MGB Register Forum

Hi everyone.
Finally got GT a few months ago and am steadily sorting things out.
One thing which is baffling me is that our drive has quite a slope on it and the B won't start easily after parking overnight. Takes a couple of minutes of churning before it will fire up. Same problem as well with the other halfs Midget.
I have been playing with Minis for around 45 years so am fairly well clued up on SUs (I guess it is a fuel problem) but this has me beat. Both cars start perfectly when on level ground.
Any ideas please.
I should say that the cars are parked facing down the slope.

Thanks
Brian

Have you tried it facing up the slope?
Just a thought.
John

Have asked a few people with Bs, this is what they said...
1.The non return valve (or check valves) on the SU fuel pumps will not stop fuel from draining from the tank to the carburetors if the car is parked facing down on a steep slope. The only thing that will stop the fuel is the needle valve in the float chamber and even that may not stop the flow depending on how the float is hinged. The best thing for people who have this problem is to install a shut off valve somewhere along the fuel line.
2.The fuel level is too close to the top of the jet tubes and draining into the carbs/intake manifold causing flooding.

Thanks for the replies.
Tried it facing upwards, better but still not good.
I suspect you are correct Dave, petrol running from the tank to the carbs.
I've ordered one of these to try out, I'll fit it just before the carbs easy to get an ignition feed to it.

http://www.ebay.co.uk/itm/Petrol-soleno ... 25ab6fbf47

Whenever I start my car I always switch on the ignition and then wait until the fuel pump stops, so I know the carbs are full whatever level it is parked on. I then pull the choke out to the maximum - check you actually have full travel as this is not always the case and if you don't have full choke it simply won't start easily.
Finally - and this made the most noticeable difference - I fitted a matched electronic distributor and coil with new plugs and leads. The difference is amazing - it starts 1st time every time now, and 'churning' over is a thing of the past. The car performs so much better as well........
Hope this helps.

One thing I omitted from my earlier post - you should ensure that the float heights are correct as per the handbook for your car. If they aren't it is possible that sitting on a slope will exaggerate the fuel levels one way or the other and this could affect the amount going - or not going - into the combustion areas.
I doubt if it is the needle valve as a defect here would likely result in flooding, if anything.
These carbs are very simple to set up and if they are clean internally there is not much apart from wear that can go wrong with them if they are left alone.
I had to make sure my choke was opening fully - I found it was about 1/4" short on full travel of the cable but once I had reset this properly everything was fine. I use a GUNSONS COLORTUNE in conjunction with a cheap suction/volume meter, and I have opened the plug gaps to 35 thou. to match the output of the new electronic distributor (set at 10 dbtdc).
Hope this helps - mine starts first time every time following the 'disciplines' I indicated in my previous post.

Thanks Jim.

I fitted the cutoff valve to the Midget as it was a bit easier and it has made no difference at all.
Im pretty sure the float levels are set up OK on both the B and the Midget but I'll double check.
One other thing I'm a bit concerned about is the oil level. It's a steep slope and although the oil is topped up OK it will all run to the front of the sump away from the pickup.
If all else fails I'll have to clear the garage of my Innocenti De Tomaso waiting restoration and put the B and the Midget in there.

A simple way to check what is happening with the oil is to remove the coil lead so it won't fire and then to spin the engine over.
If the gauge registers pressure you have pickup in the sump o.k. - if it doesn't move then you have to worry..........

Well I'm giving up on this trying to park them on the slope.
After a lot of turning over the Midget finally fired up. Very rough but managed to get it onto the flat at the rear of the house and low oil pressure. Float levels perfect. Very strong petrol smell but no leaks. Checked the oil level only to find very high over Max and obviously had been contaminated by petrol being sucked in during the turning over and run down the bores.
Changed the oil/filter, put some oil down the bores, turned it over without the plugs in. Oil pressure back up. Plugs cleaned and back in started first time, running perfectly again.

If you can smell fuel you have a leak.
Modern fuels can degrade rubber hoses - remove and check all of them around the fuel pump as well as the carburettors. If they are old just renew them - good quality fuel hose is cheap to buy. Check the copper fuel pipe - it normally lasts for ages but there may be some minor accident damage or a kink which has weakened the wall.
If you still cannot find a leak check the float needle valves - one or both might just be sticking and the carbs. might be over-fuelling and giving you the smell....
Fit an inline fuel filter just before the carbs - these are cheap, easy to fit and eminently successful if you have rust/detritus in the tank, possibly causing the float needle valves to stick hence flooding/smell..........
Finally, give thought to fitting electronic ignition; it works.