T4 ACV 2.5 TDI injector pump errors

[Snail Style]

From memory the tensioner rotates until a marking lines up flush with the head. Not 100% on that, maybe one of the others can chime in.

Tensioners will be torqued to 20nM, the cam sprocket will be the 70nM one.

[fargo]

The front tensioner goes in with the hex key opening centre line of the 2 markers.Once finger tight you rotate the tensioner until the markers line up & tighten.
The rear idler doesnt appear to have any system other than when you roate it clockwise, it will butt up against the engine & will not rotate anymore.

[jets]

I found 2 articles that stated the front tensioner bolt to be tensioned to 15nm & the rear to 20nm. Then I read another that suggests 70nm for both.

According to Elsa Win "turn idler roller until the indicator aligns with the cylinder head flange contour. Tighten securing nut to 20Nm"
The tensioning roller securing bolt is tightened to 15Nm. I'm not sure on the pump belt tensioner but on the cambelt end, over tightening can crush the housing inside & wreck it. I would not be tightening to 70Nm.

The tension in the belt is determined by the position of the pointer on the tensioner.

[fargo]

Thanks Jets. That is what I did with the Idler. it didnt make sense to leave it "floating" & when it mated up to that contour, it just seemed "right".So you think the tension on the belt is correct if I algined those marks according to the instructions?
Im kind of surprised how easy the job was actually. All those articles you linked to were a great help.
Might even contemplated doing the timing belt after this experience.

[jets]

So you think the tension on the belt is correct if I algined those marks according to the instructions?

It should be fine. One other piece of advice, if you haven't read it already is if you tension too far & the pointer doesn't line up, you must not just turn it back. The clamping screw/nut[can't remember which it is] is undone & you start again. Not doing this can ruin the tensioner.
Replacing the cam belt is more time consuming & awkward because you are working in a confined area & from underneath.
The cam position is set after first removing the pulley on the end that you have just been working, undoing your previous work.
That is why that is recommended that both belts are replaced at the same time. But as Snail Style has said, some just replace the cam belt to save time & money. After all, if the pump belt fails it doesn't wreck your engine.

[fargo]

Yep I was unsure if I went past the time mark so I loosened the tensioner & rotated in the direction to start the tensioning process again, being a little softer when the marks aligned.
I get a little confused with all of the naming conventions on here. By " pulley on the end that you have just been working" Im guessing you mean the cam "sprocket"? I refer to anything with teeth as a sprocket. Or is there another "pulley" somewhere that I need to loosen?

[jets]

Sorry for any confusion. Yes it probably closer to call it a sprocket. The sprocket you used to alter the pump timing will need to be removed to set the camshaft position.

[fargo]

I was pretty lucky with the timing I think.I made a custom edge & got the pump sprocket mark lines up with the pump body mark bang on. it has never startedor ran better. No moving the cam sprocket at all. I bought a USB ebay lead to have a crack at VCDS lite but could not get past the cable detection setup. So id didnt bother registering.

[Seano]

After all, if the pump belt fails it doesn't wreck your engine.

Err...I recall hearing/reading on the UK forum of a couple of instances where it actually did cause engine demolition due to the belt piling up/jamming and slowing the camshaft that powers it which had fatal implications for the valves. It's rare and perhaps unlikely but seemingly not impossible...

[fargo]

Does a belt actually snap? Seems to me from reading that the tensioners are what generally fails(or tension) & that creates a situation where the belt would just get its teeth chewed out & then slips & then stops . Even if the belt did snap at high revs & speed, it would stop near instantly. The timing belt is of a real concern though.

[jets]

Does a belt actually snap? Seems to me from reading that the tensioners are what generally fails(or tension) & that creates a situation where the belt would just get its teeth chewed out & then slips & then stops .

I don't really know, I can only speculate. If the insides of the tensioner is damaged during installation or is of faulty manufacture & becomes very tight & jams, that could rip teeth off. The bearings could also wear out or be made without enough grease. I would think that the area of the belt would be protesting with lots of noise.
On my first T4 I could hear a slight noise from that area & decided to change the belt, idler & tensioner. One of the bearings was a little dry [can't remember which one] & new parts eliminated the noise.

[Umai Naa!!]

Yeah, belts do snap.

I've got a similar van to yours sitting here waiting for collection after the belt snapped and the valves met the pistons.

[jets]

Yeah, belts do snap.

Just to clarify, are you referring to the cam belt or the pump belt?

[Umai Naa!!]

Both, I'm afraid.

[jets]

I tend to skip through the T4 Forums every few days & I have read many reports of broken cambelts but the ones with broken pump belts
I haven't registered in my mind. Here's one of probably many threads.

t4 2.5 fuel pump belt snapped...Please help! - VW T4 Forum - VW T5 Forum