Leaky choke

[APS]

Hi guys, I am after some advice please.
i stripped and overhauled my strombergs a few weeks ago and all was well afterwards. I found a few issues with them that was causing lumpy idle and poor performance, namely one needle was not seated in its thread properly and was therefore set very rich, the opposite side was set very lean. Also had sticky air valves etc.

Car was very responsive afterwards and I had a nice smooth idle. All has been well for a few weeks.

I had not used the car for a few days as I was undertaking other small jobs on the car. Some of which required the ignition to be switched on at times and had the fuel pump prime the system. I then began to notice a smell of fuel and noticed fuel in the engine vee.

On checking the source to be from around the choke assembly on the offside carb. Not the spindle but from around it where it seats on the carb body. The leak was happening without the engine running.
I have tried tightening the two screws, I removed the choke assembly cleaned the faces and reinstalled. In the overhaul kit gaskets were supplied for the choke assemblies, I had fitted them but subsequently read in this forum that they are not needed. So I removed it. The leak is not as bad as it was but I still feel some fuel damp when I run my finger around it.

From what I can tell these choke assemblies are above the level of the float chambers, so is it right that fuel should be getting to choke if the engine isn’t running ? I am wondering if I have a float needle problem that is not shutting off the fuel delivery to the carb or is there a separate fuel channel to the choke that allows better starting.

Thanks in advance for your help.

Alan

[Lingen]

Alan.
There is no separate supply to the choke, so there is too much fuel in that carburettor. A sticking float needle valve is a distinct possibility, but is could be that the fuel pressure is too high if the wrong pump has been fitted at some time.
Mike.

[wilf]

Are you sure the choke control discs are in the correct way around? They can be fitted 180 degrees out, and that could lead to leaks as you have.

[APS]

Thanks Lingen, I may pull the carbs out and recheck the needle valve and float height. I did do this when I rebuilt the carbs with new needle valves but you never know I may have messed up with the height adjustment. But the leak started recently, so maybe a dodgy needle valve.

is there any preferred fuel regulator that is suitable for our cars ? Seems to loads to choose from.

Wilf I had considered this especially seeing how I need little choke to start the car. But the choke is leaking when car is not running. So would this make it irrelevant if fitted 180 degrees out ?

[wilf]

I think so - the discs shut off the low of fuel when the choke isn't needed if they are fitted correctly, so it should follow that if they are the wrong way around, they might allow fuel to flow when it shouldn't. Worth checking, anyway. Ditto the fuel levels as Lingen says.

[APS]

ok thanks Wilf. so possibly two issues I can look into.
The fuel level in the float chamber and whether the choke disc is 180 degrees out.

I am more suspecting the fuel level as I did recheck the choke disc when I removed it to take out the gasket and to reclean the face of it.

I have just been out for a long drive as I had it booked in for its first MOT in 5 years this afternoon.
Choke in after short time after start and tickover was fine. I am thinking if it was 180 degrees out it would be coughing.

Anyway good news car passed MOT with zero advisories.

No fuel dampness or in the vee now engine is fully warm.

I'll recheck situation again tomorrow when engine is cold. First with choke in and again with choke pulled out to see if this makes a difference.

But I think carbs will have to come off. I'll order a new needle valve just in case before I do though. And of course the pedestal o ring.

Thanks guys.

[APS]

Just to add, I also ought to consider the possibility of too high a fuel pressure as Lingen said.

So has anyone a recommendation for a fuel pressure regulator that is proven to be suitable ?

tia

[022Dave]

So has anyone a recommendation for a fuel pressure regulator that is proven to be suitable ?

Hello Alan,

There are some cheap and very nasty pressure regulators out there, particularly on popular auction web sites, which have caused leakage & fires. I fitted a Malpassi Filter King (87mm with a glass filter bowl). It comes with a gauge, which makes setting the fuel supply pressure easy, and a blanking plug so that the (vulnerable) gauge can be removed after setting up. From memory, the kit is about £80.

Dave

[SteveD]

+1 for the Filter King, I have the 67mm (approx) one fitted.

[APS]

Hi Dave,

I very much appreciate your advice on this.
I know that site and I have seen the one you mention at about £80 which has an inbuilt filter, I've also seen many around the £25-£30 level. I intend now to take onboard your warning.

So glad I asked and really glad for the help this forum provides.

cheers Alan

[022Dave]

My Malpassi has a replaceable paper filter cartridge; some have cleanable filters. I went for the glass bowl instead of the aluminium, so that I could see any crud building up.

Dave

[wilf]

I had a Malpassi on a 7 litre yank V8, worked perfectly!

[Goldstar]

I had a Malpassi on a 7 litre yank V8, worked perfectly!

Have you had American cars Wilf? You’ve never mentioned it before

[wilf]

[APS]

Quick update. Pulled trigger and purchased the 85mm malpassi filter king with glass bowl for £82. I'll fit this next week in boot next to the fuel pump.

Switched the ignition on today to get the fuel pump to prime the carbs. No leak with choke in or choke out.
Not sure if good news as I don't have a real fix to the leaky choke assembly. Though for now I have no leak. Perhaps a sticky needle valve. I'll have to keep watch on this for a while I think.

Thanks to all.