Flooding starter carb when hot.

When queuing and the temperature gets up to about 80 degrees, fuel backs up through the starter carb and flows out of the two air intake tubes at the top in a considerable quantity and chokes the engine off. Fuel does not appear to be coming out of the normal carburettor overflow tubes at these times. The car will start again but fuel is visible at the top of the air intake tubes. I tried fitting a fuel regulator and set it on differing pressures but none made any difference to this problem. It also happens if the engine is working hard up steep hills and gets up to about 80 degrees but in these cases the engine will keep going until it clears itself when the temperature drops back down. Anybody any ideas? Posted by Td21 16/09/2016 09:22:29

Geoffrey,  It sounds like the starter carb. needs to come out for a clean. I am wondering if the little valve in the carb. is not staying closed. Over time these items do seem to collect a fair amount of detritus especially at the bottom where the needle projects. Chris Prince has available the gasket set as I expect that if not serviced for some time, the gaskets will come apart.  I know that the later TA and TC handbook have good pictures of the parts.  See also, <!-- m --><a class="postlink" href="http://sucarb.co.uk/technical-h-type-carburetter-diagram">http://sucarb.co.uk/technical-h-type-ca ... er-diagram</a><!-- m --> Hope this helps.   Richard Melbourne Posted by RichardWallach 17/09/2016 21:42:07

Many thanks for this. I'll give it a try.  Kindest regards  Geoff Widdup Posted by Td21 18/09/2016 06:14:35

Geoff,  Let us all know how you get on.  Regards,  Richard Posted by RichardWallach 18/09/2016 10:55:56

I've experienced this exact problem on my 108/G. I stripped and cleaned the starter mechanism but could find no problem with it, but did find some brown crud in the bottom of both float chambers and some hair-line cracks in one of the floats.  I've fitted 'stay-up' floats now and the car seems fine on them and now make a point of switching-off the starter carb once the car is running. I used to leave it switched on all the time and relied on the thing working properly, which it did very well for a long time. This seems to have solved the problem by and large although I still get the occasional whiff of fuel if I take a corner too enthusiastically and the tell-tale stains on the heat shield. These devices are known to be a bit of a pain on whatever car they're on.  I acknowledge that I've not really solved the problem yet, so very interested to learn now to do that. Posted by Angus D'Arcy-Drake 19/09/2016 09:12:37

Geoff Apologies for scatter gun approach which follows.  I have had the same issue with 2 different TE's. I believe the fuel level in the starting carb is determined by the level in the main ,no2 carb, and if this is higher than it should be, either because the float is sticky /holed or the main shut off needle valve is elderly &amp; working erratically  then the  fuel will overflow from the starting carb. before it comes out the main overflow which may be blocked anyway.I have replaced both the main float and the needle valve and for luck I extended the three nostrils on the starting carb by sticking a 1.5&quot;approx.  long piece of rigid nylon pipe in each one,all this appears to solved the problem.In addition I extended the heatshield downwards by about 6&quot; and at both ends by about 3&quot; with flat piece on top to shroud  nos 1&amp;6 exhaust manifolds ,these mods reduce the wave of heat that hits you on opening the bonnet and keep the unlagged fuel line  &amp;starting carb a lot cooler. On a slightly serious note the overflowing petrol on my cars ended up on/in the starter motor so if you had a flood  and were restarting the car ,the sparking starter brushes could ignite the petrol ,usually with a large  bang/sheet of flame.Fire up the Alvis literally ,so In the short term divert any overflow away from the exhaust and the starter.  The handbook has cutaway drawings of the set up which may be helpful &amp; finally my TF engined TA rallied by Roly Simmons is fitted with 2 carbs with a manual choke control, perhaps the ultimate solution?.  Good Luck, Peter Posted by Peter Martin 19/09/2016 18:10:23

Again, many thanks for the replies.  Since reporting this problem it would seem that it is an inherent problem with these carbs. Chris Prince has advised that it is so and although he has been advised why it happens he is unable to suggest a cure. So I will thoroughly clean the starter carb and extend the nostrils and report back. Out of interest I have fitted stay up floats of the next size down which has helped the fuel vapourisation problem because there is now more fuel in the float bowls to evaporate. However it didn't stop fuel evaporation in the fuel line to the carbs in recent hot weather which took about an hour to clear. My pump has not got a manual primer so I have ordered an outboard motor in line fuel pump and a non return valve which hopefully will enable me to manually pump fuel in the event of a repeat failure. Posted by Td21 20/09/2016 18:49:47

Just an update. Cleaned the starter carb, which was pretty clean anyway but this made no difference. I tried plastic tubing in the nostrils which did indeed improve matters but eventually fuel forced it's way up through the needle, overflowed and stalled the engine. I'll try lowering the float level next. Posted by Td21 24/09/2016 17:05:26

Geoffrey,  I was chatting with a chap who rebuilds SU's and is aware of the problem. He suggested that you check your timing. His opinion is that the flooding is due to what we would term backfiring but it is not perceptible. In cases that he has rectified the timing has been retarded quite significantly and this is primarily due to points wear.   Hope this helps.  Richard Melbourne Posted by RichardWallach 13/10/2016 02:14:21

Thanks for this, I'll check that as well. Posted by Td21 13/10/2016 07:49:18