Montecarlo ECU - any simple diagnostics for hall cells?

Road-race engines and ancillaries - general discussion
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Robhi
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Montecarlo ECU - any simple diagnostics for hall cells?

Post by Robhi »

Hi, I am new to the forum and slightly in awe of the expertise that appears to subscribe to the posts. I am also new to ECU and fuel management systems (my former cars being 'normally' aspirated) so I am trying to learn quickly (so please forgive any stupid questions).

I have an '82 Lancia Monetcarlo 2l fitted with Fuel injection (after market Redline Weber system) and I am trying to put the pieces together why it is intermittantly so difficult to start. I am trying to work through this in a logical manner starting with what seems to be the most obvious (to me).

It does appear that some of the wiring around the throttle position sensor and timing sensor has been damaged and repaired (looks like some of the engine bay bonnet lining has melted and dropped onto the wiring). My first guess is that the Hall pick-up sensor on the toothed crank wheel is giving a weak or erroneous signal (or maybe interferred with by electromagnetic induction where the wiring has been repaired (the wire wrap surrounding the cable now being non-continuous and supplemented by additional insulation?).

So my (first) questions are:

I presume that the hall sensor provides a simple binary type pulse as the toothed wheel rotates?
Are there any simple tests that can be carried out to see if the crank trigger sensor is working/working consistently and/or being interferred with by electomagnetic induction?
Looking at other posts it looks like I might be able to eliminate emi by fitting silicone tubing over the repaired wiring?

Any help would be much appreciated.

Best regards

Robert
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TomLouwrier
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Re: Montecarlo ECU - any simple diagnostics for hall cells?

Post by TomLouwrier »

hi Robert,

And welcome.
The Hall-sensor is an analogue device, so it gives distinct pulses alright but no digital signal. The ECU contains a converter that normalizes and digitalizes the signal for further processing by the, ehm well, processor.
The only way of checking its functioning is by hooking it up to a scope. They used to be plentiful and expensive 30 years ago, now they're mainly scarce. Besides you have to know how to work them. That is why most garages just pull parts and replace them until they happen to come across the defective one. Of course you pay for all parts... OK call me an old cynic.
If the wiring is not shielded (maybe coaxial) type, you may get away with jut checking it for breaks with an ohmmeter.
Electromagnetic interference can only be eliminated by metal shielding (Faraday's cage), not rubber. If that wasn't there in the first place, forget it for now. Assume things worked ok when installed.

Mind you, our friend Samo had a long and hard time with a similar situation on his Integrale and found out that the cause of it all was that the toothed wheel was not centred correctly, interfering with the signal and (thus) throwing the converter off so it was missing pulses. You may want to check that too.
viewtopic.php?f=5&t=2368&start=315

regards
Tom
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Simon
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Re: Montecarlo ECU - any simple diagnostics for hall cells?

Post by Simon »

Hi Robert,

Just a few questions to help put this in context:

Have you actually established whether or not the system ever functioned properly in the past - i.e. has it all been mapped up with all the cold start enrichment etc optimised?
What are the exact symptoms - problem starting from hot or cold?
Is there anything in particular that leads you to doubt the crank sensor, apart from the damaged wiring?

I'm not familiar with the Weber system, but OEM systems and electronics in general.

I would first all the earths and other connections, then check the supply feed to the ECU and sensors with a meter under cranking conditions to see if you have sufficient voltage. In terms of the crank sensor, the output of the this will depend on what type it is too. If it is a three wire device (gnd, supply and signal out) then it will be a digital square wave output (probably 0-5V). With most of these types of sensor you can check the output with a multimeter and check for a high or low when in proximity to a tooth, so you may be able to watch the meter as you rotate the crank slowly throughout the full rotation checking for a 0 or 5V at each tooth. Also check that the gap is something like 0.5 to 1mm and consistent for each tooth. If is a two wire device it will probably have a raw sine wave output. Either way a scope is definitely the best instrument to check the output like Tom says.

Good Luck, I hope this helps. Any chance of some pictures?
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Robhi
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Re: Montecarlo ECU - any simple diagnostics for hall cells?

Post by Robhi »

Many thanks for some very useful information (I am already impressed by the speed of the responses and keeness for people to share their experiences and knowledge).

The car was very difficult to start and erratic when I first got her (purchased as near clomplete car requiring further work). So I started a systemic check on wiring and moving through fuel flow through to the ignition. The spark plugs fired but appeared to be irregular and of variable strength which initially led me to consider the ignition leads and coil pack (also matched my observations of the individual exhaust ports being variably warm following attempted start ups). I tightened connections and replaced the spark leads and (coincidently?) she fired and ran smoothly at tick over until warm. I then made a few wiggles of connectors to get a sense of any loose connections. I just touched the throttle body sensor (and may have concidently brushed the connector for the crank trigger) when the engine died immediately and wouldn't restart. It was then that I noticed some old heat damage to the throttle body position sensor and that the wiring for the crank trigger sensor had also been damaged and repaired. I tested the throttle body sensor and found a smooth transistion in resistance with rotation (which appeared reasonable but I don't know the original range). On uncovering the damaged wiring for the crank trigger I found a replacement soldered in section and the original Faraday sheath missing over approximately 2-3inch length directly over the cam belt pully. So I was getting a real sense of getting close to the problem but wanted to see if I there was anything I could do to check the crank trigger.

The comments provided have been very helpful (it is a three wire sensor). Any suggestions for repairing the lost section of the Faraday sheath?

I will try to post some pictures once I have worked out how to do this.

NB I have the software for the ECU but haven't got the hardware connections and just don't wont to go there yet until I have improved my knowledge!


Many thanks
Robert
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fingers99
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Re: Montecarlo ECU - any simple diagnostics for hall cells?

Post by fingers99 »

If the sheath is damaged and you can get a replacement crank sensor at a sensible price (Aldon Automotive do the Weber stuff and will probably have one on the shelf) that's the way I'd go. They can give rise to some really strange errors.

But the sheathing is nothing super special -- as long as there is electrical continuity from one section to another you can probably get away with using the sheilding stripped from a length of TV co-axial cable.
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