# How to Prevent Digifant ECU from frying



## PASHAT (Oct 23, 2006)

Since I have had two ECU fry on me in the last two months, I have tried to look into this fairly thoroughly. The first one was likely due to bad grounds, but I carefully cleaned the grounds at the battery and tranny mount. About a month later, the ECU fried again.
What I understood was happening was that a current, likely during starting the car, has grounded through the ECU providing too much current, which burns out the ECU. When the ecu grounds, the injectors fire, and when it fries the grounds stay open, so the injectors continue to fire, filling up the cylinders with large amounts of gas.
I am interested in anyone's ideas of how to prevent the ecu from frying. I am also interested in anyone's experience in fixing a fried ecu.
I read that the traces fry, which ruins the ECU. However, I opened one of my 'fried' ecus, and the traces all looked good. I checked one that was suspect and it had continuity. I will post pictures and do some further research into this.
I am hoping that anyone with any experience on this will post in this thread. What do you do to prevent this problem, what, exactly IS the problem, and how can you fix a fried ECU?


----------



## teutoned (Jul 29, 2008)

*Re: How to Prevent Digifant ECU from frying (PASHAT)*


_Quote, originally posted by *PASHAT* »_ but I carefully cleaned the grounds at the battery and tranny mount. 

missed a ground? from driverside rear corner of cylinder head to cowl area near ecu?


----------



## PASHAT (Oct 23, 2006)

*Re: How to Prevent Digifant ECU from frying (teutoned)*

The one that goes from the valve cover to the coil mount was missing on the vehicle when I got it. I have now replaced it. Is THAT one somehow critical to the ECU? If so, why?


----------



## teutoned (Jul 29, 2008)

*Re: How to Prevent Digifant ECU from frying (PASHAT)*

yes


----------



## dkashbmx (Apr 17, 2009)

*Re: How to Prevent Digifant ECU from frying (teutoned)*

i just fried an ecu im im afriad its going to happen again because i still cant find the missing ground! i do not know where they all are!


----------



## PASHAT (Oct 23, 2006)

*Re: How to Prevent Digifant ECU from frying (dkashbmx)*

There has been a suggestion that running a lead from the ECU chassis to the battery ground will assist. However, it would appear to me that there has been an attempt to isolate the ECU from ground with plastic connectors including a plastic nut. If it is isolated from ground, putting a lead to the battery is exactly what you DON'T want.
Also, the problem with the ECU is that the injectors stay on. The injectors are on pin 12. There is a ground on pins 6, 13 and 19. It would appear that the ECU grounds are connected by the pins.
http://www.a2resource.com/elec....html
What is proposed to be happening is that pin12 is going direct to pin 13 (or another ground. but pin 13 makes sense since it is right next to pin 12). The ECU controls the injectors by controlling the injector circuit's access to ground. It connects the powered injector to ground when it want's the injectors to spray. When the ECU fries, the injectors get constant access to ground.
If i am correct about which pin pin 13 is, there does appear to be some slight discolouration of the board:

It looks like the discloured leads connect to a small PCB that runs up and down behind the central cover. perpendicular to the main board. Not sure if that will be an easy fix or not.


----------



## PASHAT (Oct 23, 2006)

*Here is the module I think controls grounding injectors*

This appears to control the injectors. It looks like there are two chips behind those plates. If those are fried, repair would be extremely difficult. Not like replacing a generic diode:










Here is a picture of the entire main CPU board.










_Modified by PASHAT at 8:59 AM 9-20-2009_


----------



## CajunSpike (Mar 11, 2009)

If somebody could repair these guys without charging an arm and a let..he'd be rich..I have a fried unit too. Havent opened it up.


----------



## Eric D (Feb 16, 1999)

*Re: (CajunSpike)*

The discoloration is most likely solder flux (rosin).
Most likely that ECU had been repaired. The PCB is wave soldered so all the other solder pads have a uniform color.
Repairs if not cleaned leave flux. 
Remove the heat sink and tell me the part # of the IC.
I suspect its a Mosfet.
I have a Digi1 ECU, but I'm not pulling it out of the car to check.


----------



## PASHAT (Oct 23, 2006)

*Re: (Eric D)*

I am 95% sure the ECU has never been repaired. The board in the picture is one that is fried though, which is why I am willing to play with it.

I will try to pull the part numbers but likely will not have time for a few days. Those metal bits do not have an obvious way of removal, and the back plate is part of the aluminum molding.
One thing that I noted is that there is no continuity between those two pins that I have circled. Perhaps those are not 12 and 13. If they are, I was under the impression that 12 should be constantly shorted to ground, which should be due to continuity between 12 and 13, unless it is making it to another ground point.


_Modified by PASHAT at 6:45 AM 9-23-2009_


----------



## Fox-N-It (Jul 23, 2003)

Its often forgotten that when hooking up a battery the Ground should be the first thing on and last thing off.
I put the + on first in an old Jetta I had and fried the ECU pumping 6 gallons of gas into the block.


----------



## PASHAT (Oct 23, 2006)

*Re: (Fox-N-It)*

You know...my kid was cleaning the battery terminals when this last happened. I am not sure if the problem preceded that, but was working at removing the negative terminal. I don't think he actually had removed it though.


----------



## jorge r (Apr 27, 2006)

*Re: (PASHAT)*

I know some boards or components use resistors as fuses. If a 5 volts circuit ampacity is 2 amperes, then they use a 10 watt resistor, if the wattage exceeds the resistor rating of 10 watts, possible reason for the resistor to open the circuit.


----------



## 2loyola2 (Sep 26, 2009)

*Re: (CajunSpike)*

These aren't chips they're resistors which get pretty hot and smooth out and bring the voltage from 12 to 5v so the chips can operate without burning themselves out. My ecu was brunt out too but I manged to fix it by soldering a diode across capacitors near the resistors to pin 1. I'll send some photos.
All the best, Baz


----------



## thesumof41is5 (Aug 6, 2009)

*Re: (2loyola2)*

ohh man that would help me out.. can you post the pictures, or can i just email you?


----------



## vr2jetta (Dec 16, 2007)

*Re: (Fox-N-It)*


_Quote, originally posted by *PASHAT* »_You know...my kid was cleaning the battery terminals when this last happened. I am not sure if the problem preceded that, but was working at removing the negative terminal. I don't think he actually had removed it though.

I wouldnt worry about that. Contrary to what Fox-N-It says:

_Quote, originally posted by *Fox-N-It* »_Its often forgotten that when hooking up a battery the Ground should be the first thing on and last thing off.

the common practice is, the ground is the first thing off and the last thing on and I'll tell you why.
If you go to remove the battery and you start taking the positive off first, there is a chance the wrench/tool you are using can come in contact with another metal surface (core support, fender, etc..) and cause a direct short. Remember, your wrench is positively charged from the battery! If you take off the ground first, it doesnt matter what you touch with the tool because the car IS the ground, as long as its not the positive battery terminal. When the ground is removed, there is no more charge going to the car.
I have shorted positive terminals plenty of times and had no negative outcome, its always the grounds in these cars.
Per Bentley, here are all the ground locations:
ground at inner RF fender
ground under RH side of instrument panel
ground at inner RH rear fender
ground at inner LH rear fender
ground under LH side of instrument panel
ground on transmission
ground at inner LF fender
ground on body near battery
ground at stud on engine cylinder head
You could always create your own 'hyper' grounding system. Get some 2 gauge wire, run it from the battery, to the original battery ground, to the tranny, to the motor, to the firewall, even to the subframe. Ive done this once before and had no electrical problems on that car. 
You may even have a bad harness and its shorting out internally.


_Modified by vr2jetta at 4:13 PM 9-26-2009_


----------



## PASHAT (Oct 23, 2006)

*Re: (2loyola2)*


_Quote, originally posted by *2loyola2* »_ My ecu was brunt out too but I manged to fix it by soldering a diode across capacitors near the resistors to pin 1. I'll send some photos.
All the best, Baz

I would like to see any methods anyone has in fixing these. I have two burnt out ones and two good ones, and would like to try to fix the burnt ones.


----------



## PASHAT (Oct 23, 2006)

*Re: (2loyola2)*


_Quote, originally posted by *2loyola2* »_ My ecu was brunt out too but I manged to fix it by soldering a diode across capacitors near the resistors to pin 1. I'll send some photos.
All the best, Baz

I would like to see any methods anyone has in fixing these. I have two burnt out ones and two good ones, and would like to try to fix the burnt ones.


----------



## vdub6v (Apr 22, 2004)

*Re: (PASHAT)*

I have been trying to get my inline conversion in my vanagon to work and I am having the same problems. Injector drivers nuking!


----------



## ZDespreaux (Aug 5, 2010)

I am having a similar problem..I changed the ecu and the car started fine but ran bad..almost like it was skipping or something then it would die and not start up again, it would try awful hard but never quite make it..my father tested one of the plugs that's suppose to read, 12v top one, 5v middle one, then a negative, to my belief none of these were correct I know for certain the 5v wasnt,. The problem occured after the engine bay was sprayed down..any ideas??


----------



## srgtlord (Jun 4, 2010)

This is why im switching to a holley 350 carbuerator


----------



## Prof315 (Jan 5, 2009)

*How to prevent Digi ECU from frying?*

Easy...... throw the stone age POS in the garbage and replace it with a Megasquirt!


----------

