My 2008 BMW 118d wont start. The start motor cranks for 1 second and then gives up

(2008 BMW 118d) Hello. I have a problem with my car, it wont start. The engine cranks sometimes 0.5 sec and sometimes 1.5 sec and it gives up. And i have no idéa what it is. I replaced my battery 3 months ago so that shouldn’t be the problem and the car doesn’t warn for bad battery charge.

This problem happend 4 weeks ago and it took like 15 tries for the engine to start, and this was going on like 2 days but i could start the engine after 10-15 tries and then the problem went away and i didn´t think much about it, but now the problem is back and i can’t get the engine to start at all.

I tried and checked the fuses for the fuses related to “Start and stop” and i checked the 20 amp fuse for the engine.

And i tried to connect the battery directly to the start motor with some separate wires and the start motor just went on cranking but the motor didn’t start.

I captured a video and posted it on Youtube so you could see for yourself.…A4ckstr%C3%B6m

I am very thankful for all the help i can get.

Thank you very much

Sincerely Viktor

Is the current problem the engine cranks ok w/the key in “start” – that rrr rrr rrrr sound – but it won’t catch and run on its own?

If so, that’s usually some sort of problem with the ignition system or the fuel system. Have you checked for spark? Fuel pump? Plenty of gas in the tank?

It’s a Diesel.

Ok, didn’t notice the “d”. Good news. The diagnosis is even easier … lol … likely a problem with the fuel system. Suspects include the fuel pump, fuel filter, injection pump.

You might check the glow plug circuit. Can it be assumed that once it has been running a bit and warmed up that it will start quickly?

A more ominous cause could be abnormally low compression but hopefully that is not the case.

The starter solenoid is failing. There are two circuits in the starter solenoid, one is the “pull” and the second is the “hold”. The “hold” circuit draws much less current and if the solenoid contacts are burned/failing there won’t be enough force to maintain good contact. Replace the starter assembly.


Hi Viktor, get a volt meter/test light on the small starter actuator wire and get someone to check there’s continuous battery voltage while it’s cranking, also I see you hit the button, does it continue to crank if you continue to hold the button pressed? If it does these cars have “comfort start “ which is a separate thing and could point to something other than the starter circuit.

Am I reading the complaint wrong? The OP said 10 to 15 tries with no start but also said he connected the battery directly to the starter but still a no-start situation even with the engine being cranked over by the starter.

An unknown is what is meant by separate wires. Does that mean heavy cable lead to the solenoid to directly power the starter armature or does it mean a small wire to energize the solenoid? Or both?
The video does not work well for me as the sound is breaking up badly.

Hello. In the video i didn’t show when i connected the battery directly. In the video i just show what usally happends when i press the start button.
The battery cable experiment i did some hours before the video

When i connected a cable directly to the start motor the startmotor started cranking instantly and kept on cranking until i removed the cable. I had my father help me and we simultaneously attached the wire and i pressed the start button inside with no success.

That fits the symptoms. Rather than replace the whole starter, you could have an auto electric shop diagnose and repair the one you have.

But can it really be the solenoid? When we wired the battery directly to the solenoid, the thing cranked and cranked and nothing happend?

Hello Darron. No there is no difference if i press it lightly or hold it. I cant force the starter by holding in the button sadly.

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So… two problems?

  1. The starter motor doesn’t reliably run.
  2. Even when it runs the engine doesn’t reliably start and run.

When you hooked up battery to the starter motor and it ran, was the ignition switch on, fuel pump running, glow plugs glowing, etc?

Probably not the starter solenoid failing if you can get the starter to operate by jumping power to it.

The starter is controlled by the computer, when the engine reaches a determined speed, the computer disengages the starter. There seems to be a problem with that function, perhaps a false signal from the crankshaft position sensor.


I’d say( being a BMW tech) you need to get someone to read out what’s happening in the CAS unit, that’s the ECU that controls the starter. There not unknown for playing up.

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I have found the solution. I towed the car in to a mechanic and he fixed it, it was the battery cable that goes from the battery down under the chassi and then away to the front of the car. That cable was corroded and damaged so the motor didn’t get enough power. I got off at a good price from the mechanic so that was good. So well, now we know what the problem was and thank you everyone for your help. I showed the mechanic all your replies so he had that as help also when he diagnosed and fixed the car. Thank you again :slight_smile: