Su carbs not Carbing....

[AndrewGilbert]

hi, we're no further forwards. The pump is a facet solid state unit, it doesn't stop when the bowls or the regulator is full. But I'm also being told this is typical of that pump.

It had a single HiF44 fitted before so the floats etc are different. The ones fitted were OK a few years back so I'm assuming they should run on this one. But I will check their angle.

It has the latter non adjustable floats, and they measure correctly so they're gapped OK.

But I'm looking at other items that the car needs so turning my attention to those first. Then, well I'll probably get it taken to someone to try and sort as its now beyond my abilities.

Basically, car drove into the garage

• Ran OK
  Engine has only got 250 miles on it since its build
  We swapped to twin SU's
  Fuel is pumping into the bowls
  We have a spark and we haven't touched the timing
  The carbs have been adjusted for its initial start
  Won't fire using easistart
  No sign of an air leak
  Plugs appear wet after trying

Next will be to drain the fuel or add some octane booster in case thats bad, then probably make a call!

[Peter Laidler]

Ah, you've found the fault yourself Andy......... That non stop fastnet pump is pumping its heart out and overwhelming the pressure stop in the fuel bowls. They're not used to it. The fuel floats want a lower pump pressure that's sufficient to STOP the bloody fuel flow when the bowls are full. It looks like your pump pressure - and non-stop too - is overloading the bowls and pretty well flooding the carbs, engine, ignition and more importantly right from the start. Or in your case, BEFORE the start - of the engine.

Those pumps are OKish (steel helmet on awaiting the incoming mortars.....) if there's a fuel return.

If non bloody stop is a typical feature of those pumps then I'm lost for wrods! You'll be a LOT further forward with a good rebuilt SU pump. That's what SU carbs were designed to use. Only my opinion of course, based on nothing more than what my mum used to call ',,,,the bleedin obvious

[Ronnie]

Something drastically wrong if it will not start on easy start , as Peter infers you must have no spark make sure your plugs are dry and sparking outside the cylinders disconnect your fuel p/p then try with easy start or 5cc good fuel down the throat of your carburettors, if your plugs have become contaminated the ceramic can become conductive as Peter said and track through to earth (NO spark), even if they work out side the cylinder's more KV required under compression, you could also give them a good cooking with a butane torch or even gas cooker. GOOD LUCK

[111Robin]

I agree with Peter. For the sake of elimination, hook up a simple gravity feed tank to the fuel inlet and try starting it. There is absolutely no reason for an A series to not start if you have compression, ignition (at the correct time) and fuel (but no too much). Bin the facet pump and fit either an SU electric (or electronic) or mechanical (if block allows). You shouldn't need to take it to a "specialist". There's nothing simpler than a BMC set up.

[Exminiman]

hi, we're no further forwards. The pump is a facet solid state unit, it doesn't stop when the bowls or the regulator is full. But I'm also being told this is typical of that pump.

It had a single HiF44 fitted before so the floats etc are different. The ones fitted were OK a few years back so I'm assuming they should run on this one. But I will check their angle.

It has the latter non adjustable floats, and they measure correctly so they're gapped OK.

But I'm looking at other items that the car needs so turning my attention to those first. Then, well I'll probably get it taken to someone to try and sort as its now beyond my abilities.

Basically, car drove into the garage

• Ran OK
  Engine has only got 250 miles on it since its build
  We swapped to twin SU's
  Fuel is pumping into the bowls
  We have a spark and we haven't touched the timing
  The carbs have been adjusted for its initial start
  Won't fire using easistart
  No sign of an air leak
  Plugs appear wet after trying

Next will be to drain the fuel or add some octane booster in case thats bad, then probably make a call!

With all due respect you are going down a rabbit hole of over thinking things ( we all do it) - dont do anything until you have worked through the above three posts. As mentioned above, just use a gravity fed fuel supply or a big squirt of Easy start.
You could try posting few photos in case something jumps out.

[AndrewGilbert]

thanks all

Good suggestion on fuel pressure, I'll check that this later today, we fitted a pressure regulator but will play with that pressure again, but yes I'll hook something up to gravity feed the system. I'm quite happy to swap the pump though, these never ran like this on my old Caterham so I'll give anything a go.
however, I think I have a brand new fuel pump at my unit, its a facet but the same as used on my 7, so I might swap those out anyhow.

Question over 1.5HS4's, should I have an overflow at some point in the system? I can't see one, nothing from the float bowl although I have the return feed to the tank from the previous carb, and on the HS4's I can see outlets blanked.

I'll grab some photos later today when I near the Mini.

[Polarsilver]

How will octain booster revive bad fuel ?... if mine would drain the original fuel & use it as weed killer.

[timmy201]

Most of the early ones have a vent here (sometimes behind a little alloy cover). Later covers have a pipe. Both need to be open to the atmosphere to allow the fuel to enter

[AndrewGilbert]

How will octain booster revive bad fuel ?... if mine would drain the original fuel & use it as weed killer.

Its around 6 mths old, so isn't old as such, but yes take your point.

[Peter Laidler]

That stale fuel thing is a bit of an old chestnut Andy. My '69 Cooper S and RCSport were left for 18 months plus a bit, during covid. The RCSport started second click of the starter while the Cooper S needed the plugs cleaning, heated with a blow torch and a quick blow job with the torch down the bores and it kicked into life like a good 'un after a couple of whirrrrrrrs of the starter

[AndrewGilbert]

Thanks Peter, is certainly smells like petrol!

I have a facet replacement pump that I'll swap over later this week to see if that helps, but I have my doubts, I adjusted the pressure reg down to a minimum just to see if that made a difference and it didn't really.

And I don't appear to have an overflow outlet.

[Peter Laidler]

The irony is that the little SU pump, original mechanical or converted with electronic guts is ALREADY pressure regulated....., delivering the right amount of fuel exactly on-time when the carbs needed it!

I'm sure that your carbs will have an overflow outlet, just where Timmy showed on his photo. The little hole also allows the carb to intake air as the fuel is used - until it gets another gulp of fuel from the pump.

Shame you don't live in or near Abingdon. Me and Dave would have you up and running in time for an afternoon beer at The Black Horse