First clinder not running - no one can figure out why

[phis2]

Hi everyone,

my cylinder one isn't firing, no matter what I do! But first the basics.

My setup (relevant parts):
- S2 3B
- compression reduction plate (8.2:1)
- EMU Black ECU
- Stock fueling system
- Stock ignition system

History of symptoms:
Last year I had this setup, without the compression reduction plate and everything worked. This winter I built the head, added the compression reduction plate and switched to single coils (R8). After starting the car, the first cylinder didn't work. I tried everything (list below), but changing back to distributor igniton to use the stock ecu made the engine run on all cylinders! So I am pretty sure, the fault has to be either the EMU (soft- or hardware), or the wiring adapter from the stock ecu plug to the EMU.

Troubleshooting:
1. Checked the map - everything looks fine. The car ran with this exact map last year.
2. Checked continuity between cyl1 injector and EMU pin-
3. Removed fuel rail and cranked engine. All injectors squirt out fuel equally.
4. Installed a new wire to the cyl1 injector on plugged it into the EMU pin for injector 6. Then I set injector 6 to replace the first one, to test if the EMU pin was faulty.
--> These tests make me believe, that the EMU, the wiring and function correctly

Troubleshooting before figuring out OEM ECU works (with sigle ignition)
1. Checked EMU settings
2. Spark plug ignites when car is running. I took it out and then startet the engine with 4 cylinders
3. Changed injectors, coils and spark plugs with other cylinders
4. Checked timing on cyl1 with a timing light
5. Removed fuel rail and cranked engine. All injectors squirt out fuel equally.
6. Switched connectors from injector 2 and coil 2 with the one from cyl1 and switched cyl1 and cyl2 in the EMU settings, to eliminate a wiring/connection fault
7. Checked compression. All good on all cylinders
8. Checked valve train visually. Removed valve cover and intake manifold to watch valves, cams, hydros move.


So all in all I have to idea, why it is working with the stock ECU, but not with the EMU. This makes me very sure, the issue is not mechanical, but a problem with the EMU or some wired close to the EMU. I checked all possibilities and can't think of anything else to test. I'm running ot of ideas of what to test, so please help me out, if you have any idea. Thanks!

[K Simmonds]

I think you've already solved your problem, if it run's fine with the stock ECU but not with the EMU then that's the componant at fault or more likely it's wiring is the problem.

If you have compression and fuel all you need is a spark at the right time.

Why drop the compression ratio so much and with a plate as opposed to doing it properly?

[phis2]

I think so too, but I have trouble locating the fault further. I rewired the first injector directly to the EMU, without any adapters. Maybe I should rewire the ignition wire the same way, just to make sure. I will take out all coils and plug, crank the engine and visually check, if the firing order is right.

My goal is 700+ hp on pump gas, that's why I need the low compression. I didn't want to take the bottom end apart this winter, because of time. New rods were already installed when I bought the car. This is just the quick solution to be able to make a bit more power this season.

[K Simmonds]

Electrical problems can be a real pain, though it's normally something really simple. I can imagine your frustration.

Fair enough on the compression reducing plate, it is a quick and cheap solution to wanting to do the job, am guessing your planning on running high boost on a large turbo.

[newsh]

Bad coilpack maybe? There are lots of fakes about. The spark might be visible but not strong enough when under compression.
I'd say possibly a bad plug but if it runs with a single coil and dizzy then the plugs should be ok.
Have you checked the dwell is correct for R8 coil packs on all cylinders?
How are you doing the swap from 3B to Emu? I guess you've made an adapter to the 3B loom with extra wires for the coilpacks?

[phis2]

I tested further and turns out the first cylinder isn't firing either, when I have the oem ecu plugged in. I have swapped the injector, ignition plug + coil and connectors previously, so it's most likely a mechanical issue. I'm not sure what could cause this issue while still maintaining full compression, but I will investigate further. Maybe one or both exhaust valves not opening (enough).

[phis2]

Update:
I removed the exhaust manifold. Exhaust valves are opening and closing as they should.
I checked the fuel injector, coil pack and spark plug by filming them in slowmo with the cam wheel in frame. They are injecting and sparking at the correct time.
I tested the compression again, just to be sure. Compression is good as well.
I checked the intake valves and swapped plugs, coils and injectors previously.

I'm now running out of ideas. If anyone has any idea - please tell me

[Tractor Dave]

You need three things for it to work. Fuel ( in right mix with air), compression (at the right time) and a good spark (again at right time).
if you are getting fuel, compression and a good spark you need to think outside the box. Are you sure physical timing is spot on? Has the intake manifold got blocked somehow? I've seen people shove paper towels into intake openings to protect them during work. Did something get forgotten?
You also haven't said if the plug is getting wet with petrol when running. Is that cylinder just flooding out?
Did someone drop something in the injector port? Has the injector cup broken up?
lots more things to check before you give up.

[phis2]

Thanks for the reply. I checked the physical timing by using a timing light and filmed the injection of the injector (into a plastic bottle) and the spark plug, so I'm sure all the timings are right. I checked the intake port + intake valves and it is all clear. Yes, the spark plug is getting wet. Injector ports are clear too and injector cups are all new and intact.

My endoscope is arriving today, I will check the intake and exhaust manifold pipes and the cylinder itself.

[Tractor Dave]

I don't think a strobe will work so well. You need to check static timing. Have you still got a dizzy? If so, set the crank on tdc using the flywheel window and check the dizzy marking is correct.

[Tractor Dave]

And also be aware that static timing can slip slightly if the top pulley keyway is damaged. I had this on my S2. Took ages to identify.

[rxl]

why dont you test your outputs in software?

[newsh]

ECU wiring for 3B (dizzy) and ABY (coilpacks) is very different, there's no way you can just swap between the two. Normally you would convert the 3B wiring to ABY first by doing the pin-swap and adding the extra wires for the other 4 coils. Then you would use an adapter plug to convert to an aftermarket ECU. At least this is how I did mine.
So I'm really struggling to understand how you can swap between the Emu/coilpacks and the 3B ECU/ dizzy setups. It's just not possible without some kind of rewiring or extra adapter plug/plugs.
Whatever. I guess you're using the hall sensor in the dizzy so static timing has to be good, in fact I would recommend it needs to be as perfect as you can get it, Zero mark on flywheel in bell housing window and marks in the dizzy. Check also that the cam wheel marks are lined up. You need to put the car in gear and roll forwards onto the flywheel mark so that the backlash is taken up, you will get a different setting if to turn the engine backwards.

[phis2]

Hi everyone, I found the problem. Three bolts around the first cylinder on the intake manifold weren't tightened. I tightened them and now everything is working fine. Thanks for your help.

[newsh]

Hi everyone, I found the problem. Three bolts around the first cylinder on the intake manifold weren't tightened. I tightened them and now everything is working fine. Thanks for your help.

So an air leak! I'm surprised it stopped the cylinder from firing but there's a lot of vacuum at idle.

Glad you got it sorted!