What size pipes on petrol pump?

[FrenchAudi]

Could some kind member please tell me the sizes (inside and outside diameters) of the supply and return flexible pipes on the A4 B5 petrol pump.

[FrenchAudi]

I'll answer my own question. Supply line is 7.5 mm I/D 3 mm wall thickness, so O/D is 13.5 mm.

[Crasher]

Triple check the hose you use is suitable for use with E10 such as Gates Barricade if they do it in that size. The VAG part number is N 900 801 05 for the latest specification at £22.40 a meter. Only use squeeze band clamps such as N 024 122 2 or the hose can leak but Norma plate clamps are nice if you can get them.

[FrenchAudi]

Thanks, Crasher.

Recently the car has needed to crank for several seconds before starting, and I suspected fuel pressure leaking back via the pump check/non-return valve.

I decided that if the pump valve is leaking it would be simpler to add another check valve after the pump than to pull the pump, which is why I wanted to know the pipe size.
In the end, not knowing how easy it is to access the pump, I made a guess and ordered an 8 mm valve, which is the correct size.

I also have a fuel pressure test rig on order, but while waiting for this, the check valve arrived, so I decided to try it out while waiting.

I had a suitable length of 8 mm Gates 3225 fuel hose. It is good for 10 Bar, and at least as good as the original hose in the 23-year-old car, so I used that.

It seems to hold the pressure in the system, as the car now starts much quicker, but I will remove the check valve and do a fuel pressure test with the original setup once the test rig arrives.

This is the check valve installation. It normally tucks down out of sight below the floor level, but I lifted it out for the picture.

Check valve fitted.jpg

[FrenchAudi]

Any comments? Favourable or not, they would be appreciated.

[Crasher]

Half of me says bodge and the other says nice fix, I wouldn’t do it but it is a pragmatic solution.

[FrenchAudi]

Half of me says bodge and the other says nice fix, I wouldn’t do it but it is a pragmatic solution.

Well, I wouldn't have done it for a customer, but it saves work and expense for me. I intend checking it from time to time.

[Crasher]

Looking at the design of the pump, the check valve must be internal, on the earlier models it was a replaceable part on top of the pump

http://emea.resource.bosch.com/AA/in...000/index.html

Top marks for using plate plate clamps though, extreme gimpness

[FrenchAudi]

I'd like to call adding another check valve "lateral thinking".

My books don't mention a repairable/replaceable check valve, so I assumed I was looking at a new pump.

I will leave the present setup until I make a pressure and delivery test, then decide on the next step.............

[FrenchAudi]

I bought a Chinese made injection pressure test kit on Ebay for £47.50. It looked pretty comprehensive but turned out to cover cars only up to about 1991.

I was about to return it, but realised that by buying a couple of adapters it could be connected satisfactorily.

The adapters arrived today, and I tested according tom the specs in the Bentley manual. The kit connected nicely, and the operating pressures were spot on, but it didn't hold pressure after stopping the engine.

The pressure loss was on the fuel rail side, so I removed the clip and tried to take out the fuel pressure regulator. I managed to turn it, but could not easily remove it.

I decided not to risk damaging it without having a new one to put in, so replaced the clip and tested the leak down again.

I must have re-seated the O-rings in the FPR, as it held 3 bar after 15 minutes, still held 2 bar after 4 hours, and just started almost immediately.