|
if the compression test is ok you could also check all the connections to the starter motor and even have the motor bench tested to see that it is turning at full speed when its cold ,if the starter is original it could easily benefit from brushes and bearings ,A slow starter motor is often overlooked as a cold starting problem
|
|
Right, I've been out and checked all the cables and to be honest the starter turns over at the same speed wether warm or cold. What's the compression test going to do?
|
What's the compression test going to do?
Determine whether or not you have low compression in any of the cylinders.
|
|
|
It will measure the cylinder compression pressures when the engine is being cranked over. The results of this can help diagnose problems such as a leaking head gasket, worn piston rings or valve problems. Just as important as the actual figure is the variation between cylinders (this should be minimal). An experienced mechanic will be able to interpret the results of the test, and perform further small tests to pinpoint where any compression loss is going.
Because a diesel engine relies solely on the heat generated by compression to ignite the fuel and air mix, good compression is vital for starting, particularly from cold. Even a healthy engine has less compression when cold than when at operating temperature, so if your engine is down on compression anyway, this will be exacerbated under cold start conditions.
Over-tight valve clearances can also cause compression loss, as the valves don't close properly.
Cheers
DP
|
Good point that thanks. I've changed plenty of head gaskets but never on a diesel. If that's the reason for the difficult first start problem then I think it puts the car in the scrap yard. It's just not economic to have it done.
Strange that the car starts throughout the day ie once it's been started say at 9am and run for 10 minutes, I can then start it a few hours later easily!
How does that work?
Jim
|
|
|
|
|
|
>>95 astra merrit 1700 "Vauxhall" diesel not isuzu. I still think a compression test would be a good start. Steve. --- Xantia HDi. - Float on!
does this mean they used different diesel engines in the corsa and astra? i have a 98 corsa an it uses the isuzu engine.
|
just a thought but have you tried priming the fuel system before trying a cold start ?when was the fuel filter last changed ?
I just wonder if you have a small fuel problem such as fuel leaking back to the tank or air ingress which you would not notice when its hot
for what its worth I still think it is worth trying another starter if you can borrow one as it could be lazy all the time and unless you can bench test it or measure its load you will never know ,our local independant will bench test for £5 and bushes and brushes on a 3.2kw bosch starter cost £40 last week ,the symptoms were the same as yours it would start hot but not cold
|
Good idea about the fuel filter. I'll try changing it.
Thanks
Jim
|
You may find the new filter comes with two sealing rings - one on the outer edge of the filter, and one about an inch in diameter close to the centre of the filter. If so, do not fit the small centre seal - remove it from the filter before fitting.
Number_Cruncher
|
The reason for the question over the engine manufacturer is because of know issues with the Isuzu diesel - most engines have know weaknesses. It seems to have a problem with valve clearances closing up about 100K (apparently due to valve seat recession?). This means that when the engine is cold it can't generate enough heat due to lack of compression to burn the fuel correctly and start the engine. On my brothers Astra it was only a problem when the engine was stone cold. Cost around £100 to have the valve shims sorted a year or so ago.
Steve.
---
Xantia HDi. - Float on!
|
glowplug - it isn't a weakness of the Isuzu engines at all. Re-setting the shims is a service item on this engine. It should be done every 18,000 miles. On many engines, this task was not done, and so, after a bit, the clearances close. If they are serviced properly, they are fine.
Incidentally, re-shimming is an easy DIY job. You first measure the clearances, and extract the shims to measure their thickness. Then, get the new shims you need, and put them in. By turing the engine over so the cam is in the right place, you can get an assistent to depress the bucket with a strong screwdriver, while you remove the shims with a small screwdriver and magnet. Beyond a micrometer to measure the shims, no special tools reqired.
Number_Cruncher
|
|
thanks for the info i may give this a go on mine i thought it would be alot more difficult than that
|
If it isn't a weakness of this engine then why do the valve clearences close up instead of getting larger. I would assume that as the cam lobes and buckets wear the valves wouldn't open as far and would seat earlier. If the valve seats are receeding faster than this wear is taking place I'd say that's a weakness. Also seems to strike that particular engine at 100K.
Steve.
---
Xantia HDi. - Float on!
|
Whether you describe valve seat recession as a weakness is a matter of semantics. With many cars with hydraulic tappets, you would be unlikely to notice until the valves themselves became geometrically incapable of seating.
Practically, these engines will need their clearances increasing a bit at every service. The recession is a fairly continuous process, it happens right from being new - even at their first 18,000 service, they need the valves opening up. I suspect it becomes more noticable at 100k, because that is soon after the point when many engines drop out of decent routine servicing - many independents either don't know these valves should be adjusted, or get frightened by the idea of shims, and so leave them alone because the engine sounds quiet. (In that way, these engines are a bit odd - even at high mileages, it is unusual to find any significant cam/tappet wear, [which is especially unusual for a Vauxhall - those who remember the 8v OHC engines prior to about 1989 when hardened camshaft material was introduced will understand!])
If the tappets are dealt with as a service item, as per the manufacturer's recommendations, then there is absolutely no problem - therefore it is not a weakness of the engine, it is a weakness of the servicing routine followed by people who have higher mileage examples of this engine.
Number_Cruncher
|
|
So...Just tried draining the fuel filter for possible water. Unscrewed the dial at the bottom and nothing came out at all? Also just had one of the plugs out and got my wife to turn on the ignition and it don't glow!?
What do you wizards think about that then ?
Jim
|
Check for voltage at the plug. If there's voltage the plugs gone, if there isn't then you start tracing it back until you find it. I take it you had the plug earthed when you did the test?
Steve.
---
Xantia HDi. - Float on!
|
Yep the plug was resting against the casing. I've just called Vauxhall and they want £44 for the glow plug control box as it doesn't have a relay. I guess that's the next thing to check?
Jim
|
So going by that "it's part of the service schedule" statement, if a manufacturer said the cambelt had to be changed every 18k that wouldn't be a weakness? Sorry but if you ask me just because it's in the service schedule doesn't mean it's not a weakness. Just a feature perhaps?
www.honestjohn.co.uk/forum/post/index.htm?t=9892
www.honestjohn.co.uk/forum/post/index.htm?t=10789
www.honestjohn.co.uk/forum/post/index.htm?t=16876
www.honestjohn.co.uk/forum/post/index.htm?t=17024
www.honestjohn.co.uk/forum/post/index.htm?t=20135
www.honestjohn.co.uk/forum/post/index.htm?t=20669
www.honestjohn.co.uk/forum/post/index.htm?t=9198
www.honestjohn.co.uk/forum/post/index.htm?t=17024
Steve.
---
Xantia HDi. - Float on!
|
I suppose that a wiring diagram would be useful in tracing the cold start system. I'd be looking for a output at the control box and if that wasn't there then a voltage at the input side of the control box. If there's no voltage then have you checked the fuses, I would think there would be a small fuse protecting the low current side that energises the control box and another fuse for the high current side that's controlled by the said control box.
How are you with electrics/electronics? Does this make sense to you?
Steve.
---
Xantia HDi. - Float on!
|
Interesting saga this. I called two local Vauxhall dealers and both said "it's a control box mate". Then I came across LMF in the midlands and he said " it's definately a relay"! So I've ordered a relay to see.
As far as the control box goes I haven't a clue what it looks like or where it is!!!
Electrics? Well I can use a meter but anything more complicated than that and I'm off fishing!
I should say that all your ideas are very much appreciated. I want to keep this car on the road as a matter of principal really. All this "chuck it away and get a new one" drives me crazy but then I'm from and older generation of engineers I suppose.
Jim
{swearing removed. DD}
|
Hi Steve
Got the meter out again over the weekend and to cut the story short I found that a 60amp fuse at the end of the system had blown!
Put in a new one and she started straight away!!!
So that's a whole lot less material for the scrap yard and a triumph for perseverance! Thanks to everybody for trying to help, your encouragement has kept me going
Jim
|
Steve,
If you service these engines correctly, there is NO problem. It is only when people skimp on servicing then there is a problem. Would you describe all the myriad OHV engines that used to need their valve clearances adjusting at every service to have a weakness?
The bottom line is that these engines were really rather good - excellent performance and economy for their time - much better than Vauxhall's own. Having to keep on top of the valve clearances during services was a small price to pay for having such an otherwise excellent engine under the bonnet.
Number_Cruncher
|
NC - I see your point, I'm all for good maintence, so much so that I change my oil twice a year despite doing only about 10k per year and I use recommended oil. But with the old engines the clearences didn't close up they got bigger making a racket not reducing the clearence leading to a non starting engine. Must agree though the Isuzu is a good engine in a Astra, driven a few mile in one or two.
Steve.
---
Xantia HDi. - Float on!
|
|
|
|
|
|
