no start after cleaning ECU board

[vag_noob]

Installed sockets and chips into 1994 ECU. Car was running great.

Then bought a can of isopropal alcohol to clean the flux and a little mold from one area of the board (had a flood last year). At the same time I pulled the TCU and swapped the chip.


After this the engine will not start. Pulled the ECU and the isopropal alcohol seems to have a bad reaction with the flux. So I cleaned and re-flowed all of the solder joints. Have tested resistance on all solder joints, all good.

Have swapped back to OEM TCU chip, no change. Cannot swap back ECU chips as I clipped them. Swapped coils back to OEM, no change.

Symptoms.

Ignition on and autocheck says OK
turn key and cranks and tries to fire, dies. May fire one cylinder and dies straight away. I think ECU is not getting / getting some signal and shuts down the engine...

Runs all output tests.
12v at injectors and coils.
5v at hall sender and maf.
Has not blown ECU fuse.

Codes are 2113 (hall sensor was fine before) then 2111 (standard RPM code)

It is possible that the fuel pump is not being switched on as I cannot hear the usual whine it makes when fuel tank is low. But I would have thought there would be enough residual pressure to start at least once..

Now just code 4444 (no faults found)

tested voltage at fuse 17 with multimeter while cranking engine, variable voltage but up to ~12 volts

[M_GORDON]

uff...
It's the ECU 80% sure. But I don't know why if U clean with isopropil W7O electricity, true??
Maybe some condenser was charged?

See if the flexible wire is on good condition

[vag_noob]

flexible wire? you mean the plug / loom?

[UrS4boy]

2113 = cam sensor. No good cam sensor = no start. EVER. (until you change it).

Everything you need to know about the G40 cam sensor and how to replace it with out totally disassembling the engine:

http://forums.quattroworld.com/s4s6/msgs/22580.phtml

[newsh]

flexible wire? you mean the plug / loom?

I think he means the grey flexible connection between the two boards

[vag_noob]

2113 = cam sensor. No good cam sensor = no start. EVER. (until you change it).

I have looked at it and have a spare but it would be a strange coincidence if it has failed at the same time I remove the ECU.

Latest code is 4444.

[vag_noob]

I think he means the grey flexible connection between the two boards

Ah yep looked fine will put that on the list :b

[vag_noob]

Copy and pasted from QW

Finally got the time this weekend to continue trouble shooting the no start after cleaning ECU board. ECU says "ok".

No vag com. Ran output tests using jumper method, all passed. All injectors click. J17 clicks when engine cranks.

Had code 2113 last week so soldered in a new hall sender, still no start and exactly the same symptoms. 3 cranks, engine pops (not a backfire) and stops.

Pulled codes again today, 2111, RPM sensor, I think that's normal for non running engine though.

I don't think there are any sensor issues as the engine was running before I pulled the ECU and TCU.

I have cranked it over 15 - 20 times since the no start issue so plugs were fouled with gas. Cleaned them off and let the cylinders air out a bit. Shows injectors are firing.

On inspection Doesn't look like a significant amount of gas in cylinders and there is obvious compression when cranking the engine with plugs in vs plugs out. And a gassy smell from the cylinders with plugs out (worst case I change the oil if I ever get it going again and continue to clean the plugs in the mean time). Cranked it with cleaned plugs, no go. Have unplugged injectors for now.

On the bright side putting the new plugs in seems to have improved the plug threads on cylinders 1 and 2, guess I got lucky.

Bought a spark plug tester but of course can't get it onto the plug down that deep hole so I just tested the plug by grounding it to the intake manifold. Spark on 1 and 2, but not on 3, 4 or 5. Swapped coil 3 to 1 and get a spark so it's not the coils (didn't swap 4 & 5 though). (2.0t coils brand new). Have swapped in OEM coils last week to test, same no start. 2.0t coils back in.

I get about 11.8 volts at all coil 12v (at coil plug) with ignition on.

I read in the thread below that the coil driver channel should show about 1k ohm resistance with the ignition switched off.

http://forums.quattroworld.com/s4s6/msgs/326900.phtml

Plug wire 3 (next to ground) I get about 0.04 (400 ohms) at the 20k ohm setting for each coil plug but it varies depending on the ground (0.03 to 0.06) I might re-test in the morning and find a better ground. But the point is all 5 coil driver channels measure the same resistance with the same ground (with my cheapo multi-meter) and 1, 2 are firing and 3, 4, 5 are not. Please correct me if I am doing this wrong.

[Sonic]

I assume you've checked the POS as it seems a bit of a coincidence 1,2 are firing but 3,4,5 are not.

[vag_noob]

Using 2.0t coils. Swapped coils, swapped to oem, I don't think it's the coils.

[vag_noob]

does anyone know the ratings for this bank of capacitors (row of 38 bottom of image), or have access to schematics for the motronic that they are willing to share? That is the row I cleaned and I may have shorted a few (or most) of them..

nevermind

http://my.execpc.com/~endlr/markings.html

[UrS4boy]

There is a history of the ignition "driver" chips dieing as in becoming dead especially after an ECU gets wet. There are NO driver chip replacements either. Even the most knowledgible Motronic ECU guy here on the S2 Forum (prj or Dmitri) has a solution. Nobody does.

*IF* you were in NAmerica, I would tell you to send your ECU to Steve Eiche in Arvada Colorado for inspection and analysis. He knows a lot about the driver chip issue.