Tdi injector pump timing

[bluespanner]

Has anyone tried adjusting it?

I had the thought while working on a sprinter 310d, it has variable fuel pump timing controlled by a needle motion sensor in injector one. Question is, why? Is it for more power? Or emissions maybe?

Roland

[CwazyWabbit]

There is a post ot two on here somewhere from PaulN where he had to adjust the timing on his pump to get rid of excessive smoke. If I remember correctly he did quite a bit of experimenting.

EDIT: This is one of the threads http://forums.lr4x4.com/index.php?showtopic=68005&page=1

EDIT2: and another http://forums.lr4x4.com/index.php?showtopic=69791&page=1

[Snagger]

Injection timing is very important on diesels, and on direct injection or common rail engines it's critical. It not only affects the colour and amount of smoke, but also affects power, torque, fuel efficiency, coking and internal temperatures. Get it badly wrong and it'll damage the engine.

Retarded fuel injection gives easy starting (because the engine is turning over more slowly, throwing the fuel in late works better), but once running will reduce performance and gives of white smoke (with a bluish tinge, but not as much as burning oil). Engine temperatures will be cooler than normal because the fuel doesn't have time to fully combust, and you will be washing the bores and head, which will give glazing or increased wear. the engine will seem smooth, though, because combustion is occurring after TDC, jarring the piston less.

Advanced timing makes the engine rougher, starting more difficult, degrades performance because the piston is still rising against the premature combustion and gives black smoke. It also elevates running temperatures and can cause coking.

Correct timing will give a little black smoke when working hard, accompanied by slight harshness and roughness, more than if retarded, but much less than if advanced. Tdis timing can be set by using the flywheel locking tool (a scrap R380 reverse light works well) and injection pump locking tool (the blunt end of a 9.5mm drill bit is a good substitute). That will get the timing about as close to perfect as is possible, assuming the pump hasn't been incorrectly assembled as happened on my 300Tdi (new pump with the input wheel on the wrong location on the shaft, so timing was impossible). You can try small variations by moving the pump body 1mm at a time in the required direction, but mark the starting position and remember to advance the pump by turning the casing the opposite way to fan rotation or to retard the pump by turning it with fan rotation, taking a test drive after each adjustment. It's doubtful that you'll see much improvement from standard, though. Td5s and TDCIs timing is done electronically from a crank shaft position sensor, so would be done through ECU mapping.