550 Intermittent Start Issue

What puzzles me is how a fuseboard problem would not be present with the car running (when the temperatures in the relay panel and vibration would be highest). In the engine bay, you would lose air cooling after the car had stopped and you'd have heatsoak, but I can't imagine any significant upwards temperature changes in the cabin (anywhere near the running temperatures of the relay panel).

And as billybob says, it seems equally puzzling that a temp sensor should cause a no start.

I'm wondering if the temp sensor error is just a symptom of a fault, not a cause. That plug behind the engine carries a lot of data, including, I believe, the immobiliser unlock signal sent from the R ECU to the L ECU. Maybe the RH ECU won't allow start if there is no comms on that line. Having said that, you might expect a fault code for that kind of thing to appear.

Perhaps Gary should hire a gymnast to check out that plug

 

Spark + fuel = igintion. No ignition means no spark and/or fuel (flooding is no spark).

So which is it? No spark and/or fuel?

If you cannot answer that question you are just crawling in the dark looking hoping to find a light switch.

 

He has both.... at least by the time he has installed test equipment on the injectors and plug leads. It's a temperature issue and presumably something common to both banks.

Is it a timing issue? Here is a list of some of the things common to both banks:

Cam Sensor
Coolant temperature sensor
Inlet Air Temperature sensor
Immobiliser
CAN Bus

The first 3 affect timing.

There is something not clear to me about timing. The WSM says that timing is based on what is happening to cylinder #1. Is the RH ECU transmitting data to the LH ECU regarding cylinder #1, or does the left bank base its timing on its own sensors? If the RH ECU is transmitting timing data to the LH ECU what path does it take? Everything seems to go through that inter-ECU connector 176:
The cam sensor sends data directly to the LH ECU via 176
IAT sensor data is processed by the LH ECU (so I assume it is being sent via 176 to the RH ECU)
Coolant temp data is processed by the RH ECU and is sent via 176
Immobiliser data is sent via 176

Could a faulty RH Bank crank sensor be causing this issue?

Regarding starting, timing and the coolant sensor:

Is the pulsing that Gary is seeing on his improvised noid light actually the "all squirt" signal and not a carefully coordinated/timed pulsing?

 

That's the million dollar question. All the wires in 176 may not be affected by temperature. Data may be sufficient for fuel and spark (initiation), but it may be bad data... hence the flooding.

Yes, it does still sound plausible that ECT is causing this issue. I assume the R ECU digitises the coolant temp data and sends it to the L ECU via 176 (rather than just retransmitting the raw data). This may be more reliable than raw data (and not corrupted by high resistance in the plugs). The ECUs will be more likely to identify bad data (and not interpret the data as the wrong temperature).

This may or may not be significant. As you may already know, the gauge uses its own sensor.

Just wish I knew more about these things.

Anyway, I guess you just have to eliminate possible causes one by one. ECT sensors and this plug have been known to cause issues. Sometimes just resetting this plug has been known to work. Is it possible to, say, take a photo of the 176 connector (or would you need a boroscope?). I'm expecting a smartphone boroscope in the mail today (to sort out my issues).

Also, it may be a good time to look at your spark plugs, especially if the car has been running rich for a while.

Wish you a fast recovery.... both for yourself and your car

 

Definitely one of my pet peeves as well.

 

Thanks for the follow-up, Gary.

Did the tech say which bank the -40 degrees was on? Was he sure it was coolant temperature and not IAT? See this thread:

https://www.ferrarichat.com/forum/posts/147965015/

I've been told that some data may not be available until the engine is running.

Anyway, you've covered all bases. Sounds like you have a win

 

Thanks, Gary.

Given that the temperature sensor worked off the car, then I suppose it was temperature sensor plug issues causing the -40c.

That is not to say your main starting problem wasn't the crank sensor. These are known to break down with heat.

 

Interesting that one temp sensor would prevent start on both banks. Do they share some info?

Will the car not run on just one bank? My 308 would.

 

Because only one coolant temperature sender is used by the engine management system, they have to share data. If you interrogate the ECUs individually (as you have to do on cars without OBD2 ports), you will be missing the data on one bank (until the ECUs start talking to each other).

There is wiring and a plug (hidden at the back of the engine) which carries this inter-ECU data.

 

Do you know if the spark checks were done with the engine hot? Or does the tech know if there has been a problem from, say, the codes?

 

How does a failing coolant sensor prevent starting? Floods it? Too lean? I still think you should get a pop unless totally flooded which you could tell by pulling plugs.

 

From the WSM:

Starting
As the engine turns the ECU has to recognise
engine timing from the sequence
of signals that are sent from the revolution
and timing sensors to synchronise
injection and ignition.
- - - -- -- -
During this phase with a speed of more
than 30 rpm, the ECU, in order to facilitate
starting, operates all the electro-injectors
simultaneously and for a time which
only depends on coolant temperature.

If there is no data, then perhaps the ECU doesn't open the injectors at all?

 

Strange.

 

First: sorry for my English, I'm an Italian guy despite my nickname.

I have a similar problem:

My car starts immediately when cold, without problems. I can drive it with no issue for miles and miles, but when I stop it I can't restart it when it's hot.

When I turn the key and use fob I have always the "check ok" light, but you hear only a "click" and nothing run. I leave the car for 10/15 minutes, eventually with the bonnet open, and after the car starts normally without smoke or other problems.

I suppose it's something due to the hot temperature of the engine bay, not only of the coolant, because if I start the engine and leave it running idle till fans starts, if I stop I can restart it with no issue.

Ferrari dealer can’t resolve.

Have you some ideas? Could be the same sensor? What do you think?

It's an annoying thing when you must stop and restart it after few minutes. All friends goes and I have to wait

 

Your issue is different. You have no cranking. Cranking is controlled by things like the Immobiliser ECU, the start relay, the battery and, of course, the starter and associated wiring.

Since the starter motor is exposed to the most heat. I would be looking in that area. When you say you can hear a click only, is it coming from the starter motor? Can you have someone listen while you are trying to start the car? If the starter is clicking, that eliminates the Immobiliser and the start relay.

The starter motor can be reconditioned by any auto electrician.

Of course, check things like the battery connections. How old is your battery?

Did your dealer replace anything?

 

Your English is excellent.