checking for spark

[Jungleboon]

Hey guys this is probably a stupid question, but my car won't and I'm sure it's getting fuel because when I pulled the plugs after trying to start they're soaked but I don't know how to check for spark which is what I keep reading should be done. Do I just pull the coils out one at a time with the spark plug in it and have someone crank it? Thanks

[Seerlah]

Yep. But during this time you want to have the fuel injectors unplugged so that you don't spray fuel while cranking. With the spark plug in the ignition coil, it needs to be grounded to the valve cover. Without the plug being grounded, it won't spark (need common, which would be ground).

[Jungleboon]

Cool thanks man, can I pull the fuel pump fuse instead of disconnecting the injectors? All the plastic in my bay is so brittle I try to mess with it as little as possible

[Seerlah]

You can. But you will still spray what's left in your lines with the pressure that is still built up in the lines. That's why it's best to disconnect the injectors. But if you pull all the spark plug you can push all that gas out of the cylinders by cranking the engine.

[Jungleboon]

Okay thanks for the info

[walky_talky20]

Just hold the accelerator pedal to the floor during cranking. That will shut off the fuel injector pulse (clear flood mode). No further action is necessary.

Sounds like you're on the right track, but if you want - continue to update this thread with your results and we can help you get this thing running again. Good Luck.

[Jungleboon]

Will do thanks for the advice I ordered a Crank position sensor because it seemed to fit the bill was only 40 bucks and I don't have vag, I haven't found time to check spark yet hopefully tonight though. When I turn just the battery on the epc light comes on though is the cps the right move?

[Seerlah]

You already purchased it. If you don't have spark, pop her in and see what happens.

[Jungleboon]

Lol yeah I already decided I guess, should be in tomorrow I will let you know

[Seerlah]

Do hope it was a Bosch unit you ordered.

[Jungleboon]

Meyle...? is it gonna fail on me?

[Seerlah]

I would not trust it. Bosch or nothing. Bosch is OEM.

[Jungleboon]

Fuuuuuuu well I'll try the new one and if it works I'll know what failed if it doesn't then I can put the OEM back in, we'll see

[Seerlah]

If you end up leaving that in your car, I would not leave it in too long. It most likely will crap on you.

In a jam I required a crank sensor to get home. Picked up an Advanced Auto one just so I could get home and prolonged swapping in a Bosch unit. One of the coldest days last winter I pull up to my credit union, come back, and car won't start. Immediately knew it was the crank sensor. Called my mother pick me up, went home and picked up my other car and tools (require a back up with what I have been through with this car), drive back to credit union, took out the Advanced Auto sensor in the freezing cold, drove to Advanced Auto for a warranty replacement, drove back to my Audi to swap the replacement in (car started right up after), pick up my mother, go back to Audi, and have her drive my other car while I drove my car out that lot. In the night time in the freezing cold, it was no walk in the park. But no way I was going to leave my car there. Might come back next day with pieces of my car missing. Thing only lasted a couple months.

[Jungleboon]

Damn sounds like I should get a back up if this fixes it, I'll remember to go OEM next time, do you know how to test if it's faulty? I have a multimeter just don't know how to read a dead sensor

[Seerlah]

Can't help you there, bud.

[walky_talky20]

You test the sensor with a scope. That's an "oscilloscope". *Note: Below photos are just random examples from about the in-tarwebs. Whenever I'm pretending to be a mechanic, I tend not to take photos. Lest people get the wrong idea.

Example of good signal pattern on a 1.8T:





In general, good signal will look nice and sharp, like this:



And a crap signal might look like this (red one):

[Jungleboon]

Haha okay so each peak I'm assuming is a tooth on the crankshaft that causes electromagnetic induction in the sensor which the oscilloscope can interpret? I don't have an oscillioscope but could I pottentially (since the sensor sends a signal that peaks at 15v according to the first graph) use a multimeter to measure the change in output when I induce the magnet in the sensor with a piece of metal? Also you are the man for having all this info, how'd you learn all this stuff?

[walky_talky20]

^Geez, you picked that up quick. You are exactly right.

"The force is strong with this one. "

You can read the output as AC volts on a meter. It won't give you nearly as good an idea of signal "quality", but it will tell you if it's completely dead or not. Which is something. You can also use the ECU to help out a little. You can watch it's RPM value with VCDS during cranking to make sure it's reading. Should show a few hundred RPM.

This information is widely known. I don't think I'm special - perhaps just a bit patient to share some things. I learn by having a desire to understand the inner workings of things. If that makes sense. And some voluntary (and involuntary) exposure opportunities. Crap. None of this makes any sense.

Because Racecar. Yeah, that makes more sense. 'Murica.

[Jungleboon]

Hahaha I was confused until that last line there. Okay so no signal=dead sensor=no start, could intermittent signal also=no start? any idea which pins to measure from?

[walky_talky20]

The sensor creates it's own signal. So you just unplug the sensor and connect to the pins directly. There are 3 pins, and 1 of them is the shield. I'd take a wild guess and say pins 1 and 2 is where you'll find the signal, but that's probably wrong. It's never what you think it is. This is where I usually talk about the importance of diagrams when doing electrical diagnostics.

[Jungleboon]

Okay I got the new sensor, installed it and still no spark on any cylinders, what do I check next

[Jungleboon]

For some further background... Several days before it died the car fired up for a split second then died, I removed the fuel pump relay, fuel pump fuse and spark plug in cylinder 1 to check if I had flooded the engine. Replace all components and car started. Worked perfectly for the next couple days several starts warm and cold. On thanksgiving morning I moved the car to make room for relatives to park, started fine, ran well. Later that day I attempted to start again and it again started for for a split second like it fired on one cylinder then died and I haven't been able to start it since.

EDIT: I also am halfway through a tank of fuel to which I added an entire bottle of Techron.

[Seerlah]

You check your fuses?

You have to have DTCs. Even if your CEL isn't illuminated, you have some. You need to scan for codes (real software) to help you further. But for the meantime, check your fuses.

[Jungleboon]

Yeah pulled every fuse in the ds door panel and the one in the ecu box. They're all fine

[Seerlah]

Check for voltage at the ignition coils. What year car? Maybe bad ICM? I wouldn't advise throwing money at in hopes one is the answer. I personally do this sometimes and regret it when I'm wrong (ie last one was primary o2 sensor and ended up being a glitch in my tune. diagnosed many variables prior).

[Jungleboon]

Yeah I'm about to take it to order vag I just don't have a windows machine so its gonna cost me a bit...

[Seerlah]

Check for voltage at the coils. Walky_talky20 is your best guide on here when it comes to actual schematics.

But since all are constantly grounded, I would assume you get pulses. But...could also be very wrong. If it were me, I would check every pin to at least try to source some form of life (mine have 4 wires...and not sure what is what). If nothing, you basically work your way back from there. If you have an ICM, check for voltage there next. If voltage before but not after, then you basically have your answer.

[Jungleboon]

2001 so no icm. And yeah I did that when my turbo failed and regretted it. I did have an intermittent p0135 02 sensor heater code but no cell when I crank the cel doesn't come on.

[Jungleboon]

How do I check voltage at coils?

[Seerlah]

If you have an AWM, I doubt that is your issue. I was basically giving instructions for the AEB.

But for testing I was referring to, you don't test the coil itself. You would want to test the connector for it on the engine harness side to see if the coil is actually getting any power. Basically eliminating variables. If you want, you could still test that out to see if your coils are getting power (doubt they are). How does the ground look for them? Inspect the wiring. It is the little 10mm bolt on top of the valve cover by cylinder 1.

[Jungleboon]

I cleaned all the ground connections with a bit of sandpaper and tightened it down earlier. Do you know which pins in the harness to test also do I test while cranking or with key in the on pos or just off?

[Seerlah]

You would need walky for this aspect. I ask him this stuff myself when I have issues that are electrical.

But I can tell you it isn't the connections so much you need to be concerned about. It is the actual wiring. They tend to short in sections you would not expect. It's the heat that does this over time.

[2000zxt]

Where are you in mass? Hate to say it but have you pulled the timing cover off?

BTW you can check almost everything from the ecu on any old regular elm327 obd2 usb serial adapter. You don't need vag com just to check stuff, get a cheap scanner on ebay or amazon and get a free obd2 program. I still used my own program for datalogging and whatnot over vag when I was on the factory ecu with both being available.

Not positive on this ecu but many times the crank signal indicates rpm and controls fueling while the cam sensor is used to spark placement, so if your belt snapped cps not turning no spark but plenty of fuel.

If you are trying to verify that any signal is there (this is a dirty test). Set your meter to AC (low setting) and then crank it over and watch the meter, just try all the pins, metering the wrong pin isnt going to damage anything (unless your meter is configured wrong in amperage mode). Youll see a few volts while signal is active, the hi frequency switching of the transistors will show up as slight ac voltage. This can work to make sure spark pulse is happening as well as injector pulse. You need a scope to actually interpret the signals, but this tells you if its there or not. If you have the car running the voltage should increase with rpm.

[Jungleboon]

My belts fine had it for about 3k miles checked it today. Marked and and cranked to make sure it was turning and it was. Could it be a bad can sensor on the front right of the valve cover? I think I'm going to bring it to a shop tomorrow :(

I'm in northeast mass on the nh border

[Seerlah]

Was told by person tuning my car that the car will still run even with cam sensor completely unplugged, just rough. We were trying to diagnose an issue with my car, and we were weeding out variables during this time. Turned out to be a Eurodyne Suite glitch out of nowhere that required fueling adjustments.

[Jungleboon]

So based on the fact that it started and died do you think its an intermittent short in the working harness?

[Seerlah]

I want to confirm the above. Update in a few.

Really don't know what your issue is and not really liking playing the guessing game. You need to diagnose your issue correctly. You need to see if you have voltage at the coils. And if not, find out why. Pretty simple. If you have fuel and compression, all you need now is spark.

edit: sorry if my post above made me come off like an a$$. wasn't my intent at all

[Jungleboon]

That's fine I understand. I'm just not that familiar with a multimeter and don't want to damage a working harness by jamming leads in all its sockets. Also having trouble getting someone to crank my car in the freezing cold. I'm gonna have AAA bring it to my local foreign auto guy tomorrow while I'm at work. While I hate letting a problem beat me I don't have the time to devote to it and I need my DD

[Seerlah]

Took more cranks, but turned over completely unplugged.

That's fine I understand. I'm just not that familiar with a multimeter and don't want to damage a working harness by jamming leads in all its sockets. Also having trouble getting someone to crank my car in the freezing cold. I'm gonna have AAA bring it to my local foreign auto guy tomorrow while I'm at work. While I hate letting a problem beat me I don't have the time to devote to it and I need my DD

You won't damage anything. That is what the prong was designed for. And def don't jam it in. If it is touching...it's touching. Just make sure you have contact.