My neighbour's 1996/7 Astra 1.7 TD has a strange problem developing (I think!), related to the fuel cut-off solenoid(s?) on the fuel pump.
He has had difficult cold starting, (turning over for ages, unevenly, then eventually starting with a cloud of smoke and still uneven for a few seconds), so I checked the glow plug feed / timer, and then replaced the glow plugs. I tested the old ones and 3 of them didn't work at all, so I thought 'job done'.
However, I then started the engine to make sure it was ok and it started within a couple of seconds, but it wasn't as instant as you would expect from a diesel (obviously letting the glowplug light go out before turning the key). So I immediately switched it off (so I could try it again) but it carried on running!
If you start the engine and then turn the key off again within a few seconds, it carries on idling. If you then leave it switched off, it will continue idling until about 12-15 seconds after you started it. (So it will run for a total of 12-15 seconds regardless of whether you try to turn it off after 1 second or 11 seconds). It's absolutely fine if you don't switch it off within that time. My neighbour (whose car it is) has never notice the fault, but has probably never tried to stop the engine immediately after starting it!
Anyway, I thought it must be the fuel cut-off / stop solenoid not closing, so I checked the feed to it: there is none (ignition on or off, engine running or not): it is earthed continuously. However, if I disconnect the 3-pin connector in the wiring that goes under the black plastic cover on the back of the pump, (above the cylindrical cut-off solenoid), the engine cuts out immediately (whether within the first 12-15 seconds or after that). One wire to this 3-pin connector has continuous earth, one is earthed with ignition off and live with ignition on, the third wire doesn't give any reading (on a test-lamp screwdriver thingy). I am wondering if the normal looking (as on most diesel cars of this age and older) cylindrical stop-solenoid is permanently stuck open or partially open and whether there is another solenoid (that the 3 wires go to, in the back of the pump), that stays open for at least 12-15 seconds after starting, even if you switch the ignition off again within that time. I can't think why it would need to do this, but presumably it's linked to an ecu or timer or immobiliser or something. When the normal stop-solenoid is working properly (ie closing as soon as the ignition is switched off), having the second solenoid staying open for 12-15 seconds wouldn't make any noticeable difference because the engine would just stop as expected when you switch off the ignition, due to the cylindrical one closing and cutting off the fuel.
So, can anyone throw any light on this strange fault?: Is my diagnosis/theory/guess about a second solenoid correct?
Also, the old type cylindrical stop-solenoid must be open, otherwise it wouldn't get any fuel through and so it wouldn't run. But there is no feed to it, so it must be either stuck open or somebody has removed the plunger, so it needs to be replaced. But then it won't start because the new one will stay shut unless I find out why there is no feed to it. Any suggestions on this?
Thanks.
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I would certainly say that you were correct in suspecting the fuel solonoid but I am not familier with the pump used by Vauxhall. The later Bosch pumps have a shielded immobiliser assembly on the pump which are quite well protected and require some brute force to remove. The year of the car is just about at the changeover point. Hopefully someone will come along with some more useful information.
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Hi Peter. Thanks for your reply. It IS a Bosch pump on this Astra, with a small black plastic cover where the 3 wires go in.
I did try to remove it but was worried about breaking it. Does it come off intact with a bit more force, or to you destroy it when forcing it off? If so, does it matter? Also, does it actually give useful access to anything anyway?!
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If its the same one that Citroen use the solonoid and module are behind a steel cover which is secured with tamperproof screws. To get to it you will have to remove the pump and then use some brute force . I have not done one myself but if you look on the 'french car forum' there are one or two that have done it on a Xantia. It might be easier to fit a secondhand pump.
Edited by Peter.N. on 28/11/2009 at 20:34
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