Front Bank Won’t Fire

I’ve been through this 2-3 other times, however, this time seems to be different. In the past when either the front or rear bank would not fire, every single time it was an electrical problem at the coil. Procedure was to pull wires off of the coil, clean everything, apply dielectric grease, tighten all of the connections, and bingo, the off-bank would come alive.

About 9 months ago, I replaced all of the wires, coils, plugs with new hardware and I haven’t had a problem until yesterday. I ran the car two weeks ago with no problems. I checked the wires and everything looked to be clean and tight. I pulled one of the plugs from the front bank and it looks as though it has not fired. The plug wasn’t even warm. I also swapped in a known-good older coil and still no spark.

I’m tending to lean towards a bad DigiPlex Ignition module. Do these tend to go bad and is ~20 years beyond their usual lifetime? My guess is they are the original units. My next steps were to:

1. Pull a front-bank plug mounted in an extender and watch the spark plug not-spark.
2. Swap the rear-bank main coil wire and move to the front-bank coil…watch for spark.
3. Swap the wire harnesses for the DigiPlex Ignition modules and see if I can create a working / not-working pattern.

As far as I can remember, the coil grounds are a single ground. There is not a separate ground for each coil. The ground wire where the DigiPlex Ignition modules are located seemed to be clean and free of any corrosion.

I welcome any and all thoughts on what to troubleshoot next.

 

Mike,

I'll check the archives when I get home, however, do you have some quick info on where the TDC sensor is and how to check if it is OK?

 

Anyone...have you heard of these DigiPlex Ignition Modules going bad that often? Granted, these are 99% probability the original units, but they look pretty robust.

 

I have not swapped the DigiPlex's yet. I got home late tonight so all I really had a chance to do was formulate my battle plan. I'll do the swapping of coil wires and DigiPlex harnesses tomorrow evening to narrow down the culprit.

If after all of the swapping, the front bank will not fire, the next most suspect area will be the TDC sensor. I'll buy two new units and while I'm under there, replace both.

Any other advice is very welcome.

 

ferrarifixer...do you have a Owners Manual page or diagram number that shows these two connections?

 

Ok...tried the following tonight. With only the rear-bank main coil wire attached, I first tried the using the rear-bank DigiPlex and it fired immediately. I then connected the rear-bank coil to the front-bank DigiPlex and it fire immediately. Good!

To solidify that the DigiPlex's were not the culprit, I tried the same procedure with the front-bank coil (rear-bank main coil wire unplugged). The front bank did not fire when connected to either DigiPlex...exactly what I wanted to see considering the price ranges I have seen for a single DigiPlex box. However, if anyone has one or a pair of MED 803A's they'd like to sell, I'll buy!

From what I've been able to gather from this thread and others that I've found this similar topic, all roads point to either:

(A) "There are two big connectors up under the LH wheel arch near the oil cooler which can get corroded and give problems too."

or

(B) The TDC Sensor for the front bank, although while I'm in there, both will be replaced.

Can anyone see a fault in the diagnosis and is there something else I should try before putting the car on jack stands?

Also, does anyone know if the P/N for a 308 TDC sensor is different between a Euro and US model? If the DigiPlex's have different numbers, I though maybe the TDC sensors would also.

PS: I've also made and installed additional grounding wires to better ground each DigiPlex.

 

Jeff is usually the first place I call, then Dennis McCann Ferrari Parts. 99% of the time, I can get what I need between both.

Appreciate everyone's help.

 

Thank you Tom!

I had downloaded other things from that site...I'll check out the 328 Wiring Diagrams.

I ordered the three TDC sensor harnesses from Ferrari-UK today...$83/each (Thank you Jeff!!) If it turns out to be just a dirty connection, then at least I've got the TDC sensors for when they do go bad.

Appreciate everyone's help.

 

OK...
- TDC sensor for the rear bank: No Problem.

- TDC sensor for the Tach: No Problem.

- TDC sensor for the front bank: How the #@$#@!!!! do you get it out and back in?? I was able to get the front bank sensor out after 1 hour of working with it. However, the studs for the front sensor are resessed into a cavity that makes re-inserting the washers and nuts almost impossible!

I'm tempted to remove the rear bonnet and lay on top of the engine, but I'd rather not do that if someone else has a bright idea on a better access point for this sensor.

Please HELP!

 

tbakowsky,

I realized early on that I'd have to remove the oil separator lines prior to pulling the front bank sensor out. I did all of that, removed the sensor, and after a little careful handwork got the new sensor in place and then started to re-insert the nuts. The problem is, the studs are down in that cavity and it is extremely difficult to place the nut on top of the stud.

Once I get these front sensor nuts on, it's less than an hour to put the car back together to where I can see if those sensors fixed the problem.

I'm so close, but after messing with those front sensor nuts for over an hour last night, I decided to put it aside until tomorrow.