ECU Start Signal

I know the start signal is supplied during the operation of the starter motor but what does the ECU do with that signal? Does it modify or control the fuel pump operation?

Thanks, Andy

Thanks. I'm not sure I understand exactly what is happening though.

When the starter is turning the engine is rotating and the distributor will be rotating, so the trigger contacts will be operating, although at a low engine speed.

What does the start signal do exactly if the trigger contact pulses are present? What is the deficiency in the trigger contact pulses that the start signal overcomes?

Thanks, Andy

Thanks. I just tried a quick test. Start signal is at 0V (so no cranking), engine is rotating at 50 RPM.

I see that the trigger contacts are generating the pulses, the fuel pump is on and the injector pulses are being generated.

So it seems the ECU believes the engine is running fast enough to turn on the fuel pump at this low speed?

The start signal is only for a non-working trigger contacts? What condition do the trigger contacts not work as they are just mechanical based on the rotation of the engine?

Thanks, Andy

Thanks. I understand it is to help the engine start - but how specifically? It seems that at the starter motor speeds (200+ RPM?) the fuel pump and injectors are running, so what else is needed?

Thanks, Andy

You wrote: "starter revs are nor enough to convince ECU of a running engine. It would normally not activate fuel pump." I tested that with my ECU and the fuel pump was on.

So what test can I perform on an ECU to see the effect of the start signal?

Or does my ECU have a fault and is running the fuel pump when it shouldn't be?

Thanks, Andy

Even if the starter motor only turns the engine only at 50RPM then the fuel pump turns on. Is the issue that the starter motor speed is inconsistent? Is that what confuses the ECU and requires the Start signal?

Your site makes me think you test ECUs. If so then I presume you must know the test criteria for the start signal.

Any help with this understanding this basic ECU functionality is greatly appreciated.

I didn't find any detailed information about it online so I am wondering if nobody really knows how it works in detail enough to actually test it.

Thanks, Andy

Dr-DJet schrieb:

Hi Andy,

Your starter does not turn your engine at 200 rpm.
 

I hooked my starter motor up, disconnected the ignition coil, connected my scope to the tach signal from the distributor and turned on the starter. I get:

  215 RPM

Andy