Strong smell of fuel in the boot and in general

[James Agg]

Hi everyone. Another post from me as I’m very much in kit car mode right now.

 

Ever since I got my RH S7 Mk 2 it always had quite a strong smell of fuel coming from the boot. There isn’t really any boot liner to write home about covering things like the sender, the neck and the breather, presumably because this car was built pre SVA. The problem I’m finding also is that the smell of fuel gets really quite strong when I go around corners and takes a very long time to clear and the problem seems to get less intense as my tank gets used. 
 

I have multiple suspicions of the cause based on this. I initially suspected my sender as I found that the send and return union welds had broken and I imagined that some fuel might have been seeping from these broken welds. I replaced the sender as my gauge wasn’t working and this fixed the gauge, but I was hoping I’d kill two birds with one stone, but alas, the fuel smell is still potent, particularly after fill up. The carb air filter gives off a slight fuel smell, but nothing on what is in the boot…

 

I’m chasing multiple possible issues that may be causing this and I’m thinking that given the age of the kit, I’m considering all new lines, electric pump to replace mechanical (mech pump possibly leaking slightly), new pressure regulator, an overhaul of all things carb and seals if not an upgrade someday. I am however having a head scratcher with the fuel filler and breather setup that I suspect to be the main culprit. I feel fairly certain that this is where the majority of the boot smell is coming from given that the problem is worse on a fuller tank and going around corners - perhaps the breather and/or the neck and accompanying seal have a leak? The problem is, these are standard Sierra, and given the age of my fuel tank, it only has a hole for the filler neck grommet to go into, which then receives the standard Sierra plastic neck. As for the breather, it doesn’t appear long enough to route fully home onto the tank union which may well be the biggest issue. Does anyone know where one might get neck, breather and grommet replaced or fabricated without paying RS Cosworth tax? Alternatively something that works instead of? I notice that newer tanks have a shoulder for a generic neck to slide and jubilee clip onto. I would have one of these welded on if it weren’t so dangerous to weld a fuel tank… Reluctant to go down the route of a different tank if I don’t have to given that I don’t really know what would fit and of course the cost if it’s not a necessary one. Anyone had the same issue with a MK2 tank setup? Keen to get to the bottom of it all as my wife and I are tired of being high on fumes 

[AndyW]

Hi James,

I can’t help you with the details of the tank in your Mk2, but I had a similar strong smell of petrol in my Superspec, which has a Fiesta Mk4 petrol tank. It was most pronounced after filling the tank and on acceleration and cornering.

I discovered 2 problems. The tank has a small 5/8”? rubber breather hose, which on my car was only about 20cm long and just stopped at tank level in the boot area behind my head. Under movement of the car with a full tank, petrol was coming out of this pipe and just running down behind the seat panel. Secondly the main filler hose and petrol cap wasn’t making a good clamping seal on the back panel, and again petrol was flowing back up the filler pipe on acceleration and running down the rear stainless panel.

My solution was to replace the fuel filler cap with a new better one with built-in tube, and also to put in a new longer breather hose that feeds back into an alloy tee into the filler hose. So more of a closed system with less openings to the air.

My Fiesta tank has stub tubes for the main filler and breather so it was easy to check all joints were tight. Not sure what you can do with the grommet to better seal the Sierra tank hole. 

[James Agg]

Yeah I think this could be much of what’s going on with mine too. My breather goes from the neck to a flared union on the tank right next to where the filler neck passes the grommet into the tank and it looks to be too short and so perhaps not creating a good seal around the flared end. Not an easy part to source as the Sierra ones will all likely be too short also as I don’t believe mine was cut down, and to make matters worse, the breather pipe has different inner diameters at each end and so it may be that I have to find somewhere that does custom made fluoro lined silicone pipe work. Where the neck/fuel filler orifice screws onto the back panel of the car, it all looks a bit bodged currently. Now to figure out all that I need and where to get it. I have found a replacement grommet but it’s billed as for an RS Cosworth (same part number) and of course £45 for a relatively simple ring of rubber. I guess I’ll have to dig into my pocket for that…

Edited June 15, 2023 by James Agg

[Sparepart]

I also had petrol fumes at the rear using the RHE supplied "box" type tank with the Sierra filler pipe rammed through the hole in the tank using the Sierra rubber grommet. As you say a new grommet is expensive, and didn't work too well. Now I am rebuilding the car, and have made a large bore filler flanged SS pipe to bolt onto the tank, and cut back the plastic Sierra filler pipe below the breather to allow for a flexible connection to the new pipe on the tank. I attach some photos of what I am hoping will fix the problem.  There is an inner ring with a slot that has nuts welded to the lower face (not visible in snap) this was carefully manoevered into the tank and the flanged pipe sealed and bolted down with a cork gasket as shown. So there is no attempt to weld anything on the thin SS of the tank, all the welding is the flange to the pipe, which I did with MIG (should really be TIG) but I have tested its "Petrol tightness" by bolting it to a flat plate and filling the pipe with petrol and checking for any signs of seepage, left overnight without problem. I am also hoping that this will cure the other problem I had, that of having to fill the tank very slowly lest petrol climbing in the filler neck shut off the fuel pump at the filling station.

[James Agg]

Nice work Sparepart. I very much like your solution. I would do the same except I have three problems. 
 

1) I do not possess a welder

2) I’m no great shakes at welding - I’ve only done it once in my life a very long time ago

3) My tank seems to have something yours doesn’t which is the flared metal nozzle for the breather pipe bolted into the tank right next to the hole containing the filler neck and the grommet, meaning that I wouldn’t have the space around the hole to do this. 
 

I imagine with your setup you could use a completely fresh filler neck hose and fresh cap and orifice solution rather than sticking with a butchered Sierra one, although your solution is pretty neat for using the original bits there. If I found a way around the problem of the metal breather nozzle at the tank end that enabled a bolting of a metal shoulder like you’ve done, I would consider changing the cap/orifice setup just so that I could have the breather nozzles matching in diameter at both ends as that would mean ditching the Sierra breather pipe that has different sizes at each end. Not a straight forward solution… I imagine you had to drill into the tank for your screw holes/rivnuts (or whatever you used.) That’s pretty nerve racking with the whole fuel vapour risk and of course ensuring that the tank goes back together swarf free.

[Sparepart]

Since I have been totally rebuilding, I have removed the tank and washed it out with detergent, so I did the flange work during this, all debris was washed out and also vacuum cleaner round interior of seams. Now, if you are going to buy the Ford fuel tank grommet, I don't think that you need to pay the £45 quids that you mention. I did some deeper investigation. If you start with a Ford parts catalogue (link below) you can find that a Mk1 Sierra fuel tank grommet has two possible reference numbers, i.e.

72GB9072AB  and 1492183      and also you can see that this part was fitted to other Ford cars, Granada, Escort, even Ka I think, anyway it's the part number thats important. Then if you Google something like "Ford 1492183" you will see that a grommet can be obtained for around £16.  Below I include a link to the online parts catalogue I used (Select Sierra Mk1, and then scroll down to the section on petrol tank, then look at the diagram and see the grommet item number 10, then follow the link on the right to the part information that shows description and other Ford cars to which it was fitted). Below there is also a link to one of the £45 offerings, and you can see that in details they show the part number as just "149" which I think must be on purpose to obscure the full part number from web search...... or am I being cynical. Also a link to a cheaper provider of the same part.  I hope this helps.

https://www.fordopedia.org/

https://www.ebay.co.uk/itm/125331672244

https://www.ebay.co.uk/p/1709767924

 

 

[James Agg]

That is all amazing! Thanks! Much easier to find parts referenced for a KA. I think my sender grommet is the same in that the sender rests on the top of the grommet inserted into the tank hole, and then it’s bolted down to form a tight seal. The grommet was not looking all that great when I changed the sender, so I could use one of these for the sender in any case, just to be belt and braces.

 

Re your filler neck fabrication, I’ve found a pre-made one…

https://www.carbuilder.com/uk/fuel-filler-neck

I might try what you’ve done with this, or possibly take it to a welder given that I have the complication of needing to avoid or even move the breather nozzle. Do you happen to know if the standard RH tank dating back to the old monocoques is aluminium? Or is it stainless? It looks a bit too shiny to be aluminium, but then again, it might just be highly polished

[dandan62]

Just to answer your last question,  my stainless monocoque RH has a stainless fuel tank which was standard I believe. 

[Sparepart]

I bought an Exmo, it has a SS tank, and as dandan says the RHE tanks of this era were SS, just plonk a magnet on your tank to confirm. In which case welding on the alloy neck is not possible. You might consider bolting it on though. I see that Burton Power sell various sized pre drilled and nutted rings that can go inside the tank. They are designed to go with their Aero filler caps..... so not in the tank in their application ..... but they have welded nuts and are "horseshoe" type so could go inside a tank. The link below is to their catalog page, at the bottom, I think the ring for the 2.25 inch cap might do. You can buy a sheet of nitrile/cork gasket material and cut your own gasket. Anyway just a thought, would need more detailed investigation.

https://view.publitas.com/burtonpower/2023-catalogue-pages/page/58

 

[HAWKNORTH]

Re the above comment about stainless steel and magnets. Some grades of stainless steel are magnetic. Ferric stainless, as per the body used for the stainless mono robin hoods for example. Pure stainless is non magnetic. Never tested the tank on my 111A to be honest. You can weld stainless but you need someone who knows what they are doing.

[James Agg]

All superb info chaps. Thanks. I will start to formulate a plan, do a proper wrecky of the job and then see how I get on. Will keep you all posted on how I go