Mgb cutting out when hot, out of ideas!
Discussion
Hi all!
Picked the car about a fortnight ago, ran lovely for a week/100 Miles no probs, now, however recently after you've been driving say 15 miles, it will suddenly lose power and start to misfire, then slowly dies until it stalls, or will idle on 2ish cylinders for a bit. Leave it 10 mins and it will go on fine for 2-3 miles and then same again!
So far I've replaced; coil, condenser, points, low tension lead. fuel systems and carbs have been stripped and cleaned, fuel pump and red rotor arm were installed recently, has been timed and tuned etc. first time it broke down the rev counter was all over the place, then replaced ht components (conks out same as before) but the rev counter works as it should!
No signs of oil water mix or pressurisation in the radiator, as did think of head gasket?
Any ideas would be greatly received!
Darren
Picked the car about a fortnight ago, ran lovely for a week/100 Miles no probs, now, however recently after you've been driving say 15 miles, it will suddenly lose power and start to misfire, then slowly dies until it stalls, or will idle on 2ish cylinders for a bit. Leave it 10 mins and it will go on fine for 2-3 miles and then same again!
So far I've replaced; coil, condenser, points, low tension lead. fuel systems and carbs have been stripped and cleaned, fuel pump and red rotor arm were installed recently, has been timed and tuned etc. first time it broke down the rev counter was all over the place, then replaced ht components (conks out same as before) but the rev counter works as it should!
No signs of oil water mix or pressurisation in the radiator, as did think of head gasket?
Any ideas would be greatly received!
Darren
Ill look into the fuel cap, over the weekend am going to take the car onto some quiet roads to do some investigating when it happens, interesting regarding the vacuum unit, ill take a look
I've kept the old condensor but it was changed just so I could rule it out, points were ok so seems both condensers are ok, I took it back to the mg specialist who did the points so pretty certain they were done properly, fuse box was also cleaned. I've borrowed another cap and leads so will try those at some point if the fault persists. Regarding the low tension lead, it's the one that attaches to the distributor body to the points post, was in a very poor way!
Carbs again were done by the mg specialist so again would be pretty sure they were done properly. Fuel pump was new when I got the car 2 weeks ago, and the garage tested then fuel flow and was very healthy, but I've not completely ruled out the fuel pump yet.
Again the rotor was from the garage, I did query it and it is one of the decent ones,
The very first time it happened the rev counter went nuts, however recently the rev counter has been steady and shown the true engine speed throught the misfiring etc.
No oil and water mix or consumption at all, both are level and clean, I am trying to go through it methodically to rule things out.
Interestingly when I started the car today the wipers, fan and radio didn't work, these haven't been used since the problems started so can't confirm then this problem started, but wondering if they're related. I found the inline fuse, replaced it with a 35A and nothing worked and the car wouldn't start, or even turn over. A new 25A and car started but no wipers etc. cleaned the original and wipers and all are back, haven't road tested it yet to see if the fault remains.
Will also add that the engine can take a while to 'catch' from cold starts
I do intend to try a few things out when the fault occurs again so rule things out
Thanks
Darren
I've kept the old condensor but it was changed just so I could rule it out, points were ok so seems both condensers are ok, I took it back to the mg specialist who did the points so pretty certain they were done properly, fuse box was also cleaned. I've borrowed another cap and leads so will try those at some point if the fault persists. Regarding the low tension lead, it's the one that attaches to the distributor body to the points post, was in a very poor way!
Carbs again were done by the mg specialist so again would be pretty sure they were done properly. Fuel pump was new when I got the car 2 weeks ago, and the garage tested then fuel flow and was very healthy, but I've not completely ruled out the fuel pump yet.
Again the rotor was from the garage, I did query it and it is one of the decent ones,
The very first time it happened the rev counter went nuts, however recently the rev counter has been steady and shown the true engine speed throught the misfiring etc.
No oil and water mix or consumption at all, both are level and clean, I am trying to go through it methodically to rule things out.
Interestingly when I started the car today the wipers, fan and radio didn't work, these haven't been used since the problems started so can't confirm then this problem started, but wondering if they're related. I found the inline fuse, replaced it with a 35A and nothing worked and the car wouldn't start, or even turn over. A new 25A and car started but no wipers etc. cleaned the original and wipers and all are back, haven't road tested it yet to see if the fault remains.
Will also add that the engine can take a while to 'catch' from cold starts
I do intend to try a few things out when the fault occurs again so rule things out
Thanks
Darren
Edited by Dbest92 on Thursday 25th April 23:45
Cheers for the advice
After some further investigation it seems to point towards the points closing up, checked them today and were way to close (10thou ish) set them up a bit wider that the books say 18fhou instead of 16 to allow for thrm closing slightly, went for a good 20 mile run driving it fairly hard to test under load and was fine, will keep an eye but thinking new points? (Only of the gap keeps closing up?), they have been set a few times but didn't expect them to close up so soon, but lesson learned!
This could explain the poor cold starting I rekon (fine when hot though)
Ill also get some more fuses for spares and they current ones look old
Furebox was cleaned and connectors replaced a few days ago by a garage.
Also today the coil ran alot cooler, the other day, just after a few mins of idling, the coil was red hot, too hot to touch, but today was warm but easy handleable, could the tight points gap cause the coil to overheat and fail momentarily?
Interestingly the rev counter did drop a few times but started working again after a few seconds? No hesitance or missing during this though.
Don't want to say for sure it's sorted but it ran fine for a decent journey today and it seems like this could have been a likely cause!
Thanks
Darren
After some further investigation it seems to point towards the points closing up, checked them today and were way to close (10thou ish) set them up a bit wider that the books say 18fhou instead of 16 to allow for thrm closing slightly, went for a good 20 mile run driving it fairly hard to test under load and was fine, will keep an eye but thinking new points? (Only of the gap keeps closing up?), they have been set a few times but didn't expect them to close up so soon, but lesson learned!
This could explain the poor cold starting I rekon (fine when hot though)
Ill also get some more fuses for spares and they current ones look old
Furebox was cleaned and connectors replaced a few days ago by a garage.
Also today the coil ran alot cooler, the other day, just after a few mins of idling, the coil was red hot, too hot to touch, but today was warm but easy handleable, could the tight points gap cause the coil to overheat and fail momentarily?
Interestingly the rev counter did drop a few times but started working again after a few seconds? No hesitance or missing during this though.
Don't want to say for sure it's sorted but it ran fine for a decent journey today and it seems like this could have been a likely cause!
Thanks
Darren
It's still on its old points at the moment
I'm starting to wonder whether the distributor is worn as the lobes on the cam look worn but it all feels tight, my midget spoilt me for this and has done many thousands on miles in its current points with no need for attention!
It's had a few 20 mile journeys and touch wood has been trouble free, since replacing: leads, cap and red rotor with another red rotor, also have cleaned the inline fuse which controls the wipers, radio and fn, these didn't work before. Finally after fiddling around with the points, they have ended up around 20 thou and the car seems to be running better for it which is strange, but seems to be ok at the moment.
I'm thinking about in time looking down the electronic ignition route, but as yet undecided, if the car stays running ok I won't touch it! But was wondering if you had any recommendations on which ones are better?
Cheers
I'm starting to wonder whether the distributor is worn as the lobes on the cam look worn but it all feels tight, my midget spoilt me for this and has done many thousands on miles in its current points with no need for attention!
It's had a few 20 mile journeys and touch wood has been trouble free, since replacing: leads, cap and red rotor with another red rotor, also have cleaned the inline fuse which controls the wipers, radio and fn, these didn't work before. Finally after fiddling around with the points, they have ended up around 20 thou and the car seems to be running better for it which is strange, but seems to be ok at the moment.
I'm thinking about in time looking down the electronic ignition route, but as yet undecided, if the car stays running ok I won't touch it! But was wondering if you had any recommendations on which ones are better?
Cheers
Right, back to square 1 again!
Same again after just 4 miles today (sometimes lasts up tp 15/20) it started misfiring and losing power, then cuts out, give it 10 mins and it'll do about a mile and same again. Rev counter stays steady and ignition light stays off until it finally cuts out.
Has had a new coil, all leads replaced and checked, new points and condenser, gap stays where it should, tested with old and new ones, a few red rotor arms, distributor cap and leads and spark plugs, fusebox and fuses, fuel pump has been replaced, carbs cleaned and fuel flow checked under different conditions, timed and tuned, fuel cap has been removed to test vacuum in the tank, the vacuum advance works on the distributor and wiring has been tested
Completely out ideas, getting irritating now as there's been too many hairy moments beside the road and dual carriageways and its been pretty dangerous especially when there's no hard shoulder and the car has no hazards, plus the specialist garage is a fair way so can't easily get there and there aren't and decent classic garages locally
Any ideas would be really appreciated!!
Same again after just 4 miles today (sometimes lasts up tp 15/20) it started misfiring and losing power, then cuts out, give it 10 mins and it'll do about a mile and same again. Rev counter stays steady and ignition light stays off until it finally cuts out.
Has had a new coil, all leads replaced and checked, new points and condenser, gap stays where it should, tested with old and new ones, a few red rotor arms, distributor cap and leads and spark plugs, fusebox and fuses, fuel pump has been replaced, carbs cleaned and fuel flow checked under different conditions, timed and tuned, fuel cap has been removed to test vacuum in the tank, the vacuum advance works on the distributor and wiring has been tested
Completely out ideas, getting irritating now as there's been too many hairy moments beside the road and dual carriageways and its been pretty dangerous especially when there's no hard shoulder and the car has no hazards, plus the specialist garage is a fair way so can't easily get there and there aren't and decent classic garages locally
Any ideas would be really appreciated!!
Edited by Dbest92 on Sunday 5th May 20:49
Update: progress 
,
I managed to get the car to cut out in the drive at home so i could have a detailed look at some parts, car cut out and stalled as it did on the road, checked the float chambers and they were empty, problem located yay!
fuel pump pumps fine from cold, however when restarting after cutting out it appears to click fairly rapidly (which i know if shouldn't) and also appears to go slow, then fast and slow etc, car wont start like this, needs 10 mins before it will run again, i know this is something that should have been looked at earlier, but when your beside the road, first concern is getting to a safe place etc.
the garage has offered to have a look again next week. The fuel pump was new apparently and think its the SU type, seems odd for it to be packing up in such a short time? I'm wondering if its a wiring/power supply/earthing fault but aren't sure, will try and have a look over the next few days before the garage takes it in. Im not overly happy with the wiring on the rest of the car as alot of it looks old and the insulation has worn of some of the wires around the car, something i will be addressing in the near future.
Regarding leads, i have tried 3 sets on it and all appear to have been fine, interesting looking at that link as that company supplying the unrated leads is only 25 mins drive from me! May look into it in time/ i know what you mean about the leads not being on properly, on some of them you can hear them click on but some are a pain regarding getting them so seat correctly.
The car is a '73 and running a 12 volt non ballasted coil mounted upside down, the previous coil was a sports coil but now has a lucas normal 12v coil, which when left idling still gets very hot which led me down the electrics path.
so hopefully the solution is in sight! As mentioned the garage are happy to sort out the fuel pump and check the wiring etc.
Its best sometimes i'd say when your at your wits end with something like this to leave it for a few days and come back with a clear head and new ideas! It did get very frustrating as there were too many times being stranded! plus you don't realise how fast modern day traffic goes until your sat 3 feet from it in a verge!!)
Darren
, I managed to get the car to cut out in the drive at home so i could have a detailed look at some parts, car cut out and stalled as it did on the road, checked the float chambers and they were empty, problem located yay!
fuel pump pumps fine from cold, however when restarting after cutting out it appears to click fairly rapidly (which i know if shouldn't) and also appears to go slow, then fast and slow etc, car wont start like this, needs 10 mins before it will run again, i know this is something that should have been looked at earlier, but when your beside the road, first concern is getting to a safe place etc.
the garage has offered to have a look again next week. The fuel pump was new apparently and think its the SU type, seems odd for it to be packing up in such a short time? I'm wondering if its a wiring/power supply/earthing fault but aren't sure, will try and have a look over the next few days before the garage takes it in. Im not overly happy with the wiring on the rest of the car as alot of it looks old and the insulation has worn of some of the wires around the car, something i will be addressing in the near future.
Regarding leads, i have tried 3 sets on it and all appear to have been fine, interesting looking at that link as that company supplying the unrated leads is only 25 mins drive from me! May look into it in time/ i know what you mean about the leads not being on properly, on some of them you can hear them click on but some are a pain regarding getting them so seat correctly.
The car is a '73 and running a 12 volt non ballasted coil mounted upside down, the previous coil was a sports coil but now has a lucas normal 12v coil, which when left idling still gets very hot which led me down the electrics path.
so hopefully the solution is in sight! As mentioned the garage are happy to sort out the fuel pump and check the wiring etc.
Its best sometimes i'd say when your at your wits end with something like this to leave it for a few days and come back with a clear head and new ideas! It did get very frustrating as there were too many times being stranded! plus you don't realise how fast modern day traffic goes until your sat 3 feet from it in a verge!!)
Darren
That's true! It seemed to point to the electrics with he rev counter initially, but as it had been off the road for so long there may have been a few other problems!
I had a look at that link, is very good and makes it seem simpler, I'm not happy with the wires to and from the coil as they're old and the insulation has rubbed off in places!
I had a look at the pump set up in a book and looks massively complicated for what it is" hence why I'm leaving it to the garage! As, as you say, would be surprising for the pump to be failing already! More inclined to think electrics!.
I have got 2 mgs and a modern unfortunately! The original plan was to sell the midget privately but it's a lovely little car and not worth a great deal so we decided to keep it and its in my dads name for now can't insure both unfortunately 
I had a look at that link, is very good and makes it seem simpler, I'm not happy with the wires to and from the coil as they're old and the insulation has rubbed off in places!
I had a look at the pump set up in a book and looks massively complicated for what it is" hence why I'm leaving it to the garage! As, as you say, would be surprising for the pump to be failing already! More inclined to think electrics!.
I have got 2 mgs and a modern unfortunately! The original plan was to sell the midget privately but it's a lovely little car and not worth a great deal so we decided to keep it and its in my dads name for now
can't insure both unfortunately I was the original poster here and the issue was a faulty fuel pump overheating when warm. The pump was new hence being ruled out, so don’t rule out ‘new’ parts! Things like cheap condensers are of very poor quality these days and can fail after short periods of time.
My guess would be along the lines of what Mr Teddy Bear says above, maybe a hole in the carb float causing flooding? Or dirt/wear in the needle/seat?
My guess would be along the lines of what Mr Teddy Bear says above, maybe a hole in the carb float causing flooding? Or dirt/wear in the needle/seat?
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