The final thing to achieve before I could think about going for a first start was the fuel system. Fuel injection runs at a far higher pressure compared to carburettors, approximately 40 – 55psi compared to around 3psi. Where a carburettor has a float chamber to provide fuel, a TB, or the injectors, have only the fuel in the fuel rail. The pressure in the rail therefore has to be maintained to ensure that for a given injector opening time a given amount of fuel is always injected.
Due to the increased pressure required I had two options, fit a swirl pot and an external injection pump or change the tank for an injection version with a built in pump. The swirl pot is an extra reservoir of fuel which is between 1 – 2lts capacity and is fed from the main tank by a low pressure pump. If the swirl pot gets over filled there is a return which feds back to the main tank. A high pressure pump takes fuel from the swirl pot and feds the fuel rail and injectors with the excess feeding back to the swirl pot.
I decided to look around for a second hand tank and pump which would work out to around the same cost as the swirl pot + pump especially when you consider that I could sell my old tank, pump and regulator to offset the cost. To this end I posted a wanted advert on Blatchat and Mick Attree came to the rescue with the offer of a barely used new tank and an R500 up rated pump. It turned out that these parts had been fitted to a race car as part of a repair by Caterham Cars. Mick had then replaced these with a bag tank at the racers request with them only having travelled a couple of miles. Overall cost was less than Caterham wanted for a new tank on its own. I arranged to meet Mick after I had dropped off my gearbox as they are both on the other side of the M25.
The fitting of the new tank was straight forward, but meant that I had to remove the rollbar in order to get the tank out / in – well it was that, or the axle!
Connecting everything up was fairly straightforward, although the tank had a couple of extra connections which I had to blank off. The supply from the tank feeds all the way along the transmission tunnel via a length of new high pressure hose and connects to the front of the TB fuel rail. It then feeds back through the pressure regulator to the tank using the old low pressure fuel hose. I fitted a one way valve to the tank vent on the top, with a length of hose and fitted my fuel level sender.
The only problem was with the fuel filler. The diameter of the inlet is smaller than that of the carb tank and also closer to the back of the car. Therefore my elbow hose was very hard to fit and had to be squashed up to fit the tank. After a short while I changed this for an in-boot filler cap as I didn’t much like the strain the elbow hose was under.