990 Cylinder Head

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Joined: Mon Oct 13, 2014 8:20 am
Location: Vallentuna, Sweden

Re: 990 Cylinder Head

Post by rid54 » Sat Apr 18, 2020 4:30 pm

If the valves do not hit the pistons (or vice versa), the pistons should be OK, I'd guess. Bad speed regulation shouldn't be a problem with the head, but rather with the injection pump (regulator not working properly).

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Re: 990 Cylinder Head

Post by Moose » Sat Apr 18, 2020 5:06 pm

Thank you for the response, yes that does make since. However I have tried two different fuel pumps with the same result. These pumps were not used for some while so perhaps both regulators may be faulty. Any tips on resolving this?

I have set the valve clearance to 0.25 mm but I can turn the engine over relatively easy with the fan belt should this be the case?

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Re: 990 Cylinder Head

Post by rid54 » Sat Apr 18, 2020 8:14 pm

Firstly: The compression may be down, if the engine turns over lightly, but to ascertain any problems, a compression test must be performed.

Secondly: The speed of a diesel engine is determined only by the amount of fuel injected. There is no throttle valve and no metering of the intake air, so there is no engine "braking" from low pressure in the intake manifold, as there is in a petrol engine at idle or low power throttle setting.

If the engine cannot settle on a proper idling speed (c:a 700 RPM or so), the idle stop on the pump may have to be adjusted. The linkage from the regulator lever by the drivers' seat must allow the speed adjuster arm on the pump to rest on the idle stop when the regulator lever is in the idle position. Every position of the speed adjuster arm away from the idle position, represents a "requested" engine speed. The regulator proper, inside the pump, will increase fuel delivery until the engint reaches the requested speed and then adjust fuel delivery until the engine settles at this speed. If that does not happen, e.g. the engine spees up too much, the regulator proper is not functioning as it should.

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