bigbravedave
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| posted on 24/10/10 at 08:07 PM |
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MGB engine won't start, fires once then dies
The old man's got an MGB engined car, Its a pretty high state of tune and has always run spot on.
After not starting it for a month, when you crank it over, it fires once, enough for the starter motor to disengage, then it dies as instantly as it
fired. It will do this every time you try to start.
It has standard coil, dizzy, ignition etc. embarresingly I have no experience of tradition ignition.
It has fuel, and a spark but im suspecting its an ignition issue.
Help!
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MakeEverything
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| posted on 24/10/10 at 08:10 PM |
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Sounds like ignition to me too.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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marcjagman
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| posted on 24/10/10 at 08:11 PM |
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Check the fuel pump by disconnecting the pipe from the carbs, make sure you are getting fuel into the SU bowls, change the points and condensor
(common fault)
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owelly
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| posted on 24/10/10 at 08:14 PM |
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I'd say check points gap first. Or give it a squirt of Easystart just to eliminate a fuel system fault. Then check for HT shorts (easy in the
dark!).
http://www.ppcmag.co.uk
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jacko
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| posted on 24/10/10 at 08:24 PM |
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Has it oil in the SU 's suction dampeners ?
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blue2cv
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| posted on 24/10/10 at 08:34 PM |
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Did they run a ballast resistor coil on those like the Fords did, had same symptom on a transit once
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steve m
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| posted on 24/10/10 at 09:26 PM |
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Potato stuck up the exhaust ?
As i have done it to a problem neighbour and they spent weeks trying to fix the problem
And then scrapped the car
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paulf
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| posted on 24/10/10 at 09:35 PM |
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After trying the above suggestions I would take the tops of the float chambers blow them out and fill with fresh petrol, also check the choke
mechanism is working correctly as they always need a bit of choke when cold.
I recently started mine after it had stood for about 4 years without turning , all I did was to clean the points with a bit of wet and dry , blow lamp
the plugs and put fresh petrol in it and away it went.
Paul
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slingshot2000
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| posted on 24/10/10 at 10:06 PM |
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quote:
Originally posted by steve m
Potato stuck up the exhaust ?
As i have done it to a problem neighbour and they spent weeks trying to fix the problem
And then scrapped the car
I wish you had shared that a couple of years ago, we have had years of grief with a neigbour over parking in our cul-de-sac !
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mark chandler
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| posted on 24/10/10 at 10:18 PM |
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If it only fires when cranking could be a couple of things.
Probally ballast resistor gone west or bad connection, with the ignition on do you see +9v at the coil?
On some cars they have the ignition wrapped up with the oil pressure, bit of a BL thing. Coil will only get power when cranking or when oil pressure
is present so could be related to this, try earting the oil pressure wire and see if it starts then.
If its carbs try squirting a bit of fuel in the carb mouths when it starts, if it runs like this it proves the electrics and points at the carbs,
altough as twin carbs is doubtful if its these to be honest as it would run roughly on one.
[Edited on 24/10/10 by mark chandler]
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britishtrident
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| posted on 25/10/10 at 07:54 AM |
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MGB is the simplest ignition system possible -- no ballast on UK market cars iginition coil is supplied straight from the ignition switch.
If it is firing while being turned on the starter it is unlikely to be an ignition fault.
Like wise if it is firing on the starter it suggests the fuel is working and delivering to the carb float bowls.
If the car is on twin SU check the carb pistons are rising and falling freely, if it is on the USA spec Zenith Stronberg CD same applies also with
a CD carb it could be the carb diaphram has a pin hole.
The other thing to check is twin SU specifiic --- the core plugs at either end of the inlet manifold balance pipe can get blown out by a back fire.
The front core plug is obvious but for the rear one you will have to feel with your fingers or use a mirror. If blown out the core plug ends up on
the scuttle in front of the heater box.
[Edited on 25/10/10 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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bigbravedave
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| posted on 25/10/10 at 08:10 AM |
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Thanks for all the suggestions, I will look at the points, It has fuel
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britishtrident
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| posted on 25/10/10 at 08:12 AM |
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quote:
Originally posted by jacko
Has it oil in the SU 's suction dampeners ?
That won't stop it starting but using too thick an oil in the carb dampers will.. 20w/50 is too thick in cold weather the oil needs to be
10w/40 or thinner --- 5w/30 or ATF is ideal.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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cliftyhanger
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| posted on 25/10/10 at 09:00 AM |
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Sorry to contradict you mr trident, but according to MGhive there are 2 coils. RB MGB's did use a ballasted coil....
if the car in question IS a rubber bumper model this would be my first port of call.
The ignition coil gets 12V when cranking from the solenoid, but onve cranking is done, this goes off, and the coil lives on a 6v feed. Or in this case
it may well not be.............
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britishtrident
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| posted on 25/10/10 at 09:17 AM |
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If you read my original post carefully it says UK market MGBs did did not use ballasted ignition this is 100% correct.
Ballasted ignition however was used by BL on cars sold in Canda & Scandinavia.
Of course some cars built for overseas markets have leaked back into the UK but not that many.
quote:
Originally posted by cliftyhanger
Sorry to contradict you mr trident, but according to MGhive there are 2 coils. RB MGB's did use a ballasted coil....
if the car in question IS a rubber bumper model this would be my first port of call.
The ignition coil gets 12V when cranking from the solenoid, but onve cranking is done, this goes off, and the coil lives on a 6v feed. Or in this case
it may well not be.............
[Edited on 25/10/10 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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pewe
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| posted on 25/10/10 at 10:21 AM |
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Just to add a curved ball to all other suggestions.
Had similar problem on mine recently.
Turned out the fuse for the electric pump had corroded.
It allowed pump to run but insufficient for full delivery i.e. pump ran but fuse wouldn't sustain big load required for full pumping.
After going through all the processes listed above I directly wired the pump and found the problem!
HTH.
Cheers, Pewe 
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paulf
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| posted on 25/10/10 at 09:43 PM |
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I also had a similar similar problem years ago, the car refused to go over 30mph and I tried everything possible including changing the cylinder head
, carbs etc.It turned out to be a weak fuel pump which was able to supply some fuel to start the car but not enough to keep up when driven.
Paul.
quote:
Originally posted by pewe
Just to add a curved ball to all other suggestions.
Had similar problem on mine recently.
Turned out the fuse for the electric pump had corroded.
It allowed pump to run but insufficient for full delivery i.e. pump ran but fuse wouldn't sustain big load required for full pumping.
After going through all the processes listed above I directly wired the pump and found the problem!
HTH.
Cheers, Pewe
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Macbeast
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| posted on 26/10/10 at 07:46 PM |
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My friend at the local MG garage, who has been repairing MGBs for 20 years, says MGBs after 1975 had ballast ignition, with the ballast resistor
wrapped in the loom.
Easiest way to determine this would be see if the coil says 9V or 12V. Easiest way to determine if the ballast resistor is at fault would be to take a
(very ) temporary feed from the battery to the coil +ve terminal and see if the engine keeps running.
I'm addicted to brake fluid, but I can stop anytime.
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Dingz
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| posted on 26/10/10 at 09:04 PM |
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I had a similar problem once it was a bad connection on the ignition switch, supply to ignition was fine in the 'start' position but when
it returned to 'run' there was no supply, check you have supply to the dissy in the run position.
Phoned the local ramblers club today, but the bloke who answered just
went on and on.
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adithorp
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| posted on 26/10/10 at 10:45 PM |
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quote:
Originally posted by Dingz
I had a similar problem once it was a bad connection on the ignition switch, supply to ignition was fine in the 'start' position but when
it returned to 'run' there was no supply, check you have supply to the dissy in the run position.
If it dies as soon as the key returns from the start position to ignition and it's not a balasted coil (BT, I've got a customer with a
very late MGB that she's had from new and it's balasted) then I'd check the igniton switch as said above.
If it's fueling related it'd be more a case of dieing away or refusing to idle/stalling rather than cutting out.
adrian
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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02GF74
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| posted on 27/10/10 at 08:37 AM |
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Fig 10.33 Typical wiring diagram, later UK models
57 Resistive cable (or ballast resistor)
Key to fig 10.33 not all items fitted to all models but I suspect that this is fog lamps and other auxilliary components.
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