When it comes to increasing the performance of your mechanical diesel engine many often ask and wonder when or if a in-line lift pump is required to handle the extra fuel volume being delivered up to the diesel injection pump. The answer definitely varies but let’s take a look into when, why and if these are even needed.
We are going to use a few of the most commonly upgraded mechanical diesel engines in Australia to investigate this topic of conversation – the Nissan Patrol TD42 and Toyota Landcruiser 1HZ, 1HD-FT, and 1HD-FTE (I know there’s an ‘E’ on the end of that – I will get to it in a minute).
But first, a quick run down on what a lift pump is and why we should consider one. On a mechanical diesel engine, fuel is drawn from the fuel tank up to the engine by a rotary style pump which is built into the fuel injection pump. This is driven by the timing gears/belt/chain and in turn the crank rotation in the engine. I have sourced a basic diagram to demonstrate this process below.
We may consider fitting a lift pump when we increase the engine’s performance requiring a more consistent flow of fuel up to the injection pump to reduce cavitation, want to take load of the fuel injection pump, or there is a mechanical fault relating to the fuel system (air leaks, injection pump leak, worn rotary pump) and are looking for a cheaper option to ‘keep the car going’.
Nissan Patrol TD42 and Toyota Land Cruiser 1HZ
These engine’s are most commonly fitted with a lift pump as they are most susceptible to the issues I’ve just out lined above. Starting first, it’s good to consider the size of the fuel lines provided from factory. The supply fuel hose to the injection pump is a factory 10mm pipe, and the return is an 8mm pipe. Not overly large in diameter. Let’s say you are about to bang a UFI 12MM 250HP injection pump on along with a UFI 18G turbo, front mount intercooler and exhaust system. This has all the ingredients to make a solid 250HP and 700NM at the wheels. Although we are now teetering on the edge of how much fuel flow those hoses can handle. Some cars can handle it, maybe they don’t have any residual build up in the tank or lines, maybe all there fuel tank breathers are clean as a whistle and there’s not a single bend or extra kink in any of their fuel hoses. But the reality is for most of these cars, that’s not the case.
To counteract this issue, we can consider fitting a lift pump inline with the fuel supply system to provide a consistent fuel supply to the injection pump, reducing cavitation, and reducing the load in which the injection pump has to operate under. In turn, this can lead to a longer life of the pump, and less wear while providing you with optimum and consistent power delivery.
Realistically, we do not need a lift pump on these engines under the 200HP and 550nm mark. We’ve found at this power level, the injection pump is not in a position to be demanding more fuel than the rotary pump inside the injection pump can provide. However, we may consider fitting one if you are suffering from one of the following symptoms:
- Fuel surging causing the vehicle to gain and lose power through the RPM range
- A reduction in power above 3000rpm unrelated to pump tuning
- The fuel pump primer is weak
- There is air being pulled into the system from somewhere along the fuel hoses under high load, this will also cause surging or misfiring
There are of course solutions to each of the problems above in which a lift pump is only masking – but my realistic approach to this is that as these cars start to age, and given the fact that they’re mostly used for off road use and not built to be show queens (Unless you own a Tik Tok and or Insta rig), that an all round solution is going to provide better value than piece by piece pulling apart the car until we find an answer, especially if trying to solve the problem at home.
Now if you are considering fitting a lift pump, here’s some key things to keep in mind when it comes to fitment.
- Fit it as close to the fuel tank as possible. They are push pumps, not pull pumps. They push the fuel up to the injection pump, not pull it up.
- Fit it lower than the height of the fuel tank. Gravity will work wonders in providing a constant supply to the pump itself if you do this. Somewhere along the chassis is good.
- Make sure you mount it the correct way up, there is an ‘upward’ position in which it needs to be fit.
- It will need to be wired in with a relay, however you can set the switch wire to trigger from the alternator sense wire so that it only actually runs once the engine is running. This will allow you to have your ignition on, to listen to music with the car off, etc. without having to have the pump running constantly.
- Rubber mount it against a solid surface. This will reduce the noise of it basically down to nothing.
- You do not need a fuel regulator to control it’s pressure. All you need is a maximum of 7 psi.
Our favourite brand of lift pump is the Carter 4600HP. We have found that this is the quietest, most robust pump available at a very reasonable price and comes with most of the fittings you need. Keep it mind though, the fittings it comes with are 1/2″ fuel hose size, so you will need to source some to suit whatever size fuel hose you run. These pumps were essentially built for carbureted engines to supply fuel up to the carby.
Toyota Land Cruiser 1HD-FT and 1HD-FTE
These two engines are a different kettle of fish when it comes to whether or not your need a lift pump. This is primarily because if you are using the engine in their factory fitted chassis (HDJ80, HDJ79, etc), they will have come factory fitted with 12mm fuel supply hose. This increase in diameter is enough to increase the threshold of when one is required. A 1HD-FTE for example, is suitable up to 400HP pretty happily without a lift pump. ALTHOUGH, I am not opposed to recommending it at this power level either. The reason for this is simple – through our data analysis on the injection pump’s hydraulic timing control (this meaning the injection pumps fuel injection timing is controlled by fuel pressure), we have found that at this power level without a lift pump fitted, the injection pump starts to lose control of it’s injection timing. There can only really be one reason for this: It’s losing it’s hydraulic pressure inside the pump. Essentially because we are demanding so much fuel through the engine to make this power, the pump cannot ‘refill’ itself in time to maintain full pump pressure. This is a great and logical reason to want to fit a lift pump as this will 100% affect engine performance above 3500rpm. The 1HD-FTE injection pump is an amazing piece of engineering, and is actually quite simple in design when dismantled, but through it’s simplicity it is able to function amazingly well.
On the 1HD-FT, as it is internally designed very similar to a 1HZ pump, it more or less falls into the same category for issues as the 1HZ, although the fact that they are normally fitted with 12MM fuel hose, just pushes that threshold a little higher before it’s ‘needed’. I would easily class a 300HP 1HD-FT as needing a lift pump, however, as the injection pump rotary pump is only so capable.
