Hi,
I wondered has anyone come across this problem with their diesel Metro, AX, Saxo, etc. Occasionally when turning on the ignition the glowplug light doesn't extinguish until the car is started (as if a temperature sensor isn't working) and then when the engine is running you can hear the relay cutting in & out, at idle this causes the engine speed to change (I assume due to electrical load). As far as I can tell the problem seems related to the water temperature sensor (green one on the front right of the cyl. head), I've tried 'tightening' the connections on this but it hasn't made any difference, I suppose it could be either a faulty sensor or a broken wire. What I really need is a good description of how the cold start system works, I've read what I can find in the Saxo owners manual but it's still a bit short on detail.
Merry Christmas and thanks!
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I?ve no experience of any Rover diesels, so this is a very broad generalisation. The glow plug is an electric heater which assists the engine firing when it?s first cranked. The relay usually incorporates a timing device to turn it off, usually about 10 or 15 seconds after the ignition is switched on. Some very old diesels (agricultural or boats) used to have a removable plug in the cylinder head to allow a wad of burning paper to be inserted, for the same purpose.
I shouldn?t think it has any connections to the water temperature sensor; probably just a loose or defective relay or a loose connection.
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Yeah, a loose or broken relay spring comes to mind
MG-Rover Problems? Click on forums.mg-rover.org
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The glowplug timer relay fitted to the PSA TUD5 engine works as follows:
The pre heat time (time to extinguish dashboard light) is determined by a thermistor inside the timer relay. The timer relay should be bolted to the coolant header tank to sense engine ambient temperature. The pre heat time is 5 or 6 secs max when cold if the correct Beru plugs are specified.
After the dashboard light is extinguished, if the engine is not started, the plugs will stay on for 20 secs, after which the unit disconnects the plugs to avoid overheat or battery discharge.
Following a successful start, the plugs remain on in the post heat mode. The duration of post heat is determined by engine coolant temperature, sensed by a thermistor screwed into the cylinder head, adjacent to, but separate from the one used by the temperature gauge. With a cold engine, the post heat can be 5 minutes, when hot a few seconds only.
Finally, there is a short circuit protection function, which causes the relay to disconnect the plugs if the current is excessive.
If your unit is buzzing, there is probably a wiring fault, or possibly a fault in the unit. Disconnect the battery before checking, as the input stud terminal is permanently live. You can open these units carefully with a hacksaw around the base to check for mechanical problems with the relay, otherwise there is nothing much else which is replaceable.
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Thanks for the info, I guess the thing I couldn't get my head around was that even after the car has been running for over 15 minutes it can and does energise it's glowplugs. I'll clean up and tighten all the terminals & try to check for broken wires but I feel a trip to the scrapyard coming on, sounds to me like a fault on the relay control unit itself.
Happy Christmas!
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It's fixed! Turned out to be a faulty coolant temperature sensor, the green one on the thermostat housing. After ringing several dealers without much luck, most wanted actual part numbers,etc. I nipped down to the local car spares, they'd got one listed (including photo!) for £5.50. It arrived about 3 hours later! Fitted in 5 minutes.
Steve.
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Steve, thanks for telling us the outcome. It would be nice if everyone did likewise.
So it was what you suspected in the first place. Good thinking, Tonto!
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