Fuel leak

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MorrisJohn
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Fuel leak

Post by MorrisJohn »

I replaced the fuel pump today on my Minor with a reconditioned original SU unit. It was straightforward enough, although there was a slight leak rising up through the threads of the outlet union that persisted despite a new washer within it and it being nipped up as tight as I dared. Anyway, I searched the forums historic threads for this issue and then used a little PTFE tape on the threads and the leak was cured.

I checked the thing thoroughly for leaks before taking it a test drive and didn’t see any.

Two miles into my test drive on country roads, with my young daughter in the car that wanted to come along for the fun, for some reason (I don’t know why, the car was driving absolutely fine!) I decided to pull into a lay-by to double check everything before getting up to higher speeds. I’m glad I did.

When I popped the bonnet with the engine running I immediately saw petrol [Don't swear or you will be banned - Admin] out of the top of the float chamber on the carburettor. I immediately killed the engine and wiped up the petrol.

Now I must say it’s never leaked before and I didn’t touch it when I was doing the fuel pump job!

I removed and inspected the, fairly new, fuel hose which was good as expected. I refitted it and ensured the jubilee clip was nice and tight. The engine wouldn’t start after this and again I saw quite a bit fuel coming from the top of the float chamber. I then called the RAC in case I couldn’t get it fixed myself.

I then removed the top of the float chamber (first checking it was securely tightened on - it was) and saw it to be full of petrol. The switch on the lid appeared to be in decent order. At least visually. I flicked the switch by moving the float chamber up and down a few times and then refitted securely.

When I put the ignition back on after that the leak was completely gone and the engine fired up as normal. I revved it and checked for leaks, there were none. Cancelled RAC. Since I was so near to home I drove it back…on checking again at home there were no further leaks.

Have any of you encountered this before? I suspect there is perhaps a problem with the switch on float chamber lid that has caused fuel to continually be pumped in there despite it being full?

As a side note my float chamber has always been a little loose. It can move from side to side by hand quite easily, despite the bolt that secures it to the carb being nipped up. All the fuel connection points are tight though and as said I’ve never had a fuel leak before. I find it curious that it’s happened when I’ve fitted a new fuel pump…but I’m confident the “new” part is good given where I sourced it.

Finally, from now on I’ll keep a fire extinguisher in both my classics. Just in case!!! Someone up there was looking out for me today.

EDIT: Apologies for my “swear word”. I consider the word used to perhaps be a little crass, but not actually a swear word, hence the use. Insert the word “pouring” instead.
Last edited by MorrisJohn on Fri Jul 22, 2022 10:45 am, edited 2 times in total.
A bad day with my Volksie still beats a good day at work!

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philthehill
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Re: Fuel leak

Post by philthehill »

The switch in the float chamber lid is actually designated the float chamber needle valve.
The needle valve is prone to leaking and may need to be replaced after prolonged use.
The needle valve can now be replaced with a Viton tipped needle which is better when using E10 fuel.
https://sucarb.co.uk/float-chambers-spa ... 096in.html(currently out of stock).
I would recommend that your needle valve is replaced with the better quality Viton tipped item.
The float chamber has some movement designed into the mount which helps alleviate fuel vibration which can lead to variation of fuel levels in the float chamber.

mogbob
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Re: Fuel leak

Post by mogbob »

ESM seem to have it in stock : -
https://www.morrisminorspares.com/fuel- ... 01-p830595
Bob
philthehill
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Re: Fuel leak

Post by philthehill »

The ESM needle valve has a different part number to that shown in the Burlen Minor SU parts list !!
The difference is that the SU needle valve offered by ESM is spring loaded. That shown in the Burlen parts catalogue for the Minor is not spring loaded.
https://sucarb.co.uk/float-chambers-spa ... oaded.html
See also that the size of the needle valve can be different. 0.070" or 0.096"
https://sucarb.co.uk/carbspec/carburett ... s/id/1907/

MorrisJohn
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Re: Fuel leak

Post by MorrisJohn »

Thanks very much gents. Every day is a school day.

In practice what difference would running the ESM kit make versus running the Burlen one? And what difference would the needle valve size make?
A bad day with my Volksie still beats a good day at work!

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philthehill
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Re: Fuel leak

Post by philthehill »

It should not make much difference.
Personally I would fit the valve that is listed by Burlen Fuels. They are the experts and successors of SU carbs.

MorrisJohn
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Re: Fuel leak

Post by MorrisJohn »

philthehill wrote: Fri Jul 22, 2022 7:50 am It should not make much difference.
Personally I would fit the valve that is listed by Burlen Fuels. They are the experts and successors of SU carbs.
Thanks again Phil. I’ve submitted a back order enquiry. Once fitted I’ll update the thread with the outcome.
A bad day with my Volksie still beats a good day at work!

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kevin s
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Re: Fuel leak

Post by kevin s »

we had the same, fitted the viton tipped valve and it was better but did it occasionally still, ended up fitting a filter king pressure regulator and it has been fine since. Ours does have some sort of aftermarket fuel pump though.
MorrisJohn
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Re: Fuel leak

Post by MorrisJohn »

kevin s wrote: Fri Jul 22, 2022 1:10 pm we had the same, fitted the viton tipped valve and it was better but did it occasionally still, ended up fitting a filter king pressure regulator and it has been fine since. Ours does have some sort of aftermarket fuel pump though.
That’s interesting Kevin. Is the king pressure regular just fitted in line between the fuel pump and carburettor?

Is this what you fitted? - https://www.scparts.co.uk/sc_en/fuel-pr ... 22594.html
A bad day with my Volksie still beats a good day at work!

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philthehill
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Re: Fuel leak

Post by philthehill »

The Filter King fuel pressure regulator and filter is a good investment.
I have one fitted to my Minor as I need to regulate the fuel pressure to the twin 45 DCOE Webers.

MorrisJohn
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Re: Fuel leak

Post by MorrisJohn »

For the benefit of anyone reading this in the future. I found this on the SU website. Some of it has already been covered…

“Assuming that the float height setting is correct, the normal cause of flooding is a small amount of dirt (i.e. rust) lodging in the float needle valve, preventing it from closing. Fuel continues to fill the float chamber, eventually overflowing or ‘flooding’. The cure is to remove the float lid and clean out any dirt from the fuel line/needle valve and reassemble. The main cause of dirt in the fuel is from residue or rust in the fuel tank. A temporary fix would be to fit an inline filter but a clean tank is the only real solution.

Another cause of flooding, often mistaken for an over high fuel pump pressure, is caused by air trapped in the float chamber. When fuel is fed into the float chamber it rises and the float shuts off the needle valve. If, however, the chamber air vent is blocked, the fuel rising compresses the air in the chamber and fuel is forced out of the jet at pump pressure.

There are several different methods of venting the float chamber, from a simple hole in the lid to overflow pipes, all of which can be blocked in various ways. If in doubt, loosen the fixing of the float lid just enough to allow air to escape and see if this cures the problem. If it does, then hunt down the blockage and remove.“
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oliver90owner
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Re: Fuel leak

Post by oliver90owner »

It was straightforward enough, although there was a slight leak rising up through the threads of the outlet union that persisted despite a new washer within it and it being nipped up as tight as I dared. Anyway, I searched the forums historic threads for this issue and then used a little PTFE tape on the threads and the leak was cured.

It irks me that people still think that taping threads, to stop a leak (where the mating/sealing surfaces are actually between flat surfaces and a washer) is a proper repair. It is not. It is a bodge. You may have hidden the symptoms, but have not cured the disease! Selection of a suitable washer, or repair of the offending surface, is the proper repair.

Perpetuating bodge repairs will catch out some unwary individual some time in the future.
kevin s
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Re: Fuel leak

Post by kevin s »

MorrisJohn wrote: Fri Jul 22, 2022 3:27 pm
kevin s wrote: Fri Jul 22, 2022 1:10 pm we had the same, fitted the viton tipped valve and it was better but did it occasionally still, ended up fitting a filter king pressure regulator and it has been fine since. Ours does have some sort of aftermarket fuel pump though.
That’s interesting Kevin. Is the king pressure regular just fitted in line between the fuel pump and carburettor?

Is this what you fitted? - https://www.scparts.co.uk/sc_en/fuel-pr ... 22594.html
I used the smaller slightly cheaper one with 4 screws on the top and set it 1.5 psi, yes it goes in the hose between the pump and carb, it's in the top right hand corner of the picture, the bracket I made and it uses what were 2 of the holes to hold the under dash felt to secure it.
rps20210808_180304.jpg
rps20210808_180304.jpg (111.89 KiB) Viewed 745 times
MorrisJohn
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Re: Fuel leak

Post by MorrisJohn »

oliver90owner wrote: Fri Jul 22, 2022 9:27 pm
You may have hidden the symptoms, but have not cured the disease! Selection of a suitable washer, or repair of the offending surface, is the proper repair.

Perpetuating bodge repairs will catch out some unwary individual some time in the future.
Perhaps I ought to have been clear in my original post. The PTFE was never intended as a permanent solution. It is what I had available at the time.

UPDATE: I removed the outlet union, carefully removed the PTFE tape and new washer. I compared the new and old washers and they looked the same. I replaced them in any case with the old brass union and the old washer (which still looked okay and I knew didn’t leak) from my old petrol pump. Hey presto, the leak is gone.
kevin s wrote: Fri Jul 22, 2022 1:10 pm
I used the smaller slightly cheaper one with 4 screws on the top and set it 1.5 psi, yes it goes in the hose between the pump and carb, it's in the top right hand corner of the picture, the bracket I made and it uses what were 2 of the holes to hold the under dash felt to secure it.

rps20210808_180304.jpg
Thank you, that’s very helpful and as they say a picture says a thousand words. I’ve ordered the same smaller one that you have.
A bad day with my Volksie still beats a good day at work!

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MorrisJohn
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Re: Fuel leak

Post by MorrisJohn »

SOLVED!

Removing the lid of the float chamber, I checked the needle was still doing it’s cut off job by blowing into it through some spare fuel hose. This confirmed it was still operating correctly.

Having then refitted the float chamber lid I tested the car for forty minutes on all road types. No fuel leaks from either the float chamber nor the pump outlet union (without the PTFE).

I can only hazard a guess that either a small piece of sediment was interfering with the needle operation (I didn’t see any). Or, perhaps by fitting the new fuel pump I ended up with compressed air inside the float chamber which led to the leak? Regardless of the cause, the above has remedied it.

Thanks again to all for their advice.
A bad day with my Volksie still beats a good day at work!

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myoldjalopy
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Re: Fuel leak

Post by myoldjalopy »

If it was simply some crud blocking the float valve, it would be worth you checking the filter in the fuel pump - not unusual for these to get choked with rust debris if neglected for some time and if they split crap will get through to the float chamber needle valve. Simply unscrew the filter and see if there is what looks like coffee grounds in there. Put a cloth underneath as you remove the filter as some fuel and crud may dribble out as you do it. I have known these filters to split so check it is in good condition before re-fitting.
MorrisJohn
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Re: Fuel leak

Post by MorrisJohn »

Well, the problem resurfaced (intermittently). I took apart the float lid, removed the needle and found a small bit of debris, which resembled a piece of brittle plastic or rubber, which had somehow worked its way into the space between the float needle and it’s seat.

Debris removed, float needle/lid gasket replaced and hopefully it’s now cured once and for all.

It’s got me thinking maybe those inline fuel filters aren’t such a bad idea after all…
A bad day with my Volksie still beats a good day at work!

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