Ford Galaxy - Glow Plug Testing and Measuring (TDI)

[Mirez]

Diesel Engines work on compression to ignite the fuel, unlike a petrol engine there is no ignition spark to worry about but in cold weather diesel can be harder to ignite so glow plugs are fitted. As the name suggests they simply screw into the cylinder and when turned on glow red/white hot in order to improve cold weather starting.

The diesel engines fitted to the Galaxy are good starters in most weather so generally give trouble free mornings however if they do struggle in very cold temperatures then it would be advisable to check and/or change the glow plugs. For this you'll need a basic multimeter, available from most hardware and electronic shops, they start at about Ã,£5 and work up to about Ã,£400 but the function we want (Resistance) is a standard feature of virtually all multimeter's.

Accessing the plugs is quite strait forward, the first thing to do is remove the upper engine cover. This is achieved by lifting the front of the cover (Red arrows) toward the sky until you feel it disengage and then sliding the whole assembly forward from the rear mounting (Yellow arrow):

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Once removed, lift off the foam insulator which will then allow you to see the glow plug rail:

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The rail is simply pushed onto the ends of each plug so can be detached by pulling it forward towards the bumper - grasp the rail close to each plug head as you pull to minimise the strain put on the cabling within the rail. With the rail removed the heads of the plugs are exposed for measuring:

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Attach one end of the multimeter to the plug head, ensure its only touching the head and not the body or the chassis. Ideally, use an insulated crocodile clip as show here:

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Finally, attach the other end of the multimeter to a good ground point. This is basically any uninsulated metal around the bay but ideally will be part of the engine and not direct to the negative terminal of the battery. The meter should now be turned on in Resistance mode as indicated by an Ohm symbol, most reasonable meters are self ranging so will detect the value accordingly but on budget meters the lowest denominator should be selected for this reading:

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Acceptable results are anything between 0.1 Ohm and 1.4 Ohm - if there is anything higher, "N/C", "OL" or "OC" displayed then the plug is considered faulty and should be renewed. Repeat the procedure for all four glow plugs observing the resistance values. Ideally, there should be less then 0.4 between each plug although unlike some other VW's the circuit is a "dumb" one and isn't capable of monitoring the individual plugs.

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