OM606 Injection Pump Timing Guide – How to Set Timing Correctly Every Time

OM606 injection pump timing is one of those topics where the internet makes it seem more critical than the engine actually experiences – but getting it right still matters for how the engine performs on your terms. Today we cover the correct process for setting timing, three methods for finding the right stroke and the critical mistake that leaves most pumps at the wrong timing after installation.

How Much Does Timing Actually Matter

The indirect injection diesel engines in the OM60x family are remarkably tolerant of timing variation. Set the pump at 12 degrees as specified. End up at 7 or 17 due to installation error. The engine fires up, runs normally and produces power. A five degree error in either direction barely registers.

Too retarded – slight sluggishness. Too advanced – slight knock at idle. Neither is catastrophic. The engine does not care the way the Facebook forums suggest it does.

What timing does affect is how the engine feels and sounds to you. Advanced timing produces a harder idle sound. Retarded timing feels softer and less responsive. For most builders the difference between 10 and 14 degrees is primarily about personal preference rather than measurable power difference.

The exception is extreme cases. 180 degrees out – on the wrong stroke entirely – is a genuine problem. The engine either will not start or runs very badly. Everything within a reasonable range around the specified setting works.

Three Methods to Identify the Correct Stroke

A four stroke engine completes one full cycle in 720 degrees – two full crankshaft revolutions. This means the crank passes through zero and top dead centre twice per cycle. Arriving at 12 degrees on the crank marker tells you nothing about which stroke you are on without additional confirmation.

Method one – oil cap and intake cam sprocket

Remove the oil filler cap. Look inside. The intake camshaft sprocket is visible. As you rotate the engine clockwise the sprocket rotates anticlockwise. There is a drill mark on the outer edge of the sprocket teeth – easily visible as you rotate. When this mark passes through your field of view you are approaching the correct stroke. Continue rotating to your timing mark on the crank. If the mark has passed through your view before you reach the timing position you are on the correct stroke.

Method two – pump timing hole

Remove the timing plug from the side of the pump. With a mirror and a helper rotating the engine you can see the lock notch inside the pump. When the lock notch is visible and centred in the hole you are at zero degrees on the correct stroke. Continue from there to your target timing position.

Method three – cam cap markings

Remove the valve cover and the cam caps. The cam cap markings and cam lobe alignment dots confirm TDC on the compression stroke. This method was covered in detail in the camshaft pinning video. Once confirmed at zero on the correct stroke rotate to your target timing position.

The Critical Installation Mistake

This is where most timing jobs go wrong and why many engines run at completely different timing than the builder believes.

The assumption: engine at 12 degrees, pump at zero, install pump, timing is correct at 12 degrees.

The reality: injection pump drive is not a solid connection. The pump sprocket has built-in timing adjustment range. Installing the pump finger tight – all three pump bolts and the French-threaded sprocket bolt – and assuming it is correct is wrong.

The correct installation process:

1. Set engine to target timing position – 12 degrees in this example
2. Install pump with all bolts finger tight only – no more
3. Remove the lock tool from the pump timing hole
4. Rotate the engine two complete revolutions and stop at the target timing position again
5. Look through the pump timing hole with a mirror
6. The lock notch will not be centred – it will be offset
7. Use the adjustment screw on the front side of the pump to move the lock notch to centre
8. Rotate the engine two more revolutions, stop at timing position, check lock notch again
9. When the lock notch centres consistently on repeated checks the timing is correct
10. Tighten all pump bolts to specification and reinstall the timing hole plug

Skipping steps three through nine and tightening the pump at initial installation virtually guarantees the timing is not where you think it is.

Running Timing at Zero

Some builders run the pump timing at zero on the pump with the engine set at 10 to 14 degrees. The result is slightly more aggressive idle sound and character. The engine does not suffer any damage. This is a valid choice for builders who want a harder sounding idle.

The pump's internal timing device – a spring loaded mechanism in the sprocket that advances timing with RPM – also modifies the effective timing significantly during running. Setting a conservative idle timing does not mean the engine runs conservative timing at higher RPM.

Running Eight Degrees

Three years of running an OM606 at eight degrees timing without knowing it. The engine ran fine throughout. This is the best evidence that these engines tolerate timing variation well. Does running at 12 or 14 perform better? Yes. Does running at eight destroy anything? No.

Check your timing. Set it where you want it. Understand that reasonable variation from the specified setting is not the crisis the forums suggest.

Summary

• OM606 injection pump timing: engine tolerates significant variation, five degree error causes minimal difference
• Three methods to confirm correct stroke: oil cap cam sprocket, pump timing hole, cam cap markings
• The installation mistake: tightening the pump without rotating the engine and checking the lock notch leaves timing completely wrong
• Correct process: finger tight installation, rotate two full revolutions, check lock notch, adjust with side screw, verify on second rotation, tighten
• Zero timing on pump with engine at 10-14 degrees is a valid choice for more aggressive idle character
• More than half of builders running these engines have never properly set their timing

Go check your timing. Bye!