VW T4 Forum - VW T5 Forum banner

1 - 20 of 22 Posts

·
Registered
Joined
·
1,821 Posts
Discussion Starter #1 (Edited)
Common 1.9TDI Conversion Issues

This is a short companion to all of the guides for converting the VW T4 to 1.9TDI power. I have tried to compile a list of common problem descriptions and solutions that seem to crop-up time and again in the hope that it will be useful to others. This list is by no-means exhaustive and I welcome suggestions for inclusion (within reason).

1. Engine Multiplug Connector

This connector can be the source of many problems for a number of different reasons. Many of the problems can manifest themselves as faults flagged by the ECU such coolant temp. sensor, crank sensor, etc. Equally, it can also cause gauges or warning lights on the instrument cluster to behave strangely (flashing oil/handbrake warning indicators at ignition off) or not work at all.



Another point related to this connector is the fact that the metal bracket (shown above) is a ground point for the instrument temp. gauges via the 10mm nut shown above. If you remove this bracket from the engine block/head and it is floating (i.e. not connected to ground via the block/cyl. head) the instrument cluster will behave strangely with flashing/pulsating warning indicators with the ignition off. The fuel/temp gauges may also read incorrectly/erratically with ignition on.

Things to watch out for:

Most people are unaware of the fact that the two parts of the connector should first be engaged and then turned clockwise until a distinct 'click' is felt/heard. If you do not feel this 'click' then the connector is not fully 'home' or 'seated' which means that some connections may not be 'made'

This connector can also suffer from corroded pins so a visual inspection is also worth doing along with a quick spray with contact cleaner.


2. Turbo Wastegate


If your van is a 1.9TD prior to carrying-out the TDI conversion, chances are you will have played with the wastegate actuator in order to increase the boost and hence squeeze a few more HP from the engine. On a TD engine, the actuator rod length controls the level of boost i.e. the shorter the actuator rod is the more boost it takes to overcome the mechanical resistance of the spring open the wastegate. This is fine for the TD engine, but can cause problems for the TDI as the wastegate is opened and hence boost regulated by the ECU.



On the TDI motor the level of boost is set by the ECU, so once the MAP (Manifold Absolute Pressure) sensor detects that the boost is about to reach the preset threshold it opens the N75 solenoid (actually N75 is modulated - switched on and off quickly) but we'll ignore that for the sake of explanation). This means that there is now a direct link between the actuator and the compressor housing of the turbo so that it can open the wastegate and reduce boost.

Obviously the step response of the 'actual boost' will never follow the commanded boost exactly (blue in the diagram). This due to the latency (delay) of the mechanical components etc. However, the ECU s/w has been designed to essentially ignore the spike or overshoot in boost under normal conditions (plus there is also some hysteresis built-in to the control loop to prevent oscillation). However if this is 'overshoot' exceeds the boost limit for more than a predefined time window then the ECU will enter limp mode.

The problem with the wastegate on the TDI motor is that the more tension that is on the actuator rod the harder it is for the compressed air from the turbo to open it (meanwhile remember that the boost is still climbing - as illustrated by the yellow trace in the diagram above). If the boost gets to the maximum allowable threshold before the wastegate is opened fully you get limp mode or an oscillation ('hunting') of the control loop . By reducing the tension on the rod, boost is regulated more quickly as the peak boost required to open the wastegate is lower. A badly adjusted rod can also cause a sort of pulsating of the boost as the control loop oscillates.

How to set-up the wastegate actuator for the TDI motor:

a) Remove the circlip from the wastegate (A).
b) Open the locknut on the actuator rod (B)
c) Remove the actuator from the wastegate (C)
d) Loosen off the rod until the 'hole' fits easily over the (closed) wastegate lever (C)
e) Remove the rod from wastegate again and turn it 8 turns clockwise.
f) Refit the rod to the wastegate, tighten the locknut, and refit the circlip.






3. Instrument Cluster


As most of you are aware (and contrary to rumours spread by those who think that it must be magic :)), the VW T4 instrument cluster can be retained if you convert to 1.9TDI. There are a few minor changes to be made. In order to make these changes however, a basic understanding of how DOP works is essential. It should be noted that this change is not always required, but I will cover it here as it can potentially cause problems with 1996-> instrument clusters.

So, what is DOP and why does it cause problems?

VAG vehicles have been using the DOP (dynamic oil pressure) system since the 1980's, this means that two oil pressure switches and engine RPM are used to determine oil pressure rather than the system of a single switch. The rationale behind the DOP system is that low oil pressure problems are typical of high-mileage VAG engines with worn bearings and oil that is hot (and thin). The combination of thin oil and worn main bearings means that the oil pressure is marginal at lower RPM where the oil pump is not spinning as fast as it does when driving. Basically the instrument cluster monitors the low pressure sensor when the engine is below 2000 rpm and the high pressure sensor above 2000 RPM.



The problem for the TDI conversion is that the later (96->) instrument clusters cannot read the engine RPM from the ECU (so DOP will not work and the oil pressure indicator will just flash) as it is a different frequency to that of the alternator W teminal. The later clusters have better signal conditioning (presumably to comply with EMC regs) and so the TDI ECU signal is ignored by the cluster. This will result in a flashing oil warning indicator at all engine speeds.

How to solve the DOP problem.

Basically all you need to do is remove the ECU generated signal from pin 12 of connector G1 on the fusebox and connect the 'w' signal. To do this cut the black/green wire coming from the ECU tape it up and then connect the 'w' terminal of the alternator to pin 12 G1 (bottom right-hand pin in the pic below).



4. 109 Relay

The infamous 109 relay seems to cause more than its fair share of problems. This is due to the fact that VAG have consistently specified a component whose rating lies right on the limits for the current carrying capacity for the contacts of the relay.



Generally one of the following is what tends to happen:

a) The contacts arc and corrode causing intermittent starting and/or strange unrelated faults to be logged by the ECU.

b) The coil goes o/c in the relay - no ECU comms, no start, dead.

c) The metal pins soldered to the relay contacts 'dry-out' caused by the fact the the contacts are always working on the limit of their current carrying capacity. Again this will cause difficult or non-starting/stalling/No ECU comms etc.

d) The contacts arc and stick (basically weld themselves together). This means that the contacts are permanently closed even at ignition off and also that all of the sensor/pump supplies are still powered-up. The giveaway to when this problem happens is that the modulating piston in the fuel pump can be heard buzzing away under the bonnet. Apart from the buzzing everything seems to work, but it will flatten your battery sharpish and can damage sensors as well as the pump if allowed to continue.


Generally speaking the aftermarket replacement relays are usually of better quality than the original VAG part as the current handling capacity of the relay tends to be higher. VAG are aware of the problem but their 'improved' replacement part seems no better than the original and is also prone to failure.

If you suspect 109 failure, remove the relay and short the contacts. If you engine starts and runs as normal, replace 109.



4. Brake Switches


The brake and clutch switches are something that are often overlooked when doing the TDI conversion and sometimes people ignore them by either disconnecting them or hardwiring them so that the effects of any faults are masked (but not eliminated). This actually has safety implications however and you should not do this .

The brake switches have three functions in terms of the electronic control of the TDI engine:

1. Most importantly, the brake switches function (in tandem) in the manner of safety interlock, such that if there is a fault with the throttle sensor where the throttle is for instance stuck at WOT, then the brake input or switch over-rides any throttle input, thus allowing the driver to bring the vehicle under control. if you eliminate the switch or indeed the brake input signal then this will not happen and it therefore has the potential to be fatal - BOSCH/VAG installed this feature to ensure that the system was fail-safe, by removing it you risk making it unsafe.

2. When the ECU senses a braking input, it decreases the amount of injected fuel thereby reducing engine shudder and helping to save fuel.

3. The brake signal is used by the ECU to disable cruise (when active).

The brake monitoring system uses two different signals to determine when the brakes have been pressed: 1) An independent ECU switch 2) a brake (lights) signal input which is fed from the switched side of the vehicle brake light switch. Problems occur when:

1. The ECU 'sees' a signal on the switch but nothing on the brake light circuit or vice versa. e.g blown brake lamp bulbs
2. One signal is 'seen' before or after another. - i.e when the switches are not setup to trigger at the same time.




5. ECU 'Memory' Fault


I have have had a number of enquiries from people regarding this fault but until recently I had never experienced it myself. Basically what happens is that the ECU reports a fault such as:

Internal Control Module Memory error 37-10 Faulty-intermittent
and try as you might you can't clear it from the fault memory.

There are actually a number of things that can cause this, and quite often people replace the ECU in order to eliminate it thinking that it must be a hardware problem. However it can actually be caused by:

1. A split in the hose from the MAP nipple on the outside of the ECU housing to the pressure transducer (inside the ECU - see diagram below) for sensing boost. When this happens the boost from the turbo basically pressurises the ECU housing and the (other) baro sensor inside the ECU (for determining geographic altitude) goes haywire. The upshot is that the ECU reports this rather erroneous memory fault!





2 A faulty 109 relay has also known to cause this fault.

3. Poor/high resistance in the battery ground for the ECU is also another common one.


To be continued
 

·
Premium Member
Joined
·
52 Posts
I take my hat off to you. I'm just returning to my conversion after the winter.

these are problems I'd have been scratching my head over.T:

Thanks dennisA:
 

·
Registered
Joined
·
61 Posts
is this the same if the 1.9d engine is replaced with 2.5 tdi?
sorry if my questions are a bit thick, i'm a chippy and know very little about these things
 

·
Registered
Joined
·
1,088 Posts
I am nearly there!!!!!

Got the engine running sweet :ILU:

One of my probs is that I have no lights on the dials without taking a live from somewhere else.

I bought some new clocks today and the wiring loom from clocks to the fusebox but still no joy.

Any ideas?

There is a beer in it for you!!!

:*
 

·
Registered
Joined
·
35 Posts
I have another problem - the wiring all seemed to be ok on the initial test and on Vag Com but 24 hours later when we started the engine it started dieseling and didn't shut off when removing the key. The injectors have been stripped and checked and are ok.
 

·
Registered
Joined
·
1,422 Posts
My 1.9tdi (1z) conversion has been somewhat botched by a past owner/installer. this means that he never performed the flashing oil light wiring doo-dah.

Now, the van is currently in the garage and im considering having them do this whilst it's there however the lad sorting my van is as lost as myself regarding the specific wiring for the alternator to fuse box.

I've read your trouble shooting guide, as well as various others but i just wanted to confirm if this will likely resolve the problems on my van.

For a start, i have no idea if a buzzer is present in my van as ive not heard it, however the light has flashed at varied intervals during all driving conditions since owning it. Sometimes it stays off and others it flashes for a good duration.

When you say "cut the black/green wire and tape it" do you mean cut the black OR green wire (rather than the black and green wire) epending on which is present in your van, and simply tape the ends to ensure the wiring is covered and leave both ends loose/disconnected?

Finally, when you say connect the "w" terminal to G12 - is this routed elsewhere in the van up until this point? if so where does it disconnect from in order to be located in G12? Im concerned about damaging things i dont understand you see!

Does this all sound correct - and will this likely be the solution to my flashing oil light?

Thanks lads and lassies!
 

·
Registered
Joined
·
9 Posts
Me too, i've cut the G12 wire and am being a thicko and cant find the 'W' wire from the alternator to connect to the G12 pin. What colour should the 'W' wire be? Other than that my conversion is done and it goes like a stabbed rat now!

Any advise would be greatly appreciated,m cheers dudes.....
 

·
Registered
Joined
·
14 Posts
Hi
this W wire had me thinking for a bit as well, but if you get under the van and look at the alternator you will see on the black outer casing where the multi plug is connected they are marked.

i followed the wires up to the multi plug above the starter motor, blue multi plug with 2 wires going in and only 1 wire coming out the back. cut the W wire threre its a red wire covered in black outer sleeve. soldered and heat shrank the connection i made, ran the wire alongside the loom into the fusebox. I cut the green and black wire ( leaving plenty of cable on the multiplug ) and soldered the pair together and heat shrank them.

before i soldered any joins i temp fixed them together and checked that it worked. felt much better once i relised the W wire is not used for anything else. If you look at the second pin in the blue multi plug, you will see that its blanked of.

hope this helps.
 

·
Registered
Joined
·
1,422 Posts
I am also under the impression that the W wire enters the fusebox in U2/1 (perhaps, although that needs clarification).

Having tried doing this today, it appears that although my wiring is untouched my new clocks (passat B4 clocks) seem to have fixed my flashing oil light themselves.

Has anybody any idea why this may be the case? Heres me chopping into wiring and getting nowhere and then suddenly realising my oil light hasnt been flashing since the clock change - however it lights up as per normal.
 

·
Registered
Joined
·
31 Posts
A challenge in the immobiliser area; the T4 has a Valeo unit with a 10 pin connector.; the donor unit is the Sienens with the 6 pin connector. How do I marry the 10 pin wiring into the 6 pin box??
 

·
Registered
Joined
·
45 Posts
Re: van wires

Hi could you let me know how and what wires to take out of the van,
Your threads are great by the way,
I have the chance of a 1.9tdi polo and will be fitting that if it will go, it's a 1998-99 model,
Not looking forward to doing it,
Thanks

Jee*<:)>
 

·
Registered
Joined
·
2 Posts
Hi all i have got a t4 tdi conversion and i have a problem with boosting, its very slow off the mark and i dont get full boost till 3500rpm, is this normal?
 

·
Registered
Joined
·
6 Posts
Does anyone know if it makes any difference to how you set up the Wastegate Actuator if you are using the AHU Turbo from the Golf rather than the ABL one:

The problem with the wastegate on the TDI motor is that the more tension that is on the actuator rod the harder it is for the compressed air from the turbo to open it (meanwhile remember that the boost is still climbing - as illustrated by the yellow trace in the diagram above). If the boost gets to the maximum allowable threshold before the wastegate is opened fully you get limp mode or an oscillation ('hunting') of the control loop . By reducing the tension on the rod, boost is regulated more quickly as the peak boost required to open the wastegate is lower. A badly adjusted rod can also cause a sort of pulsating of the boost as the control loop oscillates.

How to set-up the wastegate actuator for the TDI motor:

a) Remove the circlip from the wastegate (A).
b) Open the locknut on the actuator rod (B)
c) Remove the actuator from the wastegate (C)
d) Loosen off the rod until the 'hole' fits easily over the (closed) wastegate lever (C)
e) Remove the rod from wastegate again and turn it 8 turns clockwise.
f) Refit the rod to the wastegate, tighten the locknut, and refit the circlip.
 
1 - 20 of 22 Posts
Top