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September 2015 Homepage (Australia & NZ)
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Series Land Rover - Fault Diagnosis Exercise(Engine Start Problem)
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engine
2286cc 4cyl engine

This month we are looking at a diagnosis problem involving the reluctance to start of a 2286cc Series Land Rover petrol engine. Similar symptoms and causes apply to other petrol engines fitted as standard to Series Land Rovers, so this exercise is not specific to the 2286cc 4 cylinder version.

As commented upon on previous homepages, we must be aware that there may be more than one problem with the vehicle and they may be happening simultaneously. This is especially true of classic vehicles. So we need to group together observed faults which may have a common cause related to the problem at hand and then temporarily disregard the rest.

The main observation this month's diagnosis exercise is that, where in the past, the engine would fire-up immediately upon activation of the starter motor, it now requires repeated revolutions of the engine before there is any sign of fuel ignition. This is most marked when the engine is cold but is still present, though to a lesser degree, when the engine is warm. Use of the choke when the engine is cold gives no improvement to start-up time. The only other observation that may be retained, as of possible interest, is that vehicle performance seems to be less lively than in the past.

Well the fact that the engine runs after a single application of the starter motor(albeit after a long turnover time) suggests that the problem is either electrical or fuel related.

So lets remove a sparkplug, re-connect it to its HT lead and hold it in contact with a good earth point on the engine. The observation is that there are good sparks seen as soon as the starter motor is activated wit the ignition on. This suggests that the electrics are OK and that there is a fuel problem. So now lets re-fit the sparkplug, disconnect the fuel line from the carburettor and direct it into a small container. With the ignition OFF (or rotor arm removed if the fuel pump is electric), operate the fuel pump and observe the emission of fuel into the container. The result indicates a strong flow of fuel.

So it is looking like an internal carburettor fault due to partially blocked jets, incorrectly set float chamber level or an internal carburettor leak. But before dismantling or removing the carburettor we need to recognise that it is actually the fuel-air mixture that is ignited in the engine and not just the fuel itself. We need to check that there is sufficient air mixing with the fuel. The easiest way to do this is to re-connect the fuel pipe to the carburettor and disconnect the large rubber hose from the oil bath air filter and try starting the engine again (if you have fitted a K&N paper air filter in place of the original oil bath filter, then this should be removed).

Well the result is that the engine fires up immediately! So there is an air supply problem, but the oil in the oil bath filter is of the correct specification (standard engine oil). The oil level in the filter is also at the correct level (if too high then air will struggle to get through). Yet the air is not being drawn though it sufficiently. The hose is not partially collapsed internally, so it can only mean that the engine is not pulling sufficient vacuum to draw the air through the oil. This could explain why, with the engine warm, the engine starts a little sooner - because the oil in the filter would be warmer and hence thinner and so air would more easily be drawn through.

The observed poorer acceleration performance could also fit in with the idea that the engine is being starved of the air it needs to completely burn the fuel.

So what about the cause of the reduced engine vacuum? Well that has to be a topic for a further article.

 


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