WTB: ECM 1997 Golf GTi VR6 manual trans

This is a no-start problem. Car was driven about a week ago and all seemed fine. Tried to start engine in the heavy rain a few days ago, the engine cranks over strongly, idiot lights are good on the dash during cranking (good ign switch) but engine will not start! No DTC faults relating to a no-start problem, just one dealing with the Secondary Air Pump system. (vag-com tool)

part # 021 906 259K (Bosch 0 261 204 263/264)

The current ECM is not firing the coil pack (1 year old BERU). I tried another working coil pack. I checked power and ground at the coil pack plug (GOOD) and even checked the wiring from the ECM to the coil and it is fine. I even tried an ign coil from a 2.0 ALL COILS DID NOT SPARK STRONGLY! With the 2.0 coil hooked up I could just barely see the tinest spark in the dark.

I checked the ecm firing of the sets of sparks with an LED light and it flickers but very faintly. With the 2.0 coil hooked up I could manually ground it's center terminal and it had a very nice strong spark.

Conclusion.............Bad ECM or Bad Grounding system through for the coil pack. Bentley concluded that it is the ECM!

I am currently studying the Bentley to see if I can tell where the grounds are for the ECM.

But just in case I will need an ECM does anyone have a good one to sell? Suggestions are welcomed too! TIA

later, dave (One out of many Daves)

Reply to
dave
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I'm confused, how could you use a 2.0 coil on a 97 VR6 engine. Before you condemn the ECU did you check for a signal from the G28 (crank sensor)? Does the manual have a pin-out test from the ECU connector?

Reply to
Woodchuck

Hi Woodchuck, I was only testing the wiring and ECM with the 2.0 coil. ;-) The coil pack and the 2.0 coil will both use Power (#1), Ground (#5), and ECM signal (another ground). I can connect the coil with separate wires to #1, #5 and then any of the other terminals for the ECM signal to fire the spark.

There was no DTC for the Engine Speed Sensor. I would assume, according to Bentley, that if this sensor was not operating, then a code would be thrown. I was truly hoping that this sensor is/was the cause. Do you think I should install a new one just in case? If I crank over the engine I could read RPMs on at least one of vag-com tools Measuring Blocks, but not on all of them. That is why I believe that this crank sensor is working. If I am incorrect..........let me know.

I did mention that there was an ECM signal to the coilpack but it was super weak. 8^) Hmmm could the cranksensor throw a signal to the ECM which is too weak to fire the coilpack but strong enough to not set off a DTC?

Yes this Bentley has the ECM Electrical Test (pin-out test) procedure which is my task for tomorrow starting with testing the grounds (1,10, 33, 55,56 & 7 for the manual trans) to the ECM. On a big learning project now. lol

thanks Woodchuck!

later, dave (One out of many Daves)

Reply to
dave

More information on the no-start problem.

I bypassed the Engine Speed Sensor (Crankshaft Position Sensor) with a handheld Hall Generator. I repeated the test for spark and got that same weak spark at the test spark plug. Still no DTCs were thrown for the Speed Sensor. I did ohm the Engine Speed Sensor and it was slightly out of spec, like around 800+ instead of the 500-700 ohms. This sensor still did not throw a DTC though.

Pin Test Results. (grounds #10 for the throttle plate sensor and #33 for the knock sensors don't seem to be up to spec) Even though I found a few other problems with this car, like the throttle plate sensor is probably defective, it seems like the ECM is just not doing it's job of firing the spark. The ground (terminal #1) at the coil pack seems to be fine and that is what I assume the ECM uses to fire the particular coil pack spark plug pairs.

**************** Now I put the system back together and the engine starts and runs with good spark coming out of the coil pack. I think I will change the Engine Speed Sensor tomorrow and hope that it is the cause of this no-start problem.

later, dave BTW thanks Woodchuck

Reply to
dave

The G28-crank sensor can really play games when diaging a no start. Usually the only time it will set a fault code is if it fails while the engine is running. When you crank the engine the ECU looks for the G28 signal and if the engine doesn't see that signal it will not turn the injectors on(spray fuel) and supply spark. It never knows the engine is cranking over. The G28 has 3 pins, 1 shield and 2 for the voltage it produces while cranking which can be checked with a voltmeter but I can't remember if it's AC or DC. About 90% sure it's AC and should be at least around 1.5 volts. If you can get a hold of a digital multi-meter you should be able to measure it. Another way is use a oscilloscope and it will produce a wave signal. Did you know the sensor wheel for the G28 sensor has one tooth missing, along with G40 that's how the ECU knows where number 1 cylinder is. Just buy unplugging and plugging everything back in you may have cleaned some poor connections and fixed the car. Still my first choice is the G28 sensor. Remember VW ECU seldom fail!

Reply to
Woodchuck

Big Thanks Woodchuck! I was wondering if maybe it might be marginal, just enough to cause the engine not to start but NOT enough to throw a DTC.

Come to think of it I did not hear the injectors working until I hooked up my 'portable' hall generator. Then when I put everything back together the engine started. Maybe unplugging and replugging the crank sensor helped. I will be changing it tomorrow and crossing my fingers.

Yeah I knew some teeth were missing and the only way to change that wheel on the crank is WAY too involved for me! lol

I owe you one! ;-)

later, dave

Reply to
dave AKA vwdoc1

Previously engine would not start. It had a super faint spark only seen in almost total darkness. No DTCs indicating problem. After testing wiring, pins, components it now starts.

Update: I took the crank speed sensor (021-906-433C) off and found some metal particles on the tip of it. (I think that this car has been abused!!) Maybe this was the cause of the no-start problem. Oh and it started again this a.m. :-)

The parts manager of my local VW dealer does not even keep them in stock for the VR6 engines. They do have the 2.0s in stock so those most go with regularity.

Oh well a new sensor goes on today and fingers will be crossed! lol

later, dave (One out of many Daves)

Reply to
dave

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