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VW T4 2.5 TDI (102) ACV Sporadic timing issues

3K views 8 replies 3 participants last post by  twin slider  
#1 ·
Hi,

Wonder if anyone could shed some light on this. Have a recently rebuilt fuel pump sent back to me but when installed the timing seems to be jumping all over the shop. It seems to be jumping from about 53 up to 65 on the Vagcom TDI graph. Runs fine etc but can't get my duty cycle below 14.7%. Maybe a sticking timing valve in the pump? Should I send it back?

All feedback appreciated.

Terry T:


You tube video of what I'm talking about -

https://www.youtube.com/watch?v=Eh1Ze0Jl9Pw&t=4s
 
#5 · (Edited)
Please ignore the last post.

I will have to become a member just so I can edit/delete my previous post!

......Your PUMP timing is retarded. Injection is too late!......

The rest still applies. Nearly

As you probably know, the pump can only advance the timing (electronically) If you look at your video, at 48 secs you will see that the pump is advancing the timing when you apply the throttle and it is firing After TDC. Signals from the sensors and 5th injector are then stopping the advanced injection and once it has, the pump appears not to try to advance again, at least not past TDC.

Tensioner can jump about a lot if fuel pressure fluctuates or the belt is too tight. Some fluttering about is normal as long as it within the area of metal tab.

If this were in front of me I would adjust the timing as follows.
To advance pump timing
Lock the pump, preferably at TDC but not essential.
Slacken the tensioner pulley so that the pointer is just above the metal tab with the arrow on it
Apply more tension to the idler pulley so that the pointer and the arrow on the tensioner pulley align

Check timing with VCDS
Sorry for any confusion caused. It's an age thing
 
#8 ·
Twin Slider,

I'm a bit confused :/

......Your PUMP timing is retarded. Injection is too late!......

Surely if the pump is too far retarded the injection would be too early? Also I thought that the timing should only be setup at idle and anything above the blue line is advanced and below is retarded? I understand the timing should advance with engine revs but not sure why mine does not. As mine is fluctuating above the blue line at idle I would assume my pump timing is too far advanced as the TDI program states this in the lower box?

I tried advancing the timing and it just plots off of the graph as it says it is too advanced. When I rev with the timing advanced more the timing seems to retard if anything. I still don't know why the timing is fluctuating as that doesn't seem correct.

Not sure what you mean here? "Signals from the sensors and 5th injector are then stopping the advanced injection and once it has, the pump appears not to try to advance again, at least not past TDC."

Thanks
 
#9 ·
I'm confused too. It's a good job I do things better than I explain them!

I think your timing is out and the pump is trying to adjust/adapt by electronically advancing. You can check in measuring blocks Group 4 and rev the engine above 2500rpm and see what figures you get.

This is a good example of what should happen https://www.youtube.com/watch?v=0kVZbBjJ2n4

I do not think the timing is the cause of the fluctuation. That could be caused by a number of things. Tensioners, on either belt, Incorrect cam timing, belt too tight.

I have also heard about the woodruff key in the crank sprocket causing wear and causing scatter