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MG MGB GT V8 Factory Originals Technical - Very tough starting when cold

My 4.2L has a Carter carb w/an electric choke. Damn thing is really, really hard to start in the AM. Here in central VA this time of year we have cool, very dewy mornings. It generally catches on the first crank, then dies, then it takes ten more cranks over ten more minutes to get fired up, then it works fine. I've checked the usual suspects, like the diss cap, but everything looks fine. Any suggestions? Also, does one rev the motor when starting or just keep one's foot off the gas pedal?

I guess this is an insulting basic question for this group, but I must be forgetting something basic.
Harry M. Peeters

I always give mine a few squirts of gas before cranking & a little throttle until it runs smoothly on its own.


I also have a carter and the car has a hard time starting if rained on overnight. My problem is a loss of spark control as my dist. cap has an open inspection hole and gets wet inside. If your cap also has a hole on side ( as to ease adjusting the points ) make sure it is covered. When it does not start, check to see if you have good controlled spark by removing one of the plug leads to observe while someone cranks engine. If it does have spark and you don't smell alot of gas, squirt some carb spray/ starting fluid into carb and try to start. In the mornings when temps are low you should pump the accelerator 2-3 times and crank the engine. It should run smoothly on its own at a high idle. If it does start but simply does not stay running until at operating temp, check operation of choke. With the key on check the power and ground supplies to the choke. If Ok, make sure nothing is binding. On the choke you will see a plunger (rod going into choke) . Move this through its range of travel to make sure it moves easily. To check choke operation in morning (cold ambient temps) turn the key on , pop the hood and manually pull on the accelerator cable. If the choke works then a cam should rotate into place under the idle screw and prevent butterfly throttle blades from returning to closed position. This gives you fast idle. Also, on top of carb you should have a flap (choke valve) that should be completely flat down. As the choke warms up the flap should slowly open to allow more air in. If the valve is only slightly closed or the fast idle cam does not rotate far enough, then your choke might simply need adjustment. On later electric choke carters simply loosen the choke cover and rotate to enrichen/ lean the mixture. Good luck.

Just an idea for those with wet weather starting problems:

Use a section of inner tube cut and glued to fit around your distributor to keep water out. It can easily be removed if you are showing your car or peeled back to make points adjustments. It works great for those of us who have off-road vehicles too. Jeff.
Jeff Schlemmer

I forgot to mention: your Carter carb. - how old is the electric choke, and is adjusted per manufacturer's specs? Replacing the choke coil if it is more than a few years old is a good idea. Also, if it is not adjusted properly, a rich/lean condition will offer the results you are trying to repair. The easiest solution is a manual choke, but with a little persistence, you can make the auto work well.
Jeff Schlemmer

As far as my factory V8 goes it lives outside and is used in all weathers. It usually starts very reliably with the same 'cold' starting characteristics both winter and summer. The one exception is that the plugs seem to get 'tired' after several thousand miles and it needs more cranking. I know then to get a set of plugs in because soon it will eventually not start at all - then installing the new plugs will make it fire up instantly. I have not noticed this with any other car I have owned, routine replacement at 10k seeming to occur way before any noticeable performance problems.

Paul Hunt

Paul, what brand of plugs do you use? Just wondering. I always use NGK's standard or U-groove plug and have had excellent durability (as opposed to Champions or Bosch Platinums.)
Jeff Schlemmer

You might want to check to see if your fuel level is low in the carb after the car has sat overnight. You can check this by removing the air cleaner assembly and sweep the throttle a few times. while looking in the throat of the carb. You should have a good strong shot of fuel out of accelerater pump nozzles each time.
If not the carb may be percolating the fuel out when the engine is warm. I have found that Carter carbs will percolate especially when they are in a "warm" MGB engine bay!
You can reduce percolation by installing a thick heat insulating spacer/gasket under the carb!

Good Luck!
bill jacobson


What NGK plug do you use? I am looking for a direct replacement for the Champion L92Y (standard plug for the Buick 215 and the Rover engines with the short reach plug). I have always liked NGK and Nippondenso plugs, but their cross reference to Buick/Rover engines is a bit sketchy.

Paul Kile
Paul Kile

I've used both Champion and NGK and noticed the same effect with both.

Paul Hunt

Harry if your complaint is a "Start-and-Die" you might want to see if you have a defective choke pull-off diaphragm. It is vacuum operated and should pull the choke plate open about .250" after initial start. Apply vacuum to the diaphragm and watch what happens. If the choke plate doesn't open when you apply vacuum, replace the diaphragm. They're not expensive and do fail.

Funnily enough, after some grotty weather conditions lately (fluctuating temperatures, wind and rain, standing water when it isn't raining) the car was a bit reluctant to start today after standing a week. When it did start it missfired under load very noticeably until it warmed up. Damp ignition system I suspect.

Paul Hunt

This thread was discussed between 23/10/2000 and 28/10/2000

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