Porsche running on only 3 cylinders - EDIS ignition

[mark8solo]

This is my first megasquirt set up and it's been interesting. I have set up an old Porsche 911 with a MS 3 1.5.0 system. After figuring out the EDIS coil firing order I was able to get the engine to run on all cylinders and it ran great - started up right away idled right at 950 RPM. When I finally put the car on the road for the first time - gas station run it felt funny on the way there. I filled up then started it up to go home - fired right away and idled but when I pulled away it had no power. Back in my garage I was able to figure out it was only running on 3 cylinders 1, 3 and 5. Cylinders 2, 4 and 6 are paired with those 3 cylinders so I thought that it had to be an EDIS problem. No luck so far.
All cylinders have compression (130 psi stone cold) good visible spark and the injectors are all spraying. I don't understand how shared spark and batch injection can have half of the cylinders on an engine operating?
Coil resistance 0.6 Ohm Primary 13 K ohm Secondary - tried another coil even though readings are to spec - no change
Ignition wires - 1,2,3 - 3.9 K ohms 4 - 34 K ohm, 5 - 16 K ohm and 6 24 K ohm - tried different wires for 4 and 6 - no change
spark plugs - 6 K ohm
Injectors - 16 ohm Fuel pressure 40 psi

Hopefully someone has seen this before and can help.

[jsmcortina]

[billr]

"1, 3 and 5. Cylinders 2, 4 and 6 are paired with those 3 cylinders"

Do you mean 1&2, 3&4, and 5&6? I don't think that is correct. I recently helped another user sort out ignition on an old Porsche flat-6 and the pairing was: 1&4, 3&6, 2&5

[Targa44]

... attempt at humor deleted.

[Porsche930Targa]

Did you check the injectors?


Sent from my iPad using Tapatalk

[mark8solo]

Hi Bill
1, 3 and 5 are paired with 2, 4 and 6 so you are correct when saying that 1 and 4, 2 and 5, 3 and 6 share a coil each. This is what is so perplexing. Why have I lost these cylinders when everything looks to be corrrect. Yes Porsche 930Targa right down to the injectors spraying fuel into the combustion chamber.
I found a post yesterday about another porsche - 944 running on only 2 cylinders with the EDIS 4 set up - but there was no solution that was mentioned in the thread. I did send a reply - hopefully this was solved and maybe my solution will be similar.

Don't get hung up on engine terms - flat(cylinders arranged in a flat configuration), boxer (when running the pistons appear to be punching the opposing bank of cylinders) or opposed (horizontally opposed banks of cylinders) are all correct terms for this type of engine. Like asking for a Kleenex when you want a facial tissue, everyone knows what you need.

Maybe a solution can be found to this annoying issue.

[DaveEFI]

You've not said how you are driving the injectors, being MS3. Are you using the V3 board injection drivers for batch injection - and how are the injectors grouped to each driver?

If you are using the V3 board drivers, I'd be tempted to swap them over and see if the fault moves with them.

(Cant really imagine a fault with EDIS which would effect half the cylinders)

[billr]

"1, 3 and 5 are paired with 2, 4 and 6 so you are correct when saying that 1 and 4, 2 and 5, 3 and 6 share a coil each."

The first part of that sentence contradicts the last part (the words in red), as I read it. One of us is confused here. How about posting a sketch of the ignition wiring?

PS: Use the "test mode" to eliminate all chances of wiring/driver confusion. When spark A is tested the coil that fires should be connected to cylinders 1 & 4, etc.

[jsmcortina]

I was confused about the wiring issue too. Unfortunately, test mode cannot be used with EDIS.

What I would suggest is to make three marks on the crank pulley 0deg, 120deg, 240deg. Mark them somehow so you know which is which (one mark, two marks, three marks maybe.)
Strobe each cylinder in turn and write down which mark is close. Check that against the firing order. This will help confirm that the plugs are wired in the correct order.

Also remember that any cylinder numbers on the Ford coilpack should likely be ignored because they related to Ford V6 firing order, not your firing order.

James

[billr]

Yes, my mistake. I remembered between then and now that MS has only limited control using EDIS. Agreed, make some temporary marks on the pulley every 120 deg. and get out a simple strobe light; don't confuse this further with a dial-back light.

[mark8solo]

Thanks all

I cannot work on the car for a few weeks but when I do get back to it I will keep you posted. Some great tips that I will definitely use in my diagnosis.

[mark8solo]

Back at it today.
Had a lot of time to think about the issue and thought that maybe I had somehow wired Bank 1 (1,2,3) and Bank 2 (4,5,6) injectors incorrectly or maybe something was shorted. I checked and all is well with wiring - #33 going to #1 cyl, #32 shared with #2 and #3 cyl, #34 to #6 cyl and #35 shared with #4 and #5 cyl.
Now I'm really stumped. Car still fires up and idles great but only on the 3 cylinders. It must have something to do with ignition but I just cannot find the solution as yet.

[billr]

Have you put additional TDC marks on the pulley and checked with a strobe light on all cylinders yet?

[mark8solo]

Hi Bill
Thought that I would check here before starting on the car. REad some other posts where plugs were the culprit although I don't think this is the case but will be replacing them anyhow.
I will add the marks today to the crank pulley then check individual cyls for correct timing as you suggested if the problem persists.

[billr]

Don't worry about getting those extra marks real accurate, you are just looking for something grossly off.

[mark8solo]

OK!! Some success - #4 high tension lead was open - repaired but still nothing. I did read in another post that some plugs will fire randomly from ground side(not necessarily at electrode) to center electrode in reverse polarity. I did swap wires on coil pack but this did not change anything. Replaced plugs to Bosch platinum for 2, 4 and 6. Cyls 2 and 6 are now up and running but 5 has now shut down and 4 is still not working. I checked spark for all cyls using the timing light pick up and #2 had nothing until I replaced the plug- every other cyl had spark. #4 and 5 have spark but still not operational - I replaced #5 plug but no luck.
I checked timing with marks on crank pulley and everything is dead on. I will check #4 injector again tomorrow. Will keep you posted.
I've got one more cylinder so that's progress!

[billr]

You are at a disadvantage because you can't use "test mode" with the EDIS; and if something is wrong EDIS adds one more level of complexity to the system. Would you consider converting to simple control directly from the MS? That could be done with less than $100 in parts and a little bit of soldering/wiring.

Changing plug wires from one coil tower to the other generally has no effect; one plug in a "pair" is always "reverse polarity". Of course, if you have different types of plugs in the pair, or one is really crappy, then polarity may matter. However that is a plug issue that should be addressed so that all plugs are of equal quality.

[mark8solo]

Thank you all.
Got it all fixed. It was the plugs. I had brand new bosch super plus in the engine. Switched to bosch platinum on the 3 cylinders and everything is fine. Seems like in reverse polarity the copper plugs allow the spark to jump back from any part of the ground to the center electrode. I'm not going to analyze this too much since all is well.
Had a leak at the base of one of the the throttle bodies (#4) so I fixed that also. Idles great, starts on a dime and throttle response is good except off the line. I will be getting the autotune soon to polish it all off. I just met another Porsche enthusiast today and he has a MS1 in his 2.2. He highly recommended the Autotune and he is a computer programmer by profession. He also recommended an AEM wideband oxygen sensor which he claims is the only sensor that sends a nice clean signal that does not cause driveability issues. Could be that it is the older MS1 set up not sure but will monitor mine.

[prof315]

He also recommended an AEM wideband oxygen sensor which he claims is the only sensor that sends a nice clean signal that does not cause driveability issues. Could be that it is the older MS1 set up not sure but will monitor mine.

I have to strongly disagree here. AEM is one of several wide band O2 controllers that uses a single ground instead of separate grounds for the heater and signal. Not a good idea at all. I have NEVER seen an AEM wideband that read the same on the controller gauge as it did in the MS tuning dash without major tweaks to the calibration file. Get yourself a 14point7.com Spartan 2. Good price, great warranty, separate power and signal grounds and designed to be used with MS.

[mark8solo]

I might have to agree with you but will need to do my own research with my set-up.

Mine's up and running and I just installed a GM wideband O2 so will monitor the A/F then hopefully the autoTune will remedy some of the nasty mileage that I;m getting. Right now I'm not getting out of WUE and the CLT is not getting past 40C so I will look for another location for the sensor rather than the top under the shroud where there might be too much airflow cooling it down.

Will check in again once I've got it better.