Diesel Gods, This one is for you - Amin_{p}
Hi guys. First I should apologise for my prolonged absence owing to new working circumstances, which still applies. The problem I have is strange, in fact does not make sense to me. My car, most of you would know by now AX diesel, the old type, I mean everything is mechanical (or is it?). ok this is the mystical problem. Every-so-often (I have yet to find either a pattern for this, or even another events which it corresponds to) you can hear a relay clicking in. Once this relay clicks in, the engine revs and power drop, and the voltage in the car drops too, for example the cabin light will suddenly become dim. However, the engine remains idling and does not switch off. This lasts for a few seconds, the relay cuts out, and things are back to normal. OK these are the facts which don?t make sense to me

1) This engine is self-regulatory. I mean the pump is mechanical and there is no ignition obviously. So the only way to drop this engine?s revs is to cut the diesel supply, however in this engine this is done via a solenoid on the injection pump which either fully cuts off the supply or leaves it fully on. So I cannot figure out for the life of me, how can the engine revs drop via some electric signal.

2) This also happens when you are driving. The effect being that once its over, the engine suddenly kicks back to life, of course it drives during this period, but it clearly lacks power


3) "Sometimes" you can "just" hear something resembling a very high speed fan, similar to a turbo sound, but very faint, during this period. Before you say, this is not the radiator fan, the two events are totally unrelated and unsynchronised. I am sure this engine (the TGD) is not a turbo, and certainly not an electric turbo, and anyway if it was a turbo I would think it would increase power, not reduce it.

4) The car has absolutely nothing else (that I know off) which is connected to the engine drive chain, other than those which are running all the time (like water pump, oil pump). For example with my dad?s car, if you try to steer whilst idling, you can just feel the engine rev dropping because the hydraulic pump kicks in for the PAS, but this car does not have any such devices which can cut in to the engine power and are electronically controller.

5) Since this is certainly related to some electrical thing, because of the relay, the only thing that comes to my mind is that this relay turns on something which absolutely SUCKS all the current and the alternator needs to got overdrive and this causes engine to drop in revs. But I know this is very far fetched, but just for the moment, even if we assume it was correct, what can possibly, in a diesel engine need so much current?

Guys, Gods, whoever, I am at your mercy. any ideas? I am not so sure if this is a ?problem? or more like some characteristics of this engine/car. But I am really interested to find out how can a diesel engine, with no electrical component (like pump), loose power because of some electrical issue? Thanks for your time, it over to you?
Diesel Gods, This one is for you - Altea Ego
I know you say its not, but this realy does sound like the radiator fan.
Diesel Gods, This one is for you - Amin_{p}
no its definatly not. I have disconnected the fan and they are independant. the problem permits even with the fan off-line.
Diesel Gods, This one is for you - Altea Ego
Its not unusual for engine revs to drop with a high electrical load. The battery is a pretty puny rating on most french cars I have found. My scenic (petrol) revs used to drop when electrical loads kicked in.

Find the relay that clicks, and check what circuit it is.

Part from that, ignore it.
Diesel Gods, This one is for you - 659FBE
Amin, This is most likely to be the glowplug timer relay energising occasionally when it should be off. The high pitched whistle you hear is from the alternator, which is attempting to balance a very large load. (This is why the lights dim). The actual source of the noise is magnetic hysteresis in the alternator iron.

Apart from a faulty (Lucas) controller, the most likely cause of this is an intermittent temperature sensor in the cylinder head, or corroded wiring to it. There are two on this engine - the other one is for the dashboard display (light or gauge depending on variant). They are side-by-side near the top hose end of the cylinder head. If the wiring and connections look OK (check continuity back to the controller) I would change the sensor first.

You can test my theory by starting up the engine normally, then take it for a run with the glow plugs disconnected. Take care not to cause any shorts, otherwise your problems will be solved for all time with this vehicle.

Regards 659.
Diesel Gods, This one is for you - pmh
Following 659s well reasoned suggestion, do you have a 'glow plug on' indicator lamp on the dash display? Does this come on? Does the cct diagram show how the glow plugs could be energised without the indicator lamp lighting? What exact model is it? I will have a look at the Haynes Citroen diesel manual if you give all the details. Also check to see if interior light dims (brightens ) by the same amount during the start up phase when glow plugs are on.

The only other possibility I can think of is if the starter motor is being energised, taking a large current and just spinning, this could cause the whine you describe. If this is the case you need to get to the bottom of it quickly to prvent starter motor burning out. The click could be the starter solenoid actuating. It could be could be caused by faulty wiring or ignition switch.


pmh (was peter)
Diesel Gods, This one is for you - Amin_{p}
Guys, thanks ever so much, two excellent suggestions. Ok, the starter motor scenario for some reason looks very attractive because this car has two other issues with the starter which I explain. The car has an immobiliser. For some reason, I have yet to figure out, if the immobiliser is active (i.e. cuts of engine), be pressing the horn on the car, the starter motor cranks the engine but the engine does not actually start ( I assume because the diesel stop solenoid is cutting off diesel). Once you key in the immobiliser and the engine in on line, the horn just makes the noise, and disengages from the starter motor. Quite how the horn is linked to the starter, via the immobiliser beats me.

A second issue with the starter is that it ?on periodical basis- will never start on the first turn of key. You will have to turn the key for the second time and it works a treat. After doing this for a week or so, it is then fine, until the next time it does it, which can be in two months. However the engine has always starter, with less than four of five cranks and I have not had any ?problems? as such. then again this could be totaly unrelated to this issue.

I take the case with the glow plugs, but to me that?s a bit less likely. First of all, the dimming is similar to when I start the car but not when the pre-heaters are on (indicated by the dash light). Secondly the dash light does not come on whilst this thing is taking place, thirdly all the electrical relating to the g/p seem to be in very good working order, and last month I took each one of the out and rewired the whole thing back in.

However that is not to say the starter scenario is fully logical. There are two problems. I thought the starter motor and its push arm operated with the same signal. i.e. it is not possible for the starter to just turn without the push arm trying to force it into gear. Am I mistaken? Under what circumstance can the starter just spin, but not try to engage? Secondly if there is no lead on the motor, i.e. no engine to crank, why would it suck so much current?

The exact model of the car is J reg Citroen AX 14 TGD, Diesel 1.4 .

PS. I am not sure if this is related at all or not, but on the topic of huge currents, there is what seems to be resembling a large resistor fixed to the front of the car, just before the bumper and on top of the radiator on the outside. This thing is about 2 inches long and half an inch in diameter. I could guess it gets very hot because it had come out of its bracket , dropped on the inner part of the front bumper, and had melted its way through the bumper and was hanging just below the car. My worry is that there is an electrical fault ?it?s only a Citroen, after all - somewhere, which is somehow not burning fuses, but otherwise sucking enormous amounts of current. One more reason I am saying is that, I seem to be going through alternator belts pretty quickly. I put one on 6 month ago, and its already on its way out, so I can imagine the alternator is being loaded heavily. Apart from there, refer to my other post in ?Will I break HF?s beloved Astar? to see that the car is working beautifully, touch wood, and so far without a single hick up.
Diesel Gods, This one is for you - Clanger
The large resistor is probably the dim-dip resistor which does get hot enough to melt plastic.


Hawkeye
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Stranger in a strange land
Diesel Gods, This one is for you - 659FBE
Amin, The dashboard glow plug light does not necessarily indicate that the glowplugs are on or off, merely that when the light extinguishes, the plugs are hot enough. After the light goes out, and the engine is started, the plugs remain on in post-heat mode, even though the light is off. The post heat period depends on the resistance of the thermistor sensor in the cylinder head.

I still think you should (carefully) disconnect the glowplugs after starting and see what happens. I have met problems with this part of the pre-heating system before...

Regards, 659.
 

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