Citroen Specials Club - the club for all lightweight cyclecars

Hi all ; last Friday was a lovely warm day so I decided to go on a 100 mile round trip into the Peak DIstrict. 40 miles into the trip there is a long down hill before a short sharp uphill , at the bottom I drop a gear to start the up hill climb, the Lomax starts to loudly backfire both in the engine and exhaust , it shakes a lot and stops . I roll back down the hill and wait until my wife stops asking questions that I cannot answer . The car then reluctantly fires up and I eventually get to the top of the hill ,after a little complaining it runs perfectly for the next 60 miles . I put the problem down to dirt in the carb,which I checked and then forgot about . Today was another lovely day so I decided to do exactly the same run , and I got exactly the same problem in exactly the same place , only this time there was a car behind me who was`nt very happy , again after the same questions and the same blank looks, the Lomax reluctantly fires up and runs perfectly all the way home ... I know its not the up hill so it must be the long down hill that is causing the problem. The down hill is about two and a half miles , I am coasting , braking, changing gear but not a lot of driving . Has anybody had the same problem and found a solution ?

Regards Ray

My car too was dying after long periods of tick over/overrun ever since more ethanol has been added to petrol this year.
Cured by installing a larger no 45 idle jet to the late 2cv carb on my Pembleton, this car, fitted with dual megaphone exhausts, performs even better with a 47.5 idle .
A 45 is probably ok on a Lomax with 2 into 1 exhaust.

Hope this helps

Jack

Obviously guess work but was the coil hot by chance

Hi both thanks for the suggestions. I didnt check if the coil was hot but once I got going again there were no futher problems.

Thanks Ray

Hi Ray... Had a similar experience last year in France. Engine didn't die but was popping and banging on every downhill with a small flat spot on accelerating at the bottom of the hill. I believe that French petrol has a higher proportion of ethanol so as Jack has suggested maybe this contributed to the problem. I did think that the timing may be a little retarded but as I had the oil cooler in front of the timing chest it was a problem to adjust.
The car is off the road with the engine out at the mo (modding a 2CV gearbox with a Dyane diff) so the oil cooler is being moved so I can play with the timing.
Not sure what to do about the ethanol problem with twin Dellortos though... We will see..

Howard

Hi Ray. Sorry to hear of your woes. Curious about what ignition system you have. I’ve had a Lumenition fitted on my LOMAX 223 for about three years now and once installed and set up then that’s it, no more adjusting needed. The oil cooler is in front of the timing box, so not having to faff around there is a real plus. The car starts ‘on the button’, ticks over like a sewing machine and runs really well too. Incidentally, I’ve got a Boyer Bransden coil, NGK B7HS spark plugs fitted and I use either Shell V Power (99 RON) or TESCO MOMENTUM 99. The car seems to like them. Costs a bit more, but in the grand scheme of things...

Hi thanks for the suggestions, I have the Mehari 2cv electronic ignition which is fairly new . I went for a 40 mile run today and it ran perfectly as usual.
I suspect rolling down hill for a long time on a hot day is causing the problem . When it happend my first thought was "Fuel" then `if I am broken down where the hell am`I. So I am coming around to think that it might have somthing to do with unburnt fuel ?

Thanks again Ray

Backfire is probably due to a mixture to lean, then as it happen going down hill I will think the needle valve get stuck.

I don't think your symptoms are exactly like mine but you might like to check the article I wrote in the latest Flat Out, and also fairly recently on this forum. The problem was due to a tiny flake of debris inside the float needle chamber. Caused intermittent cut-outs over about two years. In each case after a few minutes of sitting still it restarted and ran perfectly.

Thanks CYC Cox , I did read your article in the Flat out and it was one of the first things that I checked. I have come around to thinking that it is a mixture of hot weather and unburnt fuel when coasting down hill . I have a few things to try but the hot weather has gone into hiding .

Regards Ray