348TS, no spark and no injector pulse, bank 5-8

You did ignition coils right?
How about fuses? Fuel pump etc..

Start with basics

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Are you sure you're identifying the crank sensors correctly. The higher positioned crank sensor is for the 5~8 cylinders (at the 8:30 position). This is also the one which is used for the tachometer. Is your tacho working?

https://www.ferrarichat.com/forum/threads/90s-electronics.578756/#post-146056377

Power comes directly from the left ECU and there are no disconnect plugs to check other than the ECU plug and the sensor plug. Since you've swapped ECUs, I guess the only other thing left to check is the resistance of the wiring between pins 47 and 48 of the left ECU plug and pins 1 & 2 of the sensor, respectively. Make sure there are no shorts to ground or shorts between the two wires (purple and purple-black). When doing resistance checks, make sure that you're not putting a voltage on the ECU (otherwise you will get a strange reading or perhaps even damage the ECU). Most ohmeters use a 9 volt battery, so may put more than 4~5 volts on the line (4~5 volts is normal for sensor circuits).

F348 2.7 Motronics Wiring Diagram

 

Are all the earths still firmly grounded?

 

Here is what I would check:

1) That the grounds are ALL connected properly. Check the main ground from the battery to the chassis. Then check the grounds from the wiring loom to the cam covers, or to the coolant crossover pipe under the plenum. Also that all the wires are in good shape.

2) The condition of the connectors inside the barrel connectors, located up under the rear of the intake plenum. Make sure the pins are all in good shape, clean, and making FULL contact.

3) Check in condition of the female pins on the T55 connector. The old timer pins have a tendency to become VERY loose and do not make very good contact. If you hav not repined the T55 connector with Junior POWER timer pins, you may want to do that.

4) Check to make sure the loom hasn't been cut where it passes through the "firewall" into the cabin.

I'm guessing you have some sort of wiring problem because you have swapped ECUs and the problem persists on the same bank. FYI, I HATE wiring problems! They are THE biggest pain in the ass to deal with.

Good luck.

 

Ernie, apart from crank sensor harness shielding, the crank sensor doesn't use the engine earth, but uses an internal earth in the ECU. If the crank sensor voltage was tested by putting a voltmeter across pins 1 & 2 of the crank sensor, then chassis and engine earths and engine disconnects shouldn't be an issue.

This, of course, is assuming the ECU itself is powered and earthed properly. "IOP", have you checked that you have (at least) battery power on ECU plug pin 18 and ignition power on pin 27? When testing for 4 volts, did you try swapping the red and black multimeter leads to make sure that ECU internal diodes (if any in the circuit) weren't interfering with your measurements?

 

P.S.

Left bank ECU pin 18 uses passenger footwell fuse 14, but the ignition power on pin 27 is unfused (at least externally).

Here's an updated wiring diagram:

F348 Motronics Wiring Diagram

 

Why is there 4V at the 5-8 sensor? Isn't this a variable reluctance type that generates a pulse inductively? I.E. it is a passive sensor, no power. You have stated no power at 1-4 and 1-4 fires. 5-8 has 4 V and doesn't.

 

Do we know for sure it is a passive device, John? As far as I know, the toothed gear is not magnetic, so it's not going to induce a current in a coil.

It may even be like the speedo sensor (or not):

https://www.ferrarichat.com/forum/posts/142324674/

 

Pretty sure. Had o replace on my 355. The sensor has a magnetic core. The toothed wheel modulates the magnetic field generating a current.

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P.S. Just doing some reading on variable reluctance and Hall Effect Sensors... It seems that the VR sensor has its own permanent magnet and coil, so you may be right.

Is he referring to the 1~4 bank sensor ... or where the sensor is located?

(Sorry, cross-posted)

 

As John K says, the 4 volts may actually be an error (I assumed it was normal). There may be a stray voltage on the line due to a shorted wire.

I'll let the experts answer this, but looking at the diagram, the Left ECU certainly has the potential to shut down its respective fuel pump, injectors and other engine management devices by taking an earth(ground) from the solenoid of relay "d". Relay "d" controls power to the left hand fuel pump power relay solenoid and a lot of other left bank things. Indeed, the cause of your problem could simply be a relay (although that might not explain the 4 volt discrepancy).

Anyway, back to the basics first. If the ECU is not getting power, then a lot of things won't be getting power.

(EDIT: I've noticed that the wiring diagram I posted (which is based on an original Ferrari diagram) has some unexplained "features". The pin assignments for the left and right ECUs seem to vary. Since the ECUs are interchangeable, I expected the pinouts to be identical. There may be an error in the original diagram, but hopefully this should not affect the diagnosis of your problem).

 

I've updated my diagram. Now up to version 9... It includes some extra notes and a correction to relay functions.

F348 Engine Management Wiring Diagram

 

If your aren't getting a signal from the crank sensor the ECU on that side thinks the engine is not rotating and it will not turn on the fuel pump for that side (on a dual fuel pump car).

 

To review briefly:
car ran fine before the service-correct?
Car has engine out major, in the sub-frame-correct?
Now the car wont fire on one side-correct?

You cannot "move" the "dead" sensors" symptoms by flopping componentry from side to side-correct?
On they bench, these sensors statically test within spec-correct?

If yes to all of the above, you have a transfer of data(harness) problem, or a processing of the data problem(ECU)
Motronic 2.7 is pretty cave man by todays standards-still uses a 32-pin prom chip in a receptacle on mobo...the wave soldering of these wafer boards gets funky after 30 years, and even the slightest jostleing will cause a permanent problem....Additionally, as I recall, one must pull most of the fuel pumps relays and coils relays wiring pins bundles out of their receptacles in order to pull the harnesses out through the aft bulkhead(might only be on T cabs-been along time!). In my own experience, upon reassembly, pin receptacles-females- frequently snapped together-yet when circuits failed to light-back probing these circuits showed incomplete circuits AT these plus-FYI?FWIW

 

Harness or, perhaps, power/earthing problems. He's swapped the ECUs, so it's not a processing problem.

It might not be the case here, but harness problems could include the plugs not attached to the correct items. When my local technician replaced my engine harness, he got at least 3 items in the wrong places which were resolved by doing continuity checks as per the wiring diagrams. His step by step diagnostic guide which included checking sensor resistances at the main ECU plug failed to pick up that some plugs were attached to the wrong items, because they had similar resistances/impedances.

 

IOP, you said you swapped fuel pump relays... Did you also swap the control relays D & L?

Of course, considering that an engine out has been performed, it is less likely that some electronic component has suddenly failed. It's more likely that something has been damaged, contaminated or not put back together correctly.

 

Find out why you have 4 volts applied to the bank 5-8 crank sensor and you will find your problem.

 

Slightly digressing from the topic, but the Ferrari F348 2.7 engine wiring schematic I posted above seems to have some irregularites (also found on the original Ferrari wiring diagram). For example, the middle pin (pin 2) on the left bank Auxilliary Air Valve 3-pin electrical connector is supplied by 12 volts dc. On the right bank, the middle pin goes to an earth. This is clearly an error. Also, the Throttle Position Sensors are connected to different power sources and pins on the ECUs. The Ferrari F355 2.7 engine wiring schematics show the right bank more closely matching the left bank (which is what you would expect if the ECUs are interchangeable).

I could redraw the diagram to get the right side to match the left side (as I believe the right side is in error), but I couldn't ensure it was correct. Unfortunately, I don't have a Ferrari 348 2.7 car handy, so I can't resolve this issue.

I've added question marks to highlight the problem:

F348 Motronics 2.7 Wiring Diagram

Now up to version 11.

 

BE CAREFUL!
2.7 used 1 year and 1 year ONLY in 355
reliability of wiring diagrams is sketchy at best in this era-formatting of all manuals was changing dramatically. There were NUMEROUS revisions and as I recall a couple of TSBs in this area(I was at Dealer when these cars were introduced so I am speaking from first hand experience...)
REMEBER: you CANT MOVE the problem....work from there...you'll find it...