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Toyota Aygo 1.0 fuel pump problem.


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Hi there,

Over the weekend my partners city bug developed a very nasty fuel leak, actually inside the rear of the car.

On a quick inspection the rear seat was soaked along with the rear nearside carpet. With rear seat up there was fuel all over the body and the metal cover over the fuel pump was free as the fuel had melted the mastic holding it in place. Turned the ignition on briefly and was greeted with a spray of petrol from around the petrol supply connector to the fuel pump. Realised it was NOT going to be a easy fix as it looked like a new fuel supply pipe would be needed so left the vehicle safely parked on a side road until today.

1st thing this morning called all the local Toyota, Citroen and Peugeot dealers who promptly informed me the pipes were on back order for a month to 3 months!

Decided to have a second look at the fuel pipe and pump and then discovered there was a hairline crack in the white plastic fuel pump nozzle just before the fuel pipe connector. The white plastic body of the pump was so brittle when I moved the fuel pipe the nozzle complete broke off! No alternative but to have the car recovered home.

So the fuel pipe isn't at fault but the pump needs replacing! Have sourced a used pump from the Bay place which will arrive later in the week.

Decided to remove the big blue plastic locking ring that holds the petrol pump in the tank. Long story short after lots of tapping with a hammer, drift and freeing oil, the ring finally worked free and removed it having already disconnecting the supply and return fuel pipes and 12V supply. Might add it was swelting in this heat!

Out of interest I tried refitting the ring but it doesn't want to go back on and screw down evenly! Even tried removing the blue silicone sealing ring, it looked over sized, but the locking ring still wouldn't screw down evenly. It feels a bit like a crossed thread but the thread inside the ring and on the fuel tank opening are very heavy and I was careful to start turning when the threads were lined up!

Does anyone have any advise on refitting the plastic ring successfully? A long shot I know as have searched already and there's hardly any information on this anywhere.

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Thanks for the link to the video Stecha.

Had watched stupidblokes video over the weekend and I got the locking ring off having seen how he did it, which did work eventually though I'm convinced his wasn't as tight/seized.

I've found a 3 legged universal removal tool on Amazon for under a tenner that I'm hoping will do the trick and make refitting a lot easier!

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Hi if its the big rubber sealing ring for the blue nut has the washer just become miss shaped and is now to large?.


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Hi Derek, thanks for your reply, see there's a few of us around then!

Yes it's the big fat blue sealing ring that sits between the pump and the tank.

I've cleaned all the crap, petrol and oil off it left it to air then chucked it in the fridge earlier. Just checked it now and it definately seems  to have shrunk a little and is a better fit inside the retaining ring. Think all the petrol/oil and heat had caused the silicone seaL to swell. It still smells of petrol but will leave it to air more.

Fingers crossed, when I have the special tool and the replacement pump it will all go together as intended. Going to give the plastic threads a spray with some silicone next attempt.

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The seals swell when in contact with fuel, this is what makes them seal tightly and make them a pain to remove

new seal time if you can't get it back to normal

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Thanks for that Flash22.

I think your right on that mate! I noticed the seal did have a jelly like feel to it when I first removed it. I went as far as washing the seal in swarfega to make sure it was as clean as possible and left it in the fridge until it was time to refit.

Anyway I finally got the pump replaced and everything back where it should be and working!

Even with the old pump out of the tank I found that the I had major problems refitting it on the the neck of the fuel tank, it just wouldn't screw down squarely. Came to the conclusion that either the big blue lock ring or the neck of the fuel tank was slightly out of shape. So used a craft knife and a file to make the lower portion of the threads wider which did help in getting the ring on to the tank neck and tighten it down using a trusty hammer and drift. Decided to work on the lock ring as opposed to the neck of the tank as didn't want the risk of getting plastic debris inside the tank and the fuel.

The replacement pump and three legged tool both arrived yesterday. Made sure the pump was clean, especially on top as they get covered in crap from the road. Getting the pump back into the tank is a bit awkward, there's a black nylon pipe that has to be worked in carefully along with the sender float. Took the seal out of the fridge, now a much better fit a lot firmer and got it seated properly between tank neck and the fuel pump. Tied the fuel supply and return pipes out of the way to give better access, lined up the threads on the lock ring with the tank neck and then fitted the three legged tool onto the locking ring. Pressed down firmly and slowly turned the ring keeping the ring level, didn't use a spanner it was designed, did it by hand first and then tapped the lock ring round to the point where I knew it was originally as I'd marked it, with hammer and drift.

That special tool made life so much easier and I didn't use anything as lubricant in the end. Replaced the fuel lines where they came from and popped the 12v connector back on. So before putting everything back started the engine, had to crank it about 4 or 5 times before it finally fired up and ran, made sure to check there were no leaks at this point.

Having seen the original mess under and around the pump cover plate from the original black mastic I decided to use three self tappers and large washers to hold the cover down and in place. Had to be very careful drilling the holes as the top of the plastic tank is just below but choose three spots where there was ample clearance. With the cover held nicely then used plenty of one of those hybrid sealer/adhesives, you can buy now, around the edge. Left it an hour in the hot sun and then put all the carpet back, had left it up to air and then popped the rear seat back in place.

So my partners very happy again and she's driving around as usual in her little red city bug. Still smell slightly of petrol in side as the rear seat and carpet had been soaked in fuel but sure this will eventually go given time to air fully.

As for the original leak, hair line crack across the fuel supply outlet of the pump. Of the opinion that the mastic holding the cover in place had allowed cover plate to slide across to the right and the cover had then contacted the the fuel supply connector, just needed someone sat on the rear seat and their wieght through the seat and the cover plate caused the fracture in the weakest part of the fuel pump. Surprised others had similar issues! Very dangerous really as the fuel washes the  mastic off and runs down the underside of the cover onto the the floor under the rear seat and into the footwells. Only needs a smoker in the car to spark up and it would lights out for anyone inside!




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