Fuel smell through air vents S2 ABY

[grim]

Just recently I've noticed quite a strong smell of fuel coming through the blowers when I'm stationary, but not when I'm moving. Under the bonnet it doesn't smell of fuel at all and the whole system appears dry. Under the car, around the fuel tank etc are all odorless. The only place it smells is coming through the blowers when I pull up to junctions, lights and stationary traffic.

Any idea's/advice about things to check.

For reference it's a fairly standard aby avant. Only mods are a milltek and homefries chip, everything else is stock.

[UrS4boy]

You have an engine bay fuel leak. Look again and look harder.

[driftin jo]

Have you looked under the car at the fuel line just back from the firewall ?

[grim]

I'll jack it up in the morning and get underneath to have a look where you suggest Jo. It seems odd that it smells as strong as it does in the cabin but not at all outside the car or in the bay.

[Rikki Kitto]

This happened to my mates sirocco years ago then smoke then flames, he left the car burnt out on the sea front went to pick it up the next day with a truck and the burnt out shell had a parking ticket on it

[UrS4boy]

Water Box (Cowl scuttle) drains and engine odours

I'll jack it up in the morning and get underneath to have a look where you suggest Jo. It seems odd that it smells as strong as it does in the cabin but not at all outside the car or in the bay.

If the B3/B4 water box (cowl scuttle) is anything like the C4 one, there is at least two vents at the bottom to drain water. The C4 has a rubber duct bill drain seal on one of them that tends to clog with leaves and back rain water up until it spills through holes into the passenger cabin. In a LHD C4, this will drown and potentially kill the ECU. As a result, lots of UrS owners remove that duck bill drain seal, leaving an un-obstructed hole between the water box/cowl scuttle and the under carriage of the UrS (and probably B3/B4).

"So what?" you say? The problem is that the "fresh" air for the HVAC system is drawn from the water box/cowl scuttle. Without that duck bill drain seal, the HVAC fan can draw air in, not only from the base of the windscreen but also through that drain hole. "Conveniently" (NOT) that hole is above things like down pipes and fuel lines. As a result, smoke from oil dripping from the back of the head (bad cam cover seal) landing on the down pipe and burning can be drawn into the cabin, especially when the vehicle is stopped (no air movement to blow the smoke away). On this basis, the same thing could happen with a leaking fuel line just under the firewall, just below the water box/cowl scuttle.

More C4 Water box drain info (would be similar for B3/B4):

http://forums.quattroworld.com/s4s6/msgs/92899.phtml

[newsh]

Of course on the ABY the plenum drains go left and right into the wings. The only thing in the middle is the wiper motor.

Probably still a leak in the fuel lines at the bottom of the firewall or further under the car though.

[bluequattro]

Look behind pipe clips-they rust there and of course can't be seen till your wife rips the pipes off on a box she reverses over.
Guess how I know that?!

[Donald Smith]

O.K., this is way out there, but a defective FPR will allow gas to enter your vacuum line in your ECU, which is above the passengers feet(inside the cabin). Someone with a good nose, will smell the gas(ask me how I know)

[grim]

All sorted. It was a small hose coming off the back of the FPR had worn almost through where it was touching some other pipework. Changed that small length of hose and it's all good!

[Bowie69]

Small as in vacuum hose?

If so it shouldn't have fuel in it, if it has, the diaphragm has split.

[UrS4boy]

Fuel Pressure Regulator info

Small as in vacuum hose?
If so it shouldn't have fuel in it, if it has, the diaphragm has split.

Fuel Pressure Regulator info: http://forums.quattroworld.com/s4s6/msgs/21108.phtml

[grim]

Hmmm. Well I'm no mechanic, I got my friend who is to check it out for me. He may not have called it the fpr I thought he did. It's in front of the throttle body by the fuel rail. Has a solid line coming out of the front and doubles back to a hose that's attached to a solid line that goes across the bulkhead. That appeared to be the culprit. Nothing else was damaged, wet or showing any signs of leakage.

Edit. After reading the link posted above, it must be the return to the tank that was leaking. It was such a small amount though it could only be smelt and not seen.