In a Black Saturday context, over 90% of the pumping systems for houses that were supplying water for active defence or spray systems failed during the peak of the event.

And that was everything to do with ingestion of embers into the filter, fuel lock because the pump itself got too hot, embers and debris landing on the electrical systems and burning it out, and/or simply the air was too hot that was ingested into the pump and the pump simply stopped functioning either temporarily and needed to be manually restarted.

Pumps failed quite prolifically because the petrol and diesel powered pumps couldn't handle the heat of the day, and in some cases the heat of the day and the heat of the fire.

Really dense smoke that has most of the oxygen consumed will cause the pump to drop significantly in power and possibly cut out, but it won't permanently immobilize the pump.

Diesel doesn't experience vapor lock like the petrol ones, so the vapor doesn't create the problem in the carby. So, they're a bit less heat affected and can run to a slightly higher ambient temperature than the petrol ones.

However, the diesel ones are just as susceptible to ember attack or surface fire as the petrol one. So, if the diesel pumps suck in embers into their paper air cleaners, it'll cause a flaming ignition of that paper air cleaner and that will snuff out the diesel motor, just the same as it would a petrol one.

The diesel ones do have a slight advantage, and that is around the prospects of safely refuelling them mid-fire.

A lot of pumps are supplied with enough fuel to operate for an hour, possibly two, and they’re often connected to a water supply that can last much, much longer than that. And having that tank full in the first place is step one, but the prospects of refuelling a hot pump motor while there's active embers in the air isn't very exciting, particularly if it's a petrol pump.

I'd encourage that approach (of having a larger external fuel container) and actually to remotely mount the tank, like off the pump itself. That certainly avoids the additional risk of heating from the pump and the heat feedback, which is one of your problems with vapour lock for your petrol pumps. And it also solves the issue of vibration.

Poly pipe prolifically fails when it's above ground and exposed to direct flame.

It's actually quite challenging to find spray systems that worked and persisted throughout because they're quite rare. But where they do show up as being quite effective are metal pipework, wherever it's above ground. And very frequent spray heads either mounted on the house or in that perimeter array projecting back onto the house using an impact sprinkler are the other key ones that really do work.

Petrol pumps do have that problem, and did prolifically conk out during conditions of, say, Black Saturday. So, despite them being a firefighter supply pump, the engine side of that actually isn't that adequate to work at the 40°C+ conditions running flat out under those fire conditions. Let alone handle the ember attack, the radiant heat, and whatever other heat loads are applied on it. So, they do prolifically cut out, and in a lot of cases won't be able to restart.

So, they do need to be put in quite a special protected place to be much cooler than the ambient conditions, and must be protected from embers and all those other things to have any chance of operating. And you can understand that that can be quite tricky. A steel enclosure can be quite hot. You really actually need thermal inertia around it like a masonry enclosure to really get to a point where you could get a petrol pump through one of these events.

Pumps don't like having to try and suck water from a long pipe network, so they're recommended to put near the tanks.

Obvious major problems that we've already covered is the fuel tank is quite problematic, there's inadequate protection of the actual pump itself, it's going to operate flat out for x amount of time, might be half an hour to an hour and need refuelling, and they typically cut out under the worst of the fire conditions that present.

The degree that you need to ember-proof a pump enclosure like this is that you have to be as fastidious as you would with your house itself. So, absolutely down to the 2mm gaps and entrance to avoid the pump could shut down in an ember storm by sucking embers into the inlet.

Spray systems wetting down pump shelters won't prevent embers getting to and being ingested by that pump. We see time and time again that spraying water around the place just simply doesn't stop the ember storm. The embers don't suddenly go out because there's water around.