2005 Subaru Forester, crank, no start, no spark

Hi there

I have a little body repair shop in switzerland. But to survive i started some years ago doing mechanical works too.

Now i got a car that leaves me confused. Here it is:

Car:

Subaru Forester
2005 but MY 2006
2.5XT engine EJ255
3-wire C.O.P. Ignition system


Symptoms:

Customer was driving uphill, car lost some power and had intermittend misfire
Customer pulled over, car suddenly died out
called me, i read the DTC: P0301 P0302 P0303 P0304 (misfire on each cylinder)
i cleared the codes, tried starting and with some heavy treatment on the throttle i got it to fire up
it run rough when revving, idling been ok, then it died out again
since i was not able to start it up again


checked and renewed so far:

new fuel pump (can hear it priming)
new timing belt with all rollers, tensioner and water pump (not slipped, timing was about one tooth off and now it is about 1/2 tooth off)
all ignition coils new (original subaru parts)
all spark plugs new (original subaru parts)
tested on car for spark with a HEI- Sparkplug (no spark at all)
tested 2-wire crankshaft position sensor (1,9kohm across terminals, 174-184 rpm signal on scantool while cranking)
unplugged crankshaft and camshaft position sensors and cranked (DTC codes showed up for those)
tested all wires of ignition coils for shorts (could not find any)
battery was dead almost blowing my charger (swapped it for a varta blue line)
ECU/ECM/PCM got ground
coils got power (once key is on)
coils got ground (once key is on)
injectors firing (tested with led test light, goes on and off really nice and gas smell out off exhaust after cranking for a wile)
coils got no flickering signal according to those test scannerdanner mentioned to do

To sum it up i think i am missing a coil triggering signal due to a fried coil driver in the PCM but i`m open to every suggestion

To verify if i got signal to my coils i hooked my testlight to ground and backprobed into powerfeed and it lit (tested 10.5V, if i unhook the PCM i get full battery voltage here and while cranking i get about 8-9V)
The second testlight was hooked up to ground too and to coil signal wire and did not light. As i hooked it up to batteryvoltage and backprobed to signal wire again it lit up.

With the engine cranking nothing changed in this setup. No flickering at all...


Sorry for this large post but i wanted to provide accurate information since my customer wants to be back on road soon (car is in for about one week now...)

Thank you all for helping me out.

Just some update information:

I was able to do some more tests (unfortunately i do not have a scope) on the coil signal wire.
I do read a rising and falling voltage of maximum 2 volts, but i`m not able to read a frequenzy (like i was able to read on the injector connector 4-5 Hz which was also visibly pulsing with my diy noid-light). Does anyone know, how much voltage i should be reading at signal wire?

I was also able to test-spark the old and new ignition coil on the bench. Just hooked up 12 volts, ground and left the signal wire unhooked. Then i hooked up my testlight to 12 volts and tapped on the bare signal wire and the HEI- plug sparked.

Wanted to reproduce this procedure with the coil hooked up in the car, but that didn`t work. I sure unplugged the connector of the PCM which contains the signal wires and grounded my coil with a backprobe-pin (since the connector also contained ignition-ground).
Am i missing something here?

I really hope that someone can help me figure out that problem.

I was finally able to fix it!

The problem was extrem voltage drop on the powerfeed of the ignition coils during cranking. I bypassed all connections and hooked a wire directly on battery power and on one powerfeed of the coils. Then i was able to get a spark...

Retraced those powerfeed wires and found a rottened connector (labeled as E2 in Repair Manual) behind the battery in the engine compartement.
I measured it for continuity before but did not unplug it to check... what a biiiig mistake

Thanx to all those reading this thread an making up their mind to help me.

Be blessed.

Sorry you didn't get any replies on your thread
But thank you for wrapping it up with a fix for the people reading.
What made you decide to run a power feed to the ignition coils?

Hi Noah

That`s no problem for me... Just wanted to make sure i tried everything before swapping the ECU. My question has been online for only two days and i understand that it took a lot of time to read this all and try to find an answer...

To answer your question:
As i mentioned i do not have a scope but i remembered a friend of mine does have one. A cheap little handhold in size of a smartphone.
I called him and we first measured the signal wire of the coils (coil unplugged) with the scope. Since we were getting 10.6 volt pulsed there we assumed that the ECU is triggering the coils right.
As mentioned before i installed a new battery on the biginning of this troubleshooting. My friend came up with the fact that there are only those 10.6 Volts as signal and not full battery voltage of 12.7 volts. As i cranked he wathed the voltage on the signal wire drop to about 5-6 volts.

Some hours earlier i was able to perform a benchtest on one of the coils and did get a good spark out of it. We redid this benchtest and measured voltage on the signal wire there. Cos i used a seperate battery we were getting full voltage as signal. After that we played around with some resistors to drop voltage downto 5 volts. The plug was still sparking but not that strong. Would not have been enough to start a car...

We moved on measuring the powerfeed voltage of the coil on bench while triggering it and got almost no voltage drop there.
In the car we first got those 10.6 volts and while cranking it dropped down to 6 volts.

We came to the conclusion that some resistance in the wiring harness (especially the powerfeed) must be limiting our voltage.
So we made sure that our powerfeed is not gonna run through the ECU to prevent any damage while bypassing.
Since we were missing power to the primary winding of the coils (powerfeed) we decided to directly run battery power to one coil to bypass any resistance in the original powerfeed wire.
With that setup we had full battery voltage on the coils and a nice spark while cranking.

After one hour of reading and puzzeling in the wiring diagrams of the workshop manual we were able to retrace the powerfeed to the rottened connector behind the battery.
Since Subaru does not supply this brown 16-pin-connector or any parts of it any more, i`m gonna replace the whole connector with two 8-pin-Audi- connectors.

I hope this is helping you. If you got further questions just comment. I will try to answer them as accurate as i can

PS: Just after posting i realized you may be thinking that i got a waste spark system?
This car got the C.O.P. ignition system which contains a single coil over ervery plug. Ignitor and coil driver are built in in each coil seperately.
These coils got a 3-wire-design what means they got one triggering signal wire (in my case fed with 12-14 volts squarewave signal) on pin 1 (closest to connector clip), the ground wire (switched through ECU) on pin 2 (the middle one) and finally the powerfeed wire (batterypower through ignition switch) on pin 3.

At first I did think you had a waste spark ignition, but you cleared it up in a previous post
Nice work, thanks for sharing with us!