View Full Version : DIY B5 Audi Aftermarket Fuel Pump Install

09-13-2018, 08:23 PM
Hopefully this will be helpful for anyone looking to replace their stock pump with a 39mm aftermarket one. This was done on a 2.8 A4, but should be the same for all B5 models.

This actually ended up being a little easier than I thought it'd be. I got an AEM 340 E85 compatible pump and an XS-Power 39mm fuel pump adapter.

The first step (after disconnecting your battery) is to pull the carpet out of your trunk and remove the black cover behind the rear passenger side seat that is secured by 3 screws. This gives you access to your fuel pump. Once the cover is off, mark the direction of flow on your two fuel lines or mark them in a way so that you put them back in the same spot.
Yours will probable have oem single use clamps that you'll have to bust off. Remove the electrical connector and then using a hammer and a flat head screw driver, hammer on the lips on the outer edge of that black cap to turn it counter-clockwise to loosen it. It's not a bad idea to mark the cap so you know how tight to put it back on. Keep hammering it until its loose enough to remove.
Then pull the white fuel pump cover off and you will see some wires and hoses underneath it. The black hose is clipped on so carefully unclip it to remove it. The brown ribbed hose has an OEM single use clamp (if it hasn't been replaced) so be really careful to not cut the fuel line while trying to break that clamp off. Remember which side the wires are on (or use my picture as a reference) and remove the wires. Now the white cap can be removed and set aside. Remove the black or orange tank lid gasket too.
Once that's out, you'll remove the fuel level sender. This has a little tab on the outside of it (the side that faces away from the pump) and you probably wont be able to see it. Feel around for the tab in the picture below and push it in and pull the level sensor up and disconnect its wire.
You'll notice that mine has an aftermarket wire soldered to it. This wire breaks on a lot of B5s and causes the fuel gauge to read inaccurately. Make sure the wire looks good and if it's frayed or broken, solder it or replace it while you're in there. Next use your B5 fuel pump removal tool and seat it in the 4 engagement teeth on the top of the pump... then you only need to turn it counter-clockwise like 10 to unlock the pump. The fuel pump can now be lifted out of the tank.
(what it looks like with the pump removed)
With the fuel pump out you can now unbolt the positive and negative wires on the pump and carefully remove the other single use clamp and ribbed fuel line from the pump.

Also I should mention that I was able to reuse that brown ribbed fuel line on my AEM pump, it fit perfectly. I believe that hose is 8mm or 5/16" so if you do need to replace yours you could probably do so with a fuel-purpose rubber hose.

Back to parting out your fuel pump... the next thing you'll want to do is remove the top cap on your fuel pump housing. I marked mine, you probably don't need to, but why not... You then push in the 4 tabs around the outside of the housing that you see in this picture and then remove the cap.
Then you can pull the fuel pump inner housing out of the large outer cylinder. There will be 6 rubber sleeves in there that seat the inner housing to the outer one.
You now want to remove the plastic support piece/ring that is held onto the inner housing with 6 more rubber sleeves. Remove all these rubber sleeves. Depending on the location, some might be hard to come off so just use a flathead screw driver to pry them off.
This is the furthest point of disassembly, now you'll want to start preparing your new fuel pump. The XS-Power fuel pump bracket is definitely the cheapest one and it works great, but it comes with 2 o-rings and there is no way your fuel pump will fit into the sleeve with those o-rings in there. So throw those o-rings away and slide your new fuel pump into the sleeve. It is important to make sure that your new fuel pump will be sitting in the same position as the old one height-wise so that your car will still keep fueling even when your tank is really low. I compared it to my old pump by doing this in the picture below so that the pickup tube on the bottom would be the same height.
Once the pump position is where you want it, crank that XS-Power sleeve tight and your pump will be locked in there.
With this design you won't need that ring with the extra 6 rubber sleeves, just put 6 of the rubber sleeves you removed onto the XS-Power bracket and drop it right into the big outer cylinder housing. Put the first cap you removed back on and now you have your new fuel pump-in-housing. (You will have 6 leftover rubber sleeves, the original pump design uses 12, this one uses 6).
You can now install the ribbed fuel line onto the aftermarket pump with a hose clamp (my pump came with a new clamp).
Next is the wiring... Audi uses black as the positive/supply wire and brown as the negative/ground wire (it's a weird Audi thing). The AEM pump has red as positive and black as negative. Cut your Audi fuel pump wires at a length that still gives you some slack and solder the black Audi wire to the red new one, and brown Audi to the black new one. Ignore all the electrical tape garbage in the picture below, I changed my harness since I took this picture. Electrical tape will unwrap itself when exposed to fuel so I only used heat shrink wraps on the wires. Also it is a good idea to offset your solder connections incase for whatever reason the connections become exposed down the road. These wires will be sitting in the fuel and if they ever become exposed and contact each other, they will spark and that is bad, bad news.
Now you can connect your "modified" wiring harness in the above picture to the new fuel pump. Then install your sock filter on the bottom of the fuel pump. This is how the AEM one is attached.
Your new fuel pump is now ready to drop back into the tank. This part can be a little tricky because you have to get the 3 (or maybe 4, I can't remember) tabs lined up so you can click it down and then turn it to lock it. These are the tabs in the fuel tank that you need to lock into.
You can see in this picture again that the slots on the pump housing are the ones you see on the very bottom.
You'll want to push the fuel pump in pretty good until you think they've clicked, and then grab your fuel pump tool to turn it 10 clockwise to lock it. Pull up on it to make sure it actually locked in. I had to do this a few times until I seated it correctly and turning it actually locked it. The key is to try and have it go in perfectly straight so all 4 tabs contact at the same time. When it's locked in you'll know because you can pull on it hard and it won't come up. Reinsert the fuel level sender back into its spot, it will click when it locks in. Make sure there are no wires or anything keeping the steel level sender arm and plastic ball from moving all the way up and down. Now reconnect the wires and fuel lines to the upper white fuel tank cap and seal the cap back on the top of the tank with the black or orange lid gasket. Lock that black plastic lock ring by hammering it clockwise until it's tight or lined up with the mark you originally made. Reconnect the electrical connector and fuel lines on top and you are good to go!

It might crank a little extra on the first start to get fuel through the lines, but mine started right up and the AEM pump is super quite! Can't wait to see how the pump performs under load!

09-13-2018, 09:28 PM
link to adapter you bought?

09-14-2018, 02:01 PM
link to adapter you bought?


09-15-2018, 08:10 PM
Hi there team, nice Wright up I did manage to get the cage out using a spanner and turning lifting getting angry and it popped need that tool.

My main question is that I am going for a high tune e85 and daily 98 pump ⛽, but thinking of going for a surge tank setup so needing a lift pump to fit the oem basket, I do have both the bosch size and my oem smaller cage, I'm going for 2x walbro 450 274 pumps in the tank and one on a hobs switch, it's a vr6 swap b5 aiming for 1000 hp but maby 7_8oo on pump, that should be the lift pump? Thanks for the help.

09-15-2018, 08:21 PM
This is a cool little product I think would suit your needs better. Basically turning your stock fuel tank into a surge tank, so to speak. Proper fuel pressure regulator with properly sized fuel lines should be able to handle the fuel just fine, so no need for a hob switch (turn key operation like stock). Seems much more cost efficient too (ie cost of surge tank, 3rd pump of running two in surge tank, etc).


09-16-2018, 07:52 AM
Nice and useful write ! My question is can run the new hi flow pump with stock injectors and stage 1 tune ?, this would be just for the time being as I still need to finish collecting a few more parts for my big turbo build (hx30 not installed in car yet) with that set up Id be running 550cc on stage 3 tune so do I have to do this at the same time or is the car still drivable before I fully make this transition?

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09-16-2018, 08:19 AM
You will want larger injectors for that turbo.

The fuel system on our vehicles is completely sovereign to the rest of the engine. It works on a 12v source and the pump works at a constant speed (voltage and amp speed dependant). With pump constantly running, it builds pressure in the feed line. The fuel pressure regulator makes sure the fuel "rail" (why it is best to have an fpr as close to the rail that you can, to avoid false readings with pressure drop in the line. for example, it can have 65psi closer to the pump but maintain 58psi at the rail) runs at the desired pressure, then bleeds off excess fuel (pressure) back into the tank via return line.

That fuel pressure is necessary for the injectors to run properly. With the rising rate fuel system, fuel pressure increases 1psi for every 1psi of boost. So the larger injectors you have and more boost, the more fuel flow to build adequate "pressure" is needed. A pump that flows more can keep up with the demand to keep proper pressure at the rail as the injectors spray.

Understanding that, you can run an upgraded pump on a completely stock vehicle. As long as you don't overburden the stock fpr, car will drive as normal. The fuel pressure regulator ensures proper pressure at the rail regardless of how much flow it is seeing (as long as it is not below adequate or too much for the stock fpr to handle), then dumps the excess fuel back into the tank.

09-16-2018, 01:24 PM
You think I should go bigger than 550 ? Even if Im staying stock internals

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09-16-2018, 04:01 PM
That is a big turbo for stock internals. I suggest a smaller turbo. Smaller turbo will grant faster spool, with a powerband you can actually enjoy.

09-16-2018, 06:40 PM
I have been trying to get a better deal on the srm kit but one it gets to me In NZ and duty its over 2400 dollers so sad, I'm doing new lines 8 supply and 6 return to the tank 2000cc id.
So from here on I'm stuck on what to do.
I have email srm asking if the top hat comes with the twin pump carrier and I was going to attempt to make the rest my self but no reply about that bit.

09-16-2018, 07:39 PM
You can post in the B5 S4 section, asking if anybody is running that adapter. They should know what does and does not come with it. My assumption is just the bracket comes with the actual bracket, electrical connection for top plug, and tank lid (basically the billet part and electrical connection). Then you supply your own fittings and so forth, pumps, lines, etc.

09-16-2018, 10:24 PM
A that's what I'd like to be true I'll post there sorry though this was b5 I was searching for intank help lol shot guys/girls