Astra 1.7 TDi stopped.

Hm, interesting. It's got to be OTR by Friday, though, so I've bought a towing bar, and am going to have a look at it at home (obvious loose connections, somewhere I've seen a reference to bad soldering). If that doesn't help, it'll be going to a diesel specialist who charges *much* less than the dealer who's got it at the moment. I wonder whether I could keep the old component, if so I could get them to check it, and flog it to someone if it's OK!

(Towing bar = Clarke TB2S from Machine Mart).

OK, to convey and record what might be valuable to someone (I've just saved about £600! THIS IS WORTHWHILE IF YOU HAVE ONE OF THESE CARS!):

I had no idea what this engine was, it was at the dealers so I couldn't look at it & reply to questions. Apologies. Y-reg Astra 1.7 diesel.

I bought a Clarke TB2S towing bar, which is a Good Thing[1] and retrieved the car from the dealer, along with their diagnostic sheet. I will try to send in the information thereon (spill valve?), but haven't got it to hand now. Basically, they said "New diesel pump control unit (not pump!), and wanted £770 to fix.

These CUs seem to cost £450-£550 depending where you get them (new or recon). Fitting is simple, although there may be "programming" to do for a new one, I don't know. The cheapest price I got to fix this was £580.

A careful "Google" showed there might be a fix. *Much* kudos to "Tony Sefton" for the original information.

I still don't know what "fly by wire" means.

This car has the control unit bolted to the back of the engine (pump?).

To get at it, undo the clip holding the thick black pipe onto the air filter (I think) and the clip at the other end. Take off some sort of plug that's wired in to the middle. You have to pull one end, rather like opening a matchbox, and the plug comes out. Remove the section of thick black air-pipe. You can then get at the diesel pump control unit fairly easily.

Down the back of the engine (back left as you look at it) you will see or feel a square aluminium thing *about* 5" square and 1 1/4" thick, with vertical fins on like a motorbike engine. It has a wiring plug which needs to be taken off. There are 4 10mm set bolts, one at each corner, to remove. These are not tight, an open-end spanner is OK.

When you've got the thing off, you will be surprised it's worth that amount. It has "ISUZU" written on it. Turn it over, and you will see a flat aluminium cover plate, probably with a round sticker in the middle, held into the rest of the thing with black rubbery sealer all round. Run the point of a sharp knife into the sealant around the perimeter. Then *carefully* but forcefully lever off the plate with a screwdriver. Under the plate is a circuit board. Careful not to damage any components! You're a step away from the fix. *Very near* the middle of the circuit board you will see a square post sticking up. It may have a bad solder connection. Look at the other connections on the board - see how shiny and perfect they are? *This* one is probably dull grey, and you can see that the solder does not connect the circuit board to the post at all well.

Scrape off the old solder from the square post *very carefully* and brighten the "O" that the post passes through on the circuit board. When it's clean, get a soldering iron (you can buy a new 30W one for a few pounds), let it heat well, and complete the joint.

Put the control unit cover plate back on with some sealer (*not* ordinary silicone IMO as it gives off acetic acid during the curing process, I used neutral cure frame sealent for PVC windows). Re-fit the control unit, plug, black air pipe, air pipe electric plug.

Then, you're off! *That's all there is to it*.

I spoke to a diesel specialist about this. He was very surprised! This may be a common fault. He'd done 6 in the last month, vehicles sent to him by "the trade". He was the one who quoted me the lowest price (doesn't normally deal with "the public"), so I passed this on to him. Personally, I think Vauxhall should do something about it. This is a minor fault in an expensive component.

The procedure would take (next time) an hour or less.

The message from Chris Bacon contains these words:

It means there's not physical connection (like a throttle cable) between the pedal and the pump/injection system. Instead, a position sensor on the pedal tells the computer how much ooomph you want and the computer tell the engine.

Interesting, thanks.

FWIW, speaking as an ex electronics engineer who has done far more soldering than is good for me, this type of dull grey joint is called a dry joint, and can be completely disconnected electrically even though it's still seemingly touching metal-to-metal.

You don't need to scrape off the old solder - you run the risk of damaging it if you try.

Get your soldering iron *and* some flux-cored solder intended for electronics. Plumbing solder and flux is not so good.. the flux particularly is much stronger and can damage the board.

Flux is a caustic compound which, when heated, will burn out any impurities in the solder, or from the surfaces to be joined. It will bubble out of the solder as you make the joint, leaving it bright and shiny.

Clean the tip of the soldering iron (scrape it on a wet sponge) then apply a tiny dab of solder to 'wet' the tip. This helps a lot with the heat transfer to the components.

To remake the dry joint you need the iron to be in contact with both components - the circuit board track and the post in this case. If they aren't both heated then solder will only attach itself to one side and you won't get a good joint.

Touch the wetted tip of the iron to the join between the two and after a moment the dull grey solder should melt. Apply a small amount more fresh solder, to get some flux into the joint and let it do it's stuff. When the flux bubbles out of the joint and it is all liquid, take the tip away. Don't be tempted to keep heating and cooling it to 'tidy it up' - that will probably lead to another dry joint. As long as it's neat 'enough' and not likely to short across, leave it. Try not to heat it for too long (more than a few seconds) as the PCB track can lift off the board which is not good. If there is far too much solder it can be picked off with the tip and wiped off on the sponge.

As in all things, keep your tip clean ;-)

The end result should be a smooth joint in bright shiny solder, firmly attached to both post and board.

Reminds me of a problem I had on a Merc with the fuel system relay; which involved resoldering a dry joint. I am guessing that a Merc replacement would cost IRO £100. I wonder how may cars are scrapped, or expensive units needlessly replaced, due to simple dry joints?

I'd say it's the most common reason for failure on most electronics.

The message from "Dave Plowman (News)" contains these words:

Dry joints, are one thing - there's also the situation where the item has unsoldered itself. Seen that quite a few times. I suppose you could argue that it's an extreme form of a dry joint....

This has got be thinking (a bad sign!) - what other cars use the same control unit? Corsas? Vectras? Vans? Cars other than Vauxhalls?