# What gives digifant injectors their power?



## JML III (Sep 4, 2007)

What tells the digifant injectors to pulse? I am working on a 92 cabriolet. If I hook up a test light to the injector plug, the light will flash with turning the key on and off but not when cranking the starter.


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## JML III (Sep 4, 2007)

There is a test where I use a test light on digifant control unit plug from terminal 13 to terminal 25. It is supposed to flicker but it DOES NOT!


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## WaterWheels (Aug 14, 2005)

JML III said:


> What tells the digifant injectors to pulse?


The Digifant ECU. The injectors are under constant electrical power when the ignition is on and the computer grounds them to cause the injection pulse.



JML III said:


> There is a test where I use a test light on digifant control unit plug from terminal 13 to terminal 25. It is supposed to flicker but it DOES NOT!


If the terminals are correct I can't say from here (they sound wrong off the top of my head). The big question is the test light, is it an LED type as the manual should instruct you to use? A side from maybe causing damage by using an incandesent light, it probibly would not flicker due to the nature of the bulb (current required to get it to light).


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## JML III (Sep 4, 2007)

It is an led test light and the 13 - 25 is right out of the bentley to test swiitched power to the injectors.


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## JML III (Sep 4, 2007)

The bentley says that with that test there should be a flicker. There was nothing.


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## WaterWheels (Aug 14, 2005)

If everything is correct, not doubting you, just the numbers don"t sound right (25) and I can not check from here, have you tried reversing the test light probes?


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## Fat Rabbit (Nov 18, 2001)

First, the test light needs to be an LED test light suitable for 12V DC -- other lights do not react fast enough. LED test lights can be purchased for a few dollars. I made my own. Based on your post it seems that you have an LED test light.

Second the polarity needs to be correct. If the LED test light noes not flash reverse the leads as suggested above.

I test at the main injector connector at the engine -- just unplug the connector and test across the contacts at the wire end of the connector. You will need to have someone activate the starter -- make sure the car is in neutral with the parking brake set. I prefer to do the test where it is darker so that I can see the pulses of the light better. FR

Pin 25 of the ECU goes from the ECU to the ICU. Pin 13 is in fact the famous ground connection that will kill your ECU if it is not properly grounded. I don't find ant tests between those two terminals. 

In most Digifant II cars the power to the injectors comes from the fuel pump relay to the injectors. The power supplies to one side of the injectors while the other side goes to ground through Pin 12 of the the ECU. All of the injectors pulse at once. The pulse duration is set by the ECU duration of grounding.


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## JML III (Sep 4, 2007)

I have tested the main plug at the injectors. It flashes once when I turn the key to on and once when I turn it to off. That is it. The test light is a 12v LED test light. Here is a clipping from the bentley showing what I was testing. This is in a 92 cabriolet. Maybe it is different than others?


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## WaterWheels (Aug 14, 2005)

I knew the pin locations you listed did not look to be correct for what you said you were testing. If you are trying to test injector function why are you then trying to do a test for the ignition system? I mean it even states "ignition switching function of Digifant II control unit".


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## JML III (Sep 4, 2007)

I am not specifically testing that. I tested all of them. That one did not do what it is supposed to do. I am guessing that is part of my issue.


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## JML III (Sep 4, 2007)

Maybe I am wrong. I don't know. Does anybody know where to start testing for the injectors? After I found out that it does not operate properly at the plug?


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## Fat Rabbit (Nov 18, 2001)

Water Wheels is correct we can't tell which plug you are testing-- your manual is confusing. 

The proper plug to test is a two wire electrical connector that hooks to the injector bus. It is located at the transmission end of the cylinder head -- just to the rear of the head itself. The two wires are red/black and brown.

If you are testing at that connector you need to make sure that you truly do not have pulsing there. Reverse the test lamp leads and make sure the leads are making good contact. As I said above the flicker is faint and fast. You need two people to do the test. One turns the key to start to turn over the engine while the other observes the test light.

If there is no flicker you have to investigate further. Usually that is a sign of a bad ECU. Make sure that the two or three wires that connect to the cylinder head at the hose flange stud or bolt at the transmission end of the cylinder head are intact and are clean. The wires are usually brown/black and brown and black. The ECU grounds through the black and brown wire which comes from Pin 13 of the ECU. If that wire is not connected to ground and the car is started the ECU usually shorts out and is ruined. I check visually and verify ground from pin 13 to the engine with my multimeter set to Ohms -- mine has a setting where it will buzz when there is continuity. We call that "ringing out" the wire. 

I usually make sure that 12V DC power is supplied to Pin 14 of the ECU connector through the Digifant relay with the key to start or run and also that I have power to terminal 15 at the coil. That will be a thin black wire at the coil. Pin 14 has a yellow and black wire. Your manual should have a diagram of the ECU connector -- pins 1-13 are in one row and 14-25 are in another on the connector.

Hope this helps. FR


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## JML III (Sep 4, 2007)

The manual I am using is a bentley. I have tested the plug at the fuel rail. That is the one that will flash once when I turn the key to on and once when I turn the key to off. When I was referring to 13+25 I was talking about on the ecu. I think I thought it had to do with the injectors because it calls for the plug to be disconnected. 

Additional information: The car has spark, the fuel pump turns on and has good pressure, and it has good compression. I am using an led test light and know to check polarity. I have tried another (matching number) ecu with no luck. The car was driving and started to die out under more than half throttle. Ten minutes later it was dead completely.

Tonight I will check the ohm reading between the engine ground and pin 13. 

Thanks for the help!


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## Fat Rabbit (Nov 18, 2001)

Note: If the second ECU could not find a ground it would destroy itself just like the first ECU. (IIRC the Vortex record is 4 ECUs destroyed before the wiring was connected.) The situation usually occurs when an engine is replaced or some cylinder head work is done and the ground wiring is not reattached to the head. But I have also seen situations where the wiring is broken from engine vibration or where corrosion prevents a good connection. Unfortunately if the ECUs destroyed themselves you need to find a different one. 

Also check for 12V DC at Pin 14 of the ECU connector -- that is the power for the ECU from the Digifant Relay.

If I understand your last response you are simply getting no flashing execpt for the initial "key on" flash at the injector electrical connection.

One thing I like to do on Digifant cars is to reach around behind the fuse and relay panel and snug up all of the connectors back there. I have found several cars where the connectors behind the panel will pull away and cause loss of electrical contact. FR


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## JML III (Sep 4, 2007)

I am getting 12v at terminal 14. 

By key on I mean it flashed once when the key is turned to on. 

When I check for an ohm reading between terminal 13 and the engine it jumps to 11+ ohms then goes to zero.

EDIT: Test prongs were loose on the multimeter. Ohm reading between pin 13 and the ground cable is 1.5-2 ohms.


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## JML III (Sep 4, 2007)

which terminal is the ground for the injectors?


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## JML III (Sep 4, 2007)

On the test below, is 0 ohm an okay result?


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## JML III (Sep 4, 2007)

Sorry about all the separate questions but should there be resistance between pin 5 on the 5 pin connector by the coolant bottle (the motor side plug, not the one that goes to the ecu) and the red wire at the injector plug? There is


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## JML III (Sep 4, 2007)

Found the issue. Melted wiring. Will post pictures in a few minutes. Now I need to fix the wiring but I need to figure out why this happened.


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## JML III (Sep 4, 2007)

The wires for the injector plug and the plug under the throttle body have melted. I think this explains a lot! haha


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## Fat Rabbit (Nov 18, 2001)

That would do it! I'm surprised there aren't some fuses blown with that degree of melting. Looks like you have some wiring work to do -- either that or find a different wiring harness. At least it looks like you have a decent place to work. A big short to ground would cause that. The injector wiring gets power through the fuel pump relay directly from Circuit 30 which is continual battery 12V power. I'd check out the wiring inside the injector bus. Also, it is not uncommon for the O2 sensor wiring to get routed where it touches the muffler or exhaust manifold. The usual symptom on that is blowing a lot of fuel pump fuses. But I would look at that wiring too. FR


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## JML III (Sep 4, 2007)

Any suggestion on the procedure to take for fixing the wiring? Should I pull the whole harness? Is there any possibility I could find out why this happened?


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## JML III (Sep 4, 2007)

Also, which harnesses would be interchangeable?

Car is a 1992 Cabriolet.


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## Fat Rabbit (Nov 18, 2001)

To be safe get a 1992 Cabrolet harness. Cabrolet parts may not be interchangeable with other models -- but I think a harness for a 1990-1991 Cabrolet may also work. 

Remember too you don't need to replace all of the wiring -- just harness that self destructed. You could also splice in the needed wiring -- just use wiring of the same gauge of the destroyed wires. If I did that I would solder and heat shrink the connections. I just don't trust crimp on butt splices. I've done plenty of splicing on Digifant cars. (In fact, I still have a couple of hanks of wire I bought at the Ace Hardware in Kennebunk to do some rewiring one time when I was out your way.) 

As I said earlier something must have gone to ground causing a big current draw which heated the wiring. Where the heating occured might not be exactly where the short occured. Finding out "why" in your case is entirely up to you and your investigative skills. The color of the burned wires might provide a big clue. FR


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## JML III (Sep 4, 2007)

Wouldnt I need to remove the whole harness and cut open the casing to repair the wires? I have done a lot of splicing so that is not an issue. The tubing those wires are in goes into another larger tubing.


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## Fat Rabbit (Nov 18, 2001)

Yes, you would have to open the cable far enough to splice in the needed wires. It isn't as simple as buy such and such a part and install it. If you can find a similar car in a junkyard you would have to make a decision as to how much of the wiring you would need. I doubt if you could even buy a harness new from a dealer. Over the years I have split open a number of harnesses to track down broken wires then resealed the harnesses. I have never had to remove a whole harness to repair a wire or two. I would also never run individual wires all over the place as I have seen done. But that is just me -- it is your car so you get to make those decisions. FR


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## JML III (Sep 4, 2007)

I wouldn't run it outside of the casing. I can't see being able to get to it with the harness installed though.


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## JML III (Sep 4, 2007)

Also, do you think there is a high chance of this just happening again? I haven't found what could have caused this.


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## JML III (Sep 4, 2007)

So I started pulling some of the harness apart. This picture shows what I found. 



For the plug that goes into the bottom of the throttle body; The red/blue wire has melted to the point shown and is broken. The brown/yellow ground has melted up beyond what I have cut into so far. 

For the plug that goes into the fuel rail; The solid red and the ground are both intact but the casings have melted in that section that is exposed. 

I hooked up the test light to the power and ground wires for the injectors to try it out and see if that has been the issue. It still only flashes once when I turn the ignition to on. Does anybody know if the plug under the throttle body gives any signal to the ecu to have the injectors open?


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## WaterWheels (Aug 14, 2005)

JML III said:


> This picture shows what I found. . . Does anybody know if the plug under the throttle body gives any signal to the ecu to have the injectors open?


No, the throttle switch, or its plug, have no direct effect on the injector pulses. The ECU uses the information to maybe alter the injection pulse for the two conditions the switches tell it, but the there will always be pulsing, just at different widths if need be. I strongly suggest that you stop trying to do any electrical testing until the cable harness is 100% repaired or replaced. And then I would also after testing that it is completely fixed/correct, get and use a known good ECU for any testing. There is no way to know for sure where and how much damage is done to that cable harness until it is stripped completely. Wires can burn through anywhere and even if you fix one spot there could be more hidden under the shielding. Playing around before having things back to 100% is a good way to get bad results or ruin more parts due to testing.



JML III said:


> Also, do you think there is a high chance of this just happening again? I haven't found what could have caused this.


I think you just might have discovered what caused it without knowing you did. From the position of the major damage and the position of the cable as you are working on it, it looks almost like the cable drooped down and got ripped up or pinched by the shifting rods/levers. The harness should be held up away from those parts with wire ties but yours seem to have dropped down right into the path of their movement. Not a for sure thing here, just a guess from the picture you posted.


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## JML III (Sep 4, 2007)

That is not where the harness was routed. It was zip tied up out of the way. I just have it there for more room.


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## Fat Rabbit (Nov 18, 2001)

I have to agree with WaterWheels -- repair the harness fully before worrying about why things don't work. Then, using the wiring diagram in your manual, inspect each wire for continuity from connector to connector using a multimeter or test light. That will take some time but you need to verify each wire. 

Early on I mentioned that the power for the injection system comes from (through) the fuel pump relay and grounds through the ECU. 

In a previous post I also mentioned that you may have fired the second ECU you tried because the ECU ground wire may be disconnected or damaged. Usually, if you open the ECU box you can see a burned spot on the PC board in the ECU if it is damaged. Other than that I don't know of any way to test the ECUs except by trying them in another vehicle. In theory, a VW dealer has the equipment to test an ECU but even if they have the equipment they would probably want more that what a used ECU would cost to test them. FR


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## JML III (Sep 4, 2007)

I opened up the ecu. It seems fine. There are a bunch of wires that got burnt up. Ground to the distributor, the wires for the injectors, red wire to the distributor has exposed wiring, throttle body plug completely disconnected, etc. I wish I knew which harnesses were interchangeable. I could probably find one to pull.


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## Seax_Smith (Jun 1, 2007)

When I was getting my current daily road worthy, I had to rebuild a lot of the front harnesses.

What I did was the one wire at a time approach. Used zip ties to loosely bundle everything to keep them neat as I routed them and once everything was in place and functional, I wrapped them in conduit.

The other thing I did was to "over ground" everything. The stock 16 gauge was replace with new 14 gauge and many ground paths were doubled. Was a lot of tedious pin pulling and the like, but well worth it in the end in my opinion.


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## Fat Rabbit (Nov 18, 2001)

Problem is I don't think other commonly abailable harnesses will work because your Cabrolet -- even though it is Digifant -- has a different fuse and relay panel from most other Digifant cars. A new replacement harness runs $716. Finding another 1992 Cabrolet in a junkyard -- priceless.
Otherwise DIY. FR


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## JML III (Sep 4, 2007)

You say pin pulling... Does that mean instead of splicing in sections to fix the bad wire you replaced the whole wire?

Because one of the grounds that splits into a few is burnt most of the way to the plug.


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## JML III (Sep 4, 2007)

And I was thinking, the harness im working with doesn't even plug into the fuse panel. I do have access to digifant cars that aren't ce2, I think.


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## Seax_Smith (Jun 1, 2007)

JML III said:


> You say pin pulling... Does that mean instead of splicing in sections to fix the bad wire you replaced the whole wire?
> 
> Because one of the grounds that splits into a few is burnt most of the way to the plug.


Pin pulling (not always possible) is removing the metal pin from inside the connector and running a new wire all the way through.

Sometimes you can get the pins out and uncrimp them and recrimp the new wire on, solder and heat shirnk and reinsert into the plug or socket.

Sometimes you have to scavenge a pin out of another plug.

Sometimes it is easier to find the plug or sub harness needed and splices it it. Digi does fine with splices if they are done well. 

New pins and some sockets are available new, but not so easy to figure out some times: goggle 
"Junior Timer Pin"


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## JML III (Sep 4, 2007)

The ground is melted all the way to the pin. How do I remove the pin from the ecu plug? 

Also, my soldering skills aren't all that great. I can make them strong but they don't always look good and aren't always smooth. Is this okay?


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## JML III (Sep 4, 2007)

I have been working on the harness all day. I have done 15+ repairs, some of which were to prevent an issue in the future. At this point I am just waiting to find information on how to remove the pin so I can make the ground connection. I have tried finding it using google with no luck. 

Someone give me the information so I can finish it up and get it in the car!


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## JML III (Sep 4, 2007)

All I need to do to finish it is get the pin hooked up! Anyone know how? I tried a tool made for pin removal but couldn't get it out.


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## Glegor (Mar 31, 2008)

JML III said:


> And I was thinking, the harness im working with doesn't even plug into the fuse panel. I do have access to digifant cars that aren't ce2, I think.


digifant was only in CE2 cars..

even the mk1 cabbys had digifant and CE2..


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## JML III (Sep 4, 2007)

No this car is not ce2. Cabriolets are ce1


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## JML III (Sep 4, 2007)

I see the clips that i should be able to collapse but i just can't get it out.


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## Seax_Smith (Jun 1, 2007)

JML III said:


> I see the clips that i should be able to collapse but i just can't get it out.


the pins and be an extreme pita. I put a couple of nice gouges into my fingers when I was rebuilding my front harnesses from stupidly applying too much effort.

Ended up calling someplace that sells Junior Timer pins for replacements. Also pick up a few new connectors with new pins. The connectors with the gaskets in them up in the bay are pretty much impossible to get out without a lot of patience and the right sized pickes, etc., and it you do get them out, the gaskets are not really worth reusing.

I got some out with a basic with a basic pick and/or thick paper clip bent into a "U" and/or some fly tying tools and/or one of the metal flat wire strips on the side of a windshield wiper.


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## Seax_Smith (Jun 1, 2007)

Glegor said:


> digifant was only in CE2 cars..
> 
> even the mk1 cabbys had digifant and CE2..



You positive about this?

Had an 88 Golf GL (1VW) which was wired rather differently than my 92 8 valve GTi (3VW).


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