timing belt/injection pump question

[joshh]

So I will start off by saying I have never changed a timing belt. however I have found everything fairly simple and straight forward so far. I am definetly happy that I am changing it as the crank seal was leaking oil onto the belt, and the belt was already cracking.

my question is this: yesterday I removed the timing belt and tensioner... all was good, timing marks aligned. however I came back to the van this morning and the injection pump has moved clockwise(facing the engine) by about 1". I expected some of the pulleys to shift a small amount, so I am not worried. but when I try to turn the pulley back to its position that is was starting in it feels as though it is spring loaded and keeps going back to this position. is this normal? do I just get someone to hold it in position while I put the belt on and set the tensioner?

Thanks for the help.

[joshh]

Well after talking to a mechanic at my work I have found out it could be from the van being in a warm heated garage now and the diesel expanding in the pump. However with it having resistance moving it backwards, can I move it forwards and still keep the timing right? I know some of these diesel IPs can be rotated forward two full turns and it will still be at the same timing.

[Dino]

Did you have a mark lined up on the pump sproket when you pulled the pump off? It's not uncommon for things to jump around when the belt is off, the valve springs can push the cam around a little, and the fuel pressure can push the pump around too. As long as you have marks on the cam, crank, and pump that you can line up when you put the belt on then you should be ok. Also another tip is that before you pull the belt off you can make some marks on the belt itself that you can make the same marks on the new belt so that you have the correct tension/length between the sprokets before you apply tension.

Make sure you turn it by hand 2 rotations of the crank (with the glow plugs out of course) once you have tension on the belt, that way you can see if any marks are off after the rotation before you everything else back together.

[Growlerbearnz]

It's normal and nothing to do with fuel pressure in the pump.

Inside the pump there is a cam disc with four raised lobes on the surface- as the disc turns the raised lobes push on a spring loaded plunger (which pumps diesel fuel and generates the high pressure needed by the injectors). The spring-loaded plunger also pushes back on the disc and without the belt to hold it in place, the disc will rotate until it's in the valley between lobes.

It's harder to turn in one direction than the other, but you should only ever turn it clockwise. Simply turn it until the timing marks line up, hold it there with one hand, and install the belt. Check that all your timing marks still line up, lock the tensioner, rotate the engine pulley two full turns, check that your timing marks still align, release and re-lock the tensioner. Done.

Don't neglect to change the balance belt and tensioner at the same time. If that breaks it can take out your timing belt.

[joshh]

I read in a manual it usually moves back a small amount. I changed all front engine seals, tensionerd and balance belt. Also did water pump and thermostat. Definetly was a learning experience.

[Dino]

Yeah, the first time doing a timing belt can be a bit nerve racking especially on an interference engine. But after the 50th you don't blink anymore :P