Hi everyone,
Really stuck at the moment. My mg b runs really well, but after about 20 minutes it begins to misfire, getting gradually worse till the engine stops. It will then refuse to start. After a while it will refire but the whole process starts again.
My friendly Rac man found the points gap slightly out and corrected this. On the second breakdown, he changed a condenser.
Anyone got any idea what the problem may be?
Thank you!
Misfire, then dead, mg b
Re: Misfire, then dead, mg b
Most new condensers are rubbish, same with rotor arms that can leak as soon as they get warm. Old stock arms are best if you can find them since the only current seller of new ones has gone well off the boil and now sells the same rubbish as everyone else but in a brighter colour 
.
For a condenser of the correct value that won't let you down, I can supply a CV grade (Military spec) one that you can fit either inside the can from the original or externally. Very very inexpensive plus p&p.
Failing that change the cb ignition for solid state from Britpart (through MM4x4). This is the same unit that SimonBBC sells at a much higher price, they're a tenner from MM or 6p each if you buy 100 or more from the maker in China.
The coil could also be getting hot and breaking down but first port of call has to be that condenser, the arm or witchcraft.
. For a condenser of the correct value that won't let you down, I can supply a CV grade (Military spec) one that you can fit either inside the can from the original or externally. Very very inexpensive plus p&p.
Failing that change the cb ignition for solid state from Britpart (through MM4x4). This is the same unit that SimonBBC sells at a much higher price, they're a tenner from MM or 6p each if you buy 100 or more from the maker in China.
The coil could also be getting hot and breaking down but first port of call has to be that condenser, the arm or witchcraft.
J
"Home is where you park it", so the saying goes. That may yet come true..
"Home is where you park it", so the saying goes. That may yet come true..
Re: Misfire, then dead, mg b
As above, unless your car is fitted with known high quality ignition parts, there's little point in trying to diagnose faults until it is.
Almost all sources of ignition components for these cars supply items that are better used as paperweights - utter rubbish, even when brand new. Buy a decent set of points, condensor and rotor arm (particularly the latter) from Martin at "The Distributor Doctor" and at least you will know that the fault isn't one of these.
DD supplies the properly made "red" rotor arm - don't be fooled by other "red" items available from the auction webs site of your choice, those chinese rogues are copying the red ones now, but the wuality is still awful.
I'd put money down that this will cure your fault, but if it doesn't at least you are starting from a known point regarding any further diagnosis.
Cheers
Almost all sources of ignition components for these cars supply items that are better used as paperweights - utter rubbish, even when brand new. Buy a decent set of points, condensor and rotor arm (particularly the latter) from Martin at "The Distributor Doctor" and at least you will know that the fault isn't one of these.
DD supplies the properly made "red" rotor arm - don't be fooled by other "red" items available from the auction webs site of your choice, those chinese rogues are copying the red ones now, but the wuality is still awful.
I'd put money down that this will cure your fault, but if it doesn't at least you are starting from a known point regarding any further diagnosis.
Cheers
Some people are like Slinkies - they serve no useful purpose, but they still bring a smile to your face when you push them downstairs.
Re: Misfire, then dead, mg b
Your fault is almost identical to the situation experienced on my 6 cyl Princess, i.e. no spark when hot. I totally agree with the previous posts; give the Distributor Doctor a call, chat to him and order a Red Rotor arm and as has been suggested fit a simple cheap "Hall Effect" electronic ignition set. You will wonder why you never did it before 
By the way, on the DD website is a video clip showing how the rotor arm fails, with a rather dramatic shot of the voltage arcing to earth via the Dizzy spindle instead of the spark plug via the high tension lead. It says it all
By the way, on the DD website is a video clip showing how the rotor arm fails, with a rather dramatic shot of the voltage arcing to earth via the Dizzy spindle instead of the spark plug via the high tension lead. It says it all
Re: Misfire, then dead, mg b
Best avoided as I suggested earlier, at least while they sort out their recent batch of poor quality arms that fail spectacularly when their (bonded) contact lets go and usually take out the cap with them! We used to buy from them for any students whose projects were cars that used these things but - when their customer service (really sh***y attitudeThe Distributor Doctor
) started to go downhill in proportion with the parts quality - managed to source an assortment of old stock arms and caps for the current list of such jobs. These won't last forever but the art department tell us that they have the means of creating things the Bakelite way so we're hopeful that a batch can be made, with the brass riveted as per the original - perfectly satisfactory when the correct insulation medium is used since Bakelite, unlike lighter phenolics or plastics, is stable at conditions of far greater severity than these found in a distributor.It had better work as I've located almost three stones of suitable material in old radio cabinets that can be ground back then supplemented with a little of an equivalent, sustainable shell from current crops and reformed with fresh resin, just don't tell the radio forum guys or a new identity and cosmetic surgery will be needed.
J
"Home is where you park it", so the saying goes. That may yet come true..
"Home is where you park it", so the saying goes. That may yet come true..
Re: Misfire, then dead, mg b
Very surprised to hear that JPB, although speak as you find, as they say.
Paul ( the proprietor) did say that there were some counterfeit "red Rotors" out there when I ordered mine about 3 months ago. He has resorted to marking with an embossed DD, internally, at the top of the mounting to differentiate his genuine items from the fakes.
Frankly I am surprised by your comments on the customer service issues - I found Martin to be very affable and extremely well versed in ignition technology.
Paul ( the proprietor) did say that there were some counterfeit "red Rotors" out there when I ordered mine about 3 months ago. He has resorted to marking with an embossed DD, internally, at the top of the mounting to differentiate his genuine items from the fakes.
Frankly I am surprised by your comments on the customer service issues - I found Martin to be very affable and extremely well versed in ignition technology.
Re: Misfire, then dead, mg b
It's only when you try to return their duffers to them that the bad attitude rears its head. They accused us of not fitting parts correctly! Now OK, so many of the students I look after are statemented or otherwise but they especially can - by virtue of their characteristic single minded determination - learn the most complex of procedures in an incredibly short time and retain an ability to perform it time and again at credit standard as a typical minimum. Besides, my 81 year old mother could - and often did in her mini Cooper days - fit a distributor cap and associated parts correctly so it shouldn't be and never has been too much for the staff or our students who eat, sleep and breathe their work.
I mailed over a scan of my own papers and that, instead of assuaging their doubt, prompted a reply which made it clear that they know fine well about these issues but that it's "not their fault and what exactly do we plan to do about it..."
They further told us that we shouldn't have returned the entire order as "some of the parts might have been OK."
But yes, they're pleasant enough when they're taking down the customers' card numbers and processing the payment.
If we could justify the minimum order quantity of 600 units of each item, then we would by now be buying these from the factory at a price which would make the failure rates more palatable.
I mailed over a scan of my own papers and that, instead of assuaging their doubt, prompted a reply which made it clear that they know fine well about these issues but that it's "not their fault and what exactly do we plan to do about it..."
They further told us that we shouldn't have returned the entire order as "some of the parts might have been OK."
But yes, they're pleasant enough when they're taking down the customers' card numbers and processing the payment.
If we could justify the minimum order quantity of 600 units of each item, then we would by now be buying these from the factory at a price which would make the failure rates more palatable.
J
"Home is where you park it", so the saying goes. That may yet come true..
"Home is where you park it", so the saying goes. That may yet come true..
Re: Misfire, then dead, mg b
Is it actually possible to fit a cap / arm incorrectly? 2 clips and press fit, it really doesn't get simpler.
I have misadjusted points before but I am finding it hard to think of how you would get a rotor arm on wrongly.
I have misadjusted points before but I am finding it hard to think of how you would get a rotor arm on wrongly.
Understeer: when you hit the wall with the front of the car.
Oversteer: when you hit the wall with the back of the car.
Horsepower: how fast you hit the wall.
Torque: how far you take the wall with you.
Oversteer: when you hit the wall with the back of the car.
Horsepower: how fast you hit the wall.
Torque: how far you take the wall with you.
Re: Misfire, then dead, mg b
Modern rotor arms and dizzy caps are, and there is no other word for it....... crap! Go by the personal recommendations on here for where to buy decent kit or you'll be chasing a misfire for ever.
Have you checked the engine earth lead? Had this same issue on a Triumph stag. Worth a look to see if the connections are clean and tight etc
Have you checked the engine earth lead? Had this same issue on a Triumph stag. Worth a look to see if the connections are clean and tight etc
Strive for perfection in everything you do
Re: Misfire, then dead, mg b
And that right there is exactly the problem with the customer service at the business concerned. When all is well, then they're nice as 9D but when one of the people who puts food in their mouth dares to object to shattering components then that customer is - regardless entirely of their level of competence - blamed for everything that's wrong.TerryG wrote:Is it actually possible to fit a cap / arm incorrectly? 2 clips and press fit, it really doesn't get simpler.
I have misadjusted points before but I am finding it hard to think of how you would get a rotor arm on wrongly.
I could probably think of some arms that could be persuaded to fit incorrectly but the ones I referred to were for 23, 25, 43 and 45D4s as well as the Saab/Triumph/GM Delco units and yes, we made sure that the ones fitted were correct, though the word hardly feels right in the circumstances.
J
"Home is where you park it", so the saying goes. That may yet come true..
"Home is where you park it", so the saying goes. That may yet come true..