Crank sensor / TDC Sensor

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Crank sensor / TDC Sensor

Postby jonc » Mon Apr 18, 2011 10:58 am

Turns out it was my turn to have an Alpine failure on the way home from an event (1st time for me). We'd just had a great time at the Renault Sport National meet at Heritage Motor Centre.

Cruising along the M40, the 'electronic incident' warning light came on and the revs suddenly read 0.
Nothing from the accelerator and as we eased on the hard shoulder the lights came on to show the engine had stopped. Turned over nicely but didn't fire up.

I wiggled all the wires I could think of but to no avail. Of course, when the RAC guy turned up, things had cooled down and it started first time. It only ran for about 5 miles before packing up as before.

Fuel pumps running fine, no spark, though. The RAC guy tells me that the crank sensor is a common fault on Renaults. Gets hot, goes open circuit and stops the engine. All sounds very plausible.

So, from what I've seen / read the crank sensor is the TDC sensor? Is that right?

Would this failing cause the 'electronic incident' warning light? Ideally, I'd like to plug this into the XR-25 to make sure but not sure I could get to a Renault dealer without it failing again!

Assuming it is the TDC / Crank sensor, this looks relatively easy to sort but is it difficult to get to? On top of the flywheel housing?

A wee search on the forum last night showed that many people have had trouble with this sensor. I reckon the fact that out of nowhere the RPM went to 0 would suggest that it's this sensor.

(just edited this in!) Forgot to ask. Are new TDC Sensors easy to get? Looks like an Alpine rather than Renault part number. Simon Auto have them...

Are there upgrade / better replacement parts?

Thanks in advance for any help and advice

Jon
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Postby clee » Mon Apr 18, 2011 11:18 am

You should be able to get one from Renault easily enough .Used on a few models .Swapping it is a bit fiddly .It's under the turbo oil drain pipe RHS .Best to come at it through the wheel arch .
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Postby jonc » Mon Apr 18, 2011 11:54 am

Thanks Lee.

OK, so it's something that can be done without getting the turbo off etc? I'll get onto Renault and see how things go.
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Postby clee » Mon Apr 18, 2011 12:47 pm

Yes .
It's a case of working from the top and through the arch but no need to remove the turbo .
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Re: Crank sensor / TDC Sensor

Postby Stunned Monkey » Tue Apr 19, 2011 12:45 am

jonc wrote:I reckon the fact that out of nowhere the RPM went to 0 would suggest that it's this sensor.


Ah, with reference to my other comment, I'd think you're right... and with the light coming on too.

Echoing Lee, it's a standard fit on a lot of cars. You might not even need to go to Renault.
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Postby jonc » Tue Apr 19, 2011 10:23 am

Thanks Martin - I should have looked at this before replying on the other topic!

If I wasn't to go to Renault for one, a good motor factor should have one?
It's interesting that visually it seems the same as for the R25 etc. but in the parts catalogue has an Alpine 60... part number. Aren't Renault great with this sort of thing?
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Postby Stunned Monkey » Tue Apr 19, 2011 10:49 am

Sometimes a 60 part number ends up cheaper than the 7x equivalent. For example teh reverse light switch. Even though it's an identical part.

If memory serves, the Safrane V6 has the same sensor, length of wire and everything as the UN1 PRVs.
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Postby pgoldsmith » Tue Apr 19, 2011 7:23 pm

From my memory (and it's pretty poor to be honest) when mine was replaced (same issue as you described) the sensor was similar to a R25, but it had additional heat shielding due to the poor cooling of the GTA.
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Postby Alan Moore » Wed Apr 20, 2011 11:06 am

When you connect the TDC sensor make sure that the red goes to the white and the white goes to the red. If connected so that the colours match, the TDC sensor will put out a very low output that the computer will not recognise.
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Postby jonc » Tue Apr 26, 2011 10:15 am

Alan Moore wrote:When you connect the TDC sensor make sure that the red goes to the white and the white goes to the red. If connected so that the colours match, the TDC sensor will put out a very low output that the computer will not recognise.


Thanks Alan,

I'm hoping that the new one comes with a suitable connector that makes sure that I don't get this wrong! But still worth checking.

By the way, Renault don't have any in the UK and could not suggest an equivalent part (e.g. a Safrane) and local factors couldn't find one listed for the GTA. I'll see what Renault can do, otherwise Simon has them in stock...
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Postby Stunned Monkey » Tue Apr 26, 2011 6:13 pm

Try pn 77 00 739 734 - you may need to add heat shielding.
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Postby MFaulks » Tue Apr 26, 2011 8:24 pm

They all do look visually the same, but some have a different sensor body offset relative to the two fixing holes, and hence the ignition timing would be wrong, possibly with dire consequences...

The reversed wires, isn't a reduced or distorted signal, the ecu doesn't actually know, but it is edge triggered and looks for the appropriate transition – polarity sensitive. Consequently the TDC signal gets retarded by a bunch of degrees with the wires colour matched i.e. reversed, and hence the poor running. If you were to slot the holes and advance the sensor mechanically all would be well... just to be perverse like ;-)
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Postby jonc » Wed Apr 27, 2011 10:11 am

Yeah. I had a good conversation with the parts guy at Renault about this sort of thing and specifically asked him about any alternative parts but we agreed that generally where a 60 part is specified, that's what's needed. There are loads of 77 parts elsewhere on the car, so there's something specific about it - even though it's the same for GTA and A610.

I've ordered one from Simon Auto - at least they have them in stock.
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Postby Stunned Monkey » Wed Apr 27, 2011 11:08 am

The offset sensors are a relic of the transition to unleaded petrol and were meant to be retrofitted to cars with earlier ECUs harking back to the days of 4-star.There was no distributor to rotate, they simply replaced the sensor with a retarded unit.

I know the pn I posted will fit and work but I'm pretty sure it won't include aheatshield.
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Postby jonc » Thu Apr 28, 2011 11:36 am

Thanks Martin.

I've just received the one I ordered from Germany. The red and white wires are well sealed into a thick plastic casing. Interestingly, though there is no loose-fitting heatproofing cover on the wires. With the connector block at one end and the sensor at the other there's no way (without cutting the wires) to get the old one onto the new one.

I'm going to check what the old sensor wiring is like. I know it has the loose-fitting shielding but not sure whether the wires are cased in an outer covering (as the new one is) or not.

If I need some, does anyone have any advice on where to get suitable heat shielding?

Thanks

Jon
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