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% I'm a Rover, can you love me anyway? % - delta_november

Mar. 19th, 2006

05:16 pm - % I'm a Rover, can you love me anyway? %

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I have now conclusively determined the cause of the Land Rover's engine unhappiness. The fuel pressure at the inlet of the carburetter is too high, causing the float valve to leak and the mixture to be much too rich. I had suspected this for about a year, but today was the first time I had a chance to test it.

The factory fuel pump is an SU electro-mechanical diaphragm unit. It achieves very low pressure output by using only spring force for the forward stroke of the piston. It is the return stroke that is solenoid driven. The whole system is commutated by a baroque set of clockwork driving a set of points (switches) and condensors (capacitors). This had always been balky. Some years ago I had stripped it open and added some drive transistors (the first semiconductors in the truck, to my eternal shame). Still, it was prone to stalling at inoportune times.

On my tour through the Orkneys a couple years ago (in the diesel 110 of covetousness) I picked up a new pump from a Range Rover. I was assured that this was a drop-in replacement, and initially everything worked fine. Some time later, though, the troubles started. I think its higher output pressure must have slowly damaged the carburetter float valve, causing more and more leakage over time.

The solution is to drastically reduce the pressure at the carburettor, by running a return fuel line right back to the fuel tank. Regrettably, Canadian Tire had only 10' of 5/8" fuel line in stock. This was enough to get back to the rear axle, but about 2' short of the tank. I was, however, able to run open-loop with the hose pouring fuel into a jerry can. In this configuration the engine runs like a charm!

In the next couple days I hope to find more fuel line, and finish that run. I'll also replace the existing fuel line, as it's about time. Then, maybe, after 12 months of dormancy, the Rover will move out of the garage.

My eyes are full of rust flecks, my hair is full of dust, my clothes all smell like petrol, but I am a happy man today :).