What's going on? T2 ecu

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KeithS
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Joined: Sat May 28, 2022 4:29 am
ECU Model: No ECU
Distributor: Rawspeed Engine tuning

Re: What's going on? T2 ecu

Post by KeithS »

Thanks for your input, by the way!

Well, as best as I can single-handed, checked voltages as described in the video. Input voltage to Hall Effect crank sensor is battery voltage 12.5v (or thereabouts) dropping gradually to 11.7v while cranking. Sensor ground voltage difficult to read on my meter as it's not that sensitive, but around 10 millivolts, rising and then gradually falling back while cranking, as shown in the video. Checking the signal, put the car in gear and rocked it back and forth (access on the mid-engined Porsche doesn't make it easy to turn the engine by hand) and voltage rose and fell from around 11v to zero and back again, suggesting sensor is at least 'reading' the teeth on the trigger wheel. But can't understand why there's no oscilloscope reading.

There is no fuel flow while cranking, which I put down to the ECU behaving as if the engine isn't running thanks to it somehow not responding to the crank sensor signal. I'll see if I've got a spark later - not a job I can do by myself as need someone else to crank the engine over while I look at the plug(s).
KeithS
Posts: 15
Joined: Sat May 28, 2022 4:29 am
ECU Model: No ECU
Distributor: Rawspeed Engine tuning

Re: What's going on? T2 ecu

Post by KeithS »

OK, no spark at the plugs... No fuel, no spark = no go! But interestingly when my wife turned the key for the first time, the engine gave the slightest of coughs – just a momentary hiccup - but nothing more. Seems to point to the ECU not getting any information to work with. Or?
Jon K
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Re: What's going on? T2 ecu

Post by Jon K »

It truly looks like it's not receiving proper crank signal. You mentioned waste spark so no cam sensor to overlay/sync with.

Because you said it's horrendous to replace, it may be worth it to pick up a USB Oscilloscope from Amazon to confirm what the crank sensor is seeing. I had a hell of a time with a cherry hall effect sensor (5v or 12v didn't matter) on a 60-2 wheel. 36 is prob better and you said it ran fine. It's an easy sensor to scope as it'll be square wave and should output whatever the input voltage is.

Something like this

https://www.amazon.com/Hantek-Oscillosc ... 201336421/
1992 700RWHP Pump Gas BMW
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stevieturbo
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Joined: Tue Aug 02, 2011 12:08 pm
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Location: Norn Iron

Re: What's going on? T2 ecu

Post by stevieturbo »

The scope is weird. It just seems to stop. Again, hopefully Alex will chime in as to what would cause it to stop reading.

A scope should read and pickup any signal whether good or bad. Stopping mid stream is useless.

As Jon says, it might be worth pickup up a cheap USB scope to get a real picture of the crank trigger. Although as I also already said, if there is a spare input that can be used for fast logging say at 1000Hz, then you could piggyback the signal wire to that for recording whilst cranking unless you can actually log the raw crank input in a similar manner.

As for a cough. The previous cranking as mentioned it did eventually sync up, trying to start but you had the coils unplugged. So likely it was injecting fuel at this point.
And during next cranking with coils plugged in it might try and start.

When it goes green and trying to start....not starting might be also partly down to flooded plugs or something ?
KeithS
Posts: 15
Joined: Sat May 28, 2022 4:29 am
ECU Model: No ECU
Distributor: Rawspeed Engine tuning

Re: What's going on? T2 ecu

Post by KeithS »

I'll send a mail to Alex with a link to this to see if he has some insight into what's happening (or not!).

Once I've had my morning coffee, I'll go and check a few more obvious things. The engine won't have flooded as the plugs are bone dry and as mentioned in an earlier post, with my wife cranking the engine over for ages, there is no fuel coming out of the injectors. There is pressure in the fuel lines - the pump primes the system on first turning on the ignition and can be heard running after lengthy period of cranking.

Being a Bank Holiday, I'm a little stuffed in terms of laying my hands on an oscilloscope, so in the meantime will continue to check all the basics.

Again, thanks for your input!
KeithS
Posts: 15
Joined: Sat May 28, 2022 4:29 am
ECU Model: No ECU
Distributor: Rawspeed Engine tuning

Re: What's going on? T2 ecu

Post by KeithS »

OK, I managed to start the car! I tried the old trick of pouring a little fuel down each throttle body and churned it over for ages before it coughed into life and ran. After a couple of minutes it idled. Plugged in the laptop and took a crank sensor reading - this time the green bar went all the way across and let me take a reading. I then shut it off and restarted it - it needed a little throttle opening to start. Took another oscilloscope reading but this time it looked totally different to the first, very flat and with short 'strokes'. It wouldn't let me take a reading while cranking as once again the green bar only went a short way across before disappearing.

Interestingly, the rpm figures on the oscilloscope readings are much lower than true - the idle is about 1100rpm.

First reading
First reading
Second reading
Second reading
stevieturbo
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Re: What's going on? T2 ecu

Post by stevieturbo »

I really wish they would have a proper scope trace.

Strangely beside the missing tooth line, there is another slightly extended line ? No idea what that means though. Or why there is a slightly thicker yellow line occasionally

I'm sure Alex will be able to decipher the lines.
SMR
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Re: What's going on? T2 ecu

Post by SMR »

Definitely reckon your crank sensor is intermittent / dodgy.

The first video clip shows the ECU eventually syncronise, after quite a few very brief sync attempts; this makes me think the sensor is on it's way out.

As soon as the ECU gets sync, the fuel pump should power up; this is a good simple check to see if the ECU is getting a good crank sensor signal.

I'm pretty sure the cranking fuel quantity is not related to TPS but I could be wrong.

I'd also recommend buying a USB scope and checking what the sensor is putting out when cranking.

Steve
KeithS
Posts: 15
Joined: Sat May 28, 2022 4:29 am
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Distributor: Rawspeed Engine tuning

Re: What's going on? T2 ecu

Post by KeithS »

The sensor (and whole set up) has done maybe 200 miles at the most, so I'd be pretty pee'd off if that was the case. But I did wonder...

The pump definitely runs once synched.
KeithS
Posts: 15
Joined: Sat May 28, 2022 4:29 am
ECU Model: No ECU
Distributor: Rawspeed Engine tuning

Re: What's going on? T2 ecu

Post by KeithS »

Guess what? Won't start this morning...
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