Poor starting... AFN 1998 A4

[Nigella]

Following a trip to the local garage to try and locate the source of a fuel leak around the IP, (separate thread) The car is now very difficult to start.


Is there a bolt/screw that the garage could have tightened on the outside of the IP, in error in an attempt to stop the leak but somehow have affected the starting of the engine?


I was thinking more on the lines of a poor connection on the glow plugs or a break in the GP loom as a result of the wire being moved out of the way to get to the IP.


I dont have VAGCOM yet so any reasonable suggestions welcome.

[Crasher]

They may have moved the pump on its mountings which alters the Commencement Of Injection.

[Nigella]

I was watching them and didn't see any movement at all.

They were only tightening the bolts, fuel hose unions etc and if I remember correctly, only one of the rear pump housing bolts was a little loose and maybe one 12 or 13mm bolt in the centre rear which I think did turn slightly.

[PaulF2.5TDi]

AS crasher said, the timing may have been altered.

You need somebody to check the pump timing with VCDS once it is hot.

[Nigella]

How can the timing have been altered??

Are there adjustments that can be made on the back of the unit by what appears to be tightening two case securing nuts/bolts??


What is the function of the tri sided nut/bolt on thr side of the pump between the hp injector pipes??



Thanks.. N..

[Crasher]

Seriously. before anything else, get the codes read to make sure nothing is stored and with the engine hot (over 85°C) have the Commencement Of Injection checked preferably using the extremely useful VCDS timing graph function but if another system is all that is available, follow this chart in Basic Settings 04 and observe the values in blocks 2 (A) and 9 (B) of group 000. if you took this problem to another garage who knew what they were doing, this is the very first step they would take. I will not accept the specification as being OK in range C, I aim for the central dotted line, nothing else will do....



Select Engine Basic settings Group 04
Select Display Group 000
Observe the value in display zone 7 (coolant temperature).
Specified value: Must be less than 73 which corresponds to 85 °C
Do not continue with the test until the coolant has reached the specified temperature.
The commencement of injection in display zone 2 depends on the fuel temperature value in display zone 9.
Specified value: Range C in illustration
A - Display zone 2 Commencement of injection
B - Display zone 9 Fuel temperature
Notes:
If injection start is within specified range C when tested, no adjustment is required. If the commencement of injection (timing) is outside the specification tolerances, adjust the commencement of injection as follows:
Loosen the injection pump securing bolts by approx. one turn, leaving the easiest bolt to reach till last.
By hand, hold the injection pump under tension in the direction to be adjusted.
If the commencement of injection is advanced, turn the injection pump in the engine's direction of rotation, if the commencement of injection is retarded, turn against the direction of rotation.
Carefully loosen the last securing bolt until the pump can be turned slightly and then retighten the securing bolt.
Observe the value in display zone 2 and, if necessary, repeat adjustment until the value displayed remains at the mean value for the specified range -C-
Tighten the injection pump securing bolts to 25 Nm.
Check the commencement of injection again.
Note:
After a dynamic adjustment of the injection pump, the injection lines on the injection pump must always be loosened and then tightened again (25 Nm). This relieves the strain on the pipes and prevents vibration fractures.

[Nigella]

How can the timing be out? The pump didn't move??


Are there adjustments that can be made on the back of the unit by what appears to be tightening two case securing nuts/bolts??


What is the function of the tri sided nut/bolt on thr side of the pump between the hp injector pipes??


What does the 12 or 13mm bolt do on the rear of the pump below the tri sided nut?

[Crasher]

How can the timing be out? The pump didn't move??

What they have been playing with and the symptoms suggest the pump timing is out and they know this, read on.

Are there adjustments that can be made on the back of the unit by what appears to be tightening two case securing nuts/bolts??

Which of these did they remove?

What does the 12 or 13mm bolt do on the rear of the pump below the tri sided nut?

Can you point this out?



1) 45 Nm
2) Injection pump gear
3) Woodruff key
4) 25 Nm
5) Feed line from fuel filter
6) 10 Nm
7) Injection pump cover
8) Seal
9) Fuel cut-off valve 20 Nm
10) Connection for return line 28 Nm
11) Return line to control valve/fuel filter
12) 25 Nm
13) Injection pipes Tighten to 25 Nm Remove using 3035 Always remove pipe set complete Do not alter pipe shape
14) Connector for fuel cut-off valve and start of injection valve
15) Timing DTI access bolt 25 Nm
16) Injector For cylinder 3 with needle lift sender
17) 20 Nm
18) Clamping collar
19) Bracket
20) Copper seal
21) Start of injection valve -N108
22) Strainer
23) O-ring
24) 25 Nm
25) Injection timing device cover Replace O-ring in the event of leakage
26) Bush with taper
27) 25 Nm nut with cone
28) Bracket

What is the function of the tri sided nut/bolt on thr side of the pump between the hp injector pipes??

This is the access point for setting the pump timing using a dial gauge, The bolt in the middle is where non VW tools can do the same job. Basically this tri sided bung allows access to the back of the pump lift cam for basic setting purposes.

[Nigella]

Thanks for the very very detailed post... Just what I was looking for...


None of the bolts/torx/allen nuts bolts screws were removed, only checked for tightness. Just incase they had vibrated loose over the years, none at all were undone nor attempted to be undone/removed only tightened.


Only one of the torx bolts was lose approx .75 of a turn, think it was the bottom left on your colour pikkie, holding the mounting bracket on, all of the rest were tighter than a scotsman on Burns night!


Possibly and only a very very slight chance, the centre nut in the middle of the tri sided nut may have slightly moved, but only about .001 of a turn, literally a degree or two. Might have even been the play in the socket wrench that moved, not the nut itself..... (this was the bolt I thought was under that odd shaped nut)


I will look a little closer in a short while and see if I can be more certain which one moved, I was holding the torch so if I go to the same position I should be able to be more positive.


Thanks so much for the posts you have made so far, they have been so informative and helpful and have made things look a little clearer than my clear as mud descriptions...


Hopefully they will assist many others with the same issues or questions or help them ID the parts they are trying to describe.

[Nigella]

Just been out to the car and cannot see much..


The nuts/bolt moved were as described above....


I will check first thing tomorrow in daylight and see if there are other witness marks that other bolts were moved but I am 99% positive they were not.


The nuts marked with yellow, what is the significance of these, just out of interest.... I think there were a couple on the top of the pump too....