Technical Bad earth & poor starting

[mj2k]

That was quick, to do all that work

I still keep thinking it's got to be something daft like cranking too slow, but having said that I'm sure I have read somewhere about dry joints in the ecu, and seeing as it's mounted right next to the engine where it's likely to get quite hot and wobbled about a lot, the ecu thing may not be that far fetched after all...

I suspect if you did try a 2nd hand ecu you'd need to pay to get it 'freshened', i.e. you'll need to pay someone to delete the existing security codes from the ECU, otherwise it'll give you a permanent non-start and an immo error.

 

[IanWard]

Hi Mj2k, there was 2 of us at it and was in my brothers garage which helped loads and was warm & dry. It’s definitely not cranking slowly, it spins over on the starter very well.

I might try and pull off the ECU and open up and visually inspect for any obvious signs of damage - not overly hopeful, but have come so far and still not got to the bottom of it…

 

[A3jeroen]

If it's similar to the Stilo engine, the gap between pulley and sensor needs to be very small.
As in: just not touching.

gr J

 

[IanWard]

The gap isn’t adjustable, the crank sensor sits in a fixed bracket, once the car actually starts it is fine - the gap is probably about a 1mm

 

[John202020]

There have been reports of a poor ecu earth to rocker cover, but you've probably checked that?

 

[IanWard]

Hi John, yes that was one of the first earth point we cleaned and checked

 

[IanWard]

Tried a replacement ECU, BCM, key and ignition barrel today after being convinced that was the problem as starts fine in limp (with crank sensor disconnected) and a pain to start but runs fine with it connected... long story short, no change still takes a while cranking before it fires. Put the original equipment back on (but at least managed to rule that out).

Have now managed to zero the learned settings, clear and reteach the crank sensor after doing the proxy alignment.

took the airbox off and sprayed a bit of easy start in the throttle body, did try starting so looks like the spark is there.

Took the ECU kit back and have now got a replacement fuel rail to try tomorrow. cant be much left to try now...

 

[John202020]

took the airbox off and sprayed a bit of easy start in the throttle body, did try starting so looks like the spark is there.

IF it tries to start from go with easy start that suggests wrong fuel mixture at starting?

With the crank sensor connected try disconnecting the slightly damaged Lambda sensor? Just to rule it out, are the engine temp readings correct?

 

[IanWard]

Hi John, have replaced the thermostat which has a new temp sender in it, I did doubt the old one as read full temp after 4-5 mins idleing from cold. We’ve had the lambda sensor unplugged and sorted the best we can the dodgy plug, so will try that tomorrow if the rail doesn’t fix it.

 

[IanWard]

Fixed:

@varesecraze

So finally got to the bottom of the problem, on the way to my brothers to replace the fuel rail, swung by Euro and picked up another earth lead (just on the off chance)

After having a replacement (heavy duty) earth cable fitted on the LHS of the engine to body and this tested out to work well. with <0.2v when testing to battery neg when cranking (good is typically <0.5v) presumed everything was all good.

so fitted a smaller earth strap back to the original place (body to gearbox) and fitting the fuel rail, it started perfectly as it used to. so removed the earth cable, and what do you know, deterioration in starting again...

left the fuel rail in as the donor car has 25k less on the clock.

BUT morale of the story the gearbox needs earthing, earthing the engine alone doesn't cut it, will attach photos to show for reference.

Finally feel like I have my sanity back and one very happy daughter has her car back.

 

[mj2k]

D'oh! After all that, back where you started :doh:

10/10 for perseverance and trying just about every possible thing on the car, and glad it's finally working, think I'd have been looking at it menacingly with an angle grinder long before now :worship:

 

[IanWard]

Have to admit Mj2k my patience was on the limit, that said the car did need the cambelt doing, had a full service so other than a couple of sensors not really spend too much ££ un-neccesarily, just a shed load of time.

I will certainly log this one for future reference in making sure any faulty earths are replaced back to exactly the same points. Even though the replacement cable on the left was far more robust and the car cranked over, there must have been some resistance in some electrical component that was just on the threshold...