How to test ECU

[barefootjohnny]

A friend of mine asked me if there was a way to test the ECU in his bus he just purchased and i told him i had no idea, but now i am interested. I do not know the issues hes having, but being a bus owner myself I was wondering how do you know if the ECU is going bad, is bad, or partially working?

Can someone Educate me on what all the ECU controls? I know air flow, but is there any good articles or pages i could visit to learn more?

Also, having no luck finding a rear hatch key lock for 1977 baywindow. If anyone knows of one.

Thank you!!!
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1977 VW Baywindow

[SGKent]

you swap in a known good one and see if there is any change. You put one of the two in an anti-static bag with a packet of silica gel and stash it as a known good unit in case you ever suspect that the ECU failed. You can put a NOID light on the injectors and see if the NOID light flashes so you know that the injectors are getting a pulse. Want to learn more - start here:

https://www.thesamba.com/vw/archives/manuals/afc_f...Manual.pdf




.
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George Carlin:
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Skills@EuroCarsPlus:
"never time to do it right but always time to do it twice"

[barefootjohnny]

SGkent... Thank you. I have been looking for information like that for awhile. New to this vw life.
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1977 VW Baywindow

[Wasted youth]

I have considered this problem in the past. I think Telford would be a great person to take the lead on this... there has got to be in-depth electronic analysis possibilities here. Example: my ECM/ECU on my 1988 Dodge truck took a dive. I sent it out to be rebuilt. Came back with two new resistors soldered in... so there must be a way to properly analyze these things.

[aeromech]

Smell it. Does it smell fried?

Open it up. See anything fried?

From what I understand these units can handle a lot. I believe I remember a company offering repair.

Do a google search
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Capable of leaping tall buildings in a single bound

[Wasted youth]

...and taking it a few steps further, it would be super-cool to see someone be able to tweak these for automatic air/fuel shifting when CHT gets hot. Maybe a plug-in mod?

Not my field of expertise by any means, but I bet someone could really stretch these units into somebody’s wet dream.

[TomWesty]

[Wasted youth]

Oh, I didn’t mean to market it. Just to open up the possibilities and share how it might be done.

People go bat shit crazy just on cam profiles. The arguments on Progressive carbs vs. fuel injection commands a lot of bandwidth... it would be neat to see these ECUs with their locks picked open and explore the possibilities!

[airschooled]

A few years ago, the late Karl swapped four different ECUs into his FI bus and did not note any difference in drivability or performance.

Starting your fuel-injected education with the ECU seems backwards to me- check the link SGKent posted first and learn about all the sensors and injectors, and just remember that the ECU reads the sensors and triggers the injectors.

Robbie
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[Abscate]

More time is wasted troubleshooting good ECUs than all the tea in China. Your Bus runs crappy bcause of bad tuneup parts, plugs, and junk in the gas, not the ECU. Apologies to the 1:10000 who actually have a problem.
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[telford dorr]

You can do it, but it's a lot of work. You first need a mating ECU connector (junk yard / burnt harness) and some wire and pins. Mount the following in a box:

- noid lights (LEDs with series resistors) one for each injector
- ignition simulator (NE555 oscillator circuit)
- simulator for AFS and TS2
- indicators for fuel pump drive, etc.

Probably wouldn't be worth it unless you were needing such a device frequently.

On the other hand, you could have a complete 2nd FI system (components and harness) for spares, and just hook it all up on the bench for test purposes (would still need the ignition simulator).

A more interesting device would be a unit that you could connect between the harness and the ECU which had all of the signals brought out to buffered indicators and test points, such that you could monitor all aspects of system operation while the engine was running. The connectors could obtained from a dead / scraped ECU and harness. Gut the board and use the dead ECU as the indicator / test point enclosure.

ECU's pretty much work or they don't. Other than burnt traces from faulty aux air regulators and damage from battery reversal or alternator overvoltage, I've seen few ECU failures myself.
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[SGKent]

FWIW I had to take a trip to see one of the major rebuilders of FI parts back in 2009. My visits were plural and during the process we got to know each other, and they showed me around. One of my questions was to know how they test ECU units. They open them up, look with a magnifying glass for any broken solder connections, replace things like resistors that appear to have over heated and then test them on an artificial engine. If they work they ship them out as remanufactured.

Telford won't fess up to it but he is an electronics genius, and we are damn lucky to have him as a member here.
_________________
Canned Water - the new California approved parts cleaner (except in a drought in which case rub it with sand).

George Carlin:
"Most people don't know what they're doing, and a lot of them are really good at it."

Skills@EuroCarsPlus:
"never time to do it right but always time to do it twice"

[KentABQ]

[skills@eurocarsplus]

[telford dorr]

[telford dorr]

[skills@eurocarsplus]

[Wasted youth]

Telford, do you think it would be feasible to ‘hack’ an ECU to cause it to enrich fuel/air mixture when CHT starts getting too hot?

[telford dorr]

VW keeps the ECU circuit secrets close to their vest, so it's unlikely (without a whole lotta work) to hack the stock ECU. On the other hand, you can richen the mixture by adding resistance to TS2 (or replacing it with a linear potentiometer - between 2,500 to 5,000 ohms works well). The downside is you would now have "manual choke" and incur the hassle of having to operate it all the time (which isn't too bad - I have a pot on mine because the heads have no hole for a TS2, and I find the "manual choke" kinda useful - after startup I can lean it quicker than TS2 would. I have an O2 sensor in the exhaust header and gauge to keep tabs on the mixture). Maybe a switch to switch between "manual" and "automatic"?

Any idea why your stock setup is running hot / lean? Might be easier to fix that issue instead...
_________________
'71 panel, now with FI
'Experience' is the ability to recognize a mistake when you're making it again - Franklin P. Jones
In theory, theory works in practice; in practice, it doesn't - William T. Harbaugh
When you're dead, you don't know you're dead. The pain is only felt by others.
Same thing happens when you're stupid. - Philippe Geluck
More VW electrical at http://telforddorr.com/ (available 9am to 9pm PST)

[SGKent]

if the CHT gets too hot why not just slow down instead of pouring raw fuel thru the engine trying to cool it?
_________________
Canned Water - the new California approved parts cleaner (except in a drought in which case rub it with sand).

George Carlin:
"Most people don't know what they're doing, and a lot of them are really good at it."

Skills@EuroCarsPlus:
"never time to do it right but always time to do it twice"