It certainly sounds like it could be a blown head gasket that is allowing the car’s coolant to mix with its engine oil. A brown, oily looking fluid in the radiator is a sign that this may have occurred. Check the engine oil next. If it’s milky and discoloured, then that’s another sign of a blown head gasket. That said, just because there’s no evidence of coolant in the engine oil, doesn’t necessary mean the head gasket is intact.

So, before you rip into the engine and remove the cylinder head, make sure the gasket is actually the problem. This can be done with a chemical-based test which samples the coolant and determines whether there’s any contamination in it that can be traced to the engine’s combustion. If it’s there, then the head gasket is almost certainly faulty.

The 1989 Courier was available with a 2.0-litre diesel engine or a range of four-cylinder petrol engines ranging from 2.0 to 2.2 and even 2.6 litres in capacity. You’ll need to ascertain which engine your vehicle has and then obtain the correct workshop manual for that specific powerplant. The good news is that all these engines were relatively simple and changing a head gasket should not be too taxing for anybody with average mechanical skills.

If the vehicle is running at all, then the fuel pump is working, It’s that simple. And while you’ve changed the pump twice in recent times, have you also replaced the pick-up tube that dangles from the pump and reaches down into the deepest depths of the fuel tank?

Sometimes, these tubes can split (and the split can be hard to see) allowing the pump to suck air rather than fuel if the split is exposed. Which could mean that your car, when parked on a slope sufficient to cover with fuel the split in the pick-up, started no problem. But, when parked on the flat and the fuel in the tank allowed to pool away from the pick-up tube, the split was exposed and the pump was sucking air again. It sounds like a long shot, but it has definitely happened before today.

The piece of the puzzle you've left out here is whether your Courier has a petrol or diesel engine. If it's the former, you could simply be looking at a worn out engine. These four-cylinders worked pretty hard and once they become worn, they start to blow smoke and lose power. That said, it could be something as simple as a blocked air filter element or a slack fuel pump.

If the vehicle has a diesel engine, there's a chance the intake system is choked up with black soot and oil fumes which eventually narrow the engine's breathing passages like cholesterol blocks a person's blood vessels. Suddenly, the air can't get into the engine properly and the engine loses power as a result. Again, though, it could be something completely different and apparently random such as the turbocharger's plumbing having fallen off, leaving the engine with no boost.

A word of warning, though, about driving a diesel Courier flat out everywhere. These engines were under-cooled and are notorious for overheating. Driving it with the throttle pedal on the floor is asking for problems.