Rough running and carbs flooding

[timdaw]

My Elan Sprint is running Dellorto's. Recently, after a period of little use, it started running rough and smoking quite a bit. The smoke is clearly over-fuelling. Took it for a run, and it was running rough. I took the top off the front carb and the fuel level was very high, about 19mm from the top instead of the correct 27mm. I checked the float level and that seems correct - 10g floats with 17mm float height. Rear carb similar situation. Needle valve is dellorto viton. Plugs were all very sooty. Fuel pump is the original mechanical one.

Any suggestions would be gratefully welcomed!

[gjz30075]

Floats could have developed a leak. Shake them to see if there is any fuel inside.

[mbell]

Normal causes would be:
- leaky valve
- leaking float
- fuel pressure to high

The last one is the one that is most likely to effect all cylinders, which seems to be the case. So I'd start with checking the fuel pressure.

What fuel pump are you running?

[Andy8421]

While it may not be the problem, I have been looking at how to best measure fuel pressure. There are cheapo gauges on ebay:

https://www.ebay.co.uk/itm/142459828773?_trkparms=amclksrc%3DITM%26aid%3D777008%26algo%3DPERSONAL.TOPIC%26ao%3D1%26asc%3D20220705100511%26meid%3Db0303802c10c4f57b18be7d43ae1548b%26pid%3D101524%26rk%3D1%26rkt%3D1%26itm%3D142459828773%26pmt%3D1%26noa%3D1%26pg%3D2380057%26algv%3DRecentlyViewedItemsV2&_trksid=p2380057.c101524.m146925&_trkparms=pageci%3A0b46faf0-869a-11ed-99c7-42da85d78bb4%7Cparentrq%3A584499eb1850a49f0bd7eee8fff4d4be%7Ciid%3A1

...but who knows what the calibration is like. 1psi = 27" of water, so a simple u tube manometer made of a length of plastic tube would allow the calibration to be checked. It seems both Webers and Dellortos need fuel pressure around the 2.5psi mark, so it may may sense to have a check.

Good luck.

[alan.barker]

Hi Tim,
You say original Pump but has it got a glass dome
Alan

[timdaw]

Hi Tim,
You say original Pump but has it got a glass dome
Alan

Yes, it's the original mechanical pump.

[alaric]

Hi. Could some muck have come through the fuel line to both carbs, that has affected the shut off valves? Try cleaning them?

Sean.

[alan.barker]

Maybe no filters fitted inside the Banjos.
Alan

[timdaw]

Thank you all for the suggestions. Will investigate and report back!

[Allison]

Hi, check the obvious but are you running E5 super or did you get some E10 regular in the tank? E10 does no good to anyone!

[timdaw]

Hi, check the obvious but are you running E5 super or did you get some E10 regular in the tank? E10 does no good to anyone!

Yes, always on Esso E5

[timdaw]

Hi Tim,
You say original Pump but has it got a glass dome
Alan

Actually, Alan, it doesn't have the glass dome. So it's clearly a replacement. The car was running very well before this happened, so I'm at a loss. Why would it suddenly have it's pressure increased?

Do you think it's worth replacing the pump with the glass dome type? I'd rather not use electric as it's a very orignal car and I'd like to keep it that way. I know that rebuild kits are available for the original pump but don't know if these can cope with ethanol, even though I always use E5.

I checked the float heights again and that the floats are not leaking.

[gjz30075]

Good time to check fuel pressure. Usually you can use a vacuum gauge, as its face is set up for both.
Somehow get a 'T' fitting to work after the pump to hook up the gauge and keep fuel going to the carbs.

[JohnP]

I have had two similar problems over time. One was a speck of dirt in one of the fuel shut off valves causing over filling of the float chamber and the second was some water in the carburettor solved by a good blast of compressed air.
Hope this helps.

[alan.barker]

Tim,
I fitted an all metal pump once to a 1973+2 i had and there was flooding too much pressure (made in India or somewhere exotique).
When driving not too bad but on tickover crap and flooding.
Alan