... 2011 BMW 328i... [~ December] the car would not start, [NO Crank?] called the mechanic and changed the starter...[~ March 2023] would not start again. Called the mechanic who said the starter was faulty so we exchanged it and changed it again. All good for another two months and then again it would not start... I went out to get a new battery and it started. Thought I was good but nope, after about a week I had the same issue, so I took it to the auto electrician. They kept it for a few days and when I went to get it he said all was good, just bad battery connection. [LOTS of "battery connections" -- you need to CROSS-EXAMINE folks and try to UNDERSTAND what they SAY was wrong.] I wasn't completely sure what he meant by that but it was working. This was in the beginning of May, everything was fine and then in mid June the mechanic came to do other work and he disconnected the battery and guess what? About 10 days later I am now having the same issue again. [May NOT be exactly SAME, but at least "similar", probably a bad electrical connection somewhere, loose, corroded, etc.]
So I have changed 2 starters, the starter relay [WHAT relay did you change, located WHERE? Do you mean the KL30G removable relay on right side of JB Fuse Panel? That has NOTHING to do with Starter Activation when START button is pressed. There is NO "starter relay". The CAS Module, KL50, acts as Starter Relay. That is located INSIDE the CAS Module above Driver's Left knee.] and battery to key fob. [Key Fob battery also has NOTHING to do with START button activating Starter. That only powers the Radio Wave Remote Signal when Lock/Unlock buttons on Fob are pressed.] Checked battery and it is good ( It use to start if you jumped it but not anymore) The odd thing is sometimes it will start if you push the start button like 10 times. When you try and start it all the lights come on and then the fuse box is a concert of noise. [Probably "relay chatter" from relay Contacts which do NOT remain closed due to wiring fault.] So I was thinking it is the push start button but yesterday I disconnected the IBS just to see and it started HOWEVER the start is still rough...
Welcome to the Forum!
I assume from your description that at all times when you say "the car would NOT start", you mean the Starter did NOT Crank or Turn the engine, rather than the Starter activated, but the engine did NOT fire?
DIAGNOSIS of a "No Crank" issue is difficult on ANY car. Lots of folks (including $hop$) throw parts 'cuz they do NOT know what Diagnostic Software is available, HOW to use it, or don't understand HOW the BMW E9x CAS Module works, or how to test the wiring between CAS & Starter.
FIRST Questions:
1) Do YOU/ your son want to take the time to learn basic auto Electronics, and HOW to test the system? It will take at least 5 hours of time, reviewing wiring diagrams I can supply from ISTA (BMW Dealer-Level Diagnostic Software & Shop Manual).
2) Do YOU have a cheap DMM (Digital Multimeter)? $7 HFT, $10 Amazon:
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3) Do you have a Windows OS Laptop? If you do, you can download INPA (BMW Factory-Level Diagnostic Software), along with BMW Standard Tools, and ISTA (full electronic Shop Manual) from MEGA sites linked in attached pdf: "1 E9x References". You will THEN have EVERYTHING you need to Diagnose & Understand your car. Only cost is $30 to $50 for a "K+DCAN Cable" to connect the USB port of laptop to OBD II Socket of vehicle.
4) While I would encourage you to D/DIY (DIAGNOSE/Do It Yourself), I recognize that an increasing number of folks have "given up" trying to understand "things". If D/DIY does NOT interest you, at least FIND a $hop that has INPA/ ISTA & knows how to use it. Either of those Software Programs will aid in correctly Diagnosing the cause of your "No Crank" issue.
You/$hop need to use a DMM to do tests based upon the preliminary data from INPA/ ISTA. I can provide ISTA wiring diagrams, and suggest tests to do to get started, and HOW to do those tests. ANYONE with a motor vehicle needs to have a DMM and know HOW to use it to do simple voltage tests. As example, when you have a "NO Crank" situation, there are a number of tests you can do with a simple DMM.
Initial Diagnosis Steps:
I attach several ISTA ScreenPrints which show the CAS wiring, and two connectors in the E-box which you can test with DMM for voltage, or attach a jumper from the Jumpstart Terminal to activate the Starter as a test of Starter Solenoid/ Motor. Here are the initial test steps if you have a NO Crank situation:
0) Review the attached ISTA CAS wiring diagram. NOTE the "M6510a" Starter Motor in upper-right center of diagram. NOTE the Black wire, ID "S-50" which runs from Pin #22 of the CAS Connector X13376, to the Starter "X6510" connector. That wire runs through TWO different intermediate connectors in the E-box: X6011/1 (Pin #1 of X6011 Connector), and X60531/2, on its way to the Starter Solenoid.
01) Think of this KL50 voltage from CAS to Starter Solenoid as same as "Start Relay" output to a Starter Solenoid. When START button is pressed with foot on Brake/Clutch, there SHOULD be 12V+ or battery voltage in that "S_50" wire. The X60531 connector location is shown as "X60551" in the attached diagram. Look for a "Medium-Large" White wire running from Pin #2 of that connector (same size, 2.5mm-squared, as the Black wire into X6011/1). That White wire goes to Starter Solenoid.
02) BEFORE opening E-box, if Starter is NOT cranking engine when START button pressed with foot on Brake/Clutch, measure/ record/ report voltage at Jumpstart Terminals under hood. If LESS than 12.0V, open trunk, remove trim covering battery, and measure/ record/ report voltage at battery posts. If battery voltage at posts is > 12.0 V, but voltage under hood was < 12.0 V, "Snug-up" the 10mm T-Bolt nuts on each battery terminal, and make sure TWO 13mm Nuts on Rear Power Distribution Panel (RPDP) on top of battery are "snug". See attached Photo of RPDP on my 3/2007 build 328xi as example.
1) Remove the Upper & Lower Microfilter Housings & open the E-box. If you need ISTA Procedures on either of those steps, please ask.
2) Identify the two connectors, the Black wire from CAS at X6011/1, and the White wire from X60531/2.
3) Use DMM to measure Voltage in Black wire at X6011/1. That voltage should be 12V+ or battery voltage when START button is pressed with foot on Brake. Record your finding and let us know.
4) You can "Hot-wire" the Starter Solenoid.
YOU MUST HAVE AT in PARK or MT in NEUTRAL and Handbrake firmly set, as you are DEFEATING Safety Switches in this Procedure. If you apply battery voltage to the White wire at X60531/2, going to Starter Solenoid, Starter should Crank. You can apply a jumper wire from Jumpstart Terminal to X60531/2.
There are other tests you can do WITHOUT INPA or ISTA, to determine WHY the Starter is NOT being activated. Please let us know how it goes.
George
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