Fuel pipe and fuel filter banjo bolt sizes please!

[King Fisher]

So, turns out Nick's car had a kink in the fuel pipe between the fuel pump and the fuel filter. He had to remove it, as it was a plastic pipe, and the kinks couldn't be removed. The inner diameter of the pipe was about 8mm. He replaced the pipe with a piece of rubber, flexible fuel hose, but the inner diameter of this was around 4-5mm. The new pipe fitted onto the banjo bolts, so he clamped them with some fuel pipe clips (like a jubilee but with a screw to tighten/loosen it). However, he noticed today that the banjo bolts had fuel on them, indicating that the new pipe was leaking. He's removed the pipe, and tightened the clips up even more. This SEEMS to have solved the problem, but he's worried about it, and has decided it's best to replace the pipe, and the banjo bolts to be on the safe side.

Firstly, is the inner diameter of the fuel pipe going into the filter an issue? He was told it wasn't, as the fuel system pressurises to a certain pressure and the pump will constantly supply fuel at that rate?

Secondly, what size are the two banjo bolts? One for the pump, and one for the fuel filter.

Thanks,

Tony

[phillpot]

Generally speaking bigger pipe costs more than thinner pipe, So I'd imagine neither Ford nor TVR would have not have used 8mm pipe if something smaller would have done the job?

Pressure and volume are two very different things. Stand next to a garden hose, at 3 bar, that bursts and you'll get wet. Stand next to a 6" water main, at 3 bar, that bursts and you'll get drowned!

More likely its the sealing washers on the banjo's leaking, not the bolts or fittings. Take 'em off and any decent motor factors should be able to match them.

[King Fisher]

phillpot said:

Generally speaking bigger pipe costs more than thinner pipe, So I'd imagine neither Ford nor TVR would have not have used 8mm pipe if something smaller would have done the job?

Pressure and volume are two very different things. Stand next to a garden hose, at 3 bar, that bursts and you'll get wet. Stand next to a 6" water main, at 3 bar, that bursts and you'll get drowned!

More likely its the sealing washers on the banjo's leaking, not the bolts or fittings. Take 'em off and any decent motor factors should be able to match them.

I see, I see. Hmmmm, ok. The original pipe was that heat shrink type, where it has to be heated with a heat gun so it expands, before you can push it over the banjo bolt nozzle. Obviously with the pump and filter in place on the car, a heat gun wasn't advisable ;-)

As for the washers, it could be, I think Nick's gorilla'd it all up again to be sure, but if it still leaks, he'll get new washers etc.

[junglieD]

You may remember that I recently posted about a leak from my Banjo connector from the fuel pump. It turned out my washers had degraded and tightening them didn't fix the problem. I took the old washers down to my local motor factors and bought two copper and two new fibre-based replacements. It turned out that the copper washers were marginally to large though and fuel pi**ed everywhere. The fibre ones worked a treat though and at about 10p each were a nice cheap repair. Hopefully the same thing will work for Nick.

[GreenV8S]

I wouldn't want to run the engine under load with 4mm fuel hose. That's only a quarter the area of the original, and the restriction will be increased by much more than four times due to boundary effects. If there is a problem, it will show up as fuel pressure loss under peak flow, which will result in running lean at peak power, which is absolutely the last thing you want.

[King Fisher]

It's ok chaps, he found some pipe of around 6-7 mm internal diameter, and used jubilee clips to tighten it onto the nozzle from the pump, and the nozzle to the fuel filter. Seems to have worked! Btw, is the original plastic tubing that Ford fitted to the banjo bolts a form of heat shrink diesel hose? It looks suspiciously like what they use as fuel hose on coaches......