2500M: fuel leak from filler neck?

[Renaldo]

Guys, I normally fill the tank right up, such that fuel is visible in the filler neck.

First time ever, looking at the rear of the car, I noticed fuel splashing down, onto the pavement. It stopped in short order, but I found it a bit disturbing.

The car is in my garage now, and no evidence of any fuel leaking.

I'm guessing this is probably a leak from the filler neck. Does this sound right?

If I need a new filler neck, is this an easily located part?

Ron

[heightswitch]

It'l be your vent pipe overflowing?
N.

[Renaldo]

Guys,guess my mechanical ignorance is showing.

So, the fuel may simply have been coming out the vent pipe? In other words, all may be well?

Ron

[phillpot]

Could well be the overflow if you "brimmed" it or might just want a turn on the "Jubilee" clips that hold the rubber pipe between tank and filler neck?

[Cerberus90]

Most likely, I wouldn't fill it so full you can see fuel in the filler neck. Any sort of corner and you'll probably find that more will come out too.

We had to bung the vent pipe up for a few laps at a trackday once as we got told we were leaking fuel, once the level in the tank was down a bit, we didn't need it. Obviously you don't want the vent blocked up all the time as the tank will just want to crumple as there's nowhere for air to get in to replace the fuel.

[Renaldo]

Thanks guys. I'll take a look at the clamps to make sure they're tight.

And be a little more careful about filling it so full.

Ron

[Adrian@]

IMHO the lower connection onto the tank should be double opposed clipped, and the second should be as close to the top of the neck as possible as as to stop fuel from sitting in the gap between the rubber and metal and weeping past the the crimped part of the Jubilee clip.
Adrian@
Double/triple the length of the vent pipe by taking it up into the inside of the rear wing and then back to the outside of the car.

Edited by Adrian@ on Friday 1st November 19:52

[prideaux]

Not unusual
During the LBL we had one of the Slevio pass photo guys that take pictures of those coming up approach us at the summit as he was concerned we where leaking fuel however we where taking the corners rather fast and as we went round left handed corners there was fuel coming out of the vent pipe did not help with fuel consumption
A

[jastx]

I see from your profile your 2500M is a '74, so it has the larger gas cap? My '77 has the later, smaller cap. I get gas leakage down the side of the car when gas sloshes around in the tank. The cap appears to be sealing tightly. I can't identify how or where it is leaking.



I suspect it's from where the cap is joined to its metal filler neck. The cap base curves down about 4 mm into the neck. I can feel a gap between this curved down piece and the neck. I'm thinking of applying JB Weld into that gap to seal it.

Edited by jastx on Monday 4th November 05:26

[Renaldo]

John, in my case, I've only noticed the fuel flowing out on the one occasion: when I last filled the tank to the bottom of the fuel filler neck. It surprised me, because that's how I always fill it, and I've never noticed fuel leaking out before.

Here's a picture of my fuel cap. Is it the larger one, as you've described it?

Ron

[jastx]

Yes. I owned two '74 M's back in the 70's with that larger cap (I prefer it). Never had a problem, but the cars were only a few years old then.

Edited by jastx on Wednesday 6th November 05:18