Disappearing Fuel

D

Duke

New Member
So, Duke has quite a strong fuel smell when parked so gonna look closely at the filler hose and tank but the biggest issue I have is fuel apparently disappearing when parked, but no pools on the floor or obvious leak. And we’re talking reasonable quantities!
Any clues where it could be going? I realise that’s not a lot to go on.
Also the fuel pipe is flexible hose from back to front. Any disadvantages to that? If not I’ll just replace it all with similar.
Thanks in advance.
 
I have the same issue but mainly when driving. My fuel goes down at a rapid rate. I'm averaging 12.5mpg.
 
Seriously though. How long are you parked for? The tank is open to atmosphere so you will loose some through evaporation.
If you have a leak you may not see it on the floor as it will evaporate.
Check all your fuel hoses, connections and tank for leaks. If you have a steel tank I would bin it and fit one of Tim (Commerracer) aluminium ones.
 
Have you got a silicon elbow on the tank? Some of them are only suitable for vapour and when flooded in fuel they weep. It wouldn't account for noticeable losses but has caught several people out with strong fuel smells.
Make sure the tank breather pipe isn't kinked. If it is the tank can pressurise and push fuel out of the filler neck.
Also check the sump and make sure it's not filling with petrol due to a leaking fuel pump diaphragm.
 
PaulJL said:
Seriously though. How long are you parked for? The tank is open to atmosphere so you will loose some through evaporation.
If you have a leak you may not see it on the floor as it will evaporate.
Check all your fuel hoses, connections and tank for leaks. If you have a steel tank I would bin it and fit one of Tim (Commerracer) aluminium ones.
Click to expand...
Lost just under quarter of a tank in about a week. I’ll check oil level/ smell this morning as it’s only about 3 weeks since an oil change so petrol ought to be obvious. theres no real seal on the filler cap. Should there be?
and I’ll check elbow and breather later too.
Thanks for the suggestions.
 
Yes there should be a seal
The other thing that could affect the level on the gauge is the voltage regulator that supplies the instruments. You should be getting a constant 10 volts to the gauges, if the regulator is faulty then the gauge would rise as the voltage increases, try starting the engine and see what happens to the reading after a few minutes.
 
So had a look today. Appears there’s an Ali tank with blue silicon elbow. Fuel pipe starting to crack a little along the length from the tank but not obviously weeping. Smell really strong around rear corner . Checked oil. Not overfill and no smell of petrol so think pumps probably ok.
got an SU carb and there’s a loose pipe that goes nowhere. So need to check what the SU plumbing should look like.
Gauge seems pretty steady, certainly didn’t go up while driving, although does seem to drop between starts so that could be a voltage thing.
I’m thinking evaporation is the main cause so I’ll find a fuel cap seal as a starter.
thanks again for all the suggestions.
 
Pankys covered most things - that pipe on the SU is the overflow if the float gets stuck so should be routed away from anything hot. Would only overflow if running though. The rear elbow as Panky says if blue is very likely for fuel vapour and not for sitting in petrol also the flexi filling pipes they sell only last a year or two before the same happens - the vans really smell of petrol from a few feet away - I’ve been through both types! Need a proper filler pipe made for liquid petrol contact, about £25. since fitted the correct one to mine no whiffs after two years!
Just on the regulator they do lots of funny things when faulty so worth changing to an electronic one - about £5 and a very simple fix, if faulty could also be affecting the temp gauge so worth changing
 
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Gonna be really dim now. Where will I find the voltage stabiliser? Cos for £8 that’s got to be worth the investment.

And is the blue elbow the wrong one? I thought from an earlier thread I’d read that blue was the good one?

I found a few SU diagrams on MG sites. The overflow pipe is far too short. So that’s something else.
 
So think I’ve found 1 cause of the smell. The breather pipe isn’t attached to the tank! Guessing that’s not right.
Does anyone know what diameter hose it should be so I can get a new bit.
Thanks again.
 
I do think the blues are problematic and used for vapour only for turbo intercoolers so fuel resistant not proof - tend to be blue to look nice under the bonnet. I had this issue and was ok for a year then smelt very strong of fuel without any obvious cracks - took me ages to find the source. If the van smells at the back it’s likely the fumes coming through the silicon. Obvs can’t be sure without knowing where it came from.
stabiliser will be behind the dash maybe - sometimes mounted to the gauge itself with an earth and should look like below if original.

SU overflow is like this on my Hif44 SU, the top long pipe is overflow, bottom is fuel in and the stubby one is blocked off, maybe that’s the one you mean, could be for emissions to feed the crack case fumes back into the engine for reburnimg? :)
 

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commeracer said:
Breather hose is 1/2" or 13mm, and should be attached to the tank.
Click to expand...
Cheers. I thought there was a strange short “overflow” coming from the filler and have just realised tonight that it should be attached to the tank. I think it’s one of your tanks by the look of the pictures.
 
Voltage stabiliser is down below to the left of the dash pod and is attached to the support plate that holds the parcel shelf up. It's the plate that looks like it's got a speaker hole in it and the reg is attached by a screw it the top front of the plate.
Definitely ditch the blue elbow and get a fuel proof rubber one from Speedy Spares
 
Panky said:
Voltage stabiliser is down below to the left of the dash pod and is attached to the support plate that holds the parcel shelf up. It's the plate that looks like it's got a speaker hole in it and the reg is attached by a screw it the top front of the plate.
Click to expand...
I’ll look for that tomorrow then. Never seems to get super warm on a run so might be onto something.
 
yer the old ones are rubbish anyway - I think they work by constantly switching 12v on and off to give close to 10v - the fuel and temp gauges move up really slow so you don’t see the needle waggling around everywhere :) electronic ones are much better
 
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