Glow plugs don't get fouled the same way spark plugs do. Your missing and smoking could have been caused by a couple of things, among them, air/air leak in the fuel system, cold engine with no or inadequate glow plug function, or a partial fuel system obstruction.

When you pull the car out of storage in 4 months, I recommend you start by changing the engine oil, changing the fuel filters, and putting in fresh fuel. After that, test drive and evaluate. If you are still having symptoms, I would then troubleshoot from there.

This is pretty much the plan I have for my 300D, which has been in storage since March, and which I will be reviving some time next month. I've done stuff like this a few times and found that many people tend to make a bigger deal than necessary about a car sitting for a few months.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 401,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 26,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.
99 Mazda Miata 183,xxx miles.