hipwell · Sep 19, 2019

Hey guys, got a non starting td5 here.

Last week the in laws were just on the way home when the oil light came on, just as they pulled on the drove the engine was running really rough and then cut out. I checked the oil and it was below min, so topped it up.

Never ran since

Aa man came out and had a look and plugged it in and the only faults were all 5 injectors open circuit and a crank sensor fault

We took out the ECU and the red plug was full of oil so cleaned that up and changed the injector harness and gave the crank sensor a clean.

Now it will not fire, I got it running for about 30 seconds and it was throwing out loads of black smoke then cut out.

It blows out black smoke when cranking but now won't fire at all.

Any ideas?

Aa man read the live data and it was cranking at 300rpm so I'm assuming the crank sensor is ok but maybe not?

johnlad · Sep 19, 2019

Engine running rough and oil light coming on could point towards oil pump bolt working loose. I’d remove sump to check it before attempting any more starts.

hipwell · Sep 19, 2019

johnlad said:
Engine running rough and oil light coming on could point towards oil pump bolt working loose. I’d remove sump to check it before attempting any more starts.

I think the oil light came on because the oil was below min on the dip stick though?

Stanleysteamer · Sep 20, 2019

Oil light can come on when the oil gets overheated and then becomes thinner so doesn't give as much pressure, not just because there is less oil there to give the pressure. sounds like the engine may have overheated. Or an oilway, maybe to/from the head was opened up to atmosphere, as in a head gasket scenario, which would account for smoke situation.

Bobdog · Sep 20, 2019

Stanleysteamer said:
Oil light can come on when the oil gets overheated and then becomes thinner so doesn't give as much pressure, not just because there is less oil there to give the pressure. sounds like the engine may have overheated. Or an oilway, maybe to/from the head was opened up to atmosphere, as in a head gasket scenario, which would account for smoke situation.

Err... no. Low oil would result in low oil pressure. Hot oil would have a lower viscosity, which would increase pressure if anything. Or as johnlad said, the oil pump bolt has failed, resulting in NO oil pressure.
Lack of oil can cause overheating due to excess engine friction (and resulting damage) and the OP has already stated that the oil was below minimum.

Stanleysteamer · Sep 20, 2019

Bobdog said:
Err... no. Low oil would result in low oil pressure. Hot oil would have a lower viscosity, which would increase pressure if anything. Or as johnlad said, the oil pump bolt has failed, resulting in NO oil pressure.
Lack of oil can cause overheating due to excess engine friction (and resulting damage) and the OP has already stated that the oil was below minimum.

Er yes, "Engine overheating will cause oil to thinner, preventing proper pressure to buildup. This is similar to using oil with a much lower viscosity than recommended" from https://axleaddict.com/auto-repair/What-Causes-Low-Engine-Oil-Pressure
It looks as if you have never driven a car with an oil pressure gauge. I have. The oil pressure is always higher when the oil is cold cos it's thicker, as it warms up and thins, the oil pressure drops. Peeps as old as me saw it on the gauge of their Mini De luxe, or later on the oil pressure gauges that I always fit to my kit cars.
If it gets really hot, due to lack of coolant for example, it will get below the pressure needed to keep the oil pressure light off, no matter how much oil you have in the system.
During the war, the ferry pilots, many of them women, would be prepared to fly an aircraft that had been badly shot up back to the factory for repair, provided it had a working oil pressure gauge.
I know that p1V1/T1 = p2V2/t2, but that doesn't take viscosity into account which in fact is the overiding factor here.
I have also been driven by a guy who knew he had a water leak, he just carried on driving until the oil pressure light came on then he stopped and looked for a stream,a well or a tap. But his oil level was fine, as was the pump. Yes, he was a bit mad, but we made it from the North Devon coast to Bath without breaking down.
By the way, I agree with everything else you said.

Bobdog · Sep 20, 2019

Stanleysteamer said:
Er yes, "Engine overheating will cause oil to thinner, preventing proper pressure to buildup. This is similar to using oil with a much lower viscosity than recommended" from https://axleaddict.com/auto-repair/What-Causes-Low-Engine-Oil-Pressure
It looks as if you have never driven a car with an oil pressure gauge. I have. The oil pressure is always higher when the oil is cold cos it's thicker, as it warms up and thins, the oil pressure drops. Peeps as old as me saw it on the gauge of their Mini De luxe, or later on the oil pressure gauges that I always fit to my kit cars.
If it gets really hot, due to lack of coolant for example, it will get below the pressure needed to keep the oil pressure light off, no matter how much oil you have in the system.
During the war, the ferry pilots, many of them women, would be prepared to fly an aircraft that had been badly shot up back to the factory for repair, provided it had a working oil pressure gauge.
I know that p1V1/T1 = p2V2/t2, but that doesn't take viscosity into account which in fact is the overiding factor here.
I have also been driven by a guy who knew he had a water leak, he just carried on driving until the oil pressure light came on then he stopped and looked for a stream,a well or a tap. But his oil level was fine, as was the pump. Yes, he was a bit mad, but we made it from the North Devon coast to Bath without breaking down.
By the way, I agree with everything else you said.

Since td5 oil has low viscosity anyway (5w 30) it's unlikely to be the problem. Not enough oil (as stated) is the much more likely cause. Or a failed oil pump... too high viscosity can cause delayed oil pressure build up, which can lead to excessive engine wear. Overheating was never stated as the original problem so even if you are correct about low viscosity, it's a moot point really...

Stanleysteamer · Sep 20, 2019

Bobdog said:
Since td5 oil has low viscosity anyway (5w 30) it's unlikely to be the problem. Not enough oil (as stated) is the much more likely cause. Or a failed oil pump... too high viscosity can cause delayed oil pressure build up, which can lead to excessive engine wear.

As I said, I am not saying you are wrong about low oil level, nor am I trying to say that what i said is a more likely cause. I was just pointing out that it is a factor which might bear checking out, that's all. You are also absolutely right about delayed oil pressure build up, which is why 90% of engine wear occurs on start up.

Bobdog · Sep 20, 2019

Stanleysteamer said:
As I said, I am not saying you are wrong about low oil level, nor am I trying to say that what i said is a more likely cause. I was just pointing out that it is a factor which might bear checking out, that's all. You are also absolutely right about delayed oil pressure build up, which is why 90% of engine wear occurs on start up.

I get what you are saying to a point, for example,.halfords classic oil is very thick to allow for wear in older engines. I used it in my old V8 disco and it ran much smoother but in a td5, if it needs much thicker oil, it's buggered to start with...

Stanleysteamer · Sep 20, 2019

Bobdog said:
I get what you are saying to a point, for example,.halfords classic oil is very thick to allow for wear in older engines. I used it in my old V8 disco and it ran much smoother but in a td5, if it needs much thicker oil, it's buggered to start with...

I can remember the days when bikers used to change the oil, summer to winter, then back again.

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