# Digifant wont Spark



## TBerk (Oct 9, 2000)

*SOLVED: Digifant wont Spark*

89 A2 Jetta w/ 1.8 8v. 

The thing got to be hard starting and then would stall once you did get it started, once you let off the clutch in 1st gear.

Now, following my trusty Haynes manual (which covers waaaaay too many different models of VWs and Fuel/Ign systems btw) I have discovered the following:

- Plug test at Ign Module shows battery voltage present.

- Hall Sensor (triggering) test inconclusive due to lack of LED as prescribed in manual. (The meter fluctuates a bit though, but this is a grey area.)

- Main Lead from Coil shows one initial spark upon Ign Sw to the ON position, but no further sparks during Ign Sw in the START position.

There are Ground Straps present from the Valve Cover to the Firewall & Coil Bracket, and also from the Battery to the Chassis to the Transaxle/Block.

Anybody have a way to break out whether I have a bad 'brain box' or not?


Thx,
berk


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## TBerk (Oct 9, 2000)

Any Digifant folks out there?

berk


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## Glegor (Mar 31, 2008)

everyone hates digifart...


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## WaterWheels (Aug 14, 2005)

You'll have to change that comment as I do not hate Digifant, at least the Digifant II. 

I avoid doing troubleshooting via. the Internet without lots of in-put to narrow things down. Not that it can't be done but it takes way to long and often ends with something that was overlooked being the problem. But in this case I avoid making a comment as the symtoms sound like a common problem with older Digifant, as well as L-Jetronic systems. The air sensors get old and the tracks inside become worn which causes lose of contact between the finger and the tracks. This sounds of a bad air sensor but I hate telling folks things like that and also the possibility of it being something different and cheaper. If you have an extra one or know someone with a Digifant II system, swap the air sensors and see if it clears up.

As for people hating or not hating Digifant systems, it reminds me of two different sayings I have heard over the years. "People seem to hate what they don't understand" and "There are no small rolls, just small actors". The second breaks down in automotive terms like this: "There are no bad engine management systems, just bad mechanics."


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## 1988Audi80NA (Nov 27, 2009)

Bravo to the previous post ! 

With that said here is a link covering the ignition system with some good tests to perform so you don't have to spend alot of money replacing things until you have found the culprit: 

http://www.oneilcastro.com/A2Bentley/FU03/ch3.1.2.html 

Two things 

1. Follow those tests until something conclusive is determined. 

2. when you can afford it get a test light or led they are pretty cheap. 

Good hunting


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## Fat Rabbit (Nov 18, 2001)

Buy or make an LED test light. They are not that expensive. You need one to diagnose your present issues -- at least to properly check the ignition system -- and they can be handy for other tasks. 

The one spark and then no spark issue seems to be related to the '89 model year. I've heard that symptom before here on Vortex relating to '89 Jettas. Also IIRC there was a split in electrical diagrams in 1989 when VW went to CE2. (Up to VIN 1G KW400000 and from VIN 1G KW400001.) FR


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## TBerk (Oct 9, 2000)

*Update*



1988Audi80NA said:


> Bravo to the previous post !


 Yeah, me too. 

I'm thrashing a bit with a Haynes manual that covers everything from basic CIS (which I have lots of experience with) up to Motronic. 




> With that said here is a link covering the ignition system with some good tests to perform so you don't have to spend a lot of money replacing things until you have found the culprit:
> 
> http://www.oneilcastro.com/A2Bentley/FU03/ch3.1.2.html


 Hah!, and here I just found that site myself, just this afternoon. But thank you though. 



> Two things
> 
> 1. Follow those tests until something conclusive is determined.
> 
> ...


 Thanks again. 

So far I have found the following; 

- It was harder to scavenge an LED last night than I assumed it would be. But tonight I have a sacrificial candidate, er volunteer all lined up. 

- I have measured correct behavior based on this: 3.4 Testing Hall Sender and Ignition Control Unit (all except CIS-E Motronic and *Digifant I*) http://www.oneilcastro.com/A2Bentley/FU03/ch3.4.html 

Exxxxcept for the _Hall Sender Switching Function_ test,http://www.oneilcastro.com/A2Bentley/FU03/ch3.4.3.html for which the LED test loom will come in handy. Other than that I have found power going where it should and is expected. 

Now, the fun part I have developed today is the coil doesn't seem to measure to spec; 

Primary #1 - #15 = 2 Ohms (should be more like half an Ohm or 3/4s) & the Secondary 
measured out @ 4.9K Ohms. Spec is supposed to be 6.5K - 8.5K Ohms. 

Soooo, I'm going to verify the Hall Sensor flickers the LED and I _think_ I have spare coil around, but it'll need testing to confirm it's comparable (and hasn't suffered from just sitting around). 

The main symptom I'm trying to fix is the main coil lead, when held very close to the block, will only spark once (when the Ign is turn ON) and thereafter No Spark ensues. 

btw- if your still reading along; this car was sold in California, was built in Germany- 2/89. That makes it a 1990 car doesn't it? (damn, I just realize as I type this the VIN will tell me that. Never mind...) 

Still- is it Digifant ONE or TWO? You'd think by now I'd know for sure. 


TBerk 
really stretching that 'there are no stupid questions' idiom...


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## TBerk (Oct 9, 2000)

*It aint the coil, even though its the Wrong Coil...*

Turns out I found the coil tested as one for a very early model VW, like 70's era. I'm looking into whether the Ign Module and/or BrainBox are fried. 

Any further way of determining would be great. 

Edit- Found out the coil will spark if the car is cranked and the Hall Sensor plug is given a simulated short. In other words the Hall Sensor will flicker my test LED OK and the Coil and Ign Module will spark the center lead coming from the coil. But I can't get a complete system to spark any past just On Initial Spark when the Ign Key is turned to ON. 


berk


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## TBerk (Oct 9, 2000)

I have confirmed it's a Digifant II (TWO) system btw. It doesn't have the plugs under the shifter boot to recover error codes like the Digi I system does, and so on. 

Here is where I am so far. All of the tests for "Is the Voltage where it should be and acting right?" test OK No broken wires to be found per Haynes or http://usuarios.multimania.es/erick78/FU03/ . 

Also I can test the Hall Sensor during cranking and see it send out a flickering signal in my test LED. 

Aaaaand, with the Ignition ON and main coil lead a fraction away from the block I can get the coil and so on to send out sparks at will as I temp short the Hall Sensor PLUG. 

SO, what the Frak? 


berk


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## 1988Audi80NA (Nov 27, 2009)

Sounds like the Hall switch may not be working try this test first 

http://www.oneilcastro.com/A2Bentley/FU03/ch3.4.3.html 

If you get positive results then test the Digi II cotrol unit 

http://www.oneilcastro.com/A2Bentley/FU03/ch3.4.5.html 

Figure 3-10 one of those will probably not pass. 

Just my two cents worth


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## TBerk (Oct 9, 2000)

*It turned out to be the Ign Switch after all*

Hot wired the car and it started up, vroom! 

On the way to buy a new Ignition switch. 


berk


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## 1988Audi80NA (Nov 27, 2009)

I hate it when I over tech the obvious. But glad to here you got it figured out.


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## TBerk (Oct 9, 2000)

1988Audi80NA said:


> I hate it when I over tech the obvious. But glad to here you got it figured out.


 Every dam'n thing tested under the hood was Fine, but it still wouldn't start.  :banghead: 

Then, just now, because I needed the thing out from in front of my house and back with it's rightful owner we bought an Ign Switch from Autozone, (FLAPS). :sly: 

Turns out he 1st one he gave me would have fit an early model Rabbit/Scirocco, etc (tabs on back arraigned semi circular), but the _right_ part was in the system as being for a 1992 or thereabouts. 

Anywho, now to install the new one, oh joy. 


berk


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## rick90210 (Mar 22, 2004)

how did you hotwired your car? I have the same problem (sparks once when ignition is on, but doesnt spark on crank, checked hall sensor and is ok, and power is supplied to the ignition unit) and I would like to do the same to discard the posibility that the ignition switch is faulty...

mine is a 1990 1.8L Jetta don't know exactly wich digifant is but has a ECU unit, an Ignition Unit (little thing above the ECU with a 7 wire connector), knock sensor ,hall sensor, coolant temp sensor, and a cilindrical coil...


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## 88Jetta350 (May 4, 2007)

I had this same problem with my CIS-Basic '83 Scirocco... Turned out to be a loose connection on one of the wires attached to the main negative terminal.


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## TBerk (Oct 9, 2000)

rick90210 said:


> how did you hot-wired your car? I have the same problem (sparks once when ignition is on, but doesn't spark on crank, checked hall sensor and is OK, and power is supplied to the ignition unit) and I would like to do the same to discard the possibility that the ignition switch is faulty...
> 
> mine is a 1990 1.8L Jetta don't know exactly which Digifant is but has a ECU unit, an Ignition Unit (little thing above the ECU with a 7 wire connector), knock sensor ,hall sensor, coolant temp sensor, and a cylindrical coil...


There is a plug on the back of the Ign Switch which has something like 5 colored wires:

- Big Red. (12v, be careful.)

Of the others there will be two on the largish side that you need to both have those 12v go to . (This is like the Ign Key = ON)

Then there'll be a fourth wire that'll only need to be momentary; this'll run the STARTER. (Be careful not to start in gear.) 

There's one remaining wire that you'll note is thinnish and likely grey w/ a red stripe. It serves the dash and radio and other aux stuff. (I didn't even bother with this one in the few blocks we drove to get to the FLAPS.)

The Hot 12v goes to the two switched power wires then you briefly touch the starter one time.

Disclaimer; you do this at your own risk; don't burn up your wires because you read this on the Internet.


TBerk
better yet, break out your Bentley Repair Manual...


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## rick90210 (Mar 22, 2004)

well, I tested the sw with a voltmeter. it has 5 wires, one big red, a big red with a black stripe, a small brown, a big black with a yellow stripe and a big black wire. with the voltmeter in hand, I turned the ignition on, and I could read 12V on the small brown and big black w/ yellow stripe, and if I crank it, I could read ~10v on the big red w/ black stripe wich I suppose is the one to the starter. Could this mean the sw is operating correctly?

btw, the ones I should splice togheter to turn the ignition on are the Big red + small brown + big black w/yellow stripe?


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## TBerk (Oct 9, 2000)

rick90210 said:


> well, I tested the sw with a voltmeter. it has 5 wires, one big red, a big red with a black stripe, a small brown, a big black with a yellow stripe and a big black wire. with the voltmeter in hand, I turned the ignition on, and I could read 12V on the small brown and big black w/ yellow stripe, and if I crank it, I could read ~10v on the big red w/ black stripe which I suppose is the one to the starter. Could this mean the sw is operating correctly?
> 
> btw, the ones I should splice together to turn the ignition on are the Big red + small brown + big black w/yellow stripe?


Sorry for the delay in getting back to you...

(I assume your test was with the loom plugged into the Ign switch.)

It doesn't sound like the all black wire was getting any voltage. Both it AND the one w/ a stripe where energized during normal IGN ON operation. The small wire runs up into the dash and during my temp work around was left out of the action.

dems me tinks.


TBerk


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## WaterWheels (Aug 14, 2005)

rick90210 said:


> . . . it has 5 wires, one big red, a big red with a black stripe, a small brown, a big black with a yellow stripe and a big black wire. with the voltmeter in hand, I turned the ignition on, and I could read 12V on the small brown and big black w/ yellow stripe, and if I crank it, I could read ~10v on the big red w/ black stripe wich I suppose is the one to the starter. Could this mean the sw is operating correctly?


The wires are as follows:
~ Heavy RED wire is battery voltage direct from the battery, it should read 12v all the time.
~ Heavy RED/BLACK wire activates the starter motor when the key is in the start position (spring loaded position).
~ Medium BLACK/YELLOW is the X contact or load reduction wire, it provides power to items that are not required during engine cranking to reduce the load on the battery in situations like cold weather. Say it is winter any you have the lights and heater fan switched on when you try to start, this wire is where the power for them comes from and during cranking this circuit is switched off by the ignition switch to allow more power for the starter.
~ Medium BROWN wire is the "ignition power" also known as switched power. This is where the power for everything not powered by the load reduction relay comes from, like the ignition system and ECU. This should have voltage in both the start and run position of the ignition switch.
~ Small BROWN/RED wire is most times refered to as the SU contact. It can be used in different ways for different countries and years but your's should have power with the key OFF and lose power in start/run. It inter-acts with the seatbelt interlock system I believe in US models. Here it is used often for what people there call "city lights".

Hope that helps your testing.


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## TBerk (Oct 9, 2000)

Thx WW,

I want to point out some disclaimers on my part; namely this thread began because I was trying to figure out my Nephew's Jetta's wont stay running hard to start, then no start condition.

We fixed it with a replacement Ign Switch (the back portion that is the actual switch, not the 'front' part that is the key-lock).

Since then, and because we were successful, the Jetta and the Haynes repair manual (w/ it's diags and schematics) have driven off into the sunset- I have neither nearby to refer to, just my almost 'old-timers' memory to work with.

I'm not at all sure my old and Rick90210's current troubles are the same.


TBerk


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## rick90210 (Mar 22, 2004)

I never tested the black wire since I thought it was a ground wire, but it should read voltage during the ON and START positions?


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## WaterWheels (Aug 14, 2005)

rick90210 said:


> I never tested the black wire since I thought it was a ground wire, but it should read voltage during the ON and START positions?


Yes. Above I have the ignition power listed as BROWN, this I believe was a typo in the diagram I was looking at and should have questioned it before posting as BROWN is almost always a ground in VW wiring. But the other black, BLACK/YELLOW is correct.


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## rick90210 (Mar 22, 2004)

well, my tests concluded: Red wire always has voltage, Red-black wire has voltage in START position, the Black wire has voltage in ON and START positions, and the Black-yellow has voltage in ON position, the brown wire also has voltage in ON position. so I guess the ignition sw is working... maybe the Ignition module could be the culprit? I tested the hall sensor with the led lamp and it flickers... someone sugested that maybe the distributor was the problem and that these cars (a 1990 jetta 1.8L 8V with 3speed auto and AC) have a history of failing in this area...


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