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Hello,
As a temporary daily I've bought myself an Alfa spider 2.0 16v TS from 1997. This car came through an estate sale and has stood a few years.
I now have an issue getting it to start. I've got the ECU immobilizer disabled but it won't fire.
It's got a Motronic m2.10.4 injection system.
The main relay gets a direct 12v on pin 30. Turning the ignition on sends 12v to the ecu directly and also powers pin 85 on the relay. To operate the relay it then needs a ground on pin 86 and according to the electrical diagram that should go through the ecu. Would I be correct to assume that supplying the ECU with the ignition 12v it would need to switch on the ground for the main relay?
That ground seems to be missing at the moment.🤔
Unfortunately it's got an older style OBD which I can't read at the moment. Adaptercable is on order to solve that.
Has anybody got some deep understanding about these older Motronic systems?
I'm starting to wanna torch the car...
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qilin
Part of things
Posts: 19
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On other older Motronics the main relay is grounded by the Ecu. For the Ecu to ground the relay the engine must be turning over. The crankshaft sensor sends the signal(AC) to the Ecu. No signal means no ground so no start.
Do you have a link to the wiring diagram?
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Mar 13, 2024 13:48:49 GMT
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On this version the main relay is also ground by the ecu.
When you turn the ignition on it should activate the main relay. The fuel pump runs through a fuelpump relay which is switched by the main relay. Originally the pump primes a few seconds when you turn the ignition on.
Yesterday i got another ECU. With that ECU there is an injection light that comes on when the ignition is on. It switches the relays. This ECU will now be made immo-off and I hope that solves it.
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qilin
Part of things
Posts: 19
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Mar 13, 2024 18:35:02 GMT
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I had a look at a wiring diagram and the motronic works the same as previous versions. There must be an rpm signal for the main relay to be grounded. The fuel pump relay is the same. The fuel pump ground goes back to Motronic 1.0 and later versions had the fuel pump and main relay controlled by the Ecu.
With that Motronic m2.10.4 system it is possible that it also requires a air input signal from the MAF.
The old Ljectronic had a similar principle if the air flap opened then the fuel pump would run. As in later versions meant to stop the fuel pump if the engine is not turning.
If you replace the ECU and it does not work then you know it is not the Ecu. The crankshaft sensor or sensors(x2 in first motronic) not working was a common no start pre immobilizers
Forgot to add, check the inertia switch which cuts of the ground to the fuel pump
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Last Edit: Mar 13, 2024 18:53:23 GMT by qilin
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Mar 13, 2024 19:27:22 GMT
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How do you explain that on these Motronic the fuel pump start up on ignition only then?
There is no signal from the tdc sensor at that time but the main relay and fuelpump relay need to be activated for the pump to work.
Normally these relays 'click' when the ignition is put on, the fuel pump relay deactivates after a few seconds if the car is not started but the main relay keeps activated and provides power to the coils and injectors until the ignition is switched off.
I checked the inertia switch for the pump and it works.
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qilin
Part of things
Posts: 19
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The fuel pump runs with ignition on to provide fuel pressure. It is a timed output. You can check the timing at the pump or the relay. The last time I checked on a car was about 12 seconds (not your motronic). After the set time it does not run until the car starts. Some systems have a delay before ignition on runs the pump again. You can check for your car.
These things are set in the Ecu. They are safety related, like the inertia switch.
On your car it looks like both the 85 and 86 of the main relay are linked to the ecu. From the diagram I looked at the main relay provides 12V+ to the Ecu, the AFM, idle regulator and phase regulator relay among others.
There may be a longer timed output. You could check and see.
The missing ground on the fuel pump is normal when it does not receive the signal that the engine is turning over. If the engine turns over to slowly then the signal from the rpm sensor is not correct and no start. The same with the AFM if the Ecu requires that.
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Mar 14, 2024 17:28:28 GMT
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A mate brought me another ECU. With that ECU the main relay and fuelpump relay were activated on ignition. The ignition warning light also comes on. But the coils don't fire due to the immo. I had the immo removed and replaced the fuel pump that didn't work and now it runs. So the original ECU was the problem somehow. Glad to have it running. qilin , thanks for brainstorming with me👍🏻 |
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qilin
Part of things
Posts: 19
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Mar 14, 2024 19:19:12 GMT
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That is good to hear, the only thing worse than a no start is the intermittent no start.
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