Going mental

[New Bloke]

Doesn't the pipe protrude into the tank and bend down? I understand that the fact it was pushed against the bottom caused this issue. It got quite reproducible but I've now done two circuits and so far, so good.

[ManyMinors]

Doesn't the pipe protrude into the tank and bend down?

No. It doesn't.

If you look under the car - at the front of the fuel tank - you will clearly see where the fuel pipe attaches to the outside of the tank and marries with another pipe (not replaceable as far as I know) which is INSIDE the tank.

[kennatt]

every one I have seen has the internal pipe brazed'/welded to the outside of the tank and extends into the tank,its not replacable as such without emptying the tank and re welding/or brazing into place I would be surprised if there were any other type,so I suspect that it was merely the outside pipe to pipe connection,that needed refitting,I think most have a male female brake pipe type connection.It could be that the pipe has broken off inside and when going up hill the petrol flows backwards and the system sucks air. If it only happens when low of petrol (Hope its cured now anyway) just fill it half way and see what happens. It may be ok now so that's fine .Just give your daughter a few lessons in how to push a minor back home good for the lower legs and back Good luck

[IslipMinor]

To some degree have 'been here, done that'.

Many years ago I also fitted a new fuel pipe, and at the time did not know the exact details of the pipe to tank fitting, but after fitting it found that when going up a steep (ish) hill on less than 1/4 full, I would sometimes get a hesitation under power. The problem was with the tank end fitting on the 'new' fuel line - it did not seal with the internal tube, which was loose and the pump drew air from inside the tank.

There is a soldered fitting in the forward facing side of the tank, and the internal tube is NOT soldered to it. It is loose in the side fitting and relies totally on the correct main fuel line fitting being used to seal it to the tank side fitting.

The internal tube runs horizontally towards the rear of the tank and then has a 90° bend down towards the bottom of the tank, with a mesh filter on the end. Not sure if the filter actually touches the bottom of the tank, if not it is very close.

The internal tube is swaged on the end that is inside the tank side fitting, which prevents it being removed into the tank, nor can it be withdrawn from the outside of the tank - so what has been done to seal it is not at all certain.

The main fuel line rear fitting has a long thread on it, and it must NOT bottom on the outside of the tank fitting, the length is required for it to contact the swaged internal tube and tightening the nut seals BOTH the internal tube AND the main fuel line itself. There should be at least 2 threads showing between the fuel line nut hexagon and the tank fitting. If the internal tank tube is not correctly seated, once the fuel level is below the outlet fitting, it will leak air from inside the tank (no external leak, unless the main fuel line is also incorrectly fitted.

Looking in through the sender unit hole, you can see some of what is going on, and looking into the side fitting you can see the swaged internal tube fitting, rather like a larger brake line end.

[New Bloke]

So it could be there was a gap in the inner pipe to fitting, and by bending the pipe backwards, the mechanic has closed that gap. In which case it should probably be looked at when I have used most of the fullish tank I now have.

[myoldjalopy]

To be honest, I would ask the mechanic exactly what he did do - and why..... at present, its not entirely clear and has caused a little confusion here.

[New Bloke]

Well,

I was there and saw exactly what he did, he bent the inner pipe (the confusion was caused by him assuming the pipe from bottom of tank to fuel pump was one section) away from the bottom of the tank. He thought that the pipe was pushing on the mesh and therefore was causing the obstruction. By the way, he is a bit more than "a mechanic" as he is also a mate of mine. I was loathe to get him involved before as he runs his own business.....

[IslipMinor]

With the fuel above the outlet tube, there should be no problem, as air cannot get into the fuel line - do check the fitting on the front side of the tank, as this could weep/leak if the main fuel line fitting is not seating correctly.

Lifting the internal tube up from the bottom slightly should not have caused any damage, just reduced the already miserly capacity even more! If no damage has been done, I would leave the new shape in place, as working it up and down will induce 'work hardening', and possible cracking and fracture, as well as potentially damaging the mesh filter.

As you said earlier in the posting, the bending may also have tried to seal the previous air leak, but I not want to rely on it. Check out the main fuel line external threaded fitting carefully, to make sure that it is tightening down on to the internal tube flare and that the tube nut hexagon is NOT bottoming out on the soldered tank fitting first.

[New Bloke]

A quick update for everyone, once the fuel level dropped below the pipe joint in the tank (below the take off point) the problem occurred again. The solution is to keep the tank full and not let it go below half full. My mate the mechanic has suggested we re route the fuel pipe to a new take off point by drilling a hole in the sender unit cap and running in a rubber/plastic pipe to meet up with the new pipe inside the tank. It was either that or 200 quid for a new tank and the old one seems fine apart from the inside pipe.

[David W.]

On your side of the Atlantic, I believe that's called a "Bodge."
It's not difficult to drain and drop the tank. On a workbench with everything in sight, you'll be able to make the right repair.
Of course, observe all standard precautions when working with petrol.

[IslipMinor]

It would appear that the basic problem is the connection between the main fuel pipe going to the fuel pump, and the internal pipe in the tank. The latter cannot be replaced, but so long as it has not been damaged by the work done by your mechanic, there should be a good starting point here.

Can you take a picture of the connection on the front of the fuel tank, where the main feed pipe is screwed in? Have you tried tightening this connection?

I would definitely NOT try to make a new connection into the tank - the problem is with the existing connection and/or something that your mechanic has done through not understanding how the connection works.

Even just fitting a new tank may not sort the problem, if the cause of the problem is with the main feed pipe end fitting.