Burnt Marelli ingnition module

I used a tiny amount of red rtv silicone on the distributor and stuck it to the cardboard. Trimmed it with an exacto knife in 24 hrs and it went on fine.

Interesting, Bret. I was wondering what the max temp range for it is, and it says up to 275 deg. F… I would think that is good enough for the top of the V-12s. :+1: Thanks!

Was going to swap modules to see if B bank would work and A bank would stop. Peeled back the electrical tape and found the modules are wired differently.

The harness to A module has an incomplete jumper wire. It was running. Part numbers on both modules appear as direct fit on interchange charts. Any suggestions?

Terrible job by PO fixing the wiring! Here is the electric diagram:

Both ignition amps are the same and everything should work/look the same

Wire looks bad, stiff as a pipe. I have the wiring diagram and am confused. Seems besides the PO wiring modules differently they both look wrong to me.

I would expect jumper from black to red but not blue and red twisted together before plug on B module.

I would expect jumper from black to green , which is not, but not green and brown twisted together before plug on A module .

It also appears the ignition modules have swapped positions. The A module is in the driver side per ROM but passenger side on my car.

Any suggestions on how to proceed?

This is how they should be. Counterintuitive, but A and B bank amplifiers are not aligned with the said.

My A and B harnesses are definitely swapped. I just wish I knew which wiring is correct. It seems weird that A has the jumper wire from the joined together brown and green wires to black not connected and it runs. B has the jumper wire from the twisted together blue and red wires and it ran for 80 miles and crapped out on me. It has a bit of a burnt smell to it but looks ok.

I don’t want to run the good module on B harness and take a chance that it will burn up.

I am sorry but I don’t understand you. If the module harnesses are just swapped, no reason to expect “burning”.

Both have WP and B - power and ground. If those are on the correct pins, then everything else can be checked with a multimeter.

I provided the electric diagram already, here is the explanation. Ohm the U and R wires from the B-bank module to pins 9 and 10 at the Marelli ECU (passenger footwell). Same for the N and G from the A-bank module to pins 14 and 15 and you’ll know!!

There should be no “jumpers” - the dashed lines indicate shielding.

Thank you for providing the diagram Steve but I already had it and was studying it. I realize the positioning of the modules mean nothing as far as operation goes but it is indicative of alteration. The module harnesses are not just swapped, they have the wiring bastardized differently on each one yet the car ran. There is more than one way to skin a cat but both of these look wrong.

Thank you for using the word shielding as it got me thinking in a different direction. I rechecked the jumper wires from blue and red to the black ground wire. Using magnifying glasses to aid my 61 year old eyes I now see the jumper wire is soldered onto the shielding around the power module outputs.

The shielding was not pulled back over the outer insulation and soldered there. It was soldered right over the the blue and red wires. Was not expecting that and assumed the red and blue wires were simply soldered together with the black ground wire.

There is a momentary continuity between the red wire and the ground wire, then infinity on all scales. Not so on the blue, not so on the brown and green on A module. I have my direction. Thanks for your help.

You’re welcome.
Worst case scenario - you’ll have to redo the wiring from end to end yourself.
Not too bad - just a handful of wires. Connectors obviously can be reused.
Good luck!

That’s what I would do. Remove all uncertainty, and get to what should be a “known good” set up. I’ve recently remade and extended some of the wiring in my engine bay, and have used woven plastic sheath to good effect, rather than wrapping with tape.

That is so weird. Ya gotta wonder what somebody was doing in there and why they decided to stray from the original wiring setup and create something of their own invention.

The weirdest thing, to me at least, is that this engine ran until 3 months ago…

It may have been you that said to ground that shielded cable on only one end, read it going thru forum searches. Big picture is I knew it was a mess when purchased.

Paint is nice, Flamenco Red, interior solid 8/10. Engine quiet, no cam chain rattle on decel when revving, 106K. Tracks straight, trans shifts nice, no slip, top good shape. Changed hands 3 times in less than two years. Sold for $10K in Seattle. I bought it for $4500 in San Antonio. Less than 300 miles put on it since the three sales.

Looks like a nice alloy radiator. Could be that this electrical gremlin was intermittent and drove the bodgers crazy. It finally gave up the ghost for me. Over the years have seen infinite resistance on many things until they get current, usually underground low voltage applications. The the wires just barely touching, often corroded, will conduct current.

You folks may have just helped me solve a mystery that frustrated three previous owners. Thank you all. Will probably have at it next weekend after this storm is out of Texas.

The wiring to B module may have been intermittent for some time. The A module appears to have been replaced recently with a correct Marelli part number, and the ground to the shielding has been cut. Did it short out and they simply cut the ground?

It is difficult for me to think in terms such ignorance and and poor workmanship but it looks like I will have to to sort things out.

As soon as it runs on both banks the wiring is getting redone. Who knows what has been done just waiting to fail. To me the car is not roadworthy until that is done. The woven plastic sheath was used on Honda motorcycles in the '80s, very tidy. The plastic sheath motorcycle manufacturers used would get very hard and brittle in less than ten years.

Hey Brett.
Would you have a suppliers name where I can. Get hold of that distributor cap & rotor arm .
Thanks

I have been told that cap with the letter F and Made in Italy markings indicate it is made by Facet. It is available on Rock Auto.

Last I knew the rotor arm was unavailable there. Good luck to you.

Thanks for that I will look into it, although so far the write ups on facet items have not been very encouraging.