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D2 - Fuel and Exhausts Everything to do with getting fuel into the engine, and fumes back out again

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Old 19th August 2021, 08:03 PM
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Goran Goran is offline
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Default My fuel pump story

Today I changed my fuel pump.
It wasn’t so bad, reading other people’s experiences I was expecting some horrors.
My main stumbling block was actually right at the start. The fuel sensor housing wouldn’t budge. After putting a pipe on my ‘special tool 2012A’ for more leverage a little tab on the cover broke and I was able to unscrew it until the two arrows met. Somehow the tab got jammed and wouldn’t rotate. Looks like only a part of the tab broke which doesn’t prevent the cover closing again.

I made my own tools 2012A and 3342. 3342 I made out of two pieces of oak wood joined and coated in resin. Picture below. It worked a treat but one corner of it did break off, which didn't prevent it working.

Luckily the long bolt wasn’t corroded and came out without a long handle or breaker bar. There was a moment of dread when it didn’t seem to rise up during unscrewing, but it just takes time and it slowly came out.

Taking out the pump housing wasn’t too bad. I’m not sure how much Audi’s instructions actually help. Turning anticlokwise by 45 degrees twice, etc. But eventually its easy to figure out how it wants to come out.

As Mikki says all the rubber seals seemed good, only the one on the sensor housing seemed to be getting a little bit brittle with a bit of rust from the spring. That one I coated in a bit of engine oil. Audi tradition never got back to me to confirm when the seal kit would be back in stock, they did confirm it is not in stock now.

My other fear was the plastic housing tabs. Luckily they weren’t brittle, and didn’t need to be moved with any great force to separate the halves. The trick here I found was to move the two side tabs first. Lift the back of the housing up, then rotate it out of the front hook tab. Someone on youtube prized off the hook tab first with a screwdriver. I think this is very risky as it seems a lot of force is needed.
The fuel pump wires are a bit funny, on the pump body the + is where the green/yellow wire goes, the - is where the brown wire goes. Seems counter intuitive since brown is usually +. But I just put the wires back where I found them.

I had to take a break and walk to the dealer to get some hose clamps. The ones needed are 2x 15.7 and 1x 15.3
Don't bother quoting the dealer part numbers because they are part of some kit. Just tell them the above numbers which are stamped onto the ear clamps themselves. The odd 15.3 goes on the hose on top of the fuel pump housing, the one that goes on last when the job is finished. My dealer didn't have any 15.3's so I used a 15.7 instead which seems to have worked just fine. Or you can use jubilee clips, but I prefer ear clamps for some reason.
The pump housing went back together without problems.

Re- installing the housing in the fuel tank was the trickiest part in my opinion. Here I did follow Audi instructions, but it seemed to meet a lot of resistance at the “turn 45 degrees anti-clockwise” steps.
With a bit of wiggling and moving around it finally rotated and seemed to be in good position.
Maybe I should have put some engine oil on the jet pump hose seal?

The housing seemed to sit correctly with the big seal fitted. Test fitting the long bolt I found I needed to rotate the housing by a tiny amount until the bolt could be screwed in smoothly by hand. Even after that fine adjustment the banjo bolt had difficulty going in by hand, but holding the banjo hose with pliers and wiggling allowed it to finally go in. I didn't dare to tighten the long bold to the manual 20Nm, I set the wrench to 15Nm to start with and approaching that there were some crackling and other noises, so when I got up to 15Nm I called it good and left it like that. I didn't have the small crush washers for the 'standing heater' supply line, so I engine-oiled the old ones and hope they sealed the line. I'll be removing the 'standing heater' anyway so hopefully it will be ok.
The big plastic nut I did up by feel. In theory I could have cut a square hole in that metal shelf rail to fit my torque wrench but at this stage I couldn't be bothered.

The moment of truth won’t be until tomorrow, I have to go to the petrol station to get a can of fuel before trying to start it.
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Last edited by Goran; 22nd August 2021 at 01:43 PM. Reason: Add photo
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Old 19th August 2021, 10:04 PM
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Does the polarity of this connector matter? I think I plugged it in the other way round. The wedged side outwards, smooth flat side inwards.
Although this guy in the video could have it reversed? (his wires are opposite to mine)
Damn should have taken a photo of it before unplugging.

*edit - I think I found the answer. In the same video there's a shot of the fuel gauge being removed. So I need to remove mine again and check the polarity is the same as here. I think mine is the wrong way round.

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Last edited by Goran; 19th August 2021 at 10:49 PM.
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Old 20th August 2021, 09:12 AM
MikkiJayne MikkiJayne is offline
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Its only a resistive element so its not polarised
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Old 20th August 2021, 09:15 AM
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steamship steamship is offline
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Quote:
Originally Posted by Goran View Post
The fuel pump wires are a bit funny, on the pump body the + is where the green/yellow wire goes, the - is where the brown wire goes. Seems counter intuitive since brown is usually +.
As you say, the wiring does look odd when comparing with standard electrical wiring, where brown is live (+) and green/yellow is earth (-). The brown wire on Audi cars however are ground wires.

One of those jobs you never want to do, so kudos for tackling it... and making your own tools.
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Old 20th August 2021, 01:20 PM
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Goran Goran is offline
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Quote:
Originally Posted by MikkiJayne View Post
Its only a resistive element so its not polarised
Thanks Mikki
I’ll just leave it as it is.

Is it ok to start it like this (I didn’t empty the tank), or does some fuel need to be poured in to the tank?
I’m thinking of that catch-can at the bottom of the fuel pump housing, I guess its empty now.
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Old 20th August 2021, 01:30 PM
MikkiJayne MikkiJayne is offline
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If the tank is below 1/2 then I always add a gallon or so to fill the pump housing as a precaution since the last thing you want is to dry-start a brand new pump. The filler neck is positioned so that it mostly fills the pump housing first. Much over 1/2 a tank and the housing is submerged anyway.
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Old 20th August 2021, 05:41 PM
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Goran Goran is offline
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Quote:
Originally Posted by MikkiJayne View Post
If the tank is below 1/2 then I always add a gallon or so to fill the pump housing as a precaution since the last thing you want is to dry-start a brand new pump. The filler neck is positioned so that it mostly fills the pump housing first. Much over 1/2 a tank and the housing is submerged anyway.
Thanks Mikki thats great
I’ll go to the petrol station with a jerry can. I definitely don’t want to kill a brand new pump, this is not a job I would enjoy repeating.
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Old 22nd August 2021, 01:40 PM
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Goran Goran is offline
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Its alive! 🥳

Does this mean its good for another 20 years?


Now on to the timing belt, oil cooler pipe, cam cover gasket, fuel filter
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Last edited by Goran; 22nd August 2021 at 01:50 PM.
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