MGC not starting well - any advice?

[bjpirt]

Hi all,
There seem to be a lot of car experts hanging out on these forums so maybe one might be able to help me troubleshoot why my '68 MGC Roadster doesn't like starting. I'll try to describe the symptoms the best I can but shout back with any questions...

- Turn the ignition on and the fuel pump starts ticking and then gradually stops (I assume as it builds up pressure)
- The battery is a single small-ish 12V battery that replaces the two 6V batteries it originally had - I leave it plugged in to a trickle charger so it should be full
- When I got the car in August it started fine but has got worse since then
- Try to start the engine and it turns but won't fire. I have to keep turning the key off and then on and eventually it will cough into life. This might take a minute or two.
- Once it's been run that day it will usually start first time. But it's often a week or two between runs.

Obviously it's got worse as the weather has got colder, so I'm not sure if the summer was masking the problem or whether it's just a coincidence. The things I've considered are that it might be the ignition system (though it does run fine once it's eventually started) or the fuel supply. Though I'm not really sure where to start with figuring out what it actually is short of just replacing parts left right and centre!

Any advice is massively appreciated.

Cheers,

BJPirt

[DocArbathnot]

I would check the ignition 1st, points, plugs, leads, timing etc. Make sure this is set up correctly then service, balance and set up the carbs as per the manual.

A "C" is a big old engine, are you sure your battery is up to the job?

[benters]

Provided the battery is up to the job and you havent noticed any difference in the speed in which it turns over the engine i would look at the HT Leads, Plugs, Coil, distributor and arm. . . if they are all passed there best then that could be time well spent. Could it be an air leak weakening the mixture ? is the choke cable working properly, sticking float bowl ? would pull them off just to check, (blow through the inlet and action the float to see if its shutting off properly or at all). . .

[one eyed mick]

Older type engine needs older type servicing ,plugs, points, valve clearances ,air filter , distrib cap ,leads all need checking /adjusting or replacing . After that carb service ,is choke working ?. then with a proper battery it should be good for 6k miles and do it all again . Basically you have a 1930' lorry engine with big heavey component to wirl over so the battery has to be top line ,this is not a knock I cut my teeth on these in various forms and looked after will run for ever

[PaulKemp]

You say battery is a smallish 12v
I always go for the biggest battery I can fit on road cars
My kit car has smallest I can get away with and a geared high torque starter
If you use jump leads as well when starting and it starts better then your battery is not up to the job

[PeterBurgess]

Assuming plugs, points, carb settings etc etc are correct and in good condition, the most common problem we have with early MGs is poor voltage(low) to the coil under cranking conditions. Usually caused by fusty fuse box and fuses or even poor wiring. Try a separate wired charged up 12v battery to supply power just to the coil. Sometimes one can 'catch' the engine to start by almost switching off the engine whilst cranking, the pwoer to the starter motor ceases and the voltage to the coil increases, with the engine still turning from the effects of the starter motor the engine starts. The voltage problem is one of the reasoons ballasted systems were fitted on later Bs. 8v coil boosted to 12v on cranking.

I hope this helps.

Peter

[bjpirt]

Wow, fantastic and speedy replies - thanks everyone.

I'm going to try a few things to try and sort this out I think:

- check if the battery is underpowered by using jump leads
- try connecting a battery to just the coil to see if it's the fuse box, etc
- replace the HT leads, distributor cap, rotor arm, spark plugs and maybe the coil so I know they're good

And hopefully that will sort things out. The effect of 'catching' the engine that @PeterBurgess mentioned sounds familiar so I'm quite suspicious of the fuses.

After doing some more reading of this: http://www.v8register.net/subpages/V8NOTE390.htm I'm tempted to switch the battery out anyway as it feels quite small for the size of the engine. I'm not at the workshop right now so can't check the actual specs.

Cheers,

BJPirt

[Locknut]

BJ, you never mention using the choke in your detailed description of trying to start the car in post#1. Can we assume that you are using it? The symptoms you describe sound very like the choke is not being used.

[bjpirt]

Sorry, should have mentioned that. I do use the choke when trying to start the car and have it fully out. It does seem to be working as once it's running adjusting it will adjust the idle revs of the engine.
Cheers,
BJPirt

[RichB]

bjpirt said:

Sorry, should have mentioned that. I do use the choke when trying to start the car and have it fully out. It does seem to be working as once it's running adjusting it will adjust the idle revs of the engine.
Cheers, BJPirt

Don't forget that on the SUs the choke has two operations, one to increase the revs and also to pull the jet tube down to enrich the mixture. These are adjusted by separately so it's quite possible for the adjustment that increases the revs to be working without the jet's getting pulled down enough. Usually it's the other way round though.

[Bennachie]

Points and condenser, assuming originality and not a pointless alternative.

[Phil Hill]

Random thought also around having sufficient power "left" while cranking.

Check the engine to body earth strap/lead/wire etc. This is the bain of Mini's particularly at this time of year.

Also the one from the battery to the body.

I've got a decent brand 002 battery (from a Grande Punto I think) in my MGB V8 and it starts that up no problem. CCA was a little low at 330 and only 45Ah but both still better than the twin 6v's and about half the price..........

Phil.

[bjpirt]

Thanks Phil, I'll check that too. I've just ordered a bunch of new ignition kit including a new condenser.

Fantastic comments from all - extremely helpful.

Thanks,
BJPirt

[PaulKemp]

If it transpires that it is indeed a battery problem it may be worth looking at the gel type batteries much smaller than lead acid more powerfull
Russ at Furore has a selection at a keen price

[RichB]

For a classic like an MGC I would be reverting to twin 6v batteries and fitting something like the rubber cased batteries made by Lincon batteries in Southend http://www.lincon.co.uk/

[davepoth]

RichB said:

bjpirt said:

Sorry, should have mentioned that. I do use the choke when trying to start the car and have it fully out. It does seem to be working as once it's running adjusting it will adjust the idle revs of the engine.
Cheers, BJPirt

Don't forget that on the SUs the choke has two operations, one to increase the revs and also to pull the jet tube down to enrich the mixture. These are adjusted by separately so it's quite possible for the adjustment that increases the revs to be working without the jet's getting pulled down enough. Usually it's the other way round though.

And of course it could be that the mixture is excessively lean; if the mechanism is working properly and it still doesn't cause a warm engine to bog down when the choke is pulled all the way out then you need to enrich the mixture a bit. Definitely start with all the ignition bits though, you'll never get it running right otherwise.