Fuel leak Weber DCNF 40
Posted: Mon Oct 23, 2017 8:04 pm
This afternoon I was tuning the idle circuit of the triple Webers on the spider after rebuilding them and noticed a severe fuel leak from the middle carb. It seemed to come out of the bottom of the float chamber (near the two lead plugs, definitely not above those), though I can't be sure as I was quite busy from keeping the gasoline to reach the hot engine (I had just driven it some 15 kilometers). I'll have a better look soon with a helper, a fire extinguisher nearby and a cold engine.
EDIT: I realised I had just filled the car up, I don't see how it could be relevant, but just in case.
During the rebuild we put the carbs in an ultrasonic cleaner (as seems to be normal with a carb rebuilt); could that make the lead plugs leak? I've searched and it seems the stuf we used (Tickopur R33) shouldn't give a problem.
Could a high fuel pressure cause it? I've been meaning to check it, but hadn't gotten around to it (needed to buy a gauge). As the car didn't run a pressure regulator that seems odd to me, although you never now after 40+ years (who knows what fuel pump might be in it).
Background;
We have been rebuilding the triple Webers of the Spider since it would die after seven kilometers. We completely disassembled them, but them in the ultrasonic cleaner for around 30 minutes and afterwards flushed them with water and thoroughly dried them. A lot of new parts were installed, apart from the gasket set: new mixture screws and springs, air correctors, all other springs, throttle valves, one spindle and the idle jets (stock jets). A bunch of parts were also zinc plated, so the carbs looked excellent. In the mean time we also replaced the throttle shaft running along the firewall with new bushes, the old ones were really tired.
We put it all back together, mounted them and double checked everything; all seemed good to go! So we went on the start the engine. Filled the float chambers and it fired up at the turn of the key, into a smooth idle. We were surprised to say the least. It went on to run well, but after 15 minutes I noticed fuel near the banjo bolts (quite a bit on the rear carb and a bit on the middle, none on the front one). Long story short, it turned out - it seems - to just the carbs spitting a bit a fuel, though I did replace all of the banjo bolts and fuel filter washers with bonded seals before concluding that.
However I'm also suspecting the lead plug in the top cover near the fuel filter, with todays addition.
With that leak sorted - by the looks of it at least - we went on with synching the carbs and setting the idle mixture. After that it drove great, a lot better than before. That was until the middle carb started draining itself from fuel...
Any ideas and/or similar experiences and advice are welcome!
EDIT: I realised I had just filled the car up, I don't see how it could be relevant, but just in case.
During the rebuild we put the carbs in an ultrasonic cleaner (as seems to be normal with a carb rebuilt); could that make the lead plugs leak? I've searched and it seems the stuf we used (Tickopur R33) shouldn't give a problem.
Could a high fuel pressure cause it? I've been meaning to check it, but hadn't gotten around to it (needed to buy a gauge). As the car didn't run a pressure regulator that seems odd to me, although you never now after 40+ years (who knows what fuel pump might be in it).
Background;
We have been rebuilding the triple Webers of the Spider since it would die after seven kilometers. We completely disassembled them, but them in the ultrasonic cleaner for around 30 minutes and afterwards flushed them with water and thoroughly dried them. A lot of new parts were installed, apart from the gasket set: new mixture screws and springs, air correctors, all other springs, throttle valves, one spindle and the idle jets (stock jets). A bunch of parts were also zinc plated, so the carbs looked excellent. In the mean time we also replaced the throttle shaft running along the firewall with new bushes, the old ones were really tired.
We put it all back together, mounted them and double checked everything; all seemed good to go! So we went on the start the engine. Filled the float chambers and it fired up at the turn of the key, into a smooth idle. We were surprised to say the least. It went on to run well, but after 15 minutes I noticed fuel near the banjo bolts (quite a bit on the rear carb and a bit on the middle, none on the front one). Long story short, it turned out - it seems - to just the carbs spitting a bit a fuel, though I did replace all of the banjo bolts and fuel filter washers with bonded seals before concluding that.
However I'm also suspecting the lead plug in the top cover near the fuel filter, with todays addition.
With that leak sorted - by the looks of it at least - we went on with synching the carbs and setting the idle mixture. After that it drove great, a lot better than before. That was until the middle carb started draining itself from fuel...
Any ideas and/or similar experiences and advice are welcome!