LOSS of Cam and Crank Trigger While Driving - Porsche 911

EMU BLACK / CLASSIC
, ,
1

I have converted my 1979 Porsche 911 to EFI & turbo using an emu Black.

It’s been running for 1.5 years with no major issues. I have had some cam sync issues in the past and posted about it at this thread Emu Black- Porsche 911 - Cam Sync Issue at higher rpm - Hall Effect Sensor ZF/Cherry - #29 by Mike911Aus

That issue was “bandaided” by installing a new crank sensor and also enabling the advanced filter on the cam trigger, to ignore 2 teeth either side. (from what I have read, this is not available in the latest firmware version and they are not going to add it either).

Today I went for a short drive for 15 mins, and on the way home (3 streets away) the car cut out while driving. Engine dead. Pulled over and tried to restart ; cough splutter then nothing.

It would sometimes run but then stall after seconds.

I had laptop with me so checked the scope on the triggers while cranking - nothing. completely blank. Checked my fuel pressure and pump, all functioning and reading correct pressures.

Question: if one of the hall effect sensors was faulty would that result in a completely blank scope? ie, does the scope require both sensors to be reading in order for anything to be displayed? I am thinking yes?

Other sensors are responding so ecu is functioning. After maybe 10 mins or so, I tried to start and this time it ran, so I got the car back home. I have started it a few more times and it seems fine.

However it seems that my cam error is back with a vengeance. And this time, it’s not just a glitch!

Here is the log file..https://drive.google.com/file/d/1xPb0uDv9xBSOrn044gD5A_cyiX3cZwou/view?usp=drive_link

Hoping someone else can have a look and perhaps help with my investigation.

Cam /crank triggers are halleffect and use the 5V supplied by the ecu. The 5V supply is working fine.

The day before, I did wash the car, and some water got into the engine bay, but I use a blower to dry most of the car and I used that to blow excess water from the engine bay. I have done this dozens of times in the last 2 years with no issue. But not ruling it out.

However, I would have thought, if it was water related, the car would not have started to begin with, let alone drive for 15 mins.

The wiring loom was made by me, and again, I suspect it could be my work, but if it was indeed a bad connection, wouldn’t it be ‘dead’ completely?

The issue feels “organic”…

I know it is HIGHLY UNLIKELY to be an issue with the ecu itself.. but could it be?

2

So to be clear are you using an aftermarket crank trigger kit? If so which one? Seems like your crank signal is more or less reliable but you are having problems with losing the cam sensor signal correct? If so disabling CAM sync above “X” rpms is not a band aid. The ecu only needs to sync once when starting it up and you can just disable it. I understand that you want to use it because it’s there but there really isn’t a need to have it sync’d up all the way to infinity. On my civic (which revs cleanly to 10K rpms all day long) mine is disabled from 600 rpms.

If you really want to continue using the cam sensor then I would like to know how many teeth is on your cam sensor? If more than 12, a hall effect sensor (especially those cherry style ones) simply starts blending all the teeth together because it can’t differentiate between them. This is compounded by engine noise that also can disrupt the signal. Switching to a VR sensor would be more reliable.

3

This is the cam trigger. Classic Porsche 911 2.7/3.0/3.2 Ignition Sensor Ref/Sync Module Kits – Adapt Motorsport GmbH

It uses the same Cherry / ZF sensor as the crank trigger.

My understanding is that there is a single ‘tooth’ on the cam trigger.

I tend to agree with you that setting the disable rpm to a number higher than cranking but lower than idle, is probably a fair idea to avoid sync issues after starting.

The reason I do not feel that the problem is caused by a loss of sync is because, this particular time, it would not sync at all.

The cam and crank triggers both did not show up on the scope while cranking.

4

It says on their website that they recommended running it at 8v which I’m sure your car does not.

I”m pretty sure that if you aren’t getting a scope for both that would mean that you have lost the crank trigger too. Pretty sure the emu scope needs to “see” the crank trigger before it also starts looking for the cam sync trigger pattern.

If there is a specific air gap needed for the crank trigger, consider taking it down to the smallest allowed gap and try again. If that works, just disable the cam sync around 500-600rpms and happy days. I’m quite sure engine noise is distorting your signal under high load and rpm and/or the Hall effect signal just can’t keep up (what do you rev it to?)

Do these cars use timing belts? Timing belt stretch as the rpms rise can also give slight variation in where the cam signal can fall every time.

5

Hi, thanks for the input

Timing chains are used on these engines.

Hmmm…ok.. would be good to know if this is definite.. hoping someone from ECumaster can verify?

yes, I am running at the recommended airgap. The theory of the sensor not being able to keep up at high rpm might be the reason I lose sync at those conditions, but my most recent issue is that it lost sync for 15 minutes and the car just died. And when cranking, it would not show any signal at all. That’s my most pressing concern now. (even though it’s starting perfectly every time now)

6

which website? the adapt motorsport site?

According to the website of the sensor manufacturer it shoud be good to use between 5v and 20v.

But to test this, last year when I was having the high rpm issues, I switched to using a 12V supply to the cam and crank sensors, Sadly, it made no difference and I still got the occasional higher rpm loss of cam trigger. Engine only revs to 7000redline and the issues were happening around 5500-6200.

7

Yes the website you linked shows they recommend 8v operation. Even though it says it can go up to 20v, they must have some reason to state that they recommend 8v. Speculation on my part is that it probably performs the absolute best at that voltage.

VR sensors will most always perform better than any Hall effect sensor. This is why the majority of new cars use them. They deal extremely well with heat and vibration and high rpm’s. They don’t have to have specific gaps set up to work properly. They won’t get fried like a Hall effect sensor can. They are simple. From my experience Hall effect sensors do offer pretty clear signals BUT the trigger wheels need to be wide enough. Trying to read thin trigger wheels can get dodgy. Cranks move, camshafts move. This is where a VR magnet either reads metal or it doesn’t.

I’m not saying that the Hall effect sensor can’t work. I certainly don’t want you to change up your whole trigger setup since you already purchased it. I’m just saying that it can be more finicky to get just right which is why I said to just disable cam sync to just remove that signal out of the equation as soon as it is fired up and idling. As far as the scope function, I was about 95% sure you need a primary signal in order to see the secondary (cam) signal. I know I read it in their manual sometime ago. It would appear you probably lost crank signal while it was idling.

IMG_9822
IMG_9822828×607 121 KB

8

That’s good info there. Thanks for screenshotting that.

I went back into my log file, to see if there was an option to view the 5V supply. I coudnt find it.

But what I WAS able to find, is an option to view CAM SIGNAL PRESENT.

I also logged my 12V battery.. reason being I can see when I was cranking trying to start… Looking at the log, it shows that every time I am trying to crank the car to start, I do indeed have a cam signal present.

Using the info you supplied above (thankyou) it suggests that my 3 month old crank sensor is playing up (or associated wiring etc).

Would you agree?

Screenshot 2026-01-05 151505
Screenshot 2026-01-05 1515052569×1561 227 KB

9

Yes in this log it would appear that your crank signal is indeed intermittent. I would assume that maybe the engine has tried to fire sometimes or at least sounded like it wanted to do so?

You either have a bad sensor, faulty wiring, incorrect air gap or some combination of those three. May I ask if the ZF sensor is in fact two separate sensors (two physically separate) or is it two sensors molded into the same body? There could be interference. Are you using shielded wiring? Are you using a pull-up resistor in the software?

10

they are two separate sensors.

The wiring is not shielded.

Pull up resistor is correctly selected at 1K since I am using 5V supply.

Again, I doubt it’s interference, as that would be sketchy… my car would not fire for a a good 15 minutes…

So yes, it’s either faulty wiring or faulty sensor I think. Considering the low cost of the sensors, I feel I should replace it. Or I could just go for a drive again and see if it does it, but I dont like the idea of being stranded and needing a tow!

11

Ok, pull-up is definitely what is correct. Yeah I would say a wiring or sensor issue. Sometimes the sensors can work loose and sometimes they can completely get wiped out by touching the trigger wheels by accident.

Once you do (if you decide to swap out the sensors) I would still encourage you to just disable the cam sync above 5-600 rpms and try it out. Please report back how it goes.

1 Like