Vauxhall being difficult!!!

[Simon1505]

Hi
I have a vauxhall Astra 1.7 cdti on a 54 plate. It's only done 65k and has been great up til now!! My problem with it is a difficult one to describe, every morning it starts great, even on the coldest of mornings it just bursts into action, then when I stop at a job it won't start again. The problem is so intermittent though I can not gurentee when or where it's gonna happen, sometimes it goes a week without happening, sometimes an hour. When it does happen I can bump start it fine, then turn the ignition off and then on again and it starts fine!! Since the problem started I have had the diesel filter changed, the fuel pump housing changed, the glow plugs changed and the intake pipe sealed coz somebody suggested that air was getting in it somewhere and that that pipe was the most likely cause, but it wasn't and is still catching me out as and when it wants too!! I also had a diagnostics check which revealed nothing wrong. When driving around it runs absolutely fine with no other problems, so if anyone can help I would GREATLY appreciate it.

 

[Belle427]

there is a problem with the wiring connections to the engine coolant temperature sensor on these, may be worth checking first.

 

[Simon1505]

Many thanks CH427 I will try that soon and let you know what happens. Cheers

 

[Mikefromlondon]

This might be possible, but not necessarily in your case, glow plugs in all Diesel engines are switched on by a relay controlled by a timer, which gets triggered by you turning on the ignition switch, it is likely that there is a fault in the timer that it does not reset quick enough to be retriggered again short while later, but when you are parked all night it will trigger ok even in the cold, is there any way you could put a small pilot light or an LED across the supply that is fed to the glow plugs, or in other words do not look at your dash light but monitor a seperate light attached to the relay output, this will give you a more true picture as the dash pilot light might not be wired across the relay output but rather across the timer output.

So if you connect a pilot light across one of the glow plugs and the engine or body earth, you should check that it lights up each time you attempt stsrting your car, if the light does not light up, then thats where your problem is with the glow plug timer/relay/ fuse.

dash light doesn't truely indicate if the actual power has reached the glow plugs. It is there for the driver to wait before it goes out before he can start cranking the engine.

 

[Simon1505]

Thanks mike, that is another thing to consider. My mechanic mate has only yesterday started on the other idea of the sensor that was suggested before. He found a water leak from one of the rad pipes which was spraying all over the sensors, replacing the pipe he also found that the thermostat was opening when dropped into a cup of boiling water. He said these 2 things might even be the problem, don't know what your views on that are? A friend as a mechanic is sometimes good but when several things have been tried and failed to solve the issue I should be getting the ump with the garage for me keep feeding them money!! You can't really do that with mates doing it on mates rates!! But if what he's doing ow doesn't work I will put your therory to him or try and sneak the van into a proper garage!!
Thanks again Mike, really appreciate your time
Simon

 

[Mikefromlondon]

yes your mate is doing best he can, water gushing onto sensors can render them useless, depending really on theor sensitivity to change with water, but water can also set corrosion, which in turn can make bad contacts. these things arn't straight forward, and often requires a process of ellimination, which of course also means time and money.
As for your thrmostate, it should open up when submerged in very hot water close to boiling point.....around 85C degrees onwards.

Hence why i suggseted monitoring the glow plug power rail, to see whenever your car fails to start, is the voltage available at the glow plugs, just don't rely on the dash light alone, as I said the pilot light often says all is well but it cannot tell if the glow plug power is not reaching through several reasons, and including glow plugs going open circuit, fuse being loose, loose connections somewhere,

I would run a seperate piolot LED, to use an LED, you have also got to know that you can't just wire it across +ve and -ve, it will just blow up or not light up if connected wrong way, so first check on youtube how to connect an led, it has a long lead and a short lead, long lead denotes to +ve connection or Anode, and the short lead denotes to -ve connection or cathod, and you must also use a small 1/4 watt series resitor to prevent accessive current flowing through it as otherwiose it will glow so bright for a split second and die, so on a 12v car electrics any value between 220 Ohms to all the way up to 1 Kilo ohms will be fine, lower values will allow more current and higher value will allow less current, naturally this means lower current is dim and higher current is bright, but if you just need it to test your glow plug rail to see each time you turn your ignition On, this led should light up for those few seconds that it is suppose to heat up the glow plugs. Maplin can sell you LED and 1/4 watt resistor,

If not you could just use any 12v car bulb of about 5watts rating, such as used on number plate lighting, the bulb cxan be wired any way around and does not need a resistor like an LED does. but bulbs run hot whilstr LED's run cool.

Once you have wired up your LED, make sure that you wire the long lead of the LED to your glow plug power rail and short lead to vehicle chassis.

good luck