Hello guys,

I have almost finished with my project which was to make my 1.1 as tuned as posible for road use mainly.

-Reprofiled Punto 75 cam to 280 deg and 10,45mm lift
-Ported and polished mpi head
-Higher compression
-Full custom 4-2-1 decat exhaust
-Punto 75 inlet manifold
-40mm Punto 75 throttle body

The problem here is that when i changed the inlet manifold and kept the coolant temp sensor out of Punto 75 and did a little cut and connect wiring thing with the OEM mpi wiring to fit the P75 sensor but my OBD scanner reads very low values (under 76 degrees celsious) even when i am stuck in traffic. I understood that something goes wrong when i squeezed the thermostat hose and it was hot, so the engine was running over 87degrees. So the engine overheats but the ECU doesn't read that so it doesn't give order to ventilator to open and reduse the temperature.
Any idea on what i have to do now to solve my problem?
The car now can't be moved with no risk of blowing everything up...
Cheers

Hi.
Are you saying that you have a Punto sensor in use? Sensors for temperature and levels( fuel gauge etc) are normally resistive- have you compared a Seicento and a Punto one together to confirm that they react to temperature in the same way? Remove the sensor from the car, put the Seicento and Punto ones together and leave for a while so they both are the same basic temp when you start.
Get a multimeter set to Ohms across the terminals of the both sensors and compare.
Now put the sensors in a cup of hot water for a while then repeat the measurements. They will have changed from cold but are they the same or close? It could be that the sensors are reacting differently with temperature and the OBD reading is lying to you if the resistance is not what it expected?.

Good luck

Those two sensors have different resistance that i already know. The problem is that i can't plug the OEM sensor in the P75 inlet manifold. So what i am looking for is what to do now?

Hi.
Ok. Sounds like you are half way there if you know the sensor you are using is different. I ran into similar problems with a car I swapped engines in the past.

At this point I decided to modify the manifold to fit the sensor- cheating the wrong sensor by adding/ reducing resistance when cold does not work as the way the sensor operates the resistance needs to vary. I had an aluminium cast manifold, I had the hole welded up then re-drilled to fit the sensor. A bit of ptfe tape around the thread and all was good. Do you have a plastic manifold? If so, the same could work or get an engineering shop to make an adapter. A plastic called Delrin is good for this, it machines nicely and is ok with temperature. If that doesn’t sound like something you can do maybe re-locate the sensor. Car Builder solutions (www.carbuildersolutions.co.uk I think) have a section of tube with the sensor mount welded on, you cut into water rubber hose, add this piece and re-route the wires.
One more idea, my Seicento doesn’t have a temp gauge, I am collecting parts to make a 16v conversion and I noticed on eBay that a Panda thermostat housing looked like it had a temp sensor built into it. Could that be used?

Ian

Problem solved. I managed to find same sensor as the mpi one to fit like a glove in the p75 inlet manifold. Thanks for replying!