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Non Starter 1 week 10 hours ago #200996

Well after a few problems, I managed to get the "F" started,

Ticks over and revs up OK.

The problem now is when it is cold it will only start with a "Sniff" of Easy Start, once started and warmed up it will start OK.

Any ideas as to why it does this??

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Non Starter 6 days 4 hours ago #201002

I’m no expert and have no experience on a MGTF to really help. However, it does sound a bit like no choke syndrome if it were an MGB.
Based on an ECU I had on a kit car it might be worth testing the cooling water temperature and air temperature sensor..
It is my understanding that an ECU is programmed to make the mixture richer for start-up when the cooling water is cold. It is or at least can be also programmed to enrichen the mixture for an initial number of revolutions of the crankshaft. Presumably that counting is achieved by the crank sensor and that must be working otherwise the whole thing would not run.

Be interesting to know what you find as the solution.

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Non Starter 5 days 16 hours ago #201005

https://www.dtafast.co.uk/download_files/Manuals/S%20Series%20Manual.pdf
And page 146 and the next few.
Have you always had problems starting from cold? If so it may not be the cooling water sensor but if the problem is new it could be a.failing sensor, the wrong sensor, or resistance in the wiring that is affecting the ECU .
As far as I’m aware the sensor will change its resistance as temperature changes under normal circumstances.
It would seem logical to think that a small variation in resistance somewhere will give the ECU false information and inhibit the start up process.

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Non Starter 5 days 12 hours ago #201008

Can’t argue with that other than to say that if a vehicle is left standing condensation will build & can alter resistance values, either by tracking across contacts or by corrosion on the contacts.
One will lower a value & the other raise it, by how much is a moot point, corrosion could isolate a terminal & is the most likely but I’ve experienced a tracking fault before now.

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Non Starter 5 days 12 hours ago #201009

Can I clarify. By tracking I don’t mean Bang, Sizzzzle, Arc, Flames, Belching smoke & acrid fumes, I was thinking in terms of current flowing along the damp surface forming a secondary resistance in parallel with the prime.
That would in effect lower the sensor value.
“Clarity is everything”. M

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Non Starter 5 days 8 hours ago #201010

One point I forgot to mention and I was only reminded of it as I thumbed through the pages of the pdf from dtafast, and that is the fact that the spro range and probably others including OEM ECUs will have a default value.
Looking at the small changes in output it may be that the default is close to a temperature equivalent of the thermostat opening temperature.
If that is the case then once the car is running and warm it will continue to run and re start until it cools down a lot.
It may also be a case of an aftermarket instrument has been fitted in the past with different characteristics.

I agree that tracking could be cause particularly if the car had been used with road salt present.
Either way my thoughts are check the water transducers and associated wiring first.

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Non Starter 5 days 4 hours ago #201012

Reading the ws manual it suggests the Engine Coolant Sensor is a thermistor, and that if it fails the default is to take values from the oil temper sensor. (The sensor output is used in calculating fuelling and timing and is used to provide corrections during start up)
But it also suggests that should the water sensor fail then the radiator fan should be switched in in fast mode.
There is more but based on the fan information it may suggest that the sensor is still working.
A fault code interrogation might show something.

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Non Starter 5 days 2 hours ago #201014

Looking at your profile picture I am guessing that your car is a mk1 VVC but it would be useful if this detail is included as the advice can differ.

As a mk1 it will only be OBD1 so the ECU can only be read be read by a few scanners such as the www.pscan.uk
As a VVC it will have a MEMS 2.0J ECU.

The K series engine has 2 coolant temp sensors. One has a single lead and is for the dash temperature. To test it earth the wire and the gauge will go to the top.

The more important sensor is the one with two wires. It tells the ECU the coolant temperature and thus control fuelling and ignition. If it is telling the ECU that the engine is warm the ECU will not supply enough fuel and the ignition will not have the correct advance. The only way to see what temperature the sensor is seeing is to plug in an OBD reader and read the coolant temp.

If the ECU gets no signal from the coolant sensor it assumes the engine is too hot and it will run the radiator fan. To check this unplug the sensor and the fans should run.

Home to black Alfa Romeo 159 3.2 V6 Q4 ,green MGF VVC and red MG Maestro T16.

MG - the friendly marque.

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Non Starter 4 days 4 hours ago #201018

Here is a graph showing resistance change with temperature for a thermistor.
Presumably the device in the car will have an initial value, and once hot that will or should change.
It might be worth getting a connector (jtpo?) fitted with two wires that could be connected to a multimeter measuring resistance then starting the car (if you can with the easy start) and watching what happens to the resistance as the engine warm up.
Risk is all yours as in the usual way.
Potentially an alternative might be to measure resistance cold, then reconnect the standard wiring. Start the engine and let it warm up to standard conditions, then stop the engine disconnect the wiring and measure the resistance. Couple it all back up and restart and then stop and cool down naturally.
Otherwise change the transmitter and see if it cures the problem.

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Last edit: Post by Bertl. Reason: pic inserted
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