Fuel leak on full boost?

[nefarious]

OK I posted a little while ago about my 900's unwillingness to boost beyond the orange (despite the fact that it was happily doing so up to a couple of weeks ago).

Now I've got two new pieces of evidence to solve the problem, so if anyone can help me shed any light on this it would be most appreciated...

When boosting to the top of the orange there is a strong smell of petrol. Also, after running on the motorway for a bit, boosting in 5th the temperature was creeping up beyind the half way point.

Now the overheating would, to me, point to running lean, which I s'pose would be fitting with a petrol leak, which would fit with the smell. BUT, there's no obvious leak from around the fuel rail/FPR/injectors. Where could it be leaking from that it would only do it on full boost?

[Alex]

You could test for the leaks by pressurising the hose that runs to the FPR using a foot pump or similar.

[nefarious]

Is the hose before the FPR at constant pressure, or does it vary with demand for fuel?

[gerryp]

The fuel pressure regulator makes sure that the fuel pressure stays a fixed amount (2.5, 2.8 or 3 Bar) above the pressure in the inlet manifold. So as the boost pressure goes up so does the fuel pressure.

Thus a small leak may bcome apparant on full boost 'cos the fuel pressure is also higher.

When this gets on the hot engine it will stink the car out.

I would suspect the banjos, sealing washers and fuel pipe as it joins the banjos.

Best of luck 8)

[900 spg]

Hi,
I would check the 90 degree hose going into the fuel rail. This hose developed a leak on my 1987. It leaked slightly under full boost but was otherwise fine. It was difficult to figure out as the leak was minor. However, note that fuel spitting on a hot engine could be a major thing. This is really easy to replace and you could even attempt it if it has not been done already. the usual story of old hoses, etc.

best regards

dusan

[Willy Wonka]

I would start by presurising parts of the system as mentioned. The small line that feeds both the presure sensor and switch, should hold pressure. If it does not then the leak would be direct to the inside, leading to strong smells and screwed up presure readings.

[nefarious]

Found the little bugger. As a last ditch attempt to solve the problem without having to dismantle and pressure test, I took the car for several full boost runs, stopping after each and sniffing along the pipe. Turned out to be a small split in the hose where the fuel line meets the FPR. Put a whole new pipe on and some proper hose clips.

phew...let the modding continue.....

cheers for the help guys...

[gerryp]

Congratulations - er, if you've got any photos of the test procedure we could publish them, I'm sure they would be edifying. (cackle)