Fuel Leak

[Tintin]

I have a suspected fuel leak on my "new to me" Series 1 4.2. There is the usual slight smell of fuel (together with oils, solvents and other general workshop smells) in the garage every morning but on opening the boot of the car the smell of petrol vapour is very strong indeed. I have had the boot floor and side panels out, checked over the pumps, filters (recent set up by previous owner) and the glass bowl valence filter and the hoses; I have wiped my fingers over all joints and fittings and checked the security of all connections; I have inspected underneath around the tanks and pipes - but can pick up no evidence of a liquid fuel leak.

If a tank is leaking I would have thought that the smell would have been greater outside the car than in the boot.

I am now stuck for ideas - is this a problem others have come across? Any suggestions gratefully received.

Robbie

[ptjs1]

Robbie,

Two suggestions:

Check for any perishing of the tank to filler pipes. This can sometimes be difficult to spot.

Fuel vapour has an annoying tendency to permanently stick to fabrics from any previous leak. Remove any boot carpets or mats etc, air the boot then check over coming days.

Good luck

Paul

[mike020150]

When checking all the pipes, don't overlook the vent pipes. Whilst you are checking, make sure they are clear and not blocked with general debris. Mike.

[Tintin]

Thanks both for the suggestions. I will post a conclusion when I finally get to the bottom of it.

R

[oldtimer]

Hi Robbie,
Although mine is a V12 with extra hoses I have frequently had the smell of fuel in the boot. I have owned this car for about 40 years and am now on the third set of SU fuel pumps mounted in the boot. The last pump change was about two years ago. It was at this time I discovered that the rubber fuel hoses had set like concrete making it impossible to tighten the hoses on to their respective stub pipe connections. I ended up changing all the hoses in the boot together with the steel braided hoses under the bonnet. Is the smell there any more - blowed if I can remember.
Any replacement hoses must be ethanol complyant - too late tonight - past my bedtime - but will give you my supplier details if you require them.

A pipe which is subject to corrosion and gets sadly neglected is the feed pipe from the tank into the boot. This pipe passes through the tunnel in which the rear silencer sits. I cannot remember if it passes above or below the tail pipe of the rear silencer. Hope that makes sense ! Worth a look at .

Several arrangements of tank venting is used over the course of time which needs looking into but not tonight

I hope that helps a little

Oldtimer

[Tintin]

Thank you for your input OT. I am working through a process of elimination. Last weekend I tore off the duct tape sealing the holes in the valence panels between the boot and tank cavities. The air in the tank cavities was fresh - so I don't think it is a tank or tank fittings problem. Then I made up an airtight tent of polythene and stuck it down to cover the O/S pump, filter, glass bowl and associated pipes. Next day - same strong smell. Yesterday I made up an airtight tent to cover the entire spare wheel well and all fuel components. This morning the smell is still there but less.

The pumps filters and hoses were replaced in 2011 except for a short steel braided hose linking the glass bowl filter (also not replaced - but see elimination process above).

I am now focussing on the filler caps (vapour smell around O/S cap) and will fit new seals "O" rings and gaskets to both caps when the parts order arrives later this week. Will also take opportunity to dismantle, assess and clean the two way vents in the filler caps.

In the meantime plenty to do - firstly cleaning up one of the filthiest engine bays I have ever seen!

Robbie

[oldtimer]

Hi Robbie, You seem to have this job well in hand, just a case of perseverance I suppose. I have a new pair of rear silencers to fit and was weighing up the job today, Whilst there I looked for the fuel pipes that pass from the boot through the tunnel in which the silencer hang and then out to the fuel tank. These pipes pass beneath the silencer tail pipe and hidden behind a lip in the lower panel. In my case they are buried in underseal or maybe silicon sealant. As I said earlier, may be worth a look.

I don't believe the tank caps would have any bearing on that fuel smell in the boot but certainly agree with examination of the two way vent valve in the cap to ensure correct operation. Although usually perfectly serviceable the rubber seals simply sticks to it's metal seat and needs lifting to release.

Good luck
Oldtimer

[Tintin]

At last I think I'm there - and it has been a learning curve! In the end and after much fruitless investigation I bought a combustible gas detector; this handy piece of kit quickly identified the issue as porous fuel hoses. No liquid fuel was visible - only the vapour coming off the rubber was detectable. I was surprised because I had only a couple of months previously changed the hoses - I got the replacements from a well known specialist fuel system business, the same place I sourced the replacement SU pumps and I never thought to question the suitability of the hose supplied. Much has been written about ethanol compatible hoses on the board and I kick myself for not questioning the supplier on this point.

Once I identified the source I did some research. What was supplied and I fitted was R7 hose; the ethanol compatible hose is R9. R7 can allow 30 times more hydrocarbons to escape than R9 - the R9 limit is 15g/sq.m. per day.

The other thing I am doing is making up additional metal fuel pipe to reduce the R9 hose and therefore the vapour loss into the boot to a minimum.

I can recommend a decent combustible gas detector as an essential aid to tracing difficult to find fuel leaks.

Robbie

[alec2824]

That is a worrying find! That means that ALL "rubber" fuel lines are prone to excessive fuel vapour build up unless of the latest ethanol resistant material. There are millions of vehicles out there with this potential problem - including mine!

[oldtimer]

Robbie,
A most enlightening thread. Your determination to track the problem is of benefit to us all with the Series XJ's. You have given me cause for concern as I have replaced all the boot and under bonnet metal braided hoses within the last couple of years. My reason for changing them was because they became rock hard with age. I was assured at the time that the hoses I purchased were Ethanol compliant but at this stage I am unsure of that validity --- will need to do some checking.

I did chuckle at the description of the devise you bought, namely a combustible gas detector. On first reading, it sounded as though it blew up if it found vapour . So it is a detector of combustible gases . I've never seen one of these, perhaps you would bring it along to Kemble .

I can see the merit of replacing the rubber hose with metal tube as far as its practical, While you are at it , it may be worth replacing the metal feed pipe that links the base of the fuel tank into the boot. This pipe is prone to corrosion were it passes beneath the exhaust tail pipe

Thanks again for the information
Oldtimer

[Tintin]

Thanks, OT. Your focus on the correct use of English is well taken and reminds me of the example my old English master used at school:- "The car pulled up with a jerk. The jerk got out".

Robbie

[Tintin]

Well, that didn't go as planned at all!

I fitted R9 hose which was an improvement but by no means a cure for hose permeability. Further research turned up Gates Barricade hose which I have now fitted and does appear to have cured the problem of fuel vapour in the boot. The following link to the Gates site may be of interest when choosing fuel hose for any particular application:- http://www.gmcmhphotos.com/photos/data/ ... _Final.pdf

Robbie

[Jaginblack]

Hi
I'm new the club,and the site.
I purchased a series 3,4.2 ,a few months ago. It's only running on one tank,the N/S one which is new,I will sort out the other one in time.Also I was getting a strong fuel smell inside, no visible leaks.
Then back on a very hot day a leak appeared ,the rubber hose from the tank to the line.i have used some braided fuel hose.
Now after reading the posts,I'm not sure which hose I should use?
Also the last time I parked it up I had approximately a1/4 of a tank of fuel showing on the gauge. I didn't get to use it for about 3 weeks,when I did the gauge was showing empty ?
Any advice would be much appreciated.

[Tintin]

Hi Jaginblack

I am not intimate with the Series 3 fuel system so my comments may be of limited value to you but the following may help.

Any "rubber" hose you use must be "Ethanol compatible" for long term safe use. Not all ethanol compatible hose deals with the issue of vapour permeability. "Barricade" hose does address the issue of vapour permeability and should be used where vapour (smells) may otherwise build up in confined spaces.

The issue highlighted in the above thread is the smell of petrol in a confined space caused by porosity of the hose - the hose does not actually leak liquid petrol but gives off vapour. If you have a liquid leak, that suggests mechanical failure of the hose/fuel line components (replacement required).

Loss of 1/4 tank in 3 weeks suggests a significant liquid leak or inadvertent transfer of fuel from one tank to another (covered in another thread).

Robbie