Marelli Starter problem (?)

[Andyblahblah]

The issue is with my '78 128 2-door, but I think the starter motors are the same (?)

No issues starting and running until it sat for a week, then when I cranked it, I must have had a fuel delivery issue because it wouldn't fire. After turning it over for a while (being reasonably gentle) I got to the click-buzz/no-turn-over/dead-battery stage. After letting the engine sit for a while, trying to jump the battery with my truck, charging the battery overnight, I still got the click in the solenoid of a dead battery.

I recognized that I probably burned out the solenoid, so I pulled the motor and rebuilt. Cleaned everything, scuffed up the copper bits and brushes, greased pivots and tested - both solenoid and motor drive work fine, though perhaps not as much torque as it could/should (I didn't really want to stick my finger against the gear to test... again.) Reinstalled with still no cranking. I've done this twice now, with no change.

Some facts:
- Commutator strips are slightly worn and concaved where the brushes rub, but would that cause complete failure
- I've refreshed the grounds and connections
- flywheel turns over
- I've tried putting the car in gear and cranking manually in an attempt to line up the starter teeth w/ the flywheel

I have a replacement starter on the way to test, but wanted to see if there was another place to start digging. Can post pics, but motor is currently installed.

Also, any parts gurus know if this motor is as direct a replacement as it looks?
https://shop.advanceautoparts.com/p/car ... 7CL2*15006#

Thanks all!

[Odoyle]

Yes this is a good looking marelli starter unit, for best price I'v ever seen

[Andyblahblah]

I thought so, but it says not a fit for X1/9, Strada or 128 1300 engines.
Emailed them to find out if it's just a stock pic.

[Andyblahblah]

.

[spider2081]

I think the 75 has a white nylon connector on the driver side fender well. The connector can have 2 or 3 cavities. One has brown wires the other has red wires. the brown wires feed power to your ignition switch, the red wires are power from the ignition switch to the starter solenoid. This connector is a common cause of the starter solenoid not properly engaging.
Also the 74 Spiders had a starter interlock relay mounted on the passenger side fender well. It would prevent the starter solenoid from engaging unless the drivers seat belt was being used. This relay could be in your 75 depending on the manufacturing date of your car.

[Andyblahblah]

I think the 75 has a white nylon connector on the driver side fender well. The connector can have 2 or 3 cavities. One has brown wires the other has red wires. the brown wires feed power to your ignition switch, the red wires are power from the ignition switch to the starter solenoid. This connector is a common cause of the starter solenoid not properly engaging.
Also the 74 Spiders had a starter interlock relay mounted on the passenger side fender well. It would prevent the starter solenoid from engaging unless the drivers seat belt was being used. This relay could be in your 75 depending on the manufacturing date of your car.

This starter is in my 1978 128, not the Spider, but I'll follow up to see if there is a connector from the ignition switch.
I'm getting power at the solenoid when I turn the key, but I'll check for a drop in voltage. (And I've cranked the car w/o being in the seat.)

[DieselSpider]

The bigger problem may be that the ignition switch is not providing enough current to the starter solenoid causing it to prematurely overheat and burn out.

I like to run a line off the positive lug feeding the starter through a 20 amp fuse to a 40 amp lighting relay to trigger the starter and use the original line coming from the ignitions switch to just provide the few milli-amps required to close the contacts on the relay. This can take a 10 to 15 amp load off the ignition switch when starting and greatly increase the life of the starter motor, starter solenoid, flywheel gear, starter drive and ignition switch.

[Andyblahblah]

Problem solved - turns out the commutator wear was the problem. Looks like even though the starter is engaging and turning, it can do it weakly and therefore unable to turn the flywheel.

Bought a $65 replacement from eBay to see if it'd work (an upgrade is $250 from Midwest Bayless) and presto - turns over like a newlywed.
Here is the link, though I missed out on some cheaper ones. Can also search: "Starter Motor-Starter 16465 Reman"
https://www.ebay.com/itm/Starter-Motor- ... 2749.l2649

@DieselSpider - thanks for that tip, I have some extra relays from another project.

Thanks all!

[geospider]

++ on the relay. Put one on and it starts faster than any newer car we own.

regardless of what starter you use and is working: add the relay.

[DieselSpider]

++ on the relay. Put one on and it starts faster than any newer car we own.

regardless of what starter you use and is working: add the relay.

That extra current will help things run cooler and last longer. Once the starter solenoid starts to cook then it engages more weakly and the contacts that feed the starter motor start to burn after which it snowballs leading to cooked brushes, faster commutator wear along with promote ignition switch failure.

Starters only should run for a few brief seconds so extreme commutator wear on a vehicle that's not used for in town delivery service type driving should be viewed as a warning sign that there is a problem with the current feeding the starter motor.

With the diesel conversion it became even more critical since the starter is not in the 850 Watt range but draws 2 Kilowatts and is much more costly to replace. $15 for a 40 amp relay, socket and fuse holder is really cheap insurance compared to whats at risk.