This month I've been mostly...

Wasn't there a TV sketch show back in the 1980s or 1990s that had a character who would come out of his shed and say: 'This week I've been mainly...' Invariably the sentence would be completed by something mundane like '...eating sprouts.' Well, I feel a bit like that because this month I've been mainly working on Reliant three-wheelers and their carburettors!

Let's start with the Robin. I took this for my first proper drive and it ran very nicely all the way to the workshop. However, on the way home I was pulling up a long hill when it started to splutter. I made it to the top before the engine finally died and fortunately I was able to pull off the road and into a field entrance.

The problem felt for all the world like fuel starvation as the engine would splutter and start to die, then pick up for a moment before fading again. Pumping the throttle made no difference when it was struggling, and there was an inevitability about its eventual stutter to a halt.

The fuel gauge indicated well over half a tank, but of course I had no idea whether or not that was accurate.

I had a look around under the bonnet, but could not see anything amiss. After five minutes or so I tried the engine again and it fired up. The nearest garage was only a mile away, so I made it there and filled up – only around 2½ gallons, so the gauge wasn't lying. I still had several miles to go before I was home and although I made it under my own steam, there was one point as I was cruising along when the engine started to die again, but before stopping completely it picked up and then kept going.

The engine bay on a Robin is not the most accessible of working environments, so back at base I took off the SU carburettor in order to inspect it on the bench. It seemed to be brand new, but the float chamber was very loosely attached to the carb body. I tightened up its securing bolt

and refitted the carburettor to the engine, filled its float chamber with fresh petrol and then took it out for a test run. I made it a few hundred yards before it died completely, and no amount of waiting and coaxing would get it to run again. Fortunately the Robin is a small and light car, so pushing it back home was embarrassing, but not too difficult.

Next I rigged up a temporary supply of petrol directly into the float chamber. The engine duly fired straight into life, and kept running for some time – though of course this was standing still on the drive rather than driving along. At the same time, I had put the disconnected end of the fuel pipe from the mechanical fuel pump on the engine into a jug to catch any petrol that came out while this was unattached to the carburettor. To my surprise, even with the engine running, the jug remained empty.

So now I was getting somewhere, but it still left a number of potential culprits to which the finger could be pointed. The easiest one to check was for a blocked breather on the fuel cap causing a vacuum in the tank that the pump could not overcome. This was unlikely because it normally takes a period of running for enough fuel to be extracted so that the vacuum can be built up, but removing the filler cap made no difference so that one was ruled out.

To see if the fuel pump itself was at fault, I connected a hand pump into the pipework and tried without success to pull some fuel through to the jug using that. OK, so now I was looking at either a damaged pipe, or a blocked pick-up point in the tank itself. I blew back down the pipe and into the tank to see if that would clear any blockage there. That made no difference initially, but then the hand pump spat out an initial burst of petrol before settling down to a regular flow. I also found a couple of sections of fuel pipe that were hard and split, so replaced them with new and connected everything back up to the carburettor. This time the engine fired up and ran happily, and it has been an instant starter and reliable runner ever since.

Meanwhile, on the Regal, no amount of fiddling and finetuning the carburettor settings would coax it into a reliable and stable idle. In the end, I had to conclude that it was not the carburettor settings that were the problem so much as air leaks somewhere upsetting the mix. I did have a brand new and unused carburettor that I had bought during the restoration, so fitted that instead and it instantly cured the idle problem.

However, whereas the Robin on its SU will start instantly even after a lengthy period of inaction, the Regal's Zenith seems to drain back down and take a lengthy period of churning on the starter before the mechanical fuel pump manages to fill the float chamber. I hate churning an engine over in this way, particularly if I have an early start and the neighbours are still asleep, so I bought an Su-style Hardi pump and fitted that in the boot. Now, no matter how long the Regal has been standing, turning the key sets the pump into action and all I have to do is wait for its clicking to stop, then the engine will fire right up.

ABOVE: The SU carburettor on the Reliant Robin looks like a brand-new unit, but the bolt holding its float chamber on was very loose.

ABOVE: Neither the mechanical fuel pump on the engine nor this temporary hand pump would pull fuel through initially.

ABOVE: Simon did find some decayed fuel pipes, and after replacing them the problem has so far not returned.

ABOVE: Simon had rebuilt the Zenith carburettor that came with the Regal (back), but had also bought a NOS replacement (front).

ABOVE: He always prefers having an electric fuel pump on a car that is only used occasionally, so fitted this low-pressure Hardi pump in the boot of the Regal.

ABOVE: Simon wanted to blank off the fixing point for the now unnecessary mechanical fuel pump on the engine. From this old bracket off a broken office chair...

ABOVE: ...he made up a suitable blanking plate. The light green paint happened to be some engine enamel left over from the Midget restoration. Waste not, want not...