HELP! Car won't start when engine hot...

[gurgli]

Hi all,

I drive around for aprox 15 minutes, switch off the engine, try to start it 10 minutes later and it just turns over for a long time without starting.
There are no problems with the start if the engine is cold. Has anybody got a clue where to begin to look for the fault?
I have a 316i 1988 with an M10 engine

[mrLEE30]

Blue engine temp sensor is the first place i would start, it looks like a square plastic block about 2cm long and its blue with two wires coming out of it, can be found toward the front of the inlet manifold if you look from the drivers side of the engine bay (RHD cars). there may be a brown one(this is your sender unit for temp guage) and somewhere underneath it will be a blue one.

FYI this is the sensor that tells the ECU how hot the engine it and the fuel air mixture is adjusted to suit the engine temp.

Use a multi meter set to measure resistance (Ohms), remove the wires from the blue sensor and when the engine is cold you should get somewhere around 2000-2500ohms if you ,measure across the pins on the sensor. Now with the engine warm check it again and it should read around 250-400.... if it does not replace it...... it is read correct then let us know and we will tell you the next step to try.

mrlee

[gurgli]

Blue engine temp sensor is the first place i would start, it looks like a ...... and we will tell you the next step to try.

mrlee

Thanks a bunch, I will try this during this weekend and let you know how it works out ;o)

[gurgli]

Blue engine temp ...... it is read correct then let us know and we will tell you the next step to try.

mrlee

Hi again,

The darn thing seems to be OK. It had 400 Ohm when hot and 2 kOhm when almost cold. Any suggestions for next step?

I can add that if I hold the throtle down 100% and turn the engine for 5 seks, then wait for 20 sek and start again without throtle, it runs!

Best regards - Gurgli

[djezd]

what has you mpg been like recently? if it has been declining slowly then perhaps check the fuel pressure regulator. i had a hot start problem that went to stalling when hot because the engine was been flooded.

search the forum for tests.

[mrLEE30]

thats a bummer, as this is normally the problem.

next step would be to check the condition on the spark plugs, remove and see what colour they are, are they black, do they appear wet and oily, or are they brown?

then with the engine running spray carb cleaner around the air flow meter, and pipes connecting the AFM to the throttle body and then to the inlet manifold, does the engine note/or idle speed change? if so could be an air leak, this may be undernaeth the big inlet pipe where you cannot see.

if thst does not work my next suggestion would be to swap the air flow meter and if possible throttle body, or as above the fuel pressure reg.

[liam012]

after a engine is up to temp park the car up and switch it off.
10 mins later pull out a spark plug on each cylinder and see is there any distinct smell of petrol.
If not the blue temp sensor and not leaky injectors i would have a guess at crank position sensor starting to go as they are heat sensitive when on the verge of dying.
hth

[mrLEE30]

thats a bummer, as this is normally the problem.

next step would be to check the condition on the spark plugs, remove and see what colour they are, are they black, do they appear wet and oily, or are they brown?

then with the engine running spray carb cleaner around the air flow meter, and pipes connecting the AFM to the throttle body and then to the inlet manifold, does the engine note/or idle speed change? if so could be an air leak, this may be undernaeth the big inlet pipe where you cannot see.

if thst does not work my next suggestion would be to swap the air flow meter and if possible throttle body, or as above the fuel pressure reg.