24 replies to this topic

[RogerJJW]

All, I'm new to the forum so bear with me apologies in advance I have been reading other posts for past week to get an answer.

So I've a 1997 Cooper MPI 52,000 miles ,just finished full body strip down reweld and spray job, before this I carried out service to engine including coolant/stat brakes and new exhaust system inno may be backwards but that's how I done it.
Far as your can figure the temperature gauge was working fine before hand.

Initially I first noticed the cat was getting very hot smoking inside car from under handbrake and over fueling evident from the tail pipe then I noticed when engine was run up the temp gauge would just make it to top side of the cold and no more.

After reading other posts I've drained coolant flushed out rad and block and through heater matrix ( as this wasn't getting full heat), checked new stat that id fitted previous and found it to be sticking so tested then fitted a new one, filled system slowly squeezing on top pipe as I went left cap off to help remove air on warm up then replaced, noticed spring clip under expansion bottle was to low and not on the tail of bottle so moved this up no weeping from bottle now . When car runs now good heat in cab from heater temp gauge still just out of blue and fan kicks in when idled for approx 20 mins also when I unplug CTS it comes on right away.

Replaced spark plugs and leads, old plugs showed clear over fueling.

Replaced expansion cap

Replaced CTS and fitted the loom repair soldering it in and heat shrinking.

Traced all wiring as per sprocket answer to another user ( invaluable Thankyou) from CTS to ECU and back to connector beside relays right of bulkhead all wiring clear with minimal resistance.

As it is now temp gauge still only getting to top side of blue I can't see clear evidence of overfueling from tail pipe.
The cat is just touching heat shield so I'm going to remove it and clean up existing heat shield and cover them with zircoflex I think you call it and refit hopefully that will cure cat issue over heating tunnel.

Was starting to think its a fault in ECU or is it fault at the guage itself is this common? Fuel gauge ( same gauge is working fine but don't think this is a pulse signal that requires use of the voltage stabilizer the fuel gauge uses I believe any help advice is most welcome as it's doing my head in , if I have overlooked something please let me know thanks

[Ado1379]

You haven’t mentioned that you’ve replaced the sensor? Do you have a fault code reader to hand?

[RogerJJW]

Hi thanks for getting back as above this is the sensor I replaced along with the loom, "Replaced CTS and fitted the loom repair soldering it in and heat shrinking" is there an other sensor I should if changed that would effect things , unfortunately I don't have a code reader and don't know anyone with minis in Northern Ireland at the minute

Edited by RogerJJW, 12 August 2020 - 10:04 PM.

[viz139]

Just to be sure, it is the coolant sensor at the stat you changed and not the oil temperature sensor on the front of the block. If the fueling is correct and idle drops when engine is warm it suggest that the sensor side of things are ok but the only real way to be sure is a diagnostic reader that will tell you what the ECU is seeing.

[RogerJJW]

Hi Viz thanks again yes it's the coolant temp at thermostat I changed and the loom , idle drops back to 850-900 rpm after about 5 mins running from cold , in going to take dash out today and test from 13way connector to gauge , I'm going to be stuck it seems with out a reader , looking at drawings again the voltage stabilizer at gauges serves both temp and fuel and fuel gauge seems ok ,going to take dash out today and test from 13way at bulkhead to gauges for continuity,any idea what voltage I should see from ECU to temp gauge ,thanksv

Edited by RogerJJW, 13 August 2020 - 08:58 AM.

[Ado1379]

Hi thanks for getting back as above this is the sensor I replaced along with the loom, "Replaced CTS and fitted the loom repair soldering it in and heat shrinking" is there an other sensor I should if changed that would effect things , unfortunately I don't have a code reader and don't know anyone with minis in Northern Ireland at the minute

Apologies roger I must’ve skipped over that bit!
Where abouts in NI are you? I’m from Carrickfergus, I don’t have a code a reader but I’m trying to source one too. If I manage to sort myself out I’ll give you a shout.

I have been trying to go through mems rosco and mems diag programs but it seems they don’t support the Mems2j at the minute so back to trying to find a ‘cheap one’.

[Quinlan minor]

Just a thought, but when you open up the dash, check the needle is free to move throughout its range. If it has been out/stored during the restoration, it may have taken a knock or have some crap/corrosion holding the needle back. Worth a look?

[Ado1379]

Just a thought, but when you open up the dash, check the needle is free to move throughout its range. If it has been out/stored during the restoration, it may have taken a knock or have some crap/corrosion holding the needle back. Worth a look?

Would shorting the puns out on the plug do this easier? Just a thought as it would trick the car into thinking it was really hot a the gauge would have a full scale deflection?

[Quinlan minor]

Would shorting the puns out on the plug do this easier? Just a thought as it would trick the car into thinking it was really hot a the gauge would have a full scale deflection?

 

I would caution against that. The sensor circuit goes to the ECU, which then sends the output to the gauge. Might be worth checking the connections at the ECU, though.

[RogerJJW]

Hi Ado , im in Larne not to far from you feel free to pm and call for yarn anytime.
Ado/Quinlan, had dash out today and tested wiring and all is clear ,also checked earth to plug ,didn't fancy shorting plug for couple reasons 1. 'Shorting the plug at the sensor loom to trick ECU' wouldn't work as the sensor is basically thermistor and doesn't operate like a switch on/off instead dependant on engine temp resistance changes at sensor, from this ECU determines temp based on resistance and sends I think a pulse signal to from ECU via 13way connector on bulkhead to gauge, if I knew what signal/voltage ECU sends vrs resistance at given temp I could temporarily link plug at sensor with a fixed value resistor to simulate normal temp. 2. I know the engine is at proper temp and above as the cooling fan kicks in after approx 15-20mins I checked gauge today for dirt dust as you suggested was a little bit didn't seem to restrict needle , what I did notice was dirty contacts on the plug in the back of the cluster and also the flimsy plastic circuit track sheet on the back of gauges ( given suspected low voltage signal any impedance I assume will effect it)cleaned these both up and put tension on the plug pins ( bent them out abit) and reformed plastic track sheet , had ECU out other day when testing wiring from CTS to Ecu and to 13way and plugs at ECU seem ok need to wait to tomorrow hopefully stat gaskets will arrive so I can run to temp see if it made any difference, also Speedo cable was laying over loom to gauges so don't know if this may of been pulling it out slightly,Any idea on on voltage signal from ECU is it 5v and is it pulse signal ? Any idea of the resistivity of the CTS at normal engine temp ,thanks appreciate your help and thoughts.

[Quinlan minor]

 Any idea of the resistivity of the CTS at normal engine temp ,thanks appreciate your help and thoughts.

Pretty sure they're the same SPi and MPi

 

http://www.theminifo...ensor-or-is-it/

 

[Ado1379]

If I run mine up to normal temperature tomorrow I can take the resistance down from it. But this must be working correctly as the fan engages. The cooling fan is controlled by the ECU on MPI’s not by a desperate switch like the SPI.

[RogerJJW]

Thanks for that will read through that , I'm pritty sure new CTS is working ok just thinking if I knew resistivity and what voltage / ECU sends to gauge I could link the plug on loom with resistor and test signal going to gauge to see if ECU is giving correct signal out.

[Ado1379]

Hi mate, I can now read MPI live data and fault codes. Pm me if you still need to use it. Thanks

[Alice Dooper]

If you're getting really stuck, I suggest you give Cian at CC Mini's a wee call.  He's really good with SPI's and MPI's and has code readers etc...  Sorted my MPI odd O2 sensor problem.

 

He's just outside Lisburn and does the odd house call.  He's on Facebook and the trader section here.