she goes back to MMC, slightly early because of this specific issue. Once this is sorted I'll look at the "B58 GEN 2 PCV Delete Kit".

I'd have to check compatibility, but this looks to be the one to go for: B58 Gen 2 PCV Delete Kit