Please help... he won't start :(

[simmitc]

Do NOT replace ignition items, it sounds like the ignition side is working fine. As Phil says, it is probably the mixture that needs to be adjusted. Before doing that though, check that the air filter is clean - if this is blocked then it can restrict air flow. However, most likely that you need to slightly weaken the mixture. Do this is small steps as per the manual, but basically turn the jet adjusting nut so that you screw it slightly further into the bottom of the carb. Move it one flat at a time and check for an improvement. You may need to slightly increase the idle speed.

You're getting to know the car, once you've both got used to each other, then you'll find it's an excellent and enjoyable relationship.

[radioactiveman]

It seems that you need to set the fuel/air mixture. See wksp manual for process.
Oil leaking from the rear of the sump is common and is not related to engine wear. Just replace the sump gaskets and end corks.
If oil is leaking from the rear engine return scroll (there is no oil seal at the rear of the crankshaft) - oil will show itself from the jiggle pin hole in the bottom of the bell housing - is there any oil dripping from the jiggle pin hole?

I’m not sure about the jiggle pin. However I saw it was on the sump, I also felt up the back of the sump and it was greasy with oil so it does sound like the gasket of which you speak. I’ll look in Haynes and see how doable that sounds.

I’ll also have to treat myself to one of those colortune things!

Do NOT replace ignition items, it sounds like the ignition side is working fine. As Phil says, it is probably the mixture that needs to be adjusted. Before doing that though, check that the air filter is clean - if this is blocked then it can restrict air flow. However, most likely that you need to slightly weaken the mixture. Do this is small steps as per the manual, but basically turn the jet adjusting nut so that you screw it slightly further into the bottom of the carb. Move it one flat at a time and check for an improvement. You may need to slightly increase the idle speed.

You're getting to know the car, once you've both got used to each other, then you'll find it's an excellent and enjoyable relationship.

I replaced the air filter when I replaced the spark plugs.

And yeah, you’re right. I’m new to it all so it seems a bit overwhelming but it’s already starting to feel more approachable. I also have to remind myself that I have a another car so if he stays in the garage for a few weeks it doesn’t really matter, there’s no point stressing.

[simmitc]

Another thought on the oil - crankcase pressure can force oil out of the rear of the crank, as Phil says, there is no seal, only an Archimedes scroll. Can you post a picture of the engine breathing - carb, rocker cover, tappet chest cover and we can see what arrangement you've got; it can get altered over the years.

[radioactiveman]

I believe this is the picture you were asking for:

8DA0F94E-6C5F-4379-A39D-C180D279793A.jpeg (2.18 MiB) Viewed 727 times

7E071C84-BE2B-4362-AEF1-556F2728A0CF.jpeg (2.82 MiB) Viewed 727 times

I did have another thought about tweaking the mixture.

If I’m in a situation where it won’t really run without choke/revs how would I be able to adjust it properly? I guess I can lean it off a small bit and see if it will stay running with no choke?

[philthehill]

Leaning if off will make it worse.
I would suggest that you wind the main jet down one flat at a time with the engine running and the choke pushed in. You may have to employ a little choke to start the process but push the choke in as soon as you can. Under the damper chamber is a brass plunger. If you push that plunger up the engine revs should rise slightly and then fall back. If that happens the mixture is right.
You have the sealed breather system. The oil filler cap should be vented to allow air to be sucked in - transit the crankcase & absorb crankcase fumes - the fumes then exit the crankcase via the oil separator canister/carb - the fumes are then burnt in the combustion chamber.
This is the vented cap you should have installed. The non vented cap will not help with crank case pressure or crankcase fumes.
https://www.morrisminorspares.com/engin ... 03-p830482
I would be tempted to ditch that fuel filter between fuel pump and carb. Some in line filters are notorious for causing fuel problems Replace with a plain tube.

[simmitc]

I normally agree 100% with Phil, but in this case, I got the impression that the car was running rich and therefore it does need to be made leaner, not richer. If it was too lean, then it would be hunting rather than lumpy. The "lift" test should tell us for certain. In either case, increasing the idle speed via the throttle stop screw might be a good start so that the choke "fast idle" is not needed, then make a final adjustment to idle speed when the mixture is settled.

The breathing is probably the best that you can get, as long as the oil filler cap is correct as Phil says.

[philthehill]

As I understand it the car only runs with the choke pulled out then the mixture is too lean. The mixture needs to be made richer and that can only be obtained by screwing the main jet down. The mixture needs to be at the right ratio (around 14-1) when running.

[radioactiveman]

Thank you both for your help.

I will order a new cap. Would the increased pressure have any negative impact on the running/idling? (or any other undesirable consequences?)

I was able to put the choke in and the car ran pretty well (this is my first one so I can't be certain how it compares to others), but when I got back and stopped in the garage the car seemed to struggle like it might stall. I was only able to stop it from stalling by giving it some gas or by pulling out the choke a little. This struggling wasn't instant as I was able to do normal driving, stopping at junctions etc however it was reasonably quick after pulling up.

[philthehill]

Having the wrong oil filler cap may increase the crank case pressure which could lead to oil bypassing the crankshaft scroll.
The choke to throttle lever (on the carb) may need to be adjusted. When the choke is pulled out the choke opens the throttle slightly. See BMC wksp manual illustration BBB.5 for details. Pulling out the choke may just open the throttle enough to stop the engine stalling.

[radioactiveman]

Thank you. A new cap will be purchased... hopefully that stops some (all? we can dream) of the oil decorating the garage! Although, one thing that did occur to me is that I have a brake servo which I have a feeling is something to do with a vacuum... I’m not sure if that make any difference.

In other similar ‘lumpy idle’ posts I’ve read people mention checking the distributor/leads etc, is that worth checking?

I’ve also seen people talk about an overflowing float bowl. My understanding being that the problem disappears at revs due to the excess fuel being burnt. Is that worth ruling out (and how?)

[kennatt]

I wouldn't bother with a colour tune,the Moggy has its own mixture check via the lifting pin at the underside of the carb.when the mixture is correct,as you press the pin up into the carb, just press it until you feel resistance then lift it again just a very small distance(Not fully up). When correct the engine speed will rise,then fall back and the engine will run ,bumpy is the best way to describe it,it's technically called hunting.Let go of the pin and it will drop to normal . If the speed rises and stay up too rich, turn the big nut under the carb into the carb try pin again. If engine speed drops and engine stalls too weak,turn nut down,try pin again. Without needing to look at the manual........ The basic setting for the mixture, is screw the nut right into the carb body then unscrew counting twelve flats this is the basic position,and then do the pin check as above.
Don't start messing with any other setting on the system you could cause other faults. I would suggest that the fault you have is, as previous posters have said,a simple mixture or idle setting, and will be easily sorted with a simple mixture adjustment. and as Phil has ponted out the cap needs changing
good luck.

[myoldjalopy]

If the float chamber is overflowing (as queried by 'the OP) it will be easy to see fuel dripping from it. But there seem to be two trains of thought in this thread now - one that the mixture is too rich, another that it is too lean. Were it me, I would start by simply increasing the idle speed slightly and see if it still struggles to idle. If it then seems to run better it would next be worth checking the mixture strength by the lift pin.

[radioactiveman]

I've got caps, oil and filters (oh my!) on order so I will report back how I get on. I'm sure there's a limit to the damage I can do

[radioactiveman]

Sadly the covid got me this week so I was running low on enthusiasm. Regardless, I had a bit of a play; I upped my idle speed and leaned off the mix a touch (only about half a flat). I did get to a point where I can have the choke fully in.

https://www.youtube.com/watch?v=CDKBVAk3lCc (Ignore the flashing lights - I wanted to see how those accuspark things worked)

I'm concerned I'm now idling too high, but it's progress. I feel like a monkey with a hammer

I will probably watch a few videos of the 'lifting the carb' piston trick as I'm not really sure what I'm supposed to hear if I'm honest.

[philthehill]

The correct idling speed can be determined by depressing the clutch with the engine running - if the ignition light starts to flicker but not go out the idling speed is correct.
As regards lifting the damper - the idling speed should rise slightly and then fall back. If the revs rise and then fall back the mixture is correct.

[radioactiveman]

Hello everyone! Hope you're keeping well.

Another installment in my rubbish idling/running saga... I took the car out today after a few weekends of being preoccupied with other things (who'd have thought buying an old car and an even older house was a good idea )

Anyway, this time I noticed a couple of issues:

1) The fuel pump was ticking constantly about once every second. I'm pretty confident this wasn't the case previously.
2) There was a distinct petrol smell that didn't dissipate. Again, new.
3) There was fuel dripping from the float chamber onto whatever the metal thing below it is called.

This has led me to believe I may have something wrong with my float chamber (I'll be honest it was 3 that really nailed this diagnosis).

I presume it's stuck or the float has gone porous or something?

I also wonder if this could be the issue I was having all along... it's just got worse where I've been doing very little driving

Anyway, thank you all for sticking with me and should I just replace the float assembly, with something like this? https://www.ebay.co.uk/itm/265054525766 ... bBEALw_wcB

[Wearytraveller]

Take care, petrol leaks can result in fires and total losses, don't drive until this is sorted!

Two things could be happening here.

1. The float could be punctured, therefore it will not be bouyant enough to press the needle into its seat and cut off the fuel supply to the float chamber. This will cause the fuel level in the float chamber to rise, giving a mixture which is too rich, and much more dangerously, causing fuel to leak out onto a hot exhaust manifold.

Remove the float, give it a shake, hold it up to the light and see if you can see or hear petrol sloshing inside it. If so, bin it. If it looks ok, plunge it into a jar of nearly boiling water (hold it down the bottom with a pair of pliers. If bubbles emerge from it, it has a leak. Bin it. (The hot water causes the air to expand and create pressure, which will escape if there are any holes).

If leaking, replace with one like you have correctly identified.

2. The needle valveand jet in the float chamber lid could be at fault, for two reasons. A speck of dirt, or piece of rubber from a deteriorating fuel hose could get between the conical needle valve and its seat, preventing it from shutting off the fuel supply correctly. Alternatively, the needle valve could be worn-it may have a wear rige around it where it contacts the seat- which can also prevent it from shutting off the fuel supply. As with a punctured float, this can cause at best a randomly overly rich mixture, and at worst, dangerous fuel leaks/

If worn, replace with a viton-tipped needle valve from Burlen fuel systems/various other suppliers. The viton rubber conical tip is ethanol proof, and does not wear itself or the seat like the original brass version, and they are well proven for many years as reliable. A n example of when modern materials are a genuinely useful and sensible improvement.

If it is dirt causing problems, replace fuel filter, and replace rubber petrol hose in case that is breaking up and releasing particles. See my recent post in the 'hints' section of the forum regards petrol hose- do check yours for safety, and go for Gates Barricade if you need to replace.

Check the bottom of the float chamber is clean while you've got the lid off. Sediment and any particles of dirt which make it through the needle valve and seat collect here and can be cleaned out before they cause problems in the jet of the carburettor.

Afterwards, adjust carburettor mixture setting and idle speed as per manual.

Kind regards, Chris.

[Wearytraveller]

Just thought I'd add a bit more about the fuel pump, apologies if this is teaching you to suck eggs!

The pump is powered by an electric solecnoid (electromagnet) which pulls a diapraghm against a spring, filing a chamber with petrol. When it has done this, a contact point (simple elctrical switch) is pushed open, cutting off power to the solenoid, and the spring forces the petrol out the pump towards the carb. The cycle repeats itself, tick, tick tick. Each tick is a champer full of petrol being sent to the carb. When the float chamber is full to the correct height, the float pushes the needle valve into the seat, resisting the pressure of the pump. The pump is set up so that the cycle is paused once a small pressure is achieved (think of it as the pump 'detecting' that the float chamber is full, even though it is all done mechanically).

When you first turn on the ignition, there should be rapid ticking as the pump fills the float chamber. It will then stop once full. It will tick now and again to keep the slight pressure up (there are two valves in the pump which do not seal perfectly, hence the occasional tick).

Once you start the engine, the pump will tick much more frequently as it keeps the level in the float chamber constant while the engine is drawing fuel through the carb. At higher revs and higer load the ticking will happen more and more often.

If, while driving, the fuel pump suddenly starts really hammering, pull over asap. Either:
-You have a fuel leak after the fuel pump (dangerous as petrol will be leaking out under pressure in the engine bay),
-You are about to run out of fuel. In this case the pump is sucking up air from the fuel tank and will clatter away like mad. The engine will stop once what is in the rubber hose is used up- 200yards tops.
-Much more rarely, there may be an air leak en-route to the pump. The pump is sucking up petrol from the tank, so any leak and it will just draw in air which is easier than dragging up fuel. A corroded pick up pipe in the tank itself, or a damaged or corroded petrol pipe running under the car may cause this.

Kind regards, Chris.

[radioactiveman]

Thank you much for your comprehensive reply!

I decided against messing about with the fuel bits whilst the engine was hot. I’ve left it to cool down (and to seek counsel from the Internet )

I’ve got a new fuel line to fit anyway (from ESM) without a filter (as I keep being told I don’t need one), so I guess

[Wearytraveller]

Check the new rubber petrol hose every couple of months, especially the inside of any bends, and at each end where the hose clips put it under pressure. Don't be suprised if it lasts less than a year. There are a lot of bad batches around at the moment, and it's a time bomb- even the best-willed, quality orientated parts suppliers won't know they've been given a bad batch until the complaints roll in 10 months later...

Kind regards, Chris.