Improve Fuel Flow to Injection Pump

One of the weaknesses of the pumps on both the 2/4/600’s and the 25/45etc is the fact that the fuel pump has to suck the fuel all the way from the tank. When we are approaching the limits of their capacity or even exceeding them a phenomena occurs which can be very damaging. The pump starts to suck so hard from the tank that it creates small air bubbles in the fuel. This is known as cavitation. This cavitation can cause serious damage to the pump so we need to avoid it. The usual symptoms are after hard acceleration the car coughs and splutters as if it is running out of fuel for several seconds until the fuel demand has dropped so it recovers and the air is bled out of the fuel.

In order to prevent this you can add an external lift pump to the system. This is an electrical pump that sucks fuel from the tank and delivers if to the fuel pump under a slight positive pressure. This avoids the cavitation and fuel shortage problem. My recommendation is to use a small low pressure fuel pump that delivers a few psi. A modern fuel pump for a fuel injected engine is far too powerful, one for a carburettor car is much more suitable. You also need to pay some attention to how the pump is wired to work but it is a simple mod that can improve fuel delivery in fairly highly tuned engine (above about 140bhp)