General E46 Forum
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|10-29-2013, 11:27 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 DMM (digital multimeter), 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.
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 fuel 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.
If the engine stalls, or will not start when the gas is under ¼ tank, the fuel pump is weak and should be replaced.
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.
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.
Locate the electrical connections on the starter solenoid.
There are 2 large and 2 small terminals. The large terminal that is toward the top should have constant battery voltage.
The small terminal that is facing toward the driver’s side 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”.
The starter can also get stuck. 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 the small terminal on the starter solenoid with the key in the start position, the most likely problem is the ignition switch.
A failing ignition switch may cause intermittent no start and/or other strange symptoms.
Wiggle the key as you start the car, that sometimes works if the switch is bad.
b, Clutch switch
A defective clutch switch, or not pressing the clutch pedal far enough will prevent starting.
c, Auto safety switch
This is the equivalent of the clutch switch on an automatic, allowing the engine to start only in “P” and “N”.
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 at the plugs.
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 may be similar to that of a bad ignition switch, no power at 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. Check these.
-Some of the fuses on the fuse panel, like #30, or 54 can prevent the engine from starting. It’s a good idea to inspect all fuses in the glove compartment if you’re dealing with a hard to diagnose no start problem.
-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
DME (ECU) failure is uncommon on the E46, but not unheard of.
A scan would reveal if the DME is faulty.
d, 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.
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 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, located on the positive battery terminal, has likely been activated.
e, Bad gas
No start after the car was sitting for a long time.
f, No gas in tank
Fuel gauge is inaccurate, reading too high.
g, Aftermarket alarm system
Aftermarket alarm system is not disarmed, or malfunctioning.
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|10-29-2013, 12:14 PM||#2|
Join Date: Jan 2008
Location: New Jersey
My Ride: German
Nicely done. Need more threads like this.
|10-29-2013, 12:20 PM||#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.
Selling a set of Style 98 Wheels with tires!
|10-29-2013, 12:23 PM||#4|
Join Date: Aug 2013
Location: Kissimmee, Fl
My Ride: 2004 330I ZHP
E46 NO START - A list of possible causes
Very good write up
Sent from BimmerApp mobile app
Do as you please with your car...it's no ones business!!!
|10-31-2013, 06:39 PM||#7|
Thanks guys! This was a fun project and it'll hopefully help some people.
|11-03-2013, 06:55 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, 07:39 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!
2001 325ci - ZSP/ZPP - Build Date: 05/01 - 182k miles - ZF 5HP-19 - Jet Black - Black Leather - Bone Stock - OEM Parts
Last edited by Unforgivable818; 11-03-2013 at 07:41 PM.
|11-03-2013, 11:18 PM||#12|
I appreciate all the positive feedback!
Unforgivable, I agree, it's a good idea to replace the VR preventetivaly.
|11-04-2013, 07:19 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, 07:32 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
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