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|10-29-2013, 10:27 AM||#1|
E46 NO START – A list of possible causes
If your car won't start, the fix can be as simple as replacing the battery, but there are many other potential causes and troubleshooting can be challenging.
The following is an overview, intended to help with the diagnosis.
1. Low voltage
a, Bad battery
If the starter isn't cranking, or there is only a click, first check battery voltage with a digital multimeter (see photo in post 39), or using the OBC hidden functions. It needs to be at least 12V for the starter to be able to crank, while full battery voltage is close to 12.6V.
b, Faulty alternator
The battery may have died because the alternator isn't charging it.
To test the alternator, first start the car by charging the battery, by jump start, or push start. Measure battery voltage with the engine running, it should be close to 14V, or slightly over.
c, Bad connections
If the battery and alternator are OK, but voltage is low at the starter, there could be a loose, or corroded connection in the electrical system, causing a voltage drop.
The ground strap under the engine on the passenger side, or battery terminals are suspect.
d, Parasitic draw
If the engine runs fine when the battery is charged, or after a jump start, but the battery is dead by morning, there could be a short in the system draining the battery overnight.
This is referred to as parasitic draw and on the E46 it is usually caused by a faulty final stage resistor (FSR) of the blower motor.
Aftermarket equipment can also draw enough power to cause a no start.
2. Fuel related
a, Fuel pump
If the starter is cranking, but the engine isn't starting, the most likely issue is the fuel pump.
There are a number of ways to verify:
- listen for the pump to prime when key is turned to position #2
- check for fuel at the fuel rail at the Schrader valve
- measure the actual fuel pressure (or lack thereof) at the rail
- spray starting fluid into the intake, if the engine stars briefly, fuel isn't reaching the engine.
You can also remove the fuel pump cover and whack the pump, this may get it going temporarily.
This "method" can come in handy if you're far away from home.
b, Fuel filter
A clogged, or restricted fuel filter usually causes engine performance problems, but it can also contribute to no/hard start.
c, Fuel pressure regulator
On 325i/330i this is part of the fuel filter, so by replacing the filter, the FPR will also be renewed.
On 323i/328i it's separate from the filter.
These rarely fail on the E46, but it's a possibility.
No start due to no, or low fuel pressure can be caused by a defective fuel pressure regulator.
d, Bad gas
- No start after the car was sitting for a long time.
- If your car runs rough and/or won't start right after filling up with gas,
the fuel might be contaminated.
e, No gas in tank
- If the engine stalls, or will not start when the gas is under ¼ tank, the fuel pump is weak and should be replaced.
The gas tank has two lobes and a weak pump isn't able to transfer fuel from the other lobe.
- Fuel gauge maybe inaccurate, reading too high.
If battery voltage is sufficient at the starter's electrical connections and the starter is not cranking, it is most likely defective.
Replacing the starter isn't easy, so make sure the diagnosis is correct before you undertake this task.
Suggestions for troubleshooting:
Remove the airbox and the intake boots to gain access to the starter.
Measure voltage on two of the terminals on the starter solenoid.
Terminal "B" should have constant battery voltage.
Terminal "C" is energized by the ignition switch via EWS module when starting the engine.
Remove the wire from this terminal, measure voltage on the wire with the key in start position.
If battery voltage is present at both, the starter is probably defective, although there are some other possibilities,
described in "Additional causes of no start".
You can also test the starter by jumpering, or "hot wiring" it.
This is done by applying direct voltage to some of the terminals.
When voltage is applied to terminal "D", the starter motor should spin without cranking the engine.
When voltage is applied to terminal "C", the starter should crank the engine.
The starter can also get stuck. If voltage is sufficient, but the starter only clicks, this may be the case.
Tap the starter while a helper attempts to crank the engine. If it is stuck, this may get it going.
4. Switches and sensors
a, Ignition switch
If there is no power at terminal "C" on the starter with the key in the start position, a possible problem is the ignition switch.
In this case the starter won't crank, but crank/no start is also possible with a bad switch.
A failing ignition switch may cause intermittent no start and/or other strange electrical symptoms.
Wiggle the key as you start the car, that sometimes works if the switch is bad.
Check battery voltage at fuse 29 while starting. This is the ignition switch input to the DME. (see photo in post 60)
Check battery voltage at pin 15 on the coil harness with the ignition on. (see photo in post 61)
No crank/no start
Check battery voltage on the black/blue wire at the ignition switch connector with the key in the start position.
This wire supplies voltage to terminal "C" via the EWS module while starting.
No voltage in any of the tests indicates a defective switch.
b, Clutch switch
A defective clutch switch, (or not pressing the clutch pedal far enough) will prevent starting.
If battery voltage is OK and starter doesn't crank, this is one of the possible issues.
To test the switch, bypass it by inserting a jumper wire in its connector. (wires violet/yellow and black/blue)
c, Auto (neutral) safety switch
This is the equivalent of the clutch switch on an automatic, allowing the engine to start only in "P" and "N".
A defective auto safety switch will exhibit the same symptoms as a bad clutch switch - no crank.
d, Crank position sensor
The DME needs the signal from this sensor to fire the plugs.
A faulty crank sensor usually throws a code, making diagnosis simple.
If there is no code stored for this sensor, but no spark is suspected, check for spark.
See post 62 for info on how to check for spark.
If there is spark, the crank sensor must be doing it's job.
e, Camshaft position sensor
A defective cam sensor most often results in driveability problems, like stalling, loss of power and rough running, but it can also prevent the engine from starting. This usually causes CEL, too.
5. Fuses, relays and modules
a, Immobilizer (EWS)
A faulty EWS module, a key that is not coded to the module, or damaged will prevent the engine from starting.
The symptoms will be similar to that of a bad ignition switch, no power at terminal "C" on the starter solenoid.
Try a second key, if neither starts the car, the EWS is probably not the issue.
A scan is necessary to detect EWS faults.
- E-box fuse pack: under the hood on the driver's side where the DME and other electronic components are located,
there is a fuse pack, containing 5 fuses. These are related to engine management.
Fuse #3 sends power to both fuel pump relay and the crank sensor.
- main fuse panel: check fuses 9, 22, 27, 29, 30 (ignition switch), 54 (fuel pump), and 49, 67 (EWS).
Inspect all fuses in the glove compartment if you're dealing with a hard to diagnose no start problem.
- high amp fuses above main fuse panel (fuseable links).
There is an 80 amp for the DME and DME main relay, and a 50 amp fuse for the ignition switch.
- main harness fuse: behind the carpeting on the passenger side shock tower there is a large fuse.
The cable here supplies the relay panel, so if this fuse is blown, almost everything will be out.
c, DME main relay
Unlike the older models, this isn't problematic on the E46.
However, it should be tested if there is no spark.
d, Electronic Control Unit (DME)
DME failure is also not common, but possible.
A scan with a BMW specific scanner usually reveals if the unit is faulty.
There may be no codes stored. If there is no spark, or injector signal
and all DME inputs and wiring are OK, the DME needs replacing.
e, Fuel pump relay
No power at the fuel pump may be caused by a bad fuel pump relay.
When checking for power at the pump, the engine needs to be cranked.
Terminals at the relay board can be jumpered to test the pump/relay.
If the pump runs with the terminals jumpered, but not when the relay is in place, the relay is defective.
6. Additional causes of no start
a, No compression
An engine needs spark, fuel and compression to run.
If your car won't start and for certain there is spark and fuel,
test engine compression.
At times a condition called cylinder wash down can occur.
A lot of cranking without starting dumps a lot of fuel into the cylinder,
which washes the oil off the piston rings, leading to loss of compression.
b, Engine seized
An internal mechanical failure can cause the engine to lock up.
Try to turn the crankshaft manually to see if the engine is frozen.
The crankshaft can not rotate due to liquid in the combustion chamber.
This can be fuel, coolant, or oil, caused by a leaking fuel injector, headgasket, or a malfunctioning CCV system.
Remove spark plugs and crank the engine if this is suspected.
d, Battery safety terminal
If your car won't start after an accident, the battery safety terminal (BST), located on the positive battery terminal, has likely been activated.
There can be a bad connection at BST causing a voltage drop. In this case battery voltage is sufficient at the battery, but low at the underhood jumper terminals (see photo in post 60), causing a no crank condition.
e, Vacuum leak
Vacuum leaks usually cause rough running, or misfires, but a large vacuum leak can prevent starting.
If your car won't start after working around the intake, this is the most likely problem.
In this case the engine may start up momentarily, but stalls immediately.
f, Aftermarket alarm system
Aftermarket alarm system is not disarmed, or malfunctioning.
The link below is a troubleshooting guide by Bavauto.
It's not E46 specific, but explains the basics well.
No start troubleshooting guide
I've had my share of no start problems over the years, from no compression to bad starters and ignition switches.
Once I parked my 88' 535i for one week and it refused to start afterward.
By the time I got the car running, I inspected, tested, or replaced about 25 parts.
I read a hundred threads and still had a hard time finding the information I needed.
That's what inspired me to put a complete list together for reference.
I hope it has helped you.
If you've had a no start problem and it was caused by something
not listed here, post in this thread and tell about it!
Please include year, model, mileage and a description of the repair!
Last edited by lszlszx; Yesterday at 10:46 PM.
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|10-29-2013, 11:14 AM||#2|
Join Date: Jan 2008
My Ride: German
Nicely done. Need more threads like this.
|10-29-2013, 11:20 AM||#3|
Join Date: Oct 2012
My Ride: Jet Black 2002 330i
Re: E46 NO START - A list of possible causes
This should be stickied. Good work OP.
2002 Jet Black 330i|ZPP|Hellbeige interior|Carbon Fiber Interior Trim|Alzor 703 CSL Reps|Custom Flowmaster Catback Exhaust|LED Halo Rings|Black ECSTuning Kidney Grilles|Eonon D5150|
|10-31-2013, 05:39 PM||#7|
Thanks guys! This was a fun project and it'll hopefully help some people.
|10-31-2013, 06:14 PM||#8|
Join Date: Mar 2013
My Ride: 2003 325xi
saved it in my folder.
KJ----Trust nothing that you read, and only half of what you see---Trust but Verify for yourself.
2003 Touring 325 XiT (KJ's Ride)
2004 Coupe 325 Ci (Mrs. KJ's Ride)
|11-03-2013, 05:55 PM||#9|
Hi Guys ! if the key has gone bad will that render the car not to start ? I have put in a new battery ! lights work windows etc but she wont fire up !!! thanks Kerri ..and I will keep reading the FAQ
|11-03-2013, 06:39 PM||#10|
Join Date: Oct 2010
Location: Winnetka, SoCal 818
My Ride: 2001 325ci
Don't forget about the voltage regulator per Mango's mention @ http://forum.e46fanatics.com/showthread.php?t=923563 : "
The voltage regulator is located on the back of the alternator. It regulates voltage to ensure proper operation of the electrical system. Basically by around 6-10 years, they start to fail. This will kill a new battery. Replace it.This one is a bit tricky because you'll have to pull your alternator out to know which kind you need. There's a rounded D-shaped connector and squared off rectangle connector. Pray you have the squared off rectangle connector because it's cheaper. The D-shape connector is found by searching under the BMW Z4. "
Thanks for posting this as it's great info for all those who don't search first!
2nd Owner - 2001 325ci - ZSP/ZPP - Build Date: 05/01 - 187k miles - ZF 5HP-19 - Jet Black - Black Leather - Bone Stock - OEM Parts
Last edited by Unforgivable818; 11-03-2013 at 06:41 PM.
|11-03-2013, 10:18 PM||#12|
I appreciate all the positive feedback!
Last edited by lszlszx; 02-06-2014 at 07:08 PM.
|11-04-2013, 06:19 PM||#13|
I ordered a plastic spare key today form the dealership! $ 70.00 I needed a spare and it was that or a $ 200 one , a friend is bringing the scanner over tomorrow as well ! I am so hoping its the key , I will let you know the outcome ,
|11-06-2013, 06:32 PM||#15|
Ok! so it turns out its the starter motor, bloody thing left me stranded in the sun outside chuckee cheeses it did ! My mechanic has it out ! the brushes were worn out ! so he rebuilt it and was about to put it back in when I asked about the solenoid , thats when I stopped the job in its tracks, it appears that a solenoid was unattainable for the danzo motor and he assured me the solenoid was fine and would last ,no problem! He wants $159 for his rebuild and 300.00 for the in out ( which after seeing the extent of the work , I thought was ok ) my issue is the solenoid , I did some checking and a bosch rebuild is only $125. does anybody know if the Bosch rebuild would be a rebuilt or new solenoid , I really want to drive my car and am tempted to let him put the old one back in , but seeing the work involved in changing it again I am thinking I should go the Bosch route ! any input would be appreciated ..I really do love my car !! ..Kerri
|01-02-2014, 11:51 PM||#17|
No start is a common problem, yet information on this is scattered through hundreds of threads/posts.
I thought it would be great to have all the info in one place.
Last edited by lszlszx; 02-06-2014 at 07:12 PM.
|01-03-2014, 12:34 AM||#18|
Join Date: Jan 2014
Location: boca raton FL
My Ride: 2000 323i
Re: E46 NO START - A list of possible causes
Neutral safety switch is a very common Problem for a no crank no start situation second is the crankshaft sensor check for fuel and spark always if it pass than you are into trouble it will be something mechanical
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|01-04-2014, 11:08 AM||#19|
I don't see people having problems with neutral (auto) safety switches.
A defective crank sensor will not prevent cranking.
|01-17-2014, 09:17 AM||#20|
Join Date: Jan 2014
My Ride: E46 318i facelift
My E46, 318i, 2002 model wouldn't start (it cranked) but after BMW mechanic connected the diagnosis laptop to my car and re-programmed the EWS/DME (?) the car worked fine. The mechanic tells me that DME might have a problem (I had the EWS changed 2 weeks ago before this issue) and i should change the DME ($1500) please help
Could it be a software synchronization issue between EWS and DME?
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