Following the philosophy of making our 3-Wheeler as reliable as possible, we asked M3W Services to replace our original fuel pump for a much more reliable Walbro one.
The fuel system of our 3-Wheelers is a little bit weird. Why are we saying that? Because it is!
First, you have a fuel pump that delivers 190 litres per hour while the S&S X-Wedge engine of our little rockets needs just 45 litres per hour. Why is that? We don’t know. As simple as that. We have no idea why they decided to install such an overflowing fuel pump. Which pump is that? It’s a late 1990s Land Rover Discovery V8. We still can’t imagine why they decided to use such a pump, designed for a huge old 3.9 litres V8 engine, to feed our 2 litres V2. But it’s OK, as the S&S fuel injection takes the excess flow back to the tank.
Second, the fuel is sucked by the pump at the bottom of the right tank, through a basic inlet filter. You may expect to have another proper fuel filter between the fuel pump and the engine, before it’s injected into the cylinders, right? The answer is no: there is none. Another weird feature of our fuel injection system… So, any dirt particles shall be retained by the sock-type filter at the fuel pump’s inlet, and only.
Third, when the fuel hoses arrive to the S&S engine, the hose does not split in two in a proper Y to feed symmetrically each cylinder, but it gets first to one injector, and then continues to the second. With the high pressure and exaggerated fuel flow, there is no problem with that, and the engine runs as it should. This is not a technical issue, really. As we say, it works properly. However, some purists prefer to modify the routing and make a real Y with symmetrical hoses feeding each cylinder, as shown in the below picture.
Fourth and final, on the way back to the fuel tanks, the excessive fuel flow encounters a fuel filter. Yes, on the way back! That’s probably the weirdest part of the standard system. Why is the fuel filter on the way back to the fuel tank, and not before the injectors? Isn’t the fuel supposed to be filtered before being injected, and not after? The thing is that this fuel filter is acting more as a pressure regulator than a filter. Strange but true. It’s a simple Mahle K167 model, and its purpose is to reduce the fuel pressure in the system to the minimum 58 psi needed to feed the engine. It’s placed at the back, fixed behind the seats. Consequently, the only fuel filtration in our standard fuel system is just the sock at the fuel pump’s inlet. For sure it’s not the best design…
M3W Services offers a fuel system upgrade, consisting in a proper filter on the way to the cylinders, and a pressure regulating valve with a fuel pressure gauge fixed by the side of the oil tank. A nice solution to convert your fuel system as it should.
It’s not a critical nor mandatory modification to be done in our 3-Wheelers, but we may do it in a close future, mostly for having a proper filtration before the injectors!
But hey! We’re drifting subject here! Let’s focus: the fuel pump. The Land Rover original fuel pump is not reliable. Period. Too many of them have failed. And if you’re not carrying a spare, it can fail, or not…. But if it fails, you’re done. It’s the end of the journey with the 3-Wheeler. You’ll need to be trailered back home, or back to your Morgan workshop.
If you drive with the original Land Rover fuel pump, and don’t carry any spare, it’s like playing the Russian Roulette! Amongst those who use to tour with the 3-Wheeler, there are few carrying a spare pump. But the wisest thing to do, in our honest opinion, is to change the Land Rover fuel pump for a much more reliable Walbro one. So, the chances of being stranded on the side of the road due to a fuel pump failure are greatly reduced.
The exact model to use is the Walbro GSS342. Be careful if you buy one on the Internet! There are many Chinese fake ones around! The real Walbro GSS342 has stainless steel internals, not plastic!
This is a DIY job if you are a good handyman. In fact, as this is a quite common failure, there is a fantastic guide to do it yourself: the “5-Speeder fuel pump replacement”, by Ian Brett and Andrew Warren.
We highly recommend following their guide if you want to replace your fuel pump by yourself. You’ll need some other parts, but easy to find, and within the mentioned guide you’ll find all the necessary references.
But in our case, as our 3-Wheeler was at M3W Services for the Bleazey drive train upgrade, we included this task within our wish list. And Steve replaced it for us. He was quite surprised about the colour of the fuel in our tanks: intense blue. This is because Repsol here in Spain colours his new generation gasolines with such blue. Curious and different.
Now we have a reliable Walbro GSS342 fuel pump installed in our right tank. We keep the original one, that was still in good working conditions, as a spare. It really doesn’t take much room and I guess we’ll carry it with us for the long tours.
This is another “peace of mind” upgrade. We’re working in the right direction! Our 3-Wheeler will soon be as reliable as possible!
2 Replies to “Hangar works #24 – The Walbro fuel pump”
Good that you have the improved fuel system and more reliable Walbro pump, some more spares you no longer need to carry. Glad you liked our instructions. Your M3W gets better all the time.
Your instructions are great. Really useful! And I always appreciate your incredible work for our community. I will probably buy the missing parts to have a complete spare set, and then carry in a little bag my old pump (that still works) and the pieces but just for long tours. It really doesn’t take much space.