diesel overheat

[ShipsWoofy]

A thread on PBO got me thinking and I do not know the answer, I rarely do!

On a petrol engine if the timing is advanced the engine can overheat.

Can the same thing happen on a small diesel, if so can timing be changed diy?

I do not have a problem, just trying to gain some knowledge.

 

[[2068]]

It's a bit different.

On a petrol, timing controls the spark.

On a diesel, "timing" sets when the fuel gets squirted in (assuming a mechanical pump). If this is badly wrong, then very bad things can happen (melting pistons etc). I wouldn't attempt to tweak my pump settings myself, I'd leave it to the pros.

dv.

 

[twisterkai]

Just as the cambelt snapped on my aging diesel car the increase in power (hence change in injection timing) was phenomenal.

 

[Renegade_Master]

and then what happened?

 

[oldharry]

[ QUOTE ]
AOn a petrol engine if the timing is advanced the engine can overheat.

Can the same thing happen on a small diesel, if so can timing be changed diy?

[/ QUOTE ]

1st thing is petrol burns much hotter than diesel, so the overheating effect of incorrect timing is far greater in petrol engines. Changing the timing on a diesel can be done DIY usually, if you know what you are doing, but is not recommended as it has to be set much more precisely.

The effect of incorrect timing in a diesel is the same as petrol engines - power loss. Retarded timing simply slows it down. Advancing the timing also slows things down, but because the injector is firing too soon various things may happen. Firstly the engine fires while the piston is still rising to the top of its stroke. The result - which can be heard when the engine is running - is that the familiar diesel 'knock' gets much worse, and in bad cases before long can literally knock a hole in the piston. The fuel does not burn in the way the engine was designed to make it burn, so that hot spots can arise which may burn through pistons, and will almost certainly cause uneven heating of the head leading to gasket failure.

There are a number of different ways in which the injection pump is timed to bring the injector up to the correct pressure to open it at precisely the right time, all of which require the use of precision measuring tools in skilled hands. Lucas /Bosch 'distributor' type pumps for 4 or 6 cylinder engines require a dial gauge to measure the movement of the pump actuator to .001mm for example.

There are a number of different types of fuel pump, all requiring skill and patience to set up correctly.

It CAN be done by the knowledgeable amateur, but even trained mechanics can get it wrong, and it really is a job best left to a trained injection engineer to get it spot on. Consequently most - but not by any means all - engines have an arrangement whereby the pump can be removed and re-installed with altering the timing.

 

[ShipsWoofy]

As soon as you said about knocking a little light went on, kerching it flooded back.

It has been a long time since I have had a diesel problem, touch wood. I have never had to diagnose an injection pump or in fact a fuel timing problem.

What you say is obvious regarding the spark vs compression, I did not think very hard before asking the question.

Thank you for your comprehensive answer.