Off the road
The MG's been off the road for a couple of weeks after breaking down on an afternoon run around the block.Right now we're trying to work out what's wrong.
During the run it started to sound like it was mis-firing and losing power; the oil gauge and revs dipped. A little further down the road the revs dropped fully, I lost power and I had to coast to a stop.
It then wouldn't start. Tried several times and it would either:
Fire but not catch
Catch but cut out (choke or accelerator couldn't stop it)
Catch and then rev right round the dial (at which point I pulled the key)
All the wires/cables seem fine and fuel is getting through - checked at the filter and at the hose before it gets to the carbs. I'd initially thought it could be out of fuel, but it after putting in a can of fuel it looks like the fuel gauge might be mis-reading. Choke and throttle cable aren't sticking.
Before taking it for a run I noticed that the overflow pipes for the carbs had become loose due to perished rubber connectors and replaced them. This is the only thing I'd done, so am a bit baffled as I'd taken it for a quick run in the morning and it behaved fine.
This weekend we had a look at the points which turned out to be set too wide. We also replaced some old fuel hose from in front of the fuel filter which had become corroded. A couple of people suggested it might be a sticking butterfly valve in the carbs (fig 3), but a look at those seemed to show them working fine (though we can't see what they're doing under power as the air filters cover them).
We're getting a spark both at the points and at the plugs, so I'm pretty sure it's not a spark problem, but I've ordered some new points and a new condenser just to rule them out.
As you can see from the video, it turns over but doesn't always fire and when it does it doesn't last long. To me it seems like fuel starvation. I broke the fuel line between the filter and the carbs and we were getting about 100ml in 30 seconds which seems a tad too little (pretty sure it should get a pint in that time). Just in case the fuel filter is clogged up with bits from the fuel tank I've also ordered a new filter.