damn Caj, this is quite the tricky one, huh?
After thinking bout it, this is what I'm going to do.
I found another Q ecu and bought it, since that seems to be the only thing that will trigger the spark.
I'll take the Q ecu I have and send it in for testing and repair in the mean time.
Can anybody recommend a reputable ecu repair/testing company?
Until I know I have a 100% good ecu, I'm spinning my wheels.
Last edited by CajunSpike; 03-26-2012 at 12:47 PM.
giving up already!
You're not using a different key than you were before right? i know you have a few different ones.
Is the coil sending a signal to the dist?
Is the dist getting 12 volts? how bout the coil?
Could the timing be so far off that you would get no spark? any static way to time it?
Any luck over on the mk3 forum?
dink and flicka
Have you checked the timing and timing belt yet?
After trying 3 Q cpu's, I have stepped away for a bit.
I aligned the engine at tdc.
I could see the bump in the tranny hole, dead center.
The distributor was pointing to #1 plug wire.
I did not actually pull #1 plug and stick a screw driver in there...yet.
Nor did I view the timing marks on the timing belt...I did finally get the timing cover off.
I removed the original distributor and installed the jy part.
Alignment was set to be the same as before.
Reassembled, tried, still no spark.
The only time I've gotten spark was with the B cpu installed. After some rain and swapping in Q ecu's, it has not sparked again even with reinstalling the B ecu.
I did get the passenger side fan installed into the radiator shroud, but don't have the small belt that runs from that fan to the powered fan.
So basically I'm back to no spark and thinking hard where to go from here. A friend MIGHT be able to test the ecu's to confirm good or bad...so I'm working on that as well.
I'm also still not fully recovered from the bronchitis incident...
I just started reading this thread, I admit I haven't read the whole thing yet.
Anyway, no spark.
Motronic coils, same as DigiFant I coils, have the power stage built in.
The three wire plug in on the top carries power and ground to operate both the power stage and the coil.
Dunno wire colors, typically, the outer two are power and ground, the inner is the signal from the Motronic ECU telling the power stage when to fire the coil.
Test the outer two for power and ground with both a DVOM AND a bulb type test light. I doubt you'll find a problem there, still a simple test at this stage will eliminate doubt later., DVOM for voltage, bulb light to verify the circuit can carry some current.
Best simple test of the signal wire in the center is with a two color LED tester, it should probably alternate red<> green while cranking. I suspect the car will fail this test.
For the Motronic ECU to generate the signal to the coil's power stage, it needs the usual power and ground plus two essential inputs. One input is the Hall generator (maybe called Camshaft Position Sensor on Motronic) in the distributor housing, I think you've covered that ground already. If you want to be sure, read my posts on this thread.....
Most of the concepts I elaborated on apply to Motronic, just a bit differently.
The other major input signal Motronic needs to signal the coil is the Crankshaft Position Sensor. You should find it on the front of the block, down low in line with the crankshaft center line between #4 and the flywheel end of the block.
Best I recall, those are a two wire sensor type and those are most always inductive, they generate a low level AC voltage.
Connect your DVOM set on ACV, a 2 volt, maybe even a 200 mV range and crank the engine, you should see ACV present.
Once in a nightmare, the tone ring has come loose on the crankshaft, let's keep fingers crossed.
Inductive sensors can also be tested when removed with an ohm meter, you'll have to look up values.
They can also be tested with an AC range on the DVOM and a magnet. Connect up and pass the magnet back and forth in proximity to the sensor, each pass should produce a low voltage AC spike. This test should work with any magnetic steel like a screwdriver, socket, hammer whatever but a magnet is more dramatic.
Under the plastic flap where you've been already, the two terminals are 15 and 1.
15 is, as always on DIN spec cars, key on power.
1 is the coil ground, again, see my posts in the thread I just linked to, concept is identical, the power stage latches this to ground intermittently then releases it to open. When it is open, you'll see 15 voltage through the primary windings. You can 'see' this signal with a bulb type test light, a two color LED tester, a tach or a dwell/duty cycle meter, it'll be real hard to make this one out on a DVOM's voltage scales.
Someone elsewhere in this thread questioned if there is a static timing method for these engines.
I did come up with a static timing method for DigiFant that I expect, but haven't tested, should work just fine with Motronic. Click my sig, don't use the CIS method, it's bass ackwards for DigiFant and probably Motronic too.
Thanks for your time, tolusina.
I'll be finding an led test light as a first step.
Recap on parts:
coil/other module that goes with it. tested as per coil test page, shows good..both old and new.
crank position sensor(under the front side motor mount).
electrical end of key switch.
Swapped with used parts:
Only time it sparked was with B ecu and even then spark wasn't hot and blue.
After swapping ecu's now no spark happens at all.
Code reader shows no codes from trying to crank engine over.
Originally showed failed crank position sensor..not any more, since part replaced.
I did verify ground from ecu frame to battery with dvom.
Think I'll go back and verify continuity of ALL the crank position sensor wires and distributor wires to the ecu, then into word at a time verification of function as you specified.
Last edited by CajunSpike; 04-03-2012 at 10:20 PM.
Test the main ground cable, battery, chassis, drivetrain with the DVOM on a 2 volt DCV range. Clip one meter lead to a drivetrain ground, hold the other lead to the battery post and crank the engine. Voltage drop is what you'll be reading this way, it's the only dependably meaningful test of battery cables and many many other tests as well. Maximum allowed drop while cranking is only 0.50 VDC while brand new cables rarely get below 0.10 VDC drop. Not much of a difference in reading yet operational differences are HUGE.
You can further test a cable at various points along the cable, see if the cable itself is at fault or individual connections.
Coming to grips with voltage drop testing and the concept is hugely powerful, very versatile.
When next at the junkyard, grab some spare harness plugs. Try and get from 3" to 2' of wire still attaches and as available/possible. Look for two, three and four pin females like for the coil, cam and crank sensors, IAT, CTS and so forth. Look at oxygen sensor harnesses and knock sensor harnesses for male connectors. Look at DigiFant A1s, A2s, of course A3s, even look at other makes. Also look for males on DigiFant injector looms, Digi II has a two pin male, Digi I has a 5 pin.
Many of these plugs can be used as test leads or/and repair kits as needed.
With a spare crank position plug and leads, it becomes very easy to connect a crank position sensor to a DVOM's leads and 'see' it's ACV signal without damage to the car's wiring.
With a three pin female and male combo you can connect in series to the coil circuit power and ground, then simulate a signal on the center wire and see if the coil and it's power stage can make spark or not. You don't even need a coil to be bolted up, but you must at least clip lead the coil body to ground else nothing.
Above, I speculated that my static timing method might just work fine on Motronic, I failed to speculate that setting at zero degrees is where I'd start and probably finish.
The thread I linked above, while aimed specifically at CIS lambda ignition is conceptually very similar to most other ignition systems.
Specific to Motronic, the coil itself works exactly the same. The Motronic coil's power stage and the CIS Hall controller do about the same thing, the big difference is the inputs. The CIS Hall generator is basically the only input to the Hall controller while on Motronic the Hall generator/Cam Position Sensor has no direct connection to the power stage, instead the Cam AND Crank position sensors signal the Motronic ECU, the Motronic ECU then sends a control signal to the coil's power stage.
I mentioned a two color LED tester above, I love these things.
More powerful yet are power probe type testers that incorporate two color LED test functions as well as the ability to instantly connect power or ground to a circuit through the testers probe tip with the flick of a switch. These power probes are very slick indeed, BUT, they have a serious drawback as well.
It is very easy to send battery power to a fully grounded circuit which lets all the smoke out and ruins components and your day/week/month. You MUST know the specific circuit under test thoroughly, else if you decide to randomly 'try it', $$$$ up in smoke, down the drain. Even an accidental probe switch activation can end in disaster. Ever 'Oops' after 5 hours with no break of head scratch puzzlement? 'Oops' with a power probe can easily become Opp$ .
Here's a two color LED tester at Sears....
One characteristic of the two color LED tester is the presence of two clip leads in addition to the probe tip.
Most auto parts stores should have something similar.
Here's power probe..... http://www.powerprobe.com/powerprobe/Home.html I recommend you stay away from these, any two lead probe with a switch can get you into big trouble very very easily.
At heart I'm a part swapper...so when that doesn't work(as in this case), it leaves me wondering what to do next.
All the cars I've fixed up to this time had problems which were pretty obvious to fix.
This car looks right, having all new parts that have to do with the spark system, yet it doesn't spark, so that is hard for me.
I think we have the best mechanics anywhere...to tell you the truth.
Last edited by CajunSpike; 04-04-2012 at 03:11 PM.
Agreed. I've picked up countless tips on here. I couldn't get by without BrokeVW's input. He once instantly replied to a PM at 1:30AM.
So if I correctly read what tolusina is saying, any one of about 15 or 20 connections/wires between or within the 4 or 5 parts that you're looking at could be loose, etc. You've just got to somehow figure out which one?
By having the plugs into the parts, you can directly hook into the part...for further testing.
Obviously you won't cut the plugs off your car....just for testing purposes.
Part swapping has failed, so now I have to move to a specific testing method. Having the plugs to connect to the part(s), makes it easier.
Last edited by CajunSpike; 04-04-2012 at 05:13 PM.
Don't have a Bentley for the ABA-era, just for my Jetta's era which includes the 2.0 AEG. I don't know about yours, but my manual says under Ignition System Troubleshooting: "A complete failure of the ignition system to produce spark at the spark plugs is self-evident." Wow, thank you so much for that detailed explanation! (To be fair, it goes into a little detail later.)
Anyway, just tossing out another idea: Are the plug wires in their proper place on the coil pack? My Bentley has a diagram showing A = cyl. 1, B = cyl. 3, C = cyl. 2, D = cyl. 4.
Also, if the starter is failing to operate, check/test the park/neutral safety switch/relay.
It sounds like what you need is a kind soul to bring over a test bed (a running mk3). You could then move over one part at a time to confirm that each works to eliminate the variables. If the test bed will work with every single piece, one at a time. Then you're looking at wiring or the ECU, unless you find a really kind soul that lets you test ECU also. I suppose this is obvious and you've already considered it. I hope I don't offend, I know I sometimes get ticked when people up and offer advice that I didn't ask for. If I didn't live 1150 miles away, I'd be right over to help you test parts on my car.
Have you ohmed out your harness from the ecu to the hall sending unit, coil and vr sensor to see if there is a short that will come and go from a broken wire by moving the harness around while checking it. Are you getting the fuel pump to cycle for the 2 second priming when you first turn the key over? I have only ran into weird spark issues in the past with bad vr sensors which will seem like a dead ecu and you will get no spark or fuel pump.
Have you checked your timing to rule that out as a possible problem?
Some Cabrios came with a hydraulic tensioner that are known to fail when it does the timing belt will jump timing. Do yourself a favor,before you start checking every wire in your engine harness ( sounds like a nightmare) Check Your Timing it takes 20 minutes.
When i swapped the distributor, I had it set to #1tdc according to the distributor. there was a dimple on the flywheel i aligned center of the hole, and that matched the timing mark in the distributor, before I pulled the distributor out. as said earlier, i didn't however pull the plug to verify the piston. I figured if the timing mark on the crank matched the position of the rotor in the distributor, according to the #1 notch, I couldn't be much off.
Kammy, this car has a single coil going to a normal distributor. Have verified the firing order on the cap to actual plugs as 1-3-4-2
All suggestions welcome..even if you have to beat it into me...lol. Since I don't know much, anything you can say is more than I know.
Wiring testing so far has been limited to voltage testing on the coil and continuity testing on specific wires to make sure they flow all the way back to the ecu electrical connection.
Starter cranks over exactly as one would think it should work. Just no spark happens when engine is turning over with the starter.
I WISH I did have somebody with a running car to swap parts from...and thanks for the offer.
This one is pretty much a solo(with your help) battle.
Last edited by CajunSpike; 04-05-2012 at 11:18 AM.
I am only talking about the ignition portion of the harness. A bentley shows which wires are where on the motronic ecu harness it is numbered on the plastic. The reason I say you might have a broken wire is you keep swaping ecu's which moves the harness around so if there is a break in a ignition wire it can make contact one time amd not the next time just a thought. It should take no more tjan 30min. to check all the ignition wires for a short it is only 5 wires.
If your timing was off the check engine light would come on because the hall and vr would tell the ecu and you would get a cam sensor error in vagcom.
The problem could be literally anything, so no idea is far fetched. Have to keep in mind the reason I have this car is because it failed on the previous owner and the car was left on the street too long.
The only for sure thing was when I started, there was a code for a bad crank position sensor.
I replaced it and cleared the code. That code did not recur but since I got no spark, i started replacing parts. finally ran out of parts to change and here i am.
when I replace a ecu, I clear the codes.
crank the engine over
check codes again
this no start condition does not set a code in the reader.
the check engine does come on with key on, not trying to crank engine over.
maybe i should make a small video of what Im doing.....
this discussion is important and every fact is good to acquire. gives me things to think about till i can jump on the car again. new orleans been getting pounded with rainstorms this last week.
I will try any test you can specify in a clean 1/2/3 step by step list.
Last edited by CajunSpike; 04-05-2012 at 11:36 AM.
The original codes he had suggests a car that's not timed correctly and he has yet to check his timing, which is the first thing he should have done before throwing parts at it. If for no other reason he would at least be able to rule that out as a possible problem.
If csrgti is Dan Reed, you helped me before but you might not know it.
Long while back on just answer, I posted a question about a green 92 mk1 that was flooding the cylinders with gas.
You helped me figure out it was a bad ecu.
Thank you sir.
ok ok ok....
I'll set it to #1tdc and take some photos of the flywheel dimple, the distributor notch, and the position of the timing belt, not to mention make sure #1 is tdc by pulling the plug.
post it tomorrow if its not raining when i get home.
Last edited by CajunSpike; 04-05-2012 at 12:21 PM.
I'm not ( The Legendary) Dan Reed, But his website Helped me Too, when going from MK1/MK2 to a MK3.
Put this together hope it can help you and others,
Last edited by csrgti; 04-05-2012 at 12:54 PM.
IIf you are's till notf you are not getting fuel pump to turn on and no spark make sure the plugs for the knock sensor and the crank sensor did not get swapped around I believe they are the same style plug one is black and the other white. When I did my vr6 swap I did that amd took me a minute to figure out the plugs were one color but the sensor plug ends were different. Mine was black harness plug but white sensor plug for one and white harness plug for the other and black sensor plug. I just hooked white to white and black to black at first got no pump and spark swapped the sensors around and it fired right up.
I did replace the crank position sensor and plugged it right in where the old one came off from..but haven't touched/unplugged the knock sensor.
Still though...I'll see what color goes where.
Finally went verify timing..this is what I found.
Rotor set to #1, timing mark visible in hole. Car has auto tranny.
Pulled #1 plug, piston was visible in the plug hole.
this pic is the crankshaft position sensor plug.
Wire on right is cps and the one I plugged/unplugged.
Wire on left is knock sensor..which I didn't touch.
Also notice the plugs are different types...probably not interchangable.
Last edited by CajunSpike; 04-05-2012 at 11:49 PM.
I see three wires to the crank position sensor, that means it's a Hall effect switch. Ignore what I wrote above about two wire, inductive type senders, it doesn't apply.
Red and black are power and ground, green is the signal.
The signal should be only high or low depending on the position of the notches in the crank mounted tone ring. The 'high' state voltage should be close to the power voltage, I'd expect about 10.0 VDC but it could be 5.0 VDC.
You can probably test that sender removed from the engine by passing a steel object close by and monitoring the signal but it will have to remain connected to power and ground.
The two color LED tester will give a good indication of signal dynamically, better than a DVOM can.
Best test will be with a lab scope, but I don't expect we are going there, unless you've got a better tool stash than I'm guessing you have.
Best I can tell from your photos, the cam timing is a tooth retarded, but that shouldn't stop if from making spark, starting and running, I would not expect it to make much power though.
I really like these......
for insulation piercing tasks. There are many in the industry that feel insulation piercing causes long term damage to wiring, others (myself included) feel that the small hole made in the insulation mostly closes itself up and causes no significant long term damage. I've used these probes extensively on my own cars and never found and related issues 150k miles and years down the road later.
A good set of test leads and connectors give a good solid connection for testing eliminating the possibility that whack readings are caused by the test set up. Additionally, they free both hands for other tasks, such as operating the key while the connected DVOM faces you through the windshield.
the 'one notch off' could be because the engine may have been slightly off tdc. I got it as close as I could using the big 'nub' in the tranny timing hole. Not having seen this type engine 100% perfectly set..it could just still be slightly off tdc enough to look a notch off.
I know I just put a new cps in this thing...and I'm not getting any error codes that say the new one is bad..but i do have to wonder if the new part is actually good.
I think I will grab some wiring plugs to begin part by part testing, correctly this time.
first inclination is to test the cps. if i can get a plug that fits, I'll setup power and ground, turn over the engine, and see if the voltage on the green wire fluctuates. because of how hard it is to remove...i'm gonna do this in place.
i can see where those test clips would be useful, and no I don't have any kind of scope.
Last edited by CajunSpike; 04-06-2012 at 02:51 PM.