90 cabriolet, 1.8 8V with Digifant no start problems - Pls Help

[automark]

HI ALL,
I hope any of you with digifant f.i. experience can post helpful tips and tricks for this type as both Bentley and chiltons have failed to guide me in the right direction. I'm in the Lynnwood / Mill Creek area of Bothell,and could really use the assistance. Please read on:

I'm working on a 90 Cabriolet with the 1.8 digifant It has new:
T belt and tensioner, other belts, a couple of seals, etc. also, new
ignition components - cap rotor and wires, and plugs
is Extremely rich and will barely start when fuse for fuel pump is in
Pull the fuse for fuel pump, and it will start and run for a short period and then stop.
Once, I was able to apply a bit of throttle, say 2000 rpm, but once it used up " the residual " fuel, it stalled.
Have double checked the timing, confirmed spark, confirmed Fuel ( Plenty! ), and can't figure it out.

Please let me know if you have any suggestions, and thanks in advance!
MSH

[Fat Rabbit]

Bad ECU. Check the ground wires that connect at the coolant flange -- transmission end of the engine. If those wires are not connected it will cause the ECU to go bad. FR

[automark]

Hi FR, Thanks for the tip. The ground wires all look good, clean, and tight. I've installed a new ECT sensor, blue one for the ecu. Same problem. this time, a "backfire" while cranking blew the air intake hose to the IM off of the airbox end of it's connection.
Any other tips?
TIA, MSH

[Fat Rabbit]

Get another ECU and switch it out. FR

[twinair]

x2 on the ecu

[automark]

FR and Twinair
Thanks for the suggestion. Tomorrow night I'll have a known good ecu to install and try. Strange thing is that this one appears fine and shows good spark?

Regarding ECU's, how far off of the part number's alphabetical suffix can you go before this digi 2 type of ECU would be wrong for the car? For example,
### ### ### es
### ### ### fa

Does any of you know the correct ECU for the 90 Cab w/ 8V 1.8L?

Thanks again,
MSH

[twinair]

I have a 90 and will check when I get home tonight.

[automark]

Thanks Twinair, I have just found some theoretical data on line that says that ANY Digifant 2 ECU can run any car? I'm not sure, but they are VW people, so maybe they know. Another thing I've found is that the main VW # is
037 906 022
Then, the suffix can be:
AG
BN
AN
BC
BE
FQ
CS - this might poss be a special number on the BOSCH reman unit
M

This is all just various data points, so I don't know which goes with which.

Thanks for looking for me, I really appreciate it.
Best regards,
MSH

[Fat Rabbit]

Any ECU probably can run any engine. But I always operated under the assumption that there were differences in the ECUs and have always replaced them by PN. However, no one I have been able to find has been able to tell me the specific differences in the units based on the letter suffix to the base PN. I have asked several times over the last 10 years.

My '91 GTI took a CT or AT ECU and I never tried any other -- although I had them to try from time to time. There were also Bosch and TAN OEM ECU's. FR

[kamzcab86]

Digifant Cabriolet ECU part #s:

1990: 155998004*
1991-1993: 037997022KX

*Cabriolet-specific part

Edit: Before condemning the ECU, test the fuel pumps and fuel pump relay and Digifant Control Unit relay, if you haven't already. Also, check, clean and, if necessary, replace the grounds.


Modified by kamzcab86 at 7:16 PM 4-6-2009

[automark]

Hi Kamz, Thanks for the info.
I'm checking the Fuel pressure and that sides relays tonight. I know I've had good fueling, cause it is like it is flooded.
To ALL,
I've disconnected the connector for the o2 sensor, no change;
I've disconnected the blue connector from the ECT sensor ( which has just 2 days ago been replaced, no change;
I've confirmed timing marks yet again;
I've confirmed all grounds, again;

Tried to start with fuse #5 (fuel pump) pulled from fuse box, and it starts, a little bit, very herky jerky, and stalls within 30 seconds.

Put the fuse back in for FP, no start at all.

Very confounding, this lil Mk 1!!
Kamz,
I appreciate the Cabrio specific part # info, also. Do you know if that 155 998 004 equates to the 037 906 022 CE, where the 9 digit # is the common part, and the CE suffix seems to be for the cabrio? ( Mine appeared original, and was a CE suffix box )
I'd been on the cab-info site, and it is excellent! Thanks for that.

Anyone have any tips or suggestions ( other than pull motor and put in a new one ) ?
Thanks again!
MSH

[automark]

FR, Kammie, Twinair, et al,

It's alive! Thanks to Mark K and his "test" digi ECU, It runs again! The known good ecu that I was relying on "wasn't".
IM for details if you wish.
Thanks to all for all of the helpful, insightful, and caring contributions!
Best regards,
MSH

[kamzcab86]

Excellent! And, you have a PM.