Ignition gremlin frustrating me; no spark

[mobiuslogic]

So earlier last week I was stopped at a red light and the car just stopped. No warning, no sounds. Just shut off. Took a volt meter to the ignition coil and only read about 3.1k ohm on the secondary coil, and the Bentley says 6-8.5k ohms. So I figured the secondary shorted out and I was getting a crappy spark. So I bought a new coil and checked it before hand and it also read about 3.1-3.2k ohms. So I plugged in the coil before actually installing it (just sitting it on top of the rain tray), and the car started up, but was obviously running rough. I figured I fouled a plug, and they were definitely dirty when I pulled them out.

So I install the coil and replace the plugs at same time (gapped to .032"), and now it won't start at all again! Arg! So I used a spark plug wire tester that you hold next to the wire, and it didn't light up at all when I used it on the primary wire out of the ignition coil. I did verify the wire tester worked though first on my other car, so I know it works. I also had the parts shop verify the ignition control module worked, and it checked out as well. So what gives? Thanks for the help!

[Ghunt521]

Well i kinda had the same problem. my car would turn over but wouldnt fire at all. My fuel pump wouldnt kick on and #8 relay was going nuts so, I tried the ignition switch fire right up no stalling no nothing everything work to normal again. Was about to waste 190$ on a fuelpump that wasnt needed

[ANSAracingb]

Well i kinda had the same problem. my car would turn over but wouldnt fire at all. My fuel pump wouldnt kick on and #8 relay was going nuts so, I tried the ignition switch fire right up no stalling no nothing everything work to normal again. Was about to waste 190$ on a fuelpump that wasnt needed

Came here to post this idea. I had a bad ignition switch on my fox body mustang that would shut the power off to the engine for just a split second when going over bumps in the road and turning right, for some reason. The thing that led me to believe it was the switch was the whole "turning right" thing (steering wheel/column rotating).

I know your case has different symptoms Eliott, but ignition switches are funky like that sometimes...have you replaced yours recently, or tested it per Bentley specs?

[mobiuslogic]

Well, I can hear the fuel pump going, and I'm still getting power to everything else. Plus it does turn over, I'm just not getting a spark out of the ignition coil. Just a whole lot of rrrr-rrrrr-rrrr-rrrrr-rrrrr-rrrrr. And no fire. I'll check out the wires to the ignition coil. I don't think it's getting power for some reason...

[Rocco_julie]

Off the back of the switch are 2 black wires. this is the switched 12v. One wire goes to the dash to feed the gauges and the other directly to the coil.

[sciroccohal]

Off the back of the switch are 2 black wires. this is the switched 12v. One wire goes to the dash to feed the gauges and the other directly to the coil.

The crappy plastic ignition switches are in the top two 'unreliable items' list.

For safety, reliability and getting home....I keep a spare new one in the glove compt.
Heat and cold kill them.

Unfortunately the quality of the replacement switches has gone down considerably over the years.

when a malady like this crops up....one of the easiest diagnostics is to try the replacement switch FIRST....it's five minutes worth.

g-luck

[mobiuslogic]

I guess I need to go back and review the wiring schematics, because I don't understand how the ignition switch (with the key, right?) corresponds to the ignition coil being triggered by the ignition control module. Or is the ignition coil constantly given 12V, and only when the ignition module interrupts the 12V to it does it produce a spark when the secondary field collapses? Because the starter definitely kicks it over when I turn the key...

How can I test to see that the coil is getting 12V, and is this complicated by the coil getting 12V constantly, or is it switched 12V from the ignition module in the rain tray?

Thanks!

[BluDemon]

I guess I need to go back and review the wiring schematics, because I don't understand how the ignition switch (with the key, right?) corresponds to the ignition coil being triggered by the ignition control module. Or is the ignition coil constantly given 12V, and only when the ignition module interrupts the 12V to it does it produce a spark when the secondary field collapses? Because the starter definitely kicks it over when I turn the key...

How can I test to see that the coil is getting 12V, and is this complicated by the coil getting 12V constantly, or is it switched 12V from the ignition module in the rain tray?

Thanks!

I would grab the $14 ignition switch and give that a try. You don't even have to tear into the column to try it just unplug the old one and plug in the new and use a screw driver to start the car.

http://www.germanautoparts.com/Volks...ectrical/206/1

[mobiuslogic]

Unfortunately that $14 ignition switch is $20 by the time it makes it all the way out to me here in CA. But I'll definitely check the voltage and pin outs on those tonight. Sounds like that's probably part of the problem, although it doesn't explain why it would suddenly be a problem while stopped at a red light when it had been running fine immediately before.

[mobiuslogic]

Woot! Turns out the AutoZone hub has one in stock, and they're only about 5 minutes from my work. 26 bucks, but I get it now. Still going to test out the pins though. Found an ignition schematic online. Could also be the ground from the ignition coil to the ignition module: no ground, no spark!

Feeling like I'm on the right path though!

[mobiuslogic]

So before I put in the ignition switch, I first checked to see if I had 12V between the coil and ground. I did with the key in both the ON position and START (yes, checking voltage on the coil while a neighbor cranked the engine. Still nothing.

So I checked the wires into the ignition control module:

#1 (-) on the coil to pin 1 on the ICM: Good
Pin 2 on the ICM to battery (-): Good
#15 on the coil to pin 4 on the ICM: Good.
Pin 6 ICM to pin 12 Knock Sensor controller: Good.

And the center wire out of the ignition coil, 2.1k ohms, right on spec.

So I know I've got no wire faults on the coil, the wire connections into the ICM are good, and the coil and ICM are getting power when the key is turned on and started.

I'm starting to lean towards it being the ICM itself, but I'm not really confident about it. Years ago I had an 85 Scirocco, and when I bought it, it had an ignition fault that it wouldn't start if the car was hot and been running a long time. But would start fine and continue to run if cool or cold. If it didn't start, it just had to sit for about 5 minutes and then it would start. Turned out the ICM was getting hot, and something inside would prevent the car from starting when the ICM was too hot, but it would continue to run.

I'm just baffled right now because I know everything is connected (obvious first check), coil is good and getting power, and it started but ran rough when I connected the new coil and had it sitting on top of the rain tray, but then did not start when I installed the coil. Very very puzzled.

I'm going to hook up the ICM to some batteries and LEDs and test it myself. After all it's just a big switching transistor.

[mobiuslogic]

Alrighty, so I tested the ICM and I think it's working fine, but could be mistaken. I assumed that the ICM is just a fast switching transistor, although I don't know the actual configuration inside. Turns out it acts more like a solid state relay, but really just back to back transistors, although there is some logic in there as well. I think it's leaking too much voltage to the coil constantly, which isn't giving me a good spark.

According to the Bentley (pg 7-10, Power to Coil Primary Circuit), the coil (my LED and resistor below) "should see at least 2 volts, then drop to zero". This happens, but it doesn't drop to zero. As you can tell from the still lit LED, I'm getting a lot of voltage leaking past when the ICM isn't being triggered (2.17V to be exact from my 9V).

In operation, the ICM is triggered by grounding pin #6 to simulate a pulse from the Hall sensor (that threw me off too, I thought it got 12V to trigger the spark). When pin 6 is grounded, it connects pin #1 (coil negative) to ground. This charges up the magnetic field in the core, and when the pulse stops, the primary field collapses which zaps the secondary and creates the spark. What you can't see from the pics is that as soon as I connect the LED, it goes high, then back down to 2V (like above). But when I touch the yellow #6 to negative on the battery, it stays low, but as soon as I release it, it goes high. If I touch it again while it's still high, it instantly goes low. So it stays high to charge the field, Hall sensor pulses, primary shuts off, and bang. And if it doesn't get a pulse from the Hall sensor in time, it shuts off voltage to the coil primary. Neato! Of course if you leave the #6 grounded as if it gets a reeeaallly long pulse, it shuts off power to the coil primary as well.

But, if I'm getting too much voltage leaking past, then I'm thinking the field won't fully collapse, and I get no bang. Or the Hall sensor went out and I'm not getting a pulse. So I'll test the Hall sensor, and if it's working, I'll get a used ICM while I order one.

LED High


LED leaking while low


Circuit neato-ness. Important difference being that pin 6 is NOT connected to +, but to ground in order to be triggered.

[mobiuslogic]

So I picked up an ICM from the junkyard, and still got nothing. Tomorrow I'm going to pick up a new one. Buddy of mine at the local dealer ordered one, so I'll at least know that it isn't an issue (thanks Byran!).

I also tested the Hall sensor with my nifty test light below. Simple green 5mm LED butt spliced to a 300 ohm resistor. Still nothing. It flashed on and off while my girlfriend tried to start it.

[mobiuslogic]

Has anyone else had this same issue? I'm starting to worry that it's the knock controller or actual engine control module that died.

[SciroccoPowered]

nifty tool you got there, here is what i would do with it, the signal wire from the hall sender goes to the "knock box" ignition computer, then to the ICM, then to the negative side of the coil. Test for the ignition signal going in and out of all of those 4 items (where applicable of course) and see if you're getting a spark signal all the way to the negative coil.

Also, are you sure your timing belt didnt jump time?

[mobiuslogic]

Hi SciroccoPowered. Unfortunately I don't think that is the problem. I used a spark indicator as shown below, and it gave me no indication of spark. Maybe I'll try an inductive timing light just in case, but I'm not holding my breath. Hopefully the new ICM works. Also blew up the Bentley wiring diagrams to 11x17 for the Scirocco 16V engine controls. Going to go at it with a fine tooth comb and check every damned wire.

Is there an easy way to test the Jetronic box or the knock sensor controller?

Spark Tester
Although this spark tester worked fine on my Taurus.

[hardrocco]

I know this might sound dumb, but do you have a ground strap from the engine or cylinder head somewhere to the ignition coil bracket?

[mobiuslogic]

Not that dumb. It could easily be overlooked if it weren't already there, but it is.

[SciroccoPowered]

Hi SciroccoPowered. Unfortunately I don't think that is the problem. I used a spark indicator as shown below, and it gave me no indication of spark. Maybe I'll try an inductive timing light just in case, but I'm not holding my breath. Hopefully the new ICM works. Also blew up the Bentley wiring diagrams to 11x17 for the Scirocco 16V engine controls. Going to go at it with a fine tooth comb and check every damned wire.

Is there an easy way to test the Jetronic box or the knock sensor controller?

Spark Tester
Although this spark tester worked fine on my Taurus.

There is no diagnostic test i know of, however is what i meant is to hook up that led/resistor, to the output from the knock box that goes to the icm, and see if it's sending out a signal. that is the only way i would know of to test it.

[MacGruber]

Have you gone through every step in the Bentley for 'no spark'?
The exact steps are different between 1980-84 and 1985-93 manuals.

I was sitting at a gas station off of I-294 testing away per the Bentley and found a bad Hall sender wire, which are rather fragile. That caused my Scirocco to just stop running.

Recently a bad ignition switch led to the car running terribly after starting, but did smooth out.

[Mtl-Marc]

... and found a bad Hall sender wire, which are rather fragile.

FYI, the Hall sensor is available aftermarket as a replacement for less than 20 bucks.

[MacGruber]

The stupid harness from the distributor to the ICM or knock box is small gauge 5 volt individual wires. Bad connection at the plug or a broken wire is possible.
The 5v 2 wire cable to my sub amp is better.

[TBerk]

So earlier last week I was stopped at a red light and the car just stopped...!

Anecdotally speaking of course, and keeping in mind my example is (was) an '81 Mk1, I had trouble driving to work one morning, it got progressively harder to idle at lower revs (it would cut off) and finally failed to restart at my destination. (I had 'push started' it during the journey via residual momentum...).

It turned out to be intact but crispy and marginal Hall Sensor wires as they left the Distributor. They would test for continuity but not pass viable voltage.

[mobiuslogic]

So my girlfriend moved out of her place this weekend, which has been the Scirocco's home since it died on me a month ago. Coupled with going on vacation, I haven't had much time to keep working on it.

So last night a guy came with a tow truck to move it to the new place. Started up on the first try, but it was obviously missing (same as when I had the ignition coil sitting in the rain tray). Lots of hesitation and it would sometimes barely keep the idle going. Decide to have it towed anyways since I didn't want it to die on the road, line it up with the truck bed....and it dies.

So I'm starting to wonder if it's a timing issue. I know the belt and tensioner are only about 5 months old because I had them replaced recently. But if the belt suddenly jumped a tooth, would that cause it to instantly die? It also doesn't explain why I was getting no spark at all. I should still be getting spark even if the timing was off by a tooth.

As for the Hall sender, it sounds like that would be a cheap part to replace. Who has a decent/cheap one? GAP has a fancy Bosch for 110 bucks (I have a rectangular connector), but it only says it's for the 8V. I'm guessing it's the same for the 16V though, yes?

EDIT: Also looking to buy a used knock box and engine computer. 120 shipped seems a little steep to me though, yes?

[TBerk]

When most of us have Hall Sensor problems it not the actual sensor itself, it's usually the wire loom underneath the Dist.

I'm awaiting an email then I'm out the door but I'll follow up this eav.

TBerk

[mobiuslogic]

The actual connector to the Hall Sensor? So my test LED could register good, but that signal isn't getting to the knock box?

[mobiuslogic]

Hi Tberk,

Are you referring to the wires inside the hall sensor, or the wires in the harness that connect to the hall sensor connector? And if it is the wires inside the hall sensor, where can I get one cheap?

Thanks!

[16V_Scirocco_GTX]

Did I miss it, or did we skip over the fuel pumps? This is a 16v so we're talking about two of them, could be the internal one is dying/dead and or the external one at the same time. Plus the potential for a bad relay.

[mobiuslogic]

Hey Tobias,

I replaced the high pressure pump last August. I don't know how the in-tank pump is. But, I tried to test getting spark out of the coil, and I'm not getting anything out of it at all. Plus, I can smell fuel coming out of the tailpipe. But, I did get your picture on Facebook; I'll definitely check those wires out. Maybe adding a fuel pressure gauge might be a nifty idea...

[83mk2scirocco]

Woot! Turns out the AutoZone hub has one in stock, and they're only about 5 minutes from my work. 26 bucks, but I get it now. Still going to test out the pins though. Found an ignition schematic online. Could also be the ground from the ignition coil to the ignition module: no ground, no spark!

Feeling like I'm on the right path though!

What schematic did you find?.
I found a2resorce.com,they cover 85 to 99.
They give fuse.relay,and pin out for the block but no diagrams.
I have used the **** oit of that site.
Sounds like the old coil got too hot and pooped out.
my ign switch issues have been no crank period.
Start with a dime.
Is your wire soft or brittle,if brittle.
If brittle you may need to fix the under hood left harness.????,...

[mobiuslogic]

I used the Bentley wiring diagram. I know I'm getting fuel because I can smell it in the tail pipe, but Tobias brings up the good point of if I'm getting enough pressure.

However I know I'm not getting a spark out of the coil. I've replaced the ignition control module and the ignition coil. The plug wires were replaced Dec 2010 and I just replaced the plugs as well. I've verified the wiring to and from the ICM, the ignition coil, and the Hall sender is getting 12V. I can't remember if I checked continuity from the Hall sender to the knock box though, but I'm fairly certain I did as that would have been logical at the time (it's been a few weeks since I've had a chance to look at it).

Tobias and Tberk have mentioned it could be the wires inside the Hall sender connector, so that's the next thing I'll check, as well as double checking the timing (again). After that I'm running out of ideas.

[TBerk]

(Sorry for the delay)

Yours is a 16v (horizantal) and mine was an 8v (Vertical Dist) but the problem I had was resolved when I swapped my Distributor for a good used one from Pick n Pull.

It wasn't the downstream Wire loom, but the wires leading from the Hall Sensor to the Loom's plug/socket.

This is grain of salt type information but presented in hope it helps...

[mobiuslogic]

Well I definitely appreciate the help. Just haven't had more time to wrestle with it lately thanks to non-car issues (vacation, moving, tile floors, etc etc). But finally have some more time to deal with it pretty soon.

Starting to wonder about just saying screw it and putting in EFI. The DIY AutoTune MicroSquirt sure seems like it would work well enough for a 4 cylinder if I kept the existing distributor... You'd think with the number of people that have done it to watercooled VWs though they'd have a pre-assembled kit like the do for a Mustang 5.0 and others.

Just damned frustrating.

[TBerk]

We, the collective 'we', (as apposed to the Royal 'We'), have lots of institutional Knowledge re: MegaSqirt and it's Competitor, cousins, and "Keep'n it Stock".

Keep in mind another thought that just popped up; The 16v, Rabbit, Jetta I/II forums, as well as the Hybrid, etc, etc all have some sort of been there, done that solution ammunition for you.


Get to digg'n.

[mobiuslogic]

Well I already bought a Bahn Brenner fuel rail with regulator and injectors from a guy on craigslist, so that expensive piece is already in my hands. But yeah, I'm not excited about spending 800 bucks on the whole set up. But considering it was a pain to pass smog, it would definitely be helpful. But I'm in CA, so they are smog dicks, even if what I do is better (although the last smog guy I took it too seemed both laid back, and inept on VWs... Maybe I can squeak it through without him noticing. Lol). However there is the Microsquirt which does 2 fuel and 2 spark outputs, so if I combined it with the existing distributor and batch fueling (which seems to be the norm unless you go MS3), that would certainly be cheaper.

Just want my Scirocco back on the damn road. I miss driving it. Although plenty of people have done Megasquirt on these, so I'd probably just go with the simplest, and tried path.