This is a walkthrough on how to install an uprated fuel pump in your Liberty B4. It is highly recommended that if you will be retuning the ECU or modifying much past 'stage 1' mods that the stock fuel pump is replaced. The standard B4 fuel pump flows up to 130L/hr which is not really adequate for high(er) power outputs. The Walbro pump flows up to 255L/hr, so it provides a large safeguard over running out of flow capacity!
Before I begin a few important points-
THIS MODIFICATION IS PERFORMED AT YOUR OWN RISK. I take no responsibility if you make a mistake during the install that causes your engine to lean out or not run at all. If you are not confident to modify a critical system in your car then get a PROFESSIONAL to do the job. This is intended as a GUIDE and is in no way the final say on how to perform this modification.
You will be working in close proximity to large amounts of FLAMMABLE FUEL. Do NOT smoke, use a mobile phone or have an open flame or pilot light anywhere near your car when performing this job.
Time required:
1-4hours depending on how skilled you are! (It took me probably 4 hours in total working out a lot of stuff as I went along)
Tools you will need:
Phillips Head screwdriver
Flathead screwdriver
Socket set
Pliers
Dremel with a cutting and grinding blade (preferrably- otherwise you will need a very sharp scalpel and a very narrow file and a LOT of patience)
Parts you will need:
Walbro 500hp 255L/hr fuel pump (Part number GSS 342) (Can be bought off ebay for around $150-make sure its a GENUINE pump and not a cheap copy)
Genuine Subaru fuel filter and gaskets (If you have not replaced your filter for 40,000km or more you may as well replace it while you have everything opened up)
Fuel filter and gaskets
Fuel pump and fitting kit
The process-
First of all you will need to remove your back seat base as your fuel pump (and tank) reside underneath! There is no 1 way to accomplish this. Basically the base is held in place by two clips at the front of the left and right cushions. You need to put pressure at the back of the base and lift at the front ON ONE SIDE ONLY. Its nearly impossible to get both clips free at once. There is a fair chance you will break at least 1 of the clips as they are so tight.
Once removed you will be left with this: (note the holes where the clips go)
Remove the black press stud in the centre and pull back the black cover. Also it helps for access to pull the carpet out on both side and pull that back a little bit.
You are now left with this:
Surprisingly (for me) the fuel pump assembly is located under the drivers side panel. So remove that panel and you will have access to the fuel pump lines and assembly:
BEFORE REMOVING THE FUEL LINES- disconnect the electrical connector (grey with green tape in the above picture) which powers the fuel pump. Then start your car and run it until it dies (a second or two). Then crank engine with the starter for 5 seconds or so to remove any residual fuel pressure in the lines. Once this is done you fuel system has been depressurised and you can remove the 3 fuel lines that lead to the pump assembly (2 feed lines and 1 return line). Be careful as the plastic connectors looks fairly flimsy.
Now undo the bolts that hold the assembly in the tank. Remove the assembly GENTLY as the float which senses the fuel level in the tank jutts out at a funny angle and will catch the lip of the tank when you remove it.
Its a good idea to take the pump assembly out into your garden to tip all the fuel out that will be caught up in the nooks and crannies.
This is what the assembly looks like out of the tank:
The fuel pump is in the plastic cylindrical housing, and the fuel filter is in the metallic housing.
Remove the stock fuel pump by unclipping the little clips that hold it in. DO NOT DISCARD ANYTHING AT THIS POINT. The only things that you will not re-use are the original fuel pump and the black rubber spacer that sits between the pump and the pickup. Even though the Walbro pump will come with a new pickup 'sock', this WILL NOT fit in your tank as it connects at a 45degree angle. The new pump will only just fit in with the stock 90degree pickup and sock.
Thats the easy part out of the way. Now comes the harder and more fiddly part. Getting the Walbro pump to fit in the plastic housing. After test fitting the Walbro with the rubber spacer supplied you can see there is NO WAY the plastic housing is even close to clipping back together:
Now I appologise that I have no photo's to show how I did the next part as I was too busy trying to work out how to get it to fit myself! You will be able to put 2 and 2 together when you have the assembly there in front of you. There may be another way of doing this, but this is what I did....
Firstly you will need to cut the rubber spacer down to to bares bones thickness. Use your dremel to cut about 75% of the thickness off of the bottom. Don't worry about the guide holes you are cutting out as the spacer will be held in place by the plastic housing and pickup. You will also need to cut the rubber node on top of the space to a shape that resembles the old spacer. I put the spacer on the pump and the housing on top and marked out what i needed to cut with a texter.
Unfortunately this is not all the grinding/cutting you will need to do. I also ground away the white platic nodules on the bottom of the fuel pump itself so the spacer sits right on the base of the pump.
After doing the above, you will find you are still a few mm short of the clips being able to clip in. The only option I had was to file out the slots where the clips fit into as I could not take any more meat out of the spacer before it became non-existant.
Once you have done the above HOPEFULLY your housing will be able to clip together holding the pump in. Just remember before you do this that the pickup and sock has to go on BEFORE you clip the housing together.
Now although the pump is now held securely in the modified housing, the overall assembly has grown 'taller' by the amount you have filed out of the clip slots. For me, this meant the pickup sits quite snug on the bottom of the tank when I reinstalled it. Some people (and workshops) bash the fuel tank out to provide some clearance around the pickup, its up to you whether you do this. I haven't.....yet, and it seems to be working fine. The pickup is no a moving part so nothing is going to rub or wear against the tank.
Before putting the assembly back in the tank you can now replace your fuel filter. This is a VERY simple task compared to the fuel pump! You will need to unscrew the metal housing to access the filter. Once unscrewed, just remove the filter and replace with the new one, taking care to put the next gaskets in the correct position to seal the unit again.
Thats one dirty filter!
Rescrew the filter housing on FIRMLY and make sure the housing has cleared the guides when you twist it on.
Now place your assembly gently back into the tank, making sure the plastic float is outside of the pan that the fuel pump sits in.
Do up the screws with minimal torque and going in a reversal opposite pattern (ie where you next tighten the opposite screw to the one you have just tightened- this ensures a uniform pressure on the seal as you tighten all the bolts. The bolts need bugger all torque and they are very easy to strip the threads so be gentle!
Re-connect the fuel lines and pump electrical connector.
Before starting your engine, re-prime the system by turning your key to accessory a few times. You will hear the pump VERY AUDIBLY (its loud!) as it pressurised the lines. Start the engine and check for any leaks out of the fuel lines or around the assembly seal before replacing your rear seat. You will find the pump quietens substantially with the back seat back on. However all aftermarket fuel pumps are much louder than stock items so this is something you can either just get used to, or maybe put some sound deadening material under the back seat to further dull the noise.
As said previously, its an easy job on paper, but the housing and spacer modification make this a quite fiddly job. You will save yourself $200-$300 though that you would pay a shop to do it for you.
