Talk Morgan Forums Thread Like Summary - 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!

Perhaps the engine was not designed to just burn fuel at idle for extended periods to simply warm it up during a lay up Use it throughout the year by driving as it was intended even if this means waiting a month in my case for a gap in weather/salted roads given the awful winter we are having this year.

If the problem exists when driving the car regularly then consider the PCV kit. Gen2 B58 engines use hybrid direct and manifold injection so may not be as vulnerable to carbon build up on valve stems as earlier pure direct ones.

My tester always inspected the brake master cylinder with an assistant pressing hard on the pedal, to check that it was secure and no leaks. That saved my neck when my Gilbern brake fluid found a weak spot and dumped all the fluid on the ramp.