Golf won't start

Hi guys,

i need help with my cabby. It's golf mk1 cabriolet 1991 1.8 with digifant 2 injection system. For a long time, I am trying to get it started, but unsuccessfully. When i bought the car it was not starting, and it hasn't been driven for about 13 years. I replaced both of fuel pumps, changed filters, oil, repalced spark plugs, clean ijnectors, replaced blue temperature sensor(i revved up engine three times as manual says), changed vacuum hoses but i still couldn't run the car. Then after two weeks i finally run the car but it was starting very hard when cold and i always had to disconect blue temperature sensor. It had very bad throttle response when it was cold. Once it warmed up, it was running fine and i was able to start with blue temperature sensor plugged in. I gave the car to local mechanic and even he couldn't find where is the problem. Then i bought new engine, that was running fine in the old car and fitted it in. But even after i replaced whole engine, i am still having the same problem. Car sometimes starts, sometimes it doesn't. And if it starts and i try to add gas, it starts to hesitates and die. I changed three distributors, mass air flow sensor. I checked ECU cable with multimeter and all resistance seems to be fine. Only problem is with fuel injectors. On fuel injectors ramp i get resistance 4.5. I found two different types of manual. In fisrt one i have read, that between terminal 12 and 14, there should be resistance between 3.7 - 5 ohms, but i don't have any resistance there. So i gauge harness which goes to and from fusebox and they are all ok. I thought problem is in fuse box so i fitted in a new one, but i still have no resistance between terminal 12 and 14. Later I found different manual, that says, that if the car is older than 1990(mine is 1991) i should gauge between terminal 12 of ECU cable and terminal 5 of 6-pin connector in air plenum(red wire). But i don't know where i can find this "6-pin connecor in air plenum". Can anyone help me with this or did anyone of you have similar problem? Thanks for any response.

No one likes to read a big block of text, and some won't respond to it..myself included so I fixed it for you.


I need help with my cabby. It's golf mk1 cabriolet 1991 1.8 with digifant 2 injection system.

For a long time, I am trying to get it started, but unsuccessfully. When I bought the car it was not starting, and it hasn't been driven for about 13 years. I replaced both of fuel pumps, changed filters, oil, replaced spark plugs, clean injectors, replaced blue temperature sensor(I revved up engine three times as manual says), changed vacuum hoses but i still couldn't run the car.

After two weeks I finally run the car but it was starting very hard when cold and I always had to disconnect blue temperature sensor.

 This is the classic sign that the BLUE CTS SENSOR is bad, they go bad 5 Different ways that I have seen. No start when cold, No start when Warm, Crappily running, Broken wires in the harness to the ECU (DIgifant Controller), and a Blowed UP ECU, How can a ECU blow up.  Bad Frame to engine Grounds, Half the issues I have seen with the Digifant Cabriolets are tied to a BAD Battery to frame and frame to engine ground.  Before I did and further testing or swapage, I would replace my Battery to Frame and Frame to engine Ground wires. NEW out of the box CTS sensors have been known to be bad, it isn't that uncommon. When the Ground cables are flaky, the Electrical Flow for the starter and other things tend to find the least path of resistance in getting connectivity, I have seen bad grounds Fry Speedo Cables and the cluster, Clutch cables, along the way with the ECU, and ICM.  (ICM) Ignition control module attached to the Digifant holder in the Rain tray.

I would also verify that the Ground from the Raintray is intact to the ECU Holder.

The other issues for cold start/warmstart/crappily running are caused by the Fuel Pressure Regulator and that the residual pressure tests outlined in the Bentley nailed it every time,,,, I had a FPR cause a no start when warm only but if you waited 20 minutes it fired right up.

So originally we are down to a BAD CTS sensor on the original engine or wire, Possibly bad ECU, Possible bad Fuel pressure regulator.
One other thing I have seen give me fits was a Crank Gear shear….

It had very bad throttle response when it was cold. Once it warmed up, it was running fine and i was able to start with blue temperature sensor plugged in.
I gave the car to local mechanic and even he couldn't find where is the problem.  

Mistake, not all mechanics are attuned to the older Cabriolet, let alone electrical issues of the DIgifant IMHO.


Then I bought new engine, that was running fine in the old car and fitted it in. But even after I replaced whole engine, I am still having the same problem.

Car sometimes starts, sometimes it doesn't, and if it starts and i try to add gas it starts to hesitates and dies.

 Then the issue wasn't the engine was it, expensive mistake that a few quick questions here may have had you up and running on the original engine.

I've changed three distributors, mass air flow sensor. I checked ECU cable with multimeter and all resistance seems to be fine.

Only problem is with fuel injectors. On fuel injectors ramp I get resistance 4.5. I found two different types of manual. In first one I have read, that between terminal 12 and 14, there should be resistance between 3.7 - 5 ohms, but i don't have any resistance there. So I gauge harness which goes to and from fusebox and they are all ok.

 Don't do any more testing or swapages until you have changed out your Battery to frame and frame to engine Grounds.

I thought problem is in fuse box so I fitted in a new one, but I still have no resistance between terminal 12 and 14. Later I found different manual, that says, that if the car is older than 1990(mine is 1991) I should gauge between terminal 12 of ECU cable and terminal 5 of 6-pin connector in air plenum(red wire). But i don't know where I can find this "6-pin connecot in air plenum".  


 Which Manual are you using to get the test measurements? Bentley or Haynes? Your car if it is a 91-92-93 is newer not older, the older ones used carbs or CIS totally different…. Stay attuned to 90-ish digifant only.  There is a connector that is behind the Strut tower passenger side, I think that is the one you need to refer to, but there is no AIR PLENUM connector that I know of, there is the MAF connector and the ICM connector….

Are these the old injectors or came new with the engine, we know the engine was running in the previous car, so it isn't related to the new to you engine, well at least until you started the swapage

The injectors are fired all at one time on a digifant engine, there are specific resistance check for them that you can do to rule all of them out quickly.


It isn't the engine.  It is Electrical, Change the grounds first.

Have you verified that the wiring from the CTS sensor to the Digifant controller is intact?

Best Guess from me is either a Bad ECU, Bad ICM, Bad Grounds or broken wires between them. With the Bentley as a guide, it is very easy to measure the wires for continuity first to validate that you have good connections. Then I would think ECU blown Due to bad grounds.


Can anyone help me with this or did anyone of you have similar problem?

Thanks for any response.

Hi Briano, thanks for your large response.

I fitted new engine with it's own components. So injectors, fuel pressure regulator and ECU are also from the new one.

I meassured correct resistance of CTS on ECU terminals, so i think this is working.

Before i fitted new engine i cleaned grounds that i know about- From battery cable(i think negative) to gearbox, from ecu holder to body, from ignition coil to camshaft cover and two other grounds from bunch of cables also to camshaft cover.
Should there be more grounds?

 Is there any way to test ECU? I have read that bad ECU would fill cylinders with fuel, but that is not my case.

I have read bentley manual and document on internet with title "digifant 1 and digifant 2 repair manual". But there is no resistance between terminals 12 and 14 on ECU cable.

14 is B+in , 12 is a pseudo ground.
I wouldn't think that B+ is a short or a resistive value between the controller and the injector…

Too many individual components between the chips and other discrete components.

When you look at the diagrams for the controller the 12pin is tied to the injectors, and the injectors are being supplied B+ by the fuel pump relay, where the Pseudo is being controlled by the Controller by applying ground.

If the controller goes bad one way it will allow the injectors to spray continuously.

It isn't to say that it can't go bad and stop them from firing.

You would need a Noid light to possible see if the injectors are firing.

I'm not very good in english language(i am from Slovakia) and i don't know if i understand. It is not necessary to get resistance between terminals 12 and 14 on ECU cable?

Tomorow, just to be sure, i will change all grounds. If it won't help, where else should i look for the problem?

With all the Solid State parts of the ECU I wouldn't expect there to be any measurable resistance between Pin 12 of the ECU and Pin 14.

Pin 14 is the main power in +12VDC from the ECU relay in the fuse box.

Pin 12, is a Pseudo Ground that is given to the Injectors at the firing time determined by the ECU.  The +12Vdc in to the injectors is from the Fuel Pump Relay.

All the injectors fire at the same time, not in a staggered pattern as determined by the firing order.. It is the Compression or Exhaust that allows the fuel to be injected, or not as the pressure differential of the Cylinders causes a excessive force to keep the injectors closed. (very basic physics.)

Grounds and such are very important to the ECU/Frame/other components.

Bad Grounds usually will cause an ECU to get destroyed.  How it gets Destroyed and how that Destroyed ECU acts is a question for the Electrical gods.

In the Bentley / Haynes they are referring to the testing rig for pin assignments.  It is a large block of pin holes in a harness that connects the ECU input cable to the ECU.  So what the Haynes/Bentley is stating is the numbering of that testing block which may or may not be the exact same as the connectors on the controller.

Here is the innards of the Digi Controller a lot of thing to go bad, for only a few pinouts on the cable/connection.



I am not saying your not right, but I am saying it would be a difficult thing to statically test.

Start at the basics, TIMING, Fuel, Spark.
Are you getting Spark at the right time.

There is a Static timing of the Digifant that uses but a DVOM and the Key on, no reving of engine holding the rpm at 2250….or timing light needed, it also tests the Hall Sender as that is the wire you are looking at for a 0-11V swing.

If there is no swing during the test then your Hall sender or the ICM is bad which isn't to say that your ECU didn't take them out.

If you are getting an output of the Hall Sender, but never see the injectors fire.

I would replace the Battery to Frame and Frame to engine grounds first.

Then I would suspect the ECU.

Static Ignition Timing on VW A1 and A2 DigiFant Engines.

Currently I am not in the location of my car, but i will go there on saturday.

After I change the grounds, I will post my work (and hopefully progress) here. I would really appreciate if you could assist me, with your guidance.

And thank you so much for your help, advices and your time. I am very grateful for everything.

I took a day off from work today and went to my car. I replaced battery->frame and frame->gearbox grounds, also ignition coil->camshaft cover ground. 


 I found this cable, but can't find where it should go to, any advice please?

 

It's blue/yellow cable which changes to black cable.

The only blue/yellow I can think of goes to the oil pressure sender can. They may have moved it from the head to the Oil filter flange and needed to extend the wire.

I don't know which one do you mean. I have these three oil sensors. I don't know, if it is correct, but my harness looks like this:


 Yellow cable to low pressure switch

 



 Black/blue to high pressure switch and i think, that green/black cable is oil temperature sender?

 

Should look like:

I checked timing, measure all cables with bentley manual, all seems to be good. Car start little better now, but i have to unplug CTS sender to start when cold. If I add gas it starts to choke and die.

Only thing i haven't checked yet is fuel pressure because i don't have tool for it.

Unplugging the CTS to start when cold is a issue with the CTS.  They go bad regularly…Did you measure the resistance of it, as if the thing goes bad, it can cause a lean issue as it thinks the car is hot, and the digi leans the mixture.

CTS's have been known to be bad out of the box.

But checking the residual pressure drop is a good indication of your fuel system.  Over here you can rent pressure testers from most auto parts stores….

I have checked it more times, but only when engine was hot and the resistance was good. 

What do yo mean by "out of the box"?

Out of the box means that new parts can be defective.

It is easier for the manufacturer to let subpar parts out rather than try to find the bad ones.  When they are returned to the vendor or seller as bad, they get a refund.

Most folks don't bother, and buy another new one that may have been in the bad batch as well.
I know all too well about Defective parts being bad, and returning them to get another bad one in the next batch.  Happened to me with CTS sensors, and Spark plugs.

When I had the old plastic flanges on my ride that blue CTS sensor as well as the plastic flange was a pain in my keister…..

I replaced my plastic flange with one off a 16v Golf, that didn't have the oil cooler hoses and am using a 16V CTS sensor, and I haven't had issues with breaking flanges, or flaky cts senders.

I have a Thread in my Signature link on DIY's that says I hate plastic parts.

It could also be your o2 sensor if equipped that is causing a flooded state, the connector for that is on the rear of the valve cover right corner as you look at it.  Try unplugging that to see if there is improvement.