348 won't start - Eureka !!!

Whoooppeee is going again. !!!!

Many many thanks for all the help everyone.

Top marks to the those who mentioned the crank sensors - Ernie & Dr Ferrari, and to Zan for the spark check method.

I re-visited the crank sensors, cleaned the contacts with contact cleaner.

Checked voltages - you should see about 5v on one of the outside pins with the ignition key on. The other outer is GND, the middle one is the return signal which should be digital pulses as the engine spins - Hall effect transducers for the electronic experts.

I also checked the power modules, you should see 12v on some pins of the 5 pin connectors.

I now understand these systems a bit better.

The engine spins, the crank sensor sends digital pulses to the ECU, this then knows how fast to send signals to the power modules (12V) which then boost these to HV for the spark plugs.

Correct ?

Lesson 1 of Motronic 2.7 complete


Happiness again

Now back to the A/C, radio etc etc.

John

 

ALRIIIIIIGHT!!!!!! Oh man that's great. I thought I was an idiot, after all the suggestions. It usually is something electronic with these cars. Well good to know that the crank sensors WERE indeed the culprit. Glad you got it going. This will be of great help for others in future, that need to diagnose a hard start problem.

 

BRAVO!

 

[/embarrassment mode ON]

I've done lots of searches on crank sensors on this site and the Archives... seems to be a very common problem. In the interest of education, can somebody take a picture of WHERE these darn things are located so I'll know what I'm looking for? My car runs fine now, but when I'm stranded in the middle of nowhere, I'd like to know what to check. Is the crank sensor another one of those Stabilant-22 candidates? Is it good preventative maintenance, or should I just let sleeping dogs lie?

Pictures would help a newbie!


Thanks,
Daniel

[/embarrassment mode OFF]

 

Post #43 in other thread: "If it turns out to be the crank sensors, I will kill myself." We'll let it go this time, John!

On the illustration, the crank sensors are the two items with the pigtail connectors on the nose of the engine.

 

Where did you get that picture... it's beautiful! Is it a specific shop manual, parts manual?

I love this community. I pray I'll be able to "give back" something one day.

-Daniel

 

Here's another view - gear and oil seal removed:

 

Ditto Jack Russell! Where did you get that picture? A book? Manual?

 

John,

Glad to hear...... those connections are a very weak point and with all that heat and vibration they have a tough time staying clean and together.
In the challenge cars, we used copper RTV sealant around the connector ends where the wire enters to help keep the plug clean and together.

sounds like you understand it well... (motronic 2.7 101)

Excellent!!!!


best regards, Jim

ditto ditto jack....is a cool pic.

 

Jim,

As a generic question have you ever heard of anyone having to deguass a crank sensor wheel? I would think that over the years a field could develop that can cause errant signals to the TDC sensors although I have never heard of this happening. Remember in the old days when we used to demagnatize the heads in your cassette tape players?

 

never heard of that,ALthough i know what you mean.
I believe that the material that the wheel is made of may deter that happening.
your only real concern is the distance/clearance between the sensor and the wheel and if anything interferes with that.

best regards, Jim

 

Sorry, I wasn't around to answer the question about the source of the cutaway drawing I posted above. It's from the German book "Ferrari 348" by Werner Schruf. I've posted pix from this book on several occasions. I see it for sale on ebay all the time, that's where my copy came from. It's spendy, about $85 I think. Hardbound, with a slip cover, 283 pages, not exclusively about the 348. All in German.

 

On my crank position sensor, I do not have the 5v on one of them... and do not have spark or fuel delivery either... Any guesses where to look for the missing 5v?