Author Topic: Fuel in the sump  (Read 959 times)

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Offline Bainford

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Fuel in the sump
« on: Monday,June 04, 2018, 07:16:38 AM »
I took Friday off work so I could spend the whole day lavishing some love on the Lotus, and get it running and on the road after winter storage. At the end of the day I was ready to fire it up. Before doing so I gave a quick check of the oil level and found it to be very high on the stick, and smelled of gas. So I drained it, and removed about 10-12 litres of oil/gas mixture from the sump. The car last ran in November, at which time I changed the oil, filling the sump with 4.5 litres of Castrol 10w-40.

That was late in the evening and I haven't had the chance to investigate further. I suspect the culprit is a failed carburettor needle & seat, or perhaps more likely a carb float that doesn't float. This would presumably allow any fuel volume in the tanks that is above the carb float bowl height to drain into the engine over the course of the winter. I still find this odd, though, as the car was stored with only about 3/4 fuel load, which doesn't leave much available to drain through the carbs. I am curious as to any theories anyone may have.

Questions;
- Is it reasonable to assume that the fuel pump would provide no restriction to the fuel draining theory described above?
- Can the oil pump drive be accessed and driven with an electric drill by removing the distributor? What tool (socket, extension, etc) is needed to do this?
The Twin Cam plays the symphony whilst my right foot conducts the orchestra. At 3800 rpm the Mad Pipe Organ joins in.

Trevor

Offline RoddyMac

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Re: Fuel in the sump
« Reply #1 on: Monday,June 04, 2018, 08:02:53 AM »
Are you still running a mechanical pump?  If so, it could be the pump diaphragm. 

Offline EuropaTC

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Re: Fuel in the sump
« Reply #2 on: Monday,June 04, 2018, 08:40:49 AM »
Hmm, I think I'd prefer Rod's idea of the fuel pump to a carburettor fault. Again, I'm not familiar with the Stromberg engines but I would have imagined they are above the fuel height and even if the fuel pump valves were both open (which they shouldn't be ?) then it would still have to siphon over.

If the glass bowl is empty or very low then I'd be thinking it's leaking into the block from the pump like Rod suggests.

Offline jbcollier

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Re: Fuel in the sump
« Reply #3 on: Monday,June 04, 2018, 09:08:05 AM »
Carbs are high so unlikely to siphon more than the bit of gas in the float bowl.  The fuel pump is the more likely to be the culprit as it’s much lower down.

Offline Bainford

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Re: Fuel in the sump
« Reply #4 on: Monday,June 04, 2018, 09:13:30 AM »
Ah, fuel pump leaking directly into the block. That sounds quite reasonable. Yes, the fuel system is still pretty much factory stock, so still a mechanical pump. The glass bowl is about 3/4 filled with fuel.

I will attempt to flush the lube system by filling the sump with clean oil and running the oil pump with an electric drill. Presumably this can be done with the distributor removed. Anyone have an idea of what tool is needed to drive the oil pump?
« Last Edit: Monday,June 04, 2018, 09:18:45 AM by Bainford »
The Twin Cam plays the symphony whilst my right foot conducts the orchestra. At 3800 rpm the Mad Pipe Organ joins in.

Trevor

Offline jbcollier

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Re: Fuel in the sump
« Reply #5 on: Monday,June 04, 2018, 09:22:17 AM »
I wouldn’t worry about externally running the oil pump.  Fill with fresh oil, remove the plugs, disable the ignition and spin it over on the starter until you get oil pressure.