Flooding Carb?

[Gareth]

Hello there!

I had a bit of trouble with Phyllis this morning, on the M5...

While travelling at a fairly constant 60mph, she started to gradually lose power. Not the halting, stuttering I have previously experienced (replaced fuel pump 2 years ago - sorted problem), but a noticeable fall off.

I had only been driving for 6 miles, or so, and yes there was petrol in the tank.

The AA were called, and after much scratching of heads, I was recovered back home - but what's causing it?

My personal feeling is that the float chamber could be flooding. This may explain why I only get 32 to the gallon...? The carb' has been adjusted several times, but it's not really helped that much, and I'm still getting black/dark grey deposits in the exhaust pipe, and all over the drive.

The points, plugs, condenser &c are all in decent nick, and were checked and regapped last month. I haven't cleaned the fuel pump points, or filter yet. These are also on the list, but if it were a fuel pump problem, then surely the symptom would be intermittent faltering / stuttering, rather than a slow descent in revs.

I've not got time to attack her with the spanners until the weekend, but I'd like some pointers as to which way to weild the toolkit. Am I going to need to overhaul the carb'? Could this problem, I wonder, be the beginnings of deterioration of the needle or jet, as well as evilness in the float?
Please help - I don't quite know where to start!

[Cam]

Gareth,

It sounds like your needle valve in the top of your carb float chamber is not shutting the fuel off correctly and so the engine is getting far too much fuel which is killing it, as the moggy carb does not have an overflow.

This could be due to a very worn needle valve, or the float could be split and has filled with fuel (and so is not shutting the needle valve).

The easiest way to test for this is to take the top off the fuel bowl and see if the float is full of fuel, if it is not then blow down the inlet pipe and push the float up by hand. You will be able to tell if it is working. If you can blow through it when the float is up then the valve is duff.

The easiest way to solve either situation is to go down to the local scrappy, find a mini and take the top of the float chamber off.

There are three screws and all that you need is a flat bladed screwdriver!!

I am almost certain that the HS2 and HS4 carbs have the same float bowls, the only difference is that the mini one (late) has an overflow pipe as well as an inlet pipe.

This should cure your problem. The alternative is to order a carb service kit from Burlen fuel systems (previously SU). but I think that they are about £30.

Hope this helps, if you have any more questions please feel free as I have stripped & rebuilt many SUs (unfortunately!! ).

Cam.

[Willie]

Lo, there are quite a few possible causes of course but,since you
were bowling along at 60mph it may be heat related? Is the car
now running ok? does it start to play up only after getting really
warmed up?. If the float chamber was flooding you should have
smelt petrol fumes under the bonnet and there will be tell tale
brown stains all down the float bowl. Also the inside of the exhaust
pipe will be a VERY sooty black if it is running far too rich. If it was
flooding the needle and seat in the float chamber are easily changed
the worst part is finding a spanner with which to undo the recessed
nut!! Always fit a new assembly,never try to reseat the old ones.
(If you lose power at speed and find that the inside of the exhaust
pipe is WHITE you are suffering from fuel starvation)
Willie

[olonas]

I've found it worthwhile to find an old 3/16" Whit, I think, ring spanner and grind away the outside of the ring until thin enough to fit into the recess around the valve body. It does weaken the spanner so to avoid grazed knuckles and an "oh dear I'm bleeding" or other more suitable expletive don't use the spanner for anything else.

[Gareth]

Hmmm. I can only offer a few (vastly unhelpful, I'm sure) points...

There is a bit of a petroly smell around the carb... but it's an engine, and I've not seen one yet that doesn't have a whiff of distilled oil around it.

As for the brown stains, I can't see any, but there again the assembly isn't all that clean, to be honest.

The exhaust pipe is black on the inside, and there are sooty deposits all over the drive when the car is first started. However, it still blows out all sorts of cr*p when I'm putting her to bed in the garage, so I reckon its consistent. I think it was the same when I stopped this morning, but I wasn't hanging around to look, to be honest. Similarly why I didn't open the bonnet, but waited for the "very nice man" to arrive. The safest place on the hard shoulder is off it, after all! I've seen the HGVs wandering over onto the hard shoulder, and it's not a reassuring sight...

Overheating - a possibility, as I have recently fitted a new heater tap, which was leaking a little, although it won't tighten up any further - honest! Even my Dad's tried and can't shift it. However, there is enough water in the radiator, and I saw no steam &c this morning. I'll look into it, though. Surely, with an engine-driven fan, and the force of "ram-air" at 60mph, the radiator would be quite effective in the cooling stakes, when compared with the same setup sitting in traffic...?

I have previuosly already had a similar experience, re the fall-off in power, but it was at 20mph a few weeks ago when I forgot to push the choke in... She'd only been running for five minutes, at that point. That's what made me think about the float - and the fuel consumption.

I've been doing this "run" along the M5 for a week or two now, and I've not had any significant troubles like this before - only the aforementioned 20mph incident, and nearly running out of petrol, due to sheer incompetence!

I hope that helps, but I'm still at a bit of a loss. Could be an expensive weekend, methinks! Ah well. Anyone got a Metro carb' they'd like to give me? Hohoho

[Willie]

Lo, perhaps you could do the following simple checks to
see if you are running too rich or not.
get the engine to normal running temperature, with it ticking
over as normal find the 'Piston Lifting Pin' this is a small
spring loaded pin pointing downwards just under the front
edge of the piston chamber( the large pot on top of the
carb) and just behind the Float chamber. You could locate
this before starting the engine...and then lift it UP..you
should feel it lift the piston and you should hear a slight
plop when you release it as the piston falls down again.
With the engine ticking over, if you then lift the piston,
the engine speed should increase momentarily and then
revert to normal. IF THE ENGINE SPEED RISES AND STAYS
FASTER THEN YOU ARE RUNNING TOO RICH. If the engine
stops you are running too weak a mixture. The mixture is
adjusted by a large nut which is at the bottom of the carb
you turn it UP one flat at a time,by hand,to weaken the
mixture and down to enrich the mixture. see how you get on
with that test......it will not cost anything at all.
Regarding the fan it does nothing but make a noise above
30mph...
Willie

[Gareth]

Hello there!

I've already had a go at the adjustment of the carb, using the piston, although I have to admit it took me ages to realise what the Haynes manual was on about!
I couldn't find the pin!

When I lift the pin there is a slight increase in engine speed, but it's not very much. I have to say ~ it's a lot less than it was before I adjusted it!

Over the weekend, I'm hoping to:

• Clean the fuel pump points
• Clean the pump filter
• Check the float bowl - this, incidentally has a tab washer on one of the screws, which is labelled AUDI.... ?!
• Adjust the carb mixture
• Check and adjust all the cables
• Give that heater tap another going over - possibly adding some gasket sealant and/or PTFE tape around the thread... (it's the early tap)

Phew! I think I might be a bit busy... Well, anything to get her back on the road.

Thanks everyone!

[les]

Do you think the engine overheated? Maybe a faulty thermostat.

[Chris Morley]

Gareth,

Here's yet another possibility to consider. A blocked fuel filter / line. It can feel like the engine is simply unwilling to rev and is gradually losing power. Generally the engine stops, but should restart after a delay of 10-15 minutes. Strangely enough, there was no stuttering or kangarooing as might be expected by a fuel shortage.

This has happened to me with two different Citroens, although not in a moggie - both got progressively slower until I had to pull over onto the hard shoulder. The cause was rust & dirt from the fuel tank blocking the fuel filter. Common factors were that both cars had recently been run dry (although normally they were kept well filled), and both were on the motorway consistently cruising at 60-65mph when the loss of power occured.

[olonas]

Gareth, the AUD and number is the original specification. Do you have the full combination. I have a list of specs. and the vehicles to which the carb. was fitted, the AUD___ you have may be there.

[Gareth]

Hello there!

After the "incident" the car was left to sit forlorn for twenty minutes, or so, after which time she started and ran fine - both onto the recovery truck, and off!

Had a look at the Mog, sitting in the garage, and I found a couple of specks of white powder inside the exhaust. No-one has been in the garage, and the plaster isn't falling off the ceiling, so I can only assume it got there from the engine. Maybe it was vaporisation? That it should happen after such a short time is bewildering, but could be the cause...

I've just done a couple of miles around town (enough for the heater to warm up...) approximately 10 minutes driving each time, so not much of a test. She ran faultlessly. Weird, eh?

I'll have a bit of a pick over her tomorrow, I hope, and I might see if I can manage an extended run down the motorway, and back up the A-roads.

Do you reckon I should warn the AA?

[newagetraveller]

When people say their cars lose power and conk out when hot I usually ask them:

Have you tried the ignition coil?

My apologies if it has been mentioned somewhere else up there.

[Gareth]

hello there!

Olonas:

The float chamber does not have "AUDI" stamped upon it, but (underneath the grime) AUD 13. That's settled that problem then. It all looks to be standard Minor. I just wondered, because the faulty fuel pump I removed a while ago was not an SU pump. Hey ho.

NewAge:

The coil hadn't been mentioned, but I've had problems with contacts on there before, so they were all renewed a while back. In any case, I fitted a new coil only six weeks ago, so that ought to be fine.

If you were thinking of the heat; the coil on Phyllis is on the bulkhead, rather than atop the dynamo, since I've upgraded to an alternator which is wider. As such, the coil wouldn't fit back where it should.

I do check the coil, just to make sure all is still well, so thanks for your comments!

Just as an update to anyone who's not already really bored with this thread, I've gone over the float chamber today, and all was fine. It appeared to be working just as it should, as I completed Cam's tests.



I'm starting to think that vaporisation could really have been the cause of my maladies....

Have a look at the "Shell Optimax" thread. That stuff (which I have been using) is rated at 98 RON. Added to that, my lead-converting, octane-boosting cancer-curing pellets...
I reckon that could equate to at least 100. Have we found a cause, I wonder?

Methinks it's going to be back to Sainsbug's pool petrol.

Thanks all!

[olonas]

Hi Gareth, I wasn't suggesting the carb. spec. might be a cause of your problem. I've found AUD13 and this was the original spec. for SU's fitted to 1098cc Austin A40 Mk 2's (1962/67). Strangely enough the carb. on my Saloon was originally off an A40, my Traveller a Mini. Your carb did start off with the same internals as the 1098cc Minor, AN needle and red spring. Don't know about the jet identification sleeve colours though.

[Chris Morley]

I am right in thinking the coil on a minor is supposed to be kept horizontal to avoid overheating? Did you get the coil from a Minor specialist (I know that some modern coils aren't suitable)?

I bet the octane rating of your fuel has nothing to do with this problem - life is rarely that simple. Have you checked the fuel filter for dirt (a two minute job)?

[olonas]

Gareth, following on from previous re carb. AUD13 was also fitted to 1098cc Minor, 1962/67.

[Gareth]

Hello there!

Hopefully, this will be the last post on this subject, and I can leave you all in peace for a while! (Some hope!!)

Spent the morning getting mucky and managed to:

• Inspect fuel filter. It was clean
• Clean pump points
• Check spark plugs - also cleaned
• Regapped contacts... These had, since the last service, set themselves to 0.10... I'm thinking that wouldn't have helped matters!
• Set mixture control. When lifting the pin, the engine note is pretty much the same.

I've noticed that she's idling a lot smoother now, and just seems to be running better in general.

Many thanks for putting up with me, guys!