Club 80-90 Forums

After chucking a few bob and about a weeks worth of faffing at my 2.1 w/cooled digijet T25. I thought I had it cracked however:
Not wishing to break down too far from home and being kind to my hapless towing mate I did six circuits of junctions 7 & 8 A1(M) and back through town. So far so good. I then did a couple of trips returning via Hitchin. On the second of these there was some kind of problem at Letchworth so I went on to the next junction. By this time I had driven 57 miles on what was predicted to be the hottest day of the year. I was feeling pretty confident that I had now fixed the problem.The van cut out on the lead in to the motorway again exhibiting the same symptoms. Bugger!
The symptoms:
The problem occurs after between a few miles and on the last occasion 57 miles whereupon the engine cuts out dead as though out of fuel or sparks. When a restart is tried the engine bursts into life and dies straight away. Holding the starter in results in random firing but sustained running is not achieved. After a "cooling off" period the engine will start normally but the time of running ismore or less proportional to the period of "cooling off".
I have now bought the Bentley manual and am impressed with the checking processes. However everything is within limits while the engine runs and trouble shooting can probably only be posible under fault conditions. So I need to induce the fault while stationary at my home. I hope to induce the fault condition by say covering the radiator with cardboard and run the engine hoping that the problem is indeed temperature dependent. My feeling is that as soon as the engine starts it recieves a signal that all conditions have not been met and shuts down. This would point to some kind of feedback to the ECU posibly from a sensor - this condition being time or temperature induced. I could just replace the ECU but that would justabout complete my stock of duplicated parts and I am not convinced that this would necessarily cure the fault. Has anyone any experience related to this fault?

You have checked the big plug into the ECU, I have heard of people meticulously checking the resistance of the wires from there back to source. Fuel pressure is steady, under fault conditions??. A good hard run on a rolling road sounds like a good idea.

I can see this is very frustrating, many people have given in and gone back to the carb setup from the DG which apparantly works well, as does Variant manifolds and twin carbs. Shame though.

CJ at syncrospares has had to replace a couple of ECU's so it is not worth ignoring. A dry soldered joint will change resistance with temp.

Keep going...

Simon.

syncrosimon wrote:You have checked the big plug into the ECU, I have heard of people meticulously checking the resistance of the wires from there back to source. Fuel pressure is steady, under fault conditions??. A good hard run on a rolling road sounds like a good idea.

I can see this is very frustrating, many people have given in and gone back to the carb setup from the DG which apparantly works well, as does Variant manifolds and twin carbs. Shame though.

CJ at syncrospares has had to replace a couple of ECU's so it is not worth ignoring. A dry soldered joint will change resistance with temp.

Keep going...

Simon.

OK so I have plodded through the bentley checks and found the cold air start valve test deffective. Cleaned it with carb cleaner and dry PTFE lubed it and now it passes. So my mate has authorised another trip to Letchworth for a tow home if it doesn't work. (Five tows so far) Off we go again....
Cheers
Ken

OK so I have plodded through the bentley checks and found the cold air start valve test deffective. Cleaned it with carb cleaner and dry PTFE lubed it and now it passes. So my mate has authorised another trip to Letchworth for a tow home if it doesn't work. (Five tows so far) Off we go again....
Cheers
Ken[/quote]

Tow home number six! Anyone know of a good Watercooled Digijet expert coz I am on my last legs on this one. I changed all of the ignition system, checked all of the sensors and ancilliarys to the Bentley manual and am still stuck with this random failure where sparks, injector pulses and fuel pressure are all present and the motor starts on the button but dies straight away. I say heat related but it was failing on a comparitively cool engine today but only after a bit of a run, failure and a tow in. I am on the verge of trying to source an ECU but knowing my luck on this one I may not do the trick. Anyone had any experience of this randon/heat/time related failure?
Cheers
Ken

Faulty lambda sensors will send false signals to ECU and may cause similar running concerns.


Regards

Fritz,,,,,,,,,,,,,,

http://www.lambdasensor.com/main/bosch/ ... 0258003957

[quote="Fritz"]Faulty lambda sensors will send false signals to ECU and may cause similar running concerns.


Regards

Fritz,,,,,,,,,,,,,,

I don't seem to have one of those although I do see them on the American models in the manual.
Thanks anyway
(To be honest the engine does start every time its just keeping it going for more than a second or two which is the problem. It will always start after a "cooling off" period though so the duff sensor theory has merit)
By the way anyone in the St Evenage area of Herts got an ECU I could try out?

I would ask that question in a separate post... might get a better response.

seems that the culprit is this ECU though

kevtherev wrote:I would ask that question in a separate post... might get a better response.

seems that the culprit is this ECU though

Good advice as it got a couple of respnses. Thanks
Regards
Ken

Keep us posted on what happens, as it is so specific it will be very useful for the wiki section, you must nearly be there, and all that attention to the system will make it reliable when the fault is traced.

Good luck.

syncrosimon wrote:Keep us posted on what happens, as it is so specific it will be very useful for the wiki section, you must nearly be there, and all that attention to the system will make it reliable when the fault is traced.
Good luck.

I believe that chance favours the prepared and I aam surely putting in the prep. effort. I would like to get my hands/eyes on a logic diagram for the internals of the ECU so I could eliminate sensors/inputs which could bring about my problem. However with any "luck" a change of ECU will do the trick. As you say I should be able to write a "lights on but no one at home" supplement to the Bentley section on Digijet...
Cheers
Ken

Not sure if it it helps but,
If you 'forget' to plug the air flow sensor in (on the air box) when changing the air filter for example,
You get a fault where the engine will start, but die imediatly,
It might be worth double checking the connections to this. Does the spring clip hold the plug tight? does moving the plug / wires with the engine running produce the fault?

T

Ken,

You wrote.......

I would like to get my hands/eyes on a logic diagram for the internals of the ECU so I could eliminate sensors/inputs which could bring about my problem.

I have a Haynes manual with the VW Digifant (no digijet) system in it.
It is not something I have studied or claim to understand but there is a 'Pin Table' which lists the inputs to the various pins on the ECU (ECM).

There are four connectors listed, 25, 38, 45, and 68 pins.

I know some of the functions of the digifant will not apply to the digijet, but if it is any help I can list the pins on the 25 table which it says was used on the 87 to 91 2.1i cat. transporter.

Mike

Grun wrote:Ken,

You wrote.......

I would like to get my hands/eyes on a logic diagram for the internals of the ECU so I could eliminate sensors/inputs which could bring about my problem.

I have a Haynes manual with the VW Digifant (no digijet) system in it.
It is not something I have studied or claim to understand but there is a 'Pin Table' which lists the inputs to the various pins on the ECU (ECM).

There are four connectors listed, 25, 38, 45, and 68 pins.

I know some of the functions of the digifant will not apply to the digijet, but if it is any help I can list the pins on the 25 table which it says was used on the 87 to 91 2.1i cat. transporter.

Mike

Thanks for that Mike but the Bentley manual goes into great depth on the digijet even to the point of checking the wiring out from the ECU plug outwards. What I really want is a logic diagram for the interior of the ECU which tells of the intereaction betreen the inputs and sensors so I an see what would cause my engine to start and stop straight away. I should be getting a loan ECU on Tuesday and will be liioking to spend another few hours tlolling about waiting for the tow in session.
Cheers
Ken

You could try these guys, they list under transporter/vanagon 2.1 two ecu's that they can test and repair, they might pass on a wiring diagram.

http://www.injectioncorrection.co.uk/in ... Volkswagen

As has been said before if you forget to plug in the AFM it has these symptoms, so I would double check the wiring, and the output. Lots on vanagon.com (I think) about the wiring upgrade on the AFM, which you can do at home with a solder on resistor ( I think )

Keep the info coming.

Hi Ken

I had a simular problem with my 1.9 auto last year, and found it was the ingition coil getting hot then braking down allowed to cool she would then run as normal changed coil everthings fine.