I have as above and have finally put into the garge to get fixed, everytime I drove her she would cut out, doing 80k or 50k didnt matter (lots of fun at the traffic lights) then she would need to sit for 15mins before she would start again.We replaced the fuel pump/filter, have put stuff in her tank in case it was dirt in the fuel.As said put her in the garage yest and told the guy, hes replaced points and getting a new carurator intoday, my worry is im in no way mechanical and wonder if hes taking the piss! When I said what she was doing he said "hmmm not really sure could be a fuel problem" any thoughts or suggestions would be much appreciated, am heading to the garage again shortly so any info would be great TIA
jerichord,
Feb 25, 6:30am
you will need 2 carburetors , just get them cleaned out, sounds like , coil and or condenser to me, been there with a midget
rodg.sue,
Feb 25, 6:35am
thanks will put that to him, thanks
budgel,
Feb 25, 7:07am
This sort of thing is quite normal for British cars of that era!;-)
smac,
Feb 25, 7:39am
Kinda sounds like you're just paying to have stuff randomly replaced without actually finding the fault! Either get learning, or find a garage that actually knows the old stuff. Save yourself a lot of time and money.
ema1,
Feb 25, 7:49am
Carburetors need either replacing or overhaul or there may be a vacuum leak in the intake manifold/carby's area I suspect, the paired SU type that your MG has were very prone to going "off tune" ( due in lots of cases with owners or the uninformed "fiddling"with them!) and do require an experienced tune up person familiar with the type to sort them properly for you, I would suggest a BMC Mini specialist as the engines in the Midgets/Sprites etc are virtually the same thing as in Mini Coopers etc The ignition system needs to be thoroughly checked out for faults also, the Lucas distributors they are fitted with are getting older now and no doub't it will need a full overhaul/rebuild as shaft wear etc could be an issue along with other vagaries of the type. I had a lot to do with the BMC product in my motor trade hey day and they were and still are a load of fun even today. I owned numerous BMC vehicles over the yearsand if you can live with their foibles they are generally good old cars.Love em heaps A very good tune up/hot up book on the BMC 'A' type engines by the 'A' type engine guru David Vizard is one of the best you are going to get on the type. He knows these engines down to the n-th degree. Camshaft/valve timing can change over the years too due to cam chain stretching/ this will make itself known by chattering noise in the front of the engine, chain rattling against the timing chain/sprocket front cover. Wear & tear generally needs to be checked and addressed.
socram,
Feb 25, 8:06am
SU carbs do not go off tune!Once set up properly they are generally OK until components are worn out.
I'd certainly replace the condenser as it is cheap but I am not a mechanic, so totally agree with the comments above about taking it to a decent mechanic.
My feeling from info supplied is that it could be fuel vaporisation making it difficult to start with a hot engine, so maybe the heat shields are missing from between the carbs and the exhaust!
You state only that it won't start when warm; you make no mention of starting when cold or running without problems as long as you keep the engine running. When the engine is running, the petrol doesn't get too warm in the pipes as it flows through from the (cooler) petrol tank, but once you switch off, the heat under the bonnet will adversely affect the fuel that sits in the carb float bowls and the supply pipes.I bet it doesn't happen in cold weather!It has nothing whatever to do with Brit cars of that era either.
Wrapping the exhaust manifold to keep the under bonnet heat down is another option.The exhaust and inlet manifiolds on those cars are basically one cast iron unit, so heat transfer is inevitable.Crossflow heads, with fuel going in one side and hot exhausts going out the other are more efficient in that respect.
Do you put your foot on the throttle when trying to start it when hot!
ema1,
Feb 25, 8:08am
contd from prev post#6.The lack of camchain tensioning on this type( later 'A' series engines had modifications to the cam sprocket "rubber ring" tensioning material integral with sprocket and then a form of spring loaded tensioner was devised!
ema1,
Feb 25, 8:11am
They don't per say, normally but as I said it's generally if they are fiddled with as being the main cause! I was always tuning SU set ups virtually at every tune up session on MG's and other BMC twin SU set ups,! Dashpots on the carbs needed constant checking for lube oil etc and vagaries with free movement of the vacuum controlled needle & bell systems were also a constant maintenance item. The metal bell moving up & down inside the SU carb over time .quite short in lots of cases eventually left a metallic deposit on the "bell" walls to create tune problems, the depression variations between the 2 carbs was another major "out" of tune factor when you didn't expect it. It's actually quite a science tuning SU carbs PROPERLY not every "common joe" knows the full story & secrets even though lots think they do Wear and link shafts becoming lose are also another reason. Float levels/needle and set settings and wear are common vagaries also.I have vast experience with the type and I do actually know what I'm on about here.scoram
socram,
Feb 25, 8:17am
I am sure you do ema1.
I have been using those engines for 43 years, (44 years tomorrow.) just about all of them in twin SU form.If the car is running OK normally, then commonsense dictates that the carbs themselves are OK does it not!Hot starting is the problem - or appears to be.
Who is scoram!
smac,
Feb 25, 8:21am
Scrotal's cousin.
Ya source of problem depends on whether it's running ok before it dies. Lots more questions before any kinda diagnosis can be applies, hence the suggestion to get it to a bmc mechanic before throwing more money away.
ema1,
Feb 25, 8:22am
Opps typo there mate .sorry about that socramha ha got it right this time. Yes you obviously have experience there too but nowadays it's not as common place .is it not! Thats why I suggest a specialist on the type way early on this thread!
ema1,
Feb 25, 8:28am
That's an excellent "short" concise answer to the OP's problem right there, that is also why I suggested the BMC specialist route early on. Question is .Has this engine been running properly of late and if not how long is it since it hasn't been running properly. Issues like this gradually creep up on owners without full knowledge realizing that there are issues that are gradually creeping up! Lots of these & similar types get driven around in totally and disgustingly enemic states quite happily that I'd wager that there is and through personal experience I can categorically say the greater % of them are NOT properly tuned due to various reasons and that means when they were more common place 20 and 30 years ago also when I was in the thick of things !.
socram,
Feb 25, 8:31am
Couldn't agree more!I took my 998cc Mini Cooper to a real hick specialist many many years ago.My buddy had his 998 Cooper set up by him and he was the traditional old boy, who built all the local winning grass track motor-bikes, out in the countryside.
I tried my car on the stopwatch on the way there.0-60 (mph) 20 seconds - slow these days I know. When he'd done it I asked him when I needed to bring it back."You won't need to" was his rather abrupt response.
Tried it on the stop watch on the way back home in the same direction on the same piece of road.The 0- 60 time had dropped to 15 seconds - yet the car always ran well before!
ema1,
Feb 25, 8:38am
What isn't been realized here is that these twin SU set ups can and in the vast % of cases run quite happily out of tune! It takes a specialist who's in the know to spot that fact and they are getting rather thin on the ground these days, plus the fact that the components involved here are getting a lot older and require that much more attention nowadays. It's my bet that it's an extremely small % of the the type nowadays that are working bang on factory design specs and even back years ago the same could be said as the variables between the same types of vehicles was to say the least .WAS VAST !
ema1,
Feb 25, 8:42am
Actually .no it's not infact.that's a common misunderstanding of the carby type, as I have said previously "out of tune" paired SU carbs will perform reasonably well! It's the increasing degree of "out of tune" that is the determining factor as to whether anything gets done about it, due to a lot of owners lack of knowledge !
ema1,
Feb 25, 8:56am
Hot starting faults with SU carbs can be traced generally to faulty float levels due to to needle and seat/float levels of which I had numerous sessions sorting back in the day. High float levels/flooding were a MAJOR source of problems. Lot's of folks don't take into account that when a SU carbed engine runs rough the first thing that suffers generally is erratic fuel float levels in the carbs themselves as vibration from rough running and other sources are a big % of the problem in this area that cause variables in float levels and needle and seat problems, floats themselves fail also and I wouldn't mind $10 for every defective float I have replaced over the years .if that were the case I'd be mightly rich right now! Just adding to the equation here.vibration and general wear due to ingress if abrasive elements (dirt on linkages, metal wear deposits internally etc) produce "out of tune" states that are ongoing to the point of I doub't if there are any SU carb setups now single , twin or triple or whatever that are even anywhere near original factory design specs. The reason they are still going in good numbers is really due to their tolerance of being in various degrees out of tune and still performing satisfactorily. Once they reach an excessive degree that's when the average owner gets them looked at. Todays modern EFI fuel systems are tuned to a microscopic factory tolerance degree that the carby systems could never ever achieve or maintain but even there are the variables in them as well, modification outside of factory design parameters is the major factor here and the specialists are the ones that know there stuff in these cases too, that's what they are trained to do.it's their respective skills that vary. It's ultimately the customers that find out what these skill levels are in the end by the results they produce.! Nuff said.
richardmayes,
Feb 25, 8:57am
Rough running then dies= a fuel problem.
Running perfectly then dies, like someone just pulled the plug out of the wall = an electrical problem.
ema1 10:38am comment above seconded, too. My dad & my brother both drive identical Triumph 2500TCs, both kept in tune to a pretty high standard with bi-annual check on carb balance and setting the jets by my dad. Brother's car is higher mileage, rougher condition and a few months older than dad's car, but in spite of that, it definitely likes climbing hills better than dad's good one!
ema1,
Feb 25, 9:24am
Going back to the OP's original post , in short take the car to a reputable BMC specialist to check it completely and "be prepared" for a shock. It's my bet that the SU carbs on the car have a major out of tune problem one way or another and going by your description of hot starting problems and cutting out etc the SU carbs will need a serious complete dismantling/calibrating etc & careful checking of float levels/needle & seat items and it's my bet that overhauled or new items could be the ultimate fix here, or at the very least dismantled cleaned re needled possibly with revised needles, neoprene tipped flow jet needle & seat assemblies for SU carbs were a reasonably successful after market fix for float level problems by the way. Inlet manifold vac leaks were a problem here also, and another thing I over looked as well earlier was to check this item if it has one fitted.the PVC (Positive Crankcase Ventilation) valve diaphragm set up .often it is the case that the diaphragm rubber is shriveled up to a degree that it ceases to function and that it causes a major vac leak right there. It surprises me just how often this item got over looked by various non BMC franchise workshops years ago and the same would apply possibly more so today!
franc123,
Feb 25, 3:55pm
coil windings breaking down and working again after a cool down period ,or vent valve in petrol cap not working causing vacuum in the fuel tank that the pump can't overcome!Next time it dies crack the cap off slowly and listen for any hissing.
rodg.sue,
Feb 25, 4:00pm
OMG, im so lost with above threads, She starts usually first pop even after sitting so long in the garage unused after jump starting, head off down the raod usually takes about 5-10k before she starts to cut out, then can m,ove sometimes up to 3-4k again or once it was like 200m.She starts perfectly so it is with hot running only.Have just got home from the garage, they put new points in her, cleaned spark plugs, replaced pins in carburator (seating was worn) atcost of $103.00 per side so mechanic took it for drive and then had to get towed back to service station as she cut out again! Im now looking at a bill of $400 and still not fixed! There used to be a fab mechanic down here but he no longer does it, there are no listings in the book for specialised old cars and I dont no anybody else who has one! Im gutted, anybody want a mg going cheap!
clark20,
Feb 25, 4:05pm
socram wrote: The exhaust and inlet manifiolds on those cars are basically one cast iron unit, so heat transfer is inevitable. [quote]
Sorry Socram, the are not, cast exhaust, alloy intakes. The heat shields are important as you say.
ema1,
Feb 25, 4:43pm
Surely the MG car clubs where ever they maybe will be a good place to start to find expertise!
ema1,
Feb 25, 4:50pm
Blimey socram (there I got your user name right this time) strewth I would have thought that with 44years of experience !with these twin carb jobs you would have known they have separate alloy inlets and cast exhaust systems on em and always have done, only the single carb units used inlet/exhaust cast iron as a single piece! Heat shield between em on the twin set ups.totally different beast all together.
ema1,
Feb 25, 4:59pm
OP.go have the cars ignition checked over also on a tune scope! Gradual breakdown could be happening with the coil etc, or even in the cars ignition L.T. circuit somewhere, possibly have an auto sparky check out all the and I mean all the ignition circuits including right back to the ignition key /starter barrel switch! A competent tune scope operator should hone on any distributor faults and other faults with the ignition system also.has the condenser been replaced ! these will cause premature deterioration of the contact points even newly replaced ones. But I reckon the problem still lies with the fuel system, and the fault hasn't been diagnosed properly! Has the car as I asked earlier got a PCV system on it .if so have this checked over for function as they do cause major vac leak problems through that system and if undiscovered it will persist! Sometimes the rubber dish diaphragm can get a pin hole in it that can upset things so a mandatory replacement of the diaphragm rubber dish in the PCV system is a must if your vehicle is fitted with such a system, plus .and this is important make sure the PCV valve itself is clear of any sludge and gunk which also can foul it's operation.! Have you had sediment in the fuel tank cleaned out ! It's possible you could be getting fuel supply problems due to this .it's NOT uncommon you know. If sediment is present it won't take long to foul the fuel system up at all ! Another thing here has it got an air leak into the fuel system somewhere ! it can be the minutest leak that can cause problems like this!
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