Vauxhall Astra MK4 ECU woes - help me hack it better?

[Marc Brevoort]

Hi,

I've been having car troubles where the car suddenly cuts out. Apparently it's an ECU ussue where the ECU switches off the fuel pump. I've been told it is not economically viable to get this fixed properly, but a replacement car easily runs into the thousands. Not fun.
So where I'm standing now is either to spend lots of money on a new car, or to implement a considerably cheaper hack to keep the car on the road instead of scrapping it right away.

By what I've found so far the fuel pump relay can be bypassed to keep the pump running permanently.

http://www.vauxhallownersnetwork.co.uk/index.php?threads/question-about-fuel-pump-relay-bypass.385595/

In fact this seems to work, but means I need to wire in/out the fuel pump relay bypass before and after a drive to prevent the pump from running permanently and burning out. Clearly that's rather impractical, but it also gives me a sneaking suspicion
that the bit of ECU that controls the fuel pump relay isn't all that complex.

If anyone's at the space today or tomorrow and wants to have a look, I'd be very much obliged.

Marc

[André]

I would recommend to find the fuel pump wire from the ecu and bypass it using a relay that is triggered by the ignition or a hidden switch. the hidden switch will give you extra security and the ignition will be more convenient.

As for repairing the ecu its possibly a mosfet that died. its a bit of a dog to open and to reseal it as you will need automotive grade sealent

[Marc Brevoort]

Hi André,

Yes, Something along those lines is pretty much what I have in mind. In this case I'd say convenience matters more than added security (one less thing to explain when selling on the car). Electrically it should be straightforward enough and I still have a relay in my parts box which will probably do just fine. I could probably do with some hand-holding with the  mechanic-y disassembling/reassembling bit though.

Marc

[Matt Beddow]

I wired a relay into the ignition of my mini when I added an electric fuel pump instead of the mechanical one. Pretty straight forward if you can work out which wire is which :)

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[Bracken Dawson]

The chances of this being an ECU issue are extremely small. Sadly the instances of garages blaming behaviour they can't properly debug on the computer are very common.

Common ECU failures (which are very rare) are total failure (brick), or where they are built into the ECU, an individual ignition coil driver failing (they are very high current).

It's possible that the GPIO driving a transistor driving the relay driving the fuel pump is failed, or the little transistor is failed. But I doubt it, especially as this is intermittent. More likely there is a bad connection in the wiring loom.

:wq

[Malcolm Napier]

I have been peripherally involved in two similar issues over the last year. Firstly the electronic handbrake ECU on a friend's Renault Scenic and now a gearbox ECU an an Audi A4 Avant.

I have a friend who owns an independent garage. In both cases he suggested http://www.ecutesting.com, which in your case, I think, means http://www.ecutesting.com/vauxhall_common_ecu_failures.html. The difference in his advice also was interesting.

For the Renault he said that they have had numerous instances of trying to get the company to refurbish that ECU and it was very rarely successful. Ergo the recommendation was to buy a new unit.

For the Audi, they had done fewer replacements but each one had been absolutely fine - so go for the replacement unit.

Thus my suggestion would be to exhaust every other possibility first - as Bracken suggests, but then, if that doesn't work, remove the unit and send it to ecutesting for them to test. However, a google as to ther reliability of refurbished Astra units might also reveal this to be either really sensible (people complaining that it is a common fault and replacement units are fine) or a waste of time (people complaining that it didn't fix their problem or that the refurbished unit failed again after a short period of time or didn't cure the fault).

Regards,
Malcolm 

[Alex Gibson]

I had a similar situation with the ABS ECU on my Volvo V70.  It failed intermittently then rapidly declined.  I was lucky to find an excellent how-to on the web explaining how to take it apart and fix the root cause - a production line process error where the soldering of the power connector was very poor.  Volvo dealer wanted £500 for a unit from the same production process and £600 to fit it.

The above was just to encourage you.  

Malcolm's suggestion is good - and google search the forums separately first for the relevant ECU part and 'issue', 'fault' etc, and then for the car model and symptoms you are experiencing.  If it is a likely cause, the search results should correlate closely.

Finally, is swapping the ECU an easy job? If so can you find someone with a known good example of the same car and swap them over?   Or you could look on eBay for someone breaking the same car and buy the part checking that they did not have that fault.  If it fixes the issue, great, if not, once you get to the end and fix the issue another way, you can retest the ECU to check it does not have its own issues, and put it back on eBay for at least what you paid for it.  So little or no overall loss.

Tapped on my mobile phone.

[daprigoo]

I would not recommend borrowing someone's known good ECU to test on your faulty car unless they are a very good friend or you are prepared to repair two ECUs. This was known as "walking the fault" and led to many, very expensive, exchangeable hard disk drives being written off in the good old days

[Alex Gibson]

I know what you mean. I think it’s less common for car components to break one another, whereas a second hand example from eBay may exhibit the same issue – important to check that the seller is very confident that the car it came from did not have that fault.

 

In fact the best way to test the supposedly faulty ecu is to put it in a known working car.  As car parts normally fail safe, it would immediately confirm or eliminate the ecu as the cause, for little risk – but you need a good friend with the same car!

 

Or – is anyone advertising a refurb service for these? 

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[Malcolm Napier]

My understanding is that many ECU devices have to be paired with the car and are then locked to that car.

[Eric Rowen]

My adventures in looking at making spare car keys tends to confirm that. 

On Sun, Mar 27, 2016 at 9:46 AM, Malcolm Napier <malcol...@gmail.com> wrote:

My understanding is that many ECU devices have to be paired with the car and are then locked to that car.