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Temperature Gauge Not Reading


Best Answer Angus Fognozzle , 19 November 2017 - 11:11 AM

Progress at last! It transpires that the ecu does receive reading from the (new) sensor, but (according to the sykes-pickavant code reader thingy)  even when radiator cap blowing it only gets up to about 30 degrees centigrade, and the heater does not get warm at all. After pulling everything to pieces, it transpires that the water pump inlet was COMPLETELY blocked with corrosion. The car had been standing for ten years, but certainly the first time I've ever seen this. Anyone else seen similar? 

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#1 hilo92

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Posted 28 March 2017 - 09:16 PM

I have just replaced the Coolant Temperature Sensor and the thermostat (88 degree) on my '93 SPi. The gauge still reads below cold. I have checked the continuity of the wiring between the sensor plug and the ECU. I believe the engine to be running rich as when I coast out of gear to a stop, the engine splutters and stalls when hot. Any ideas for perculiarities to look for?

Many thanks

#2 FlyingScot

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Posted 28 March 2017 - 09:27 PM

If the ECU is reading cold your car will be running rich.......
The sensor in the inlet manifold measures the temperature and feeds the MEMS ECU, the ECU in turn feeds the gauge.
Something is wrong - blocked inlet water ways? Air lock?

The gauge should read at the white pip below the middle when operating correctly. If it doesn't chances are the ECU thinks the motor is cold is will increase fuelling - check spark plugs to confirm

FS

#3 FlyingScot

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Posted 28 March 2017 - 09:28 PM

Re read your post, if it doesn't move the gauge at all you have a wiring or ECU fault (the supply to the sensor is from the internal regulator in the MEMS ECU)

FS

#4 RedRuby

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Posted 28 March 2017 - 09:31 PM

I may be wrong on this but is the temp gauge not fed from the temperature sender in the bottom of the radiator in the SPi. The coolant temperature sender in the inlet manifold is as you said linked to the ECU as part of the engine management system.

#5 FlyingScot

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Posted 28 March 2017 - 09:33 PM

I may be wrong on this but is the temp gauge not fed from the temperature sender in the bottom of the radiator in the SPi. The coolant temperature sender in the inlet manifold is as you said linked to the ECU as part of the engine management system.

Nope, thats the thermal switch for the electric fan on an SPi which operates via a yellow Tyco relay on the bulkhead.

FS

Edited by FlyingScot, 28 March 2017 - 09:33 PM.


#6 minidave54

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Posted 28 March 2017 - 09:45 PM

The temperature sender in the bottom of the radiator is in fact a thermostatic switch. It is for the the auxiliary electric fan fitted to the inner near side wing. Should the engine get to a pre set temperature set by the switch it will automatically turn on the fan.

The coolant temperature sender in the inlet manifold does indeed feed the ECU as part of the management system, but the ECU then also feeds the coolant temperature gauge.

#7 hilo92

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Posted 28 March 2017 - 09:56 PM

I appreciate this sounds like an electrical problem. As stated, I have checked the wiring between the sensor plug and the ECU. The sensor also gave sensible resistance readings before I installed it.

#8 RedRuby

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Posted 28 March 2017 - 09:59 PM

I may be wrong on this but is the temp gauge not fed from the temperature sender in the bottom of the radiator in the SPi. The coolant temperature sender in the inlet manifold is as you said linked to the ECU as part of the engine management system.

Nope, thats the thermal switch for the electric fan on an SPi which operates via a yellow Tyco relay on the bulkhead.
FS


Thanks for that FS and mini dave. It's good to learn.

#9 FlyingScot

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Posted 29 March 2017 - 05:37 AM

Best next step would be to borrow a code reader and read what the ECU is "seeing" in case the gauge is faulty and problem lies elsewhere with the fuelling.

FS

#10 hilo92

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Posted 29 March 2017 - 06:14 AM

I better get on the scrounge then. Thanks FS

#11 Angus Fognozzle

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Posted 15 October 2017 - 07:01 PM

Any progress hilo92? - or anyone else any suggstions? My 93 SPI seems to have exactly the same issue- new temperature sensor, wiring to ECU intact, voltage regulator in instruments ok (fuel gauge works) but temperature gauge does not move- even if temperature sensor bypassed- sooty plugs and cant get through MOT due to emissions.....AARGH!!!!

I guess next is to swap ecu with a known good one, but think that needs to be matched with alarm module?



#12 Sprocket

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Posted 19 October 2017 - 01:37 PM

Firstly, I take no responsibility for any damage you may cause by following my suggestion and not grounding the correct wire safely.

 

Disconnect the body/ engine loom 13 way connector on the bulkhead. On the body loom side, locate the Green/ Blue wire. Carefully ground the connector pin for that wire, and with the ignition on, the temp gauge should read full scale hot.



#13 bigchief3679

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Posted 10 November 2017 - 12:58 AM

As someone mentioned earlier, check that the coolant pipe is indeed not blocked from the point it exits the thermostat housing, splits for the heater, and back out the manifold to the radiator hose. In addition to providing the sensor with coolant for readings, the coolant in the intake manifold heats it up aiding proper vaporisation of the air/fuel mixture for good combustion. 



#14 Angus Fognozzle

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Posted 19 November 2017 - 11:11 AM   Best Answer

Progress at last! It transpires that the ecu does receive reading from the (new) sensor, but (according to the sykes-pickavant code reader thingy)  even when radiator cap blowing it only gets up to about 30 degrees centigrade, and the heater does not get warm at all. After pulling everything to pieces, it transpires that the water pump inlet was COMPLETELY blocked with corrosion. The car had been standing for ten years, but certainly the first time I've ever seen this. Anyone else seen similar? 


Edited by Angus Fognozzle, 19 November 2017 - 11:18 AM.


#15 FlyingScot

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Posted 19 November 2017 - 12:50 PM

Progress at last! It transpires that the ecu does receive reading from the (new) sensor, but (according to the sykes-pickavant code reader thingy)  even when radiator cap blowing it only gets up to about 30 degrees centigrade, and the heater does not get warm at all. After pulling everything to pieces, it transpires that the water pump inlet was COMPLETELY blocked with corrosion. The car had been standing for ten years, but certainly the first time I've ever seen this. Anyone else seen similar?

That’s why having a code reader is really a must for these......
Good find and yes just pulled an SPi motor with a large bluey white lump cristalised in the water pump inlet

FS




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