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MG Midget and Sprite Technical - Heat related issues - fuel? + clutch

Yesterday I attended a nice Treasure Hunt in my 1970 midget.
Start location was 30 miles from home, stopped for petrol on the way, uneventful journey, everything seemed fine.

During the hunt was a different matter though.
4 times the car coughed and died, rolling to a stop and would not restart, until sat for 10 minutes or so with the bonnet up. Most of this driving was 1st or 2nd gear very narrow roads, very slow, 20 miles or so.
The car did not overheat but I'm thinking that perhaps the warm weather, combined with lots of slow speeds were causing the under bonnet temperatures to rise and cause issues.
Fuel was my guess but I really did not know what I could do by the roadside to test that theory?

Anyway event over, nice meal in a pub and an equally uneventful journey home at normal speeds.

The other problem was that 1st and reverse gear also became much harder (impossible) to select without copious crunching during the slow part of the drive. Pedal movement did not change that I noticed, and again, on the drive home gearchanges were much the same as usual.

I'm attributing heat to both these issues and am currently wading through the archives, but heat, clutch, fuel etc. are such generic terms that many posts are being thrown up!!

Any ideas would be gratefully received.
G Hawkins

Some things to consider:

1. Is the standard carburettor heat shield in place? And all the standard carb spacers and manilfold gaskets?
2. Is the fuel line from tank all the way to the carbs of the correct material, specification and route?
3. Has the car had a full full big service according to the driver's handbook (35k one I think - not got the good book to hand today)
4. Clean fuel, fuel filter and air filters?
5. Unblocked fuel lines and fuel tank vent?
6. Correct grade of spark plugs properly gapped? What colour are they?
7. Timing set correctly and all ignition bits OK condition and set correctly - distributor cap, points, condenser and leads?
8. Coil OK and mounted in a standard position?
9. Recent change of gearbox oil to correct grade?
10. When was the last time you fully flushed the cooling system, including heater matrix as well as radiator, and does it have recent antifreeze mix in it to correct strength? NIgel has a good method for flushing.

Cheers
Mike

And also - how old is your clutch fluid?
M Wood

1. Yes to all
2. Yes to all
3. Not as such no.
4. New fuel, recent air filters, no fuel filter fitted, never had one in 28 years of ownership.
5. They are fine, fuel pump is newish and was all attended to when it was swapped in, a year or so ago.
6. Spark plugs are the same type (not actual ones!) I've used for years. Colour .. can check.
7. Timing is correct as far as I know, I checked it last year. Under cap electronic ignition.
8. Coil is mounted in standard location. Okay? pass.
9. Gearbox oil changed 100 miles or so ago.
10. Cooling system flush is on the cards, bought some anti freeze last week in fact. As it stands though it does not appear to over heat, indicated temperature all day did not rise above 170 on the gauge.

Cheers.

Clutch fluid .... yep. Probably a few years old now. Can't actually remember the last time I bled it.
G Hawkins

Fuel vaporisation due to localised hotpsots in the engine bay most likely. Cover the fuel pipe in the engine bay with sleeving, e.g.
http://www.ebay.co.uk/itm/1MM-2MM-4MM-6MM-OR-8MM-HEAT-RESISTANT-CABLE-SLEEVING-VARIOUS-LENGTHS-/162029253210
Second guess be dodgy coil breaking down when hot.
Replace clutch fluid with DOT4 or preferably 5.
Which brand and grade of oil did you put in the 'box?
David Smith

Could also be dodgy rotor arm tracking when hot.
Dave O'Neill 2

G Hawkins,
I like all the ideas here ( :) ) (I'm going to try out David's heat resistant tubing for myself).

If you want my simple but effective flushing method just email me, it can also help to avoid hotspots (as will also following the directions in the Driver's Handbook).

my name (one word) at bt internet (one word) dot com - all lower case
Nigel Atkins

David

Fuel vaporisation was my conclusion on the day,
based on nothing much at all. I'll check out the sleeving.
I have been reading in the archives about the coil possibility so might just get one anyway as I don't have a spare and I don't recall how old the current one is.

I have a load of DOT 4 fluid from bleeding the brakes through a couple of weeks ago, I'm thinking I might be doing the remote clutch slave bleed mod too.

Oil I used was a 20/50, Halfords own IIRC.

Thanks

EDIT: Nigel, email sent.
G Hawkins

New coil? Modern ones are not good quality. I had a new one on a 1500 I once owned. I only changed it because the original was so old. It conked out whenever it got hot. Leave it for 10 mins and it would fire up, until it got hot again. Took it back to the shop that rhymes with T**S and got my money back. The old one was still happy when I sold the car years later.

Rob
MG Moneypit

I use Aluminum foil instead of heat resistant sleeves


Flip Brühl

Dave (O'Neil) has it!
Had exactly the same symptoms as you and it was a dodgy rotor arm i.e. one with a rivet which shorts out when the engine has run for a while. The engine cools down the rivet contracts, engine starts and the sequence is repeated - just like you,re experiencing.
If you don't have a 'red' rotor arm get a real one from the Distributor Doctor.
Jeremy MkIII

Jeremy

I am 99% sure my rotor arm is a red one I bought with the electronic ignition kit from simonbbc a few years ago .... just checked and it was in fact 7 years ago. Where does the time go.
Like the coil I don't currently have a spare so I'll get another one. Easy to swap if/when it happens again.

Thanks

G Hawkins

Graham,
the rotor arm might be coloured red without being a "red rotor arm" (if you see what I mean). I don't know what Simon BC used 7 years ago but I have a feeling, but don't trust my memory, that they might have at some stage used Dissy Docs "red rotor arm" and are now on their own(?) Powermax(?) or something called like it, or I might be mixing up suppliers.

I don't think you need a spare coil they seem to last many, many years (well good ones at least) just buy and fit when you need one, they're quite standard. You don't want to go down the road of swapping parts for the sake of it, you need logical step by step system of diagnostics.

I know I've thrown guesses about, we all get tempted to do this but you need to check things from the very start, the very basics, moving on step by logical step in a systematic way dependent on the results of each step. This may need more driving of the car, no hardship with the present weather/time of year.
Nigel Atkins

Popped into the garage for the first time since the weekend and whipped the plugs out looked fine a greying colour across the board.
Took the distributor cap off and well my memory is not what it was.
Not a red rotor arm but a black, riveted one, so much for 99% sure.

Not only is it black but it practically fell out of the dissy into my hand, and the riveted on metal strip is so loose you can hear and see it move when you shake it. Not only that but it must have been making contact with the cap 'electrodes' at some point as there is a fine coating of brassy/aluminiumy dust inside the cap and the tip of the rotor arm is most definitely shiny and worn.

I now have another question.

HOW IN THE NAME OF ALL THATS HOLY!!! did the car actually run at all??

I took it for an MOT a week ago and it was not misbehaving or making strange sounds (I'm sure my tester would have mentioned if he thought something was amiss, he's been MOTing it for years), and the run over the weekend was fine apart from the low speed cutouts ???? Could the low speed driving & heat be the cause of the catastrophically failed rotor arm?

Anyway a new rotor arm and cap will be ordered.

Thanks for the help all.

G Hawkins

Order the parts from the Distributor Doctor. His stuff is generally decent quality if a bit more expensive. Low speeds and heat should not affect a well made quality rotor arm. Sadly the quality of reproduction items is so poor that they can fall apart or fail at any time. BTW don't be fooled by 'original' Lucas components in Green boxes. They are all repro. The original Lucas items are in red boxes or blister packs and, in my experience, of superior quality.
Bob Beaumont

Dave said "Replace clutch fluid with DOT4 or preferably 5."

No don't. DOT 5 is silicone and is incompatable with other brake/clutch fluids. Confusingly DOT 5.1 is compatable.
Mike Howlett

As Nigel said, there are red rotor arms and red rotor arms.

Just because it's red, doesn't mean it's good...unless you know whose it is. Distributor Doctor sells a quality product.
Dave O'Neill 2

"His stuff is generally decent quality if a bit more expensive"


Just got a quote, yikes!
The parts had better out last me!!
G Hawkins

Graham,

glad to see you've sorted it.
I think it may well have been Dave who alerted me to the dodgy rotor arm when I was having the same experience.
The Distributor Doctor is more expensive but the parts don't fail.
Don't expect German quality though, my dizzy cap was made (very nicely it has to bes said) in India; much better quality than Chinese. It has a Bakelite feel :)

Jeremy
Jeremy MkIII

Graham,
so just how dear are the rotor and cap from Dissy Doc then?

I've had some NOS Intermotor caps that have been of very good quality.

Generally German quality isn't always as good as the reputation makes out, ask some BMW, Merc, VW ect. owners.
Nigel Atkins

Just over £28 for a cap and arm inc delivery ... To me that seems a lot.
Maybe if I did more miles I would feel differently. Maybe I should buy them and make sure I do more miles to get my moneys worth!

G Hawkins

That's about the going rate. Genuine Lucas NOS on flea bay sells for £10 for a rotor arm and £25 upwards for a cap (plus post)
Bob Beaumont

If it's a reliable fit and forget (until service interval change anyway) then it's very well worth it and as you've put the cost per mile for them will be less the more miles you do. :)

I got a couple of Beru rotor arms for my 123 fully electronic dissy at a very good price now I'm back to full price of more than 4 times as much.
Nigel Atkins

Tell me about it... just a points and condensor set from advance auto store is more then a few lunches and breakfast at mcdonalds


Prop
1 Paper

It took four breakdowns at the side of the road before I realised the black rotor arms I had were the culprit. A new one from Halfords (circa 2002 vintage) straight out the pack only lasted me about 20 miles before it failed. They always failed in the same way as well - car got warmed up after about 12miles, engine started losing power, I'd pull over and wait for the car to cool down, I'd turn round and drive 12 miles home crossing my fingers I'd make it back. Never really travelled very far in my car before I hibernated it for 12 years. Always thought it was fuel vapourisation.

Thinking I might get a D'Doctor cap and leads, just for peace of mind.
Robin

This thread was discussed between 22/05/2017 and 26/05/2017

MG Midget and Sprite Technical index

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