Technical dead battery and engine knock

[gregjo1948]

2016 Fiat 500X 2.4 L--40,000 miles--no previous problems--Drove 10 minutes to doctor appointment -came out within an hour to find completely dead/flat battery--after jumping from another vehicle, got it started--ran on all cylinders but has loud knock in the engine--got to my shop and removed the negative battery cable and charged the battery--when installing the negative cable, there is a lot of spark--nothing is on that would be drawing that much juice--no lights, no ignition, nothing to cause that much draw--there are no dash lights on (no check engine , etc.) the engine will start right up and run as it should but with the nasty knocking and if left with battery cables attached, it will rapidly drain the battery. Anybody have an idea what has happened? Does the battery draining have a connection to the engine knocking or just a coincidence? Could it be a starter/solenoid problem? Thanks for any replies, gregjo1948

 

[RalphM]

Could it be the alternator? they often have a one way drive and if the diodes
have failed it could be draining the battery and giving that drive a bad time.

 

[gregjo1948]

That's a thought for the battery drain but, doesn't explain the knock. I would think, if it was the alternator, there would be an alert on the dash.
thanks for your reply, gregjo1948

 

[Ralf S.]

What kind of knock is it? Where is it coming from (but don't get your face caught in a pulley while you're trying to find out)?

My alternator pulley failed (bearings) and that made a "clank", rather than a "knock". The pulley bearings had collapsed, and the pulley was rotating at an odd angle, and was hitting the inside of the chassis arm (it left a round ring in the paintwork). That didn't cause any lights on the dashboard until I stopped to see what it was and cut the belt off so I could get in home - no belt made the light come on.

So... check the pulley. If you can detect any play in it, it's knackered. It may be easier if you remove the belt.

Otherwise, if you have a drain you need to find out on what circuit. You can use an ammeter to measure the current out of the battery... just remove one fuse at a time, see if the current draw falls.. if not, replace the fuse and try the next one. Eventually you'll find teh fuse/circuit that has the drain on it... though that wouldn't tell you what the knock/clanking is..

Starter could fail and short the circuit, the same as the alternator.. but usually a knackered starter only knocks/clanks when you turn the engine. The easy test is to just disconnect one of the wires on the starter to see if that stops the drain... but be careful as the red lead is permanently live and it'll spark if you earth it while undoing it. Disconnect the battery first.


Ralf S.