ECR33 releases ecu feed relay during crancking

I've got a ECR33 in the shop , non runner. Link G4+ plugin ecu, not sold or installed by me.

No rpm signal during cranking. I do get a rpm signal when spinning the cas by hand.

Basically the feed from the cas is dropping to 6V which results in no rpm output on the cas. To my measurements this happens because the ecss relay(which feeds the cas) starts flickering. I've measured that too : its the ecu grounding side of the coil that gets a flickering signals. It happens quite fast as most i see is a field of induction noise.

all grounds of the ecu are good , feeds are good (no more then a 0.2 voltage drop referenced to battery ground/feed).

bridging the eccs relay results in a rpm signal during cranking. Grounding the eccs relais myself also results in a rpm signal.

it does start when you keep a charger on it , it doesnt when you try the day after

any input from someone here ?

picture included is the negative side of the relay coil measured to ground. you can clearly see it "releasing" the relay when you start cranking and then going on-off-on ... resulting in a lot of noise

The ECCS Relay is grounded via the ECU when you put ignition ON. Make sure you have enough voltage to keep the ECU "Awake" while cranking, if you don't have enough voltage the ECU will release the ground to the ECCS Relay

EDIT : Seeing that you say your car starts after charging the battery, I would start by replacing the said battery...

The ECCS relay is not controlled by the "ECU", but by a separate very simple mosfet circuit on the adapter board. The fet is controlled by pin 45 (wire from ignition switch). So when there is +12V on pin 45 the FET will ground pin 16 which is the trigger for the ECCS relay. So first thing to confirm with your scope is the voltage on pin 45 during cranking. The FET needs more than about 7V on this pin to stay "alive". The wire that supplies pin 45 has many devices connected to it (from memory fuel pump, oxy sensors, idle valve and others) so the most common issue is a bad connection or tired contact along that wire somewhere (the main contacts inside the ign switch is a common cause). If you have low voltage on pin 45 then work your way backwards to the ign switch find where the voltage drop is.

If voltage does actually look ok on pin 45 and all grounds are good but pin 16 is still dropping out then there is a chance of a hardware issue. I know there were some FETS a couple of years ago that were found to "drop out" above their quoted voltage spec so if it has been sitting around a while you potentially have one of those.

Hi Adam , thanks for that , i'll have a look.

Even when it starts i hear the relay flikkering during crancking so i'll start measuring next time i have some time.

i'll report back

Tried it a bit , with a good battery the car starts , if i put a bit of an old one in it refuses.

the picture:

lower signal is pin 45

upper signal is pin 16 (the ground for the eccs relais)

measured against the ecu ground(my scope has a common ground for both inputs)

so about 9V during cranking on pin 45. ecu doesnt keep pin 16 grounded.

ECU serial number is 48778

Yeah, it should not drop out at 9V. Talking to the tech support manager he believes yours probably is one of the ecu's affected by the bad fets that I mentioned above. Unfortunately it needs to come back to New Zealand for repair. If you can get in touch with our UK office you can ship it to them and they will handle getting it back to NZ and back to you.