Bad Cable or Bad Starter Solenoid?

[takeyourmarx]

Fairly new 2002 owner here, so be gentle🤣

 

My 02 has lost electrical power a few times now while out driving and the whole car shuts down, leaving me trying to coast to get off the road.

Usually it will not restart right away. When trying to restart sometime the dash lights come on (sometimes not), but even then there is no crank, not even a click.

And then out of nowhere it would eventually first right up and I'd clench my butt cheeks driving it home.

 

So I did all the usual cleaning of connections, grounds, and even cleaned the ignition switch wiring. I also bought a new battery because it was due anyway.

 

Well after all this, the problem persisted, but I did hear one single crank yesterday, which led me to check the starter solenoid again, which I just cleaned the leads on.

I wiggled the positive wire with the car in the on position (not started) and was able to get the dash light to come on and off again.

I also got the car to fire up, went back to wiggle the battery lead on the solenoid post (below), and got the engine to die and loose power, recreating what happens on the road.

 

 

 

So, with all of the collective knowledge here:

 

Do we think it could be the battery lead wire? Battery sits in the trunk, but battery is new and terminals clean. It seems in good condition and I cleaned it up the lead that attaches to the solenoid post yesterday before this test. Plus its pulling +12V and ~13.5V at idle. 

 

Or is it probably solenoid going bad since this is the junction where all the electric flows from. The actual started motor seems fine when it has juice.

Is there a test I'm missing to determine if its good or bad? I'm still getting used to how everything is wired up.

Is there a part to replace just the solenoid, or should I really just replace the whole starter?

Part of me prefers the solenoid because its easier haha, but from searching its not clear that there is an individual part available that's compatible.

 

Appreciate the help and insight! Happy to post a video if that helps troubleshoot at all.

 

[Son of Marty]

Do you have a large ground wire from the block to the body or battery?

[Mike Self]

The original battery setup for a 2002 has a dual battery ground strap:  a large flat strap from the battery to the block, and a smaller one from the battery to the body.  With your trunk setup, you need a heavy ground strap from the body to the block, and another one from the battery's negative terminal to the body--back in the trunk.  

 

In addition the OEM setup had a fairly thick (10 or 12 gauge) wire bolted to the positive battery terminal.  That wire carries all the current from the battery to both the fuse box and directly to the ignition switch.  I suspect that's one of the wires of the bundle fastened to the starter solenoid in your picture.  If that wire is loose or making poor contact, that would cause your dash lights not to function when you loose all your electrics.

 

A quick test:  next time this happens, turn on your headlights and see if they work.  If they don't then I would suspect that main feed wire.  Finally, are the battery terminals crimped on to their respective cables, or are they fastened on with a clamp held with two bolts.  If the latter, I would suspect corrosion or looseness under the clamp.  Undo the bolts and clean---or replace them with crimped on terminals.

 

mike

[visionaut]

It can’t be a bad solenoid if it dies while driving it..

[takeyourmarx]

I yes it's ground to a post in the trunk beneath the floor, I checked that as well yesterday.

And then there is another very large ground wire up in the engine bay from the block to body.

 

@Mike I Haven't checked the crimps however, so I'll check those next as well.

Luckily I have some lugs and heat shrink in the case those need a replacement.

Edited August 9, 2023 by takeyourmarx

[takeyourmarx]

1 minute ago, visionaut said:

It can’t be a bad solenoid if it dies while driving it..

Ok great, this helps narrow, wasn't fully sure if it could have that affect or not. 

[visionaut]

2 minutes ago, takeyourmarx said:

Ok great, this helps narrow, wasn't fully sure if it could have that affect or not. 

Loose wires ON the solenoid are a different matter..

[Mark92131]

You seem to have a lot of 12V accessories attached to the input to the starter with questionable ring connections.  This probably isn't your problem, but probably isn't helping your non-start issue.  I am having the exact same issue with my son's 1991 BMW 318IS.  My theory is heat sink into the starter/solenoid.  I would start with no issues all winter.  Now that temperatures have increased, the dash lights on, but no start/click happens after driving it awhile.  He let's it cool down and magically it starts again.  We replaced the DME relay that has been reported to cause similar issues, but that didn't fix it.

 

I'm going to pull the starter next weekend and replace it.  I'm thinking of using some thin fiber washers to isolate the starter motor from the block (phenolic spacer) to reduce the possibility of heat reaching the starter and solenoid.

 

Mark92131

[visionaut]

Check resistance/continuity not just physical connections at your grounds. Especially that battery grounding stud in the trunk..

Note: there’s also a wire missing from the right yellow ring connector in your pic

[Son of Marty]

I would run the main 12v wire to the starter and then 1 10 gauge wire to a busbar mounted on the fender, then take the rest of your power off the busbar, no stacked connections to work each other loose.

 

[jimk]

2 hours ago, Mark92131 said:

I'm thinking of using some thin fiber washers to isolate the starter motor from the block (phenolic spacer) to reduce the possibility of heat reaching the starter and solenoid.

 

The high amperage ground path from the starter motor is thru the mounting to the block.  For sure won't crank if it insulated from the block.

 

When the engine dies while driving, that means the power of the Christmas tree of wires to the chasis services is loose to give an intermittent open circuit.

[Daily02]

Since the dash goes dead when it stops running: Check the ignition switch. It could be part of the problem.

 

Regards

 

Dono

[takeyourmarx]

Thanks all for the suggestions and tips so far.

 

So I went out and started playing around again.

 

The other smaller gauge ring connector coming off post with the single red wire has a 30a inline fuse going to a small bus and then off to a relay. (Pics 1,2,3)

 

Then there are the two red wires coming into a Y  and singular O-ring it that is on the post. (Pic1, left side)

 

When I played with these two wires I was able to get the engine to die and the dash lights to come on and off. I tried to follow where these went to but lost track in jungle of hodge-poge wiring.  Where do these run to? Ignition? Would that cause the car to think its off and drop power maybe? (Pic 4&5&6)

 

 

 

Anyway there was a little corrosion on the ring connector and wire so I chopped it off and put on a fresh lug and heat shrink. I couldn't get the car to die with the same wiggle test, so it seems like a suitable band-aid for now at least. Once I get a bus bar I think I'll give the two wires separate lugs- I can already see a little corrosion beneath the yellow connectors which seem a bit janky.

 

Will update if the problem comes back right away.

 

 

 

 

[Mark92131]

46 minutes ago, jimk said:

The high amperage ground path from the starter motor is thru the mounting to the block.  For sure won't crank if it insulated from the block.

 

Wouldn't the three mounting bolts provide an adequate ground path for the starter motor?  I'm trying to isolate the aluminum mounting surface from the heat of the block, (thin fiber washers or paper gasket?), to see if that helps or fixes the issue.

 

Mark92131

[tzei]

If battery is in trunk those(?) main 12v feed(s?) is way too thin. Wire loom looks like it’s crying to ”please somebody put me out of my misery!”. At some point (like now) u need to adress that. There seems to be fixes of fixes - get rid of those asap. Take a fresh proper gauge wire from battery to starter 12v pole (and battery ground). Solenoid has a spade or m6 connector to turn it on. You can jump it with a screwdriver from 12v pole to turn (car in neutral, mind you) to see if works or not and go from there. All will be futile if main feed to starter and battery & engine to chassis ground is questionable.