This was a funny one, somehow, technically speaking. It came to sad conclusions for the previous Owner and underlines that lack of proper maintenance can lead to value loss.
This friend of mine, for whom I replaced an ECU on an Astra G, got rid of the car and bought another one, Opel Corsa C, Z12XE, 2002, at auction. Him, being lucky, had found it close to home, about 5 km. He got it cheap and soon he found out why, engine stalled at about 3 min. It wouldn't fire immediately but if he waited 1 minute, it would go ok for another 3. The good news was the chain did not rattle and engine run very nice.
He did a fault code scan check and found no errors. Then he called me for help.
It was a bit chilly outside and I was not in a mood to hang around out that much, so I really hoped that the crankshaft sensor would play up and I can catch it on the diagnostic scanner or dashboard meter. We started the car and we actually had to wait for a while to warm up. And yes, engine stopped. To my disappointment, engine rpm PID had data on start and also on dash, so no, it was no crank sensor.
I had no choice than go out and have a look. And now its about directions, where do you go? Spark, fuel, timing, relays?
I started with the relays and swapped ecu relay and fuel pump relay. No
I had a spark coil with me, we swapped. No.
Picoscope out of the box, lets look to Cam and Crank sensors, well, there was some periodical noise, but nothing suggested that there was a problem there. So no.
Next was fuel pump current and things got interesting. Watch this:
Ignore the peaks, caused by the fuel injectors (same fuse). Side note: you can actually see the ECU strategy to keep the engine running, it increases the injection time.
So, fuel pump current drops. Why? The brushes pattern does not give signs for concern. We have the following options:
- bad power supply to the pump, plus, minus
- bad fuel regulator
- bad pump.
In order to exclude the fuel pump supply voltage, we used another channel to connect to the fuel pump connector, below rear seats. And guess what, we found signs of previous work (plastics damage to the cover). Hmmm, someone has been here before. And because I was already fed up with this car, I connected also the fuel pressure transducer on another channel. And this showed up:
Blue line pump voltage, constant, no problem. Brown, fuel pressure dropping, together with pump current.
What I noticed was, fuel speed was going up, while current dropped, speed increased with 1000 rpm. And everybody now knows, when an induction motor speed increases, there is no load.
We both scratched out heads and the only option we had was the fuel pump regulator, next day scrapyard was open. So I left and boy, how wrong I was.
Later in the evening I asked him, can you send me a picture of the fuel filter?
What do you think? I think its old. Genuine GM label. Nice and rusty. Told him, before you do anything else, change that asap.
And yes, he did that next day and gladly report, no more problems. How can this be, 2002 car, 169.000 km, was that really never changed?
Can you open the old one for me please, cut it open, hand tools only, please??
Everyone loves a happy ending. Share your diagnostic success stories here.
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