I have checked power at the coils and digiplex units, and it does not go away when cranking or when Kyle on.
The schematics show that the digiplex units and coils both get their +12V from the same wire off the key switch (via junction in fuse box), so I don't think the key switch could be the problem if you see constant +12V in both places, in both ignition and crank positions on the switch. Have you tried a different known-good battery? I am trying to think of what else could correlate to the spark behavior in the video...
It's really hard to believe that two digiplexes and or two crankshaft sensors have failed... But it sounds as if the coils are getting power but NOT getting a "signal" telling them to 'spark"
I know. This is exactly what it looks like to me though. I think there is someone that can test the digiplex units. I am getting real close to paying for the test.
Thanks for the info. I did not try a new battery, but I did pull the battery and have it tested. It tested good. I also added a new ground strap from the battery to the chassis in front, and a new 8gauge ground wire from the engine to the chassis. Ironically, this was done 40 miles before the car died completely. I am wondering if the digiplex units started getting better voltage than they were before and it was enough to cause a failure? No idea. I am baffled and almost out of things to test.
I just don't understand how there was no spark while cranking but there was a brief spark after the key was turned back to ignition (presumably while there was enough rotation in the engine to trip a flywheel sensor and trigger the digiplex). That's a pretty narrow band of events. Where was the test light installed when you recorded that video?
I don't know if it's been suggested but another test is to use a separate battery (connected to the common ground) to power the digiplex units and coils. This would isolate any possible voltage drop effects from cranking the starter.
It has been suggested, but I don’t have a spare battery, and it actually is not real easy to isolate without cutting wires.
From what I saw in the schematic, you should be able to pull wiring off the relevant fuses in the fuse panel and then feed the new battery to power the ignition circuits through that route with wires and connectors. No cutting involved. Could use a jumper cable to bridge ground of new battery to old battery, or to chassis.
Maybe a good test. Is there a way to test coils to see if they are ok? Can I test resistance of the coil? I looked in the shop manual, but didn’t see anything
You can test the resistance in the coils with a multi-meter. Typical ignition coil primary resistance is around 0.5 - 2.0 Ohms. Secondary resistance is typically 5.0 - 15.0 K Ohms. Primary is checked with a multimeter probe on the + and the other on the - terminals of the coil. Secondary resistance is checked with a probe on the - terminal and the other on the spark plug wire terminal on the coil. I have never seen specs on the Ferrari coils so I can't give you a more specific resistance of those coils but anything in the ranges above SHOULD allow the coil to function, even if it's not to maximum efficiency.
I tested the coils, here are the results I got. Coil 1: Primary 1.3 ohms Secondary 3.7K ohms Coil 2: Primary 1.0 ohms Secondary 3.75K ohms I think these readings seem reasonable, so I am assuming that they are ok. These were tested with the wires unplugged so that it did not affect the reading. I also took the time today to run a good 10 ga ground wire to the Digiplex units... No difference at all. The car will still not even sputter. I measured the Frequency of the RPM sensor while cranking, and it seemed to be a consisted .47, so I think that it is putting out a good signal to the Digiplexes.
I have a question about spark plugs. My car has a little bit of a non-standard setup for a euro car. My car has stock plug wires, black plug extenders (non-resistor) and resistor plugs. (NGK BPR7ES) Euro cars typically use red (resistor) plug extenders and non-resistor plugs. The car has run great up to this point, but do you have any thoughts on this configuration? Could it cause any issues?
I've worked on car engines since I was 15 years old and based on my understanding of the posts/symptoms/tests described, cannot come up with anything to explain the problem OTHER than two failed Digiplexes, two failed crank sensors, a combination of one bank failed Plex and the other bank failed crank sensor, or a failed speed sensor. My mechanic brain rebels at the multiple component simultaneous failure diagnosis that would be required of the Plexes/ crank sensor failure. As described, the car was running with one bad cylinder - no or poor spark - then eventually went to no sparks at all. I don't see how the Plexes could be damaged in a way to cause that. The Plexes don't direct the spark, the distributor does that. IOW, a failing Plex can't 'decide' to eliminate a spark to one cylinder, they would fail by shutting off the signal to the coil or maybe randomly sending the signal to the coil out-of-sync with the crank sensor. A failed crank sensor would stop the spark to ONE bank but not both. Frankly, the speed sensor seems the likely suspect in the PRESENT situation - no spark. But the initial problem - no/poor spark on one cylinder/bank doesn't fit that diagnosis! Further, again if I read/understood/remember correctly, the speed sensor was checked. I don't recall, was it checked only for resistance or actual output voltage while the starter was cranking the engine? If not tested for voltage while cranking, you should do that. I have to say (again) that I'll be very interested to hear the solution! At the moment, my diagnosis is: It beats the heck out of me!
In my mind, the progression from one dead cylinder to no spark at all may or may not be related, especially if a lot of poking/prodding preceded the final failure. So I probably wouldn't try to make connections between the two a necessary condition of theories. There is one clue to maybe explore more. Before it died completely, the OP said the car would only stay running with a high idle (1800 RPM). Assuming that was spark related as well, what would that point to? Loss of spark at low RPM. A bunch of things could cause that, but since I also think it would be unlikely for both coils or both digiplexes to simultaneously fail, I'd be looking at the flow of juice to the coils and digiplexes. Could be on the ground side but I am more likely to suspect the battery and charging system based on experience.
I have worked on a lot of cars, but never professionally, so I really appreciate you all helping to answer my stupid questions. I know this thread has been confusing as things change, so let me try to summarize it to see if it changes your thoughts on anything. Initial problem: Slow idle (800-900 or so) with a miss. When I looked with a thermal camera, I could see that cylinder 4 was not firing at idle, so I focused there for the cause of the issue. I thought that there was no spark, but after further testing, it had very very weak spark at idle. Phase 2: After more testing, I found that week spark was across all cylinders, not just 4, but for some reason it affected 4 worse than the others. I think this may be because of a partially clogged fuel injector which is still an outstanding question. Phase 3: I found that if I turned in the throttle plate screw on the throttle body, the car would idle smoothly, and the miss went away, but it would only idle at about 1500-1800 RPM. if I backed it back out even the slightest bit, it would drop back to 800 with the miss. I thought maybe the screw had worked itself loose, but maybe this was just compensating for another issue. Phase 4: I decided to leave the high idle and drive the car to see how it behaved. It ran great for about 40 miles, and then just died at 60 MPH. It has not fired a single cylinder since this point. Not even a sputter. Tests/work so far: +12v at the coils CONFIRMED +12v at the Digiplexes pin 8 CONFIRMED Ground at Digiplexes pin 9 CONFIRMED Checked all fuses Checked all related relays (as far as I know) Replaced distributor cap and rotor on bank 1-4 Replaced all spark plugs Removed the battery and had it tested. Tested good. Replaced 2 plug extenders that "felt loose". All plug extenders were .7 ohms Alternator tested low (12.5v), but this is when the car was idled down. It tests at 13.7 above 1100 RPM. Continuity from pin 11 on Digiplexes to coils CONFIRMED Resistance on crank position sensors tested at around 720 ohms tested at the Digiplex boxes pins 1 and 5. Did not test voltage. Resistance on RPM sensor tested at around 725 ohms at Digiplex pins 2 and 3. Voltage while cranking at about 1.6VAC at the digiplex boxes. Coils were tested. Primary 1.0-1.3 ohms Secondary 3.75K ohms Added a new ground from the battery to the chassis at the front of the car Added a new ground between the engine and the chassis at the rear of the car Added a new ground to both Digiplex boxes. Fuel pump runs if safety plug removed or touching the idle plate. have not tested pressure or flow No spark on the coil wire according to my spark testers. (thus eliminating distributor and rotor) Tested output on Digiplex boxes pin 11 with multimeter. Very low voltage (.2vdc) Not sure if this is because of testing with multimeter. NOT TESTED Idle Air Control Valve WUR Fuel pressure What am I missing here? I have an appointment to check into the asylum on Wed at 4:00.
Odds are that an early test disturbed something injecting new/additional issue(s) causing the current problem. It is very doubtful that you suffered dual failures simultaneously. I think it is time to start over at the top and verify all of cables and connections again. I would re-examine everything electrical that I touched and everything in proximity. FWIW, I was testing my AAV. Had it disconnected at one point in the testing. The car would start, run perfect for a very short time and cut off dead. If the car does not sense the proper resistance then it shuts down. Sent from my iPhone using FerrariChat
I have thought that and rechecked everything I can think of. Probably not a bad idea though to start back at the top of the list and do them all again.
"Probably not a bad idea though to start back at the top of the list and do them all again." I agree; it's what I'd do. FWIW, I've seen a lot automotive mysteries over the years but this one is certainly a good one!!
Could it be that your regulator is shot, sent too high a voltage when you went 60mph and blew both digiplexes? Know anyone with a digiplex car who can try them on their engine?
I did think of that as well. I am going to pull the alternator and get it checked over the next week.
You performed a voltage check and, if I recall, got 13+ volts at some elevated (not idle) RPM. That indicates the voltage regulator is not overcharging. But, as mentioned in a previous post, going through the entire process again may find something that was overlooked.
Just thought of this... Did you unplug/change anything related to the crankcase sensors? If I remember correctly from some past threads, if you were to switch them (so that the front bank crank sensor is connected to the rear bank ECU and visa versa) there would be no spark. I may be mis-remembering that but other folks here - like Steve or RifleDriver - would know for sure. Of course, if you didn't make any change in the plugs/wiring/connections, that can't be the problem.
