ive been trying to set the pump timing using timing pins, i get it set spot on then when i take the pins out & turn the engine through 2 revolutions i put the pump pin in but the flywheel pin is always a tiny bit out, i can put a screw driver in the hole and move the flywheel to the correct place and insert the pin, the pump pin still moves freely. is this ok?. engine is a 200 tdi. thanks for any replies martin
jamesmartin
Well-Known Member
not righht yet ,only turn crank clock wise during setting if you go other way go a bit further and the the right way to get all back lash out of the timing fit crank pin make sure its not bent align cam mark go for slightly after mark if not possible to get exact,then fit pump pin tension belt ,tighten 3 x bolt on pump sprocket then turn over twice , fit crank pin slacken belt tensioner and reset tension recheck cam marks slacken 3 x pump bolt fit pin then retighten pump bolt ,turn over twice and recheck pinsand cam mark
NEVER EVER turn an engine backwards, whether it has a belt or a chain for driving the camshaft and injection pump. Even when doing valve clearances, turn the engine only the way it runs.
In a CHAIN engine, turning it backwards is a great way to rip the timing chain tensioner to bits, and in a belt engine the little bit of free play in the teeth and the pulleys WILL throw the timing out a little if you turn the engine the wrong way.
In a CHAIN engine, turning it backwards is a great way to rip the timing chain tensioner to bits, and in a belt engine the little bit of free play in the teeth and the pulleys WILL throw the timing out a little if you turn the engine the wrong way.
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jamesmartin
Well-Known Member
bollocks ,free play in engine components is the reason that if you do turn it back wards you need to to it a reasonable amount before you turn the rigth way to make sure you have taken up all free play ,there are some chain driven mechanisms that are sprung loaded and therefore cant be turned back wards as this releases tension and lead to chain jumping a tooth but in his engine tensioner isnt spiring loaded
I had a few Gardner engines that would run backwards if you stalled them in gear a certain way.
Funny to watch smoke coming out of the air filter and the exhaust sucking air in
Yes indeed Storm, "Experts" often start their reasoned arguments with words like that.
For the rest of you who are not as "expert" as JamesMartin seems to be, I suggest you take very good advice based on about 50 years of engine building experience - "do not rotate engines backwards", and especially not when setting cam / valve / ignition / injection TIMING.
The stress and strain that this places on the timing chain or belt tensioner may well be more than the tensioner can withstand, and as there is practically NEVER any good reason for turning an engine backwards, why take the risk?
Remember, when the engine is running, the crankshaft sprocket is PULLING the belt or chain down on the tight side, and pulling pretty hard. This takes up all the slack, and the timing can be set accurately. As soon as the chain/belt leaves the crankshaft sprocket it is SLACK, and it immediately runs over the tensioner, which should press the chain/belt just enough to take up all the slack and apply the correct tension. In a chain engine the correct tension is damn-all, enough to take up all the slack and just a little more. In a belt engine, the belt is kept quite tight. But the TENSIONER is NOT intended to take heavy strains imposed by reverse rotation.
There's no point in arguing with an expert like JamesMartin, so the best I can do for the rest of you is to offer good advice.
Bollocks ...
give us an example of an engine in which this can happen.
Lots of engines use chain tensioners that use a light spring assisted by oil pressure (hydraulic chain tensioner), and turning one of these backwards is asking for BIG trouble.
Here is from the a site I found on Google a moment ago. It is worth reading, but only by people like me who are not "experts" already.
Posted: Thursday, October 04, 2007 9:33:52 PM
Rank: Meccanico
Joined: 4/21/2006
Posts: 66
Location: Novato CA
Let me explain why turning the engine backward is a dangerous practice regarding the chain tensioner.
It is not a matter of a "wives tale" with no technical justification.
When the engine is running in forward direction, the crankshaft is pulling the chain in the "forward"
direction (in our case, counterclockwise) against the resistance of the cams opening the valves.
This is considerable resistance. The "tensioner" (slack remover) is always located on the back side, where there is no work being done by the chain. Therefore, the slack remover does not have to overcome any tension created by mechanical resistance to push against the chain to keep it tight. The slack remover pushes the chain into a vee path.
When you turn the engine backward, the previous back side becomes the "forward" side. When going backward, there is resistance that did not exist before because the chain is opening the valves on the back side. Very few, if any, slack removers are strong enough to overcome this resistance, they are not able to maintain the vee path of the chain. Instead, they collapse against the resistance, allowing the chain to take a straight path. The resistance of opening the valves causes the chain to take a straight path.
This CHANGES THE TIMING, the relationship between the crankshaft and the camshafts. This timing is established by the length of the chain AND ITS PATH. When you go from a vee line to a straight line, even though there is a constant number of links in the chain, the timing has been changed.
In normal timing, the valve(s) is NEVER wide open at TDC. There is no possibility the valve will contact the piston. However, if the valve timing is way, way off, when the valve is wide open it may contact the piston at TDC, with disastrous results. This is more likely in a high performance or diesel engine because that engine will have high lift cams and high compression created by the piston dome projecting further into the combustion chamber. This engine will likely have long duration valve timing, so that the possibility of valve/piston collision is closer to "normal" timing.
All of this is relevant to our engines. DO NOT turn your engine backward.
jamesmartin
Well-Known Member
i appologise for my reply had a bad day then too many beers ,
Ahhh... too many beers ... always seems like a great idea at the time!
So James, thanks for that.
