Camshaft Drive D4D

[Max34]

Hi Can anyone enlighten me as to how the camshaft is driven on a Hilux D4D engine. I have read two reports on changing the timing belt and both state that if the belt fails the valves will be bent? On my engine the camshaft is connected to the diesel pump only and not the crankshaft so either the camshaft is chain driven or the diesel pump is chain driven and then this in turn drives the camshaft via the belt. I have no history on my Hilux so really want to change the belt soon. (If the camshaft is chain driven and it drives the diesel pump, there is less urgency). Thanks guys in anticipation.

[dervdave]

Belt driven, change soon as my friend !

[Max34]

Hi Dervdave,

thanks for the prompt reply. The photo is great to show the timing belt between the camshaft and diesel pump. What I don't see is the connection to crankshaft. Sorry if I worded my original question badly. One of these must be chain driven and from an engineering point of view it would make more sense if the diesel pump is driven - the chain length would be short. Any subsequent chain wear/ sprocket wear would have less effect on the valve timing and pump timing. If you could imagine the camshaft driven by a chain it would likely be four times as long so any wear in the chain and sprockets would be 4 times worse.

I am no expert on diesel, my background is Ferrari as a factory engineer for 6 years and prior to that a senior trainer for BMW - 13 years in that role. Even did a qualification in TV and video repair to understand electronics.

[dervdave]

You`ve lost me

[Devon Aygo]

Drive between crank and diesel pump is via sprockets ( Toyota terminology ) and then timing belt from pump to cam shaft, no chains involved

[Max34]

Brilliant news. Many thanks, best I go buy the belt a bit quick. Thanks again.

[Max34]

Just wanted to post a thank you to dervdave and Devon Aygo for their help. Bought a new timing belt today and will get on with fitting tomorrow.

A good tip in the great photo dervdave supplied, it shows the tensioner to the left of the diesel pump, which means the diesel pump drives in a clockwise direction. As does the camshaft. So too the crankshaft as the serpentine belt tensioner is to the left of the crank pulley when facing the front of the D4D engine. This is quite conventional, I have only ever known one engine to rotate counter clockwise - the rotary NSU engine from an RO 80 in 1972.

If the diesel pump is therefore driven by gears it will take three gears - an idler between the pump and crankshaft. If only two gears are used the diesel pump would be turning counter clockwise as we see from Dave's photo that isn't the case. It would need to be helical gears to keep the noise down and they are expensive from a production point of view - but hardly any wear and very accurate.

Thanks again boys - you are keeping my grey matter in trim.