[Mastermixlee]

Really hoping for some help here if possible.

I have a 335i and friday night I drove to the gym and parked up. An hour and a half later I got out and got in the car. Put the key in the ignition, put my foot on the brake and pressed the start button. The car cranked but did not start. I tried again but no luck. Suspecting low battery as it had just got colder that night I had someone come to me and charge my battery, again no luck. I had to get it recovered home in the end by my breakdown service.

I have been checking everything I can think of over the weekend and cannot get it started. I have JB4 installed and tried plugging in the usb cable and reading the codes but it would not connect. I tried removing the JB4 to see if it was that causing the problem, still no luck. I checked all the fuses in the very difficult to get to compartment at the back of the glovebox...all ok.

I removed the rear seat and removed cover for fuel pump and when attempting to start I can hear the pump making a noise.

I have checked voltage at the power cable that feeds the jb4 (and ECU? that connects to the same power cable as JB4) and there is no voltage there when key in ignition and start button pressed (without foot on brake) but lights come on dash.

Im assuming there should be power there whilst in that state as normally thats the state where you would connect the jb4 to computer to update firmware.

I replaced my High Pressure Fuel Pump approx 1 year ago.

Anyone have any ideas? I currently have my car on driveway which obviously wont start so cant even drive it to the garage :-(

[Meshyo]

How long ago did you install your jb4?

[Mastermixlee]

installed jb4 about a year ago. not an issue with that. :-(

[J44KPR]

I guess to see if the battery is low you can leave the ignition on with music playing for about 1 min, then dash should flash low & switch off
I was told it had to be charged through the connections in the engine bay too

[phil200tdi]

Eh?

I thought you said the car cranked but wouldn't fire.

If you had a dead battery it would click. I'd be checking the fuel pump...

[Mastermixlee]

Car cranks but doesn't start. Checked for power at power connection where jb4 connects in ecu box area and no power? Got power at the 50amp fuse connection but none on the red wire to jb4 that connects to the orange power connection. Can hear fuel pump under seat making whirring noise with the cover removed. Dont know how to check whether it's working 100% though. I'm confused as to why there wouldn't be power to jb4 though when key in ignition and start button pressed. It normally connects when you update jb4 firmware in this way...

[G82Dude]

Could it be the high pressure fuel pump?

[Mastermixlee]

Well I changed the high pressure fuel pump about a year ago when had misfire and long crank starts. But this just isn't starting at all. And I'm confused as to why I don't have voltage at the jb4 power cable. Anyone know how the ignition sequence goes on this car? Or anyone have a wiring diagram?

[q_jonblaze]

points to the ecu if you ask me....the fact that you cannot read it means that there is something wrong there.

[Meshyo]

Any update on this?

[Mastermixlee]

Yes! The beast is up and running again. Was an extremely stressful time lol felt like I was missing a limb whilst it was off road! Found two wires had fused together near the resister next to the coil packs. Weird how the car drove fine there and then just wouldn't start afterwards :-S maybe they were worn and the vibration of going to start the car just done the last bit. Cut the wires out and rewired it. Taped up the wires to prevent from happening again and it runs like a beauty again! :-D was getting so stressed with it I was borderline just gonna sell it and go put down deposit for a new m5... But insurance on that beast would kill for my age. But once it was all up n running again I went for a looooong drive and fell in love again :-P

[Meshyo]

Originally Posted by Mastermixlee

Yes! The beast is up and running again. Was an extremely stressful time lol felt like I was missing a limb whilst it was off road! Found two wires had fused together near the resister next to the coil packs. Weird how the car drove fine there and then just wouldn't start afterwards :-S maybe they were worn and the vibration of going to start the car just done the last bit. Cut the wires out and rewired it. Taped up the wires to prevent from happening again and it runs like a beauty again! :-D was getting so stressed with it I was borderline just gonna sell it and go put down deposit for a new m5... But insurance on that beast would kill for my age. But once it was all up n running again I went for a looooong drive and fell in love again :-P

Great news! M5 wouldnt be a bad shout surely :P

[ssc330d]

Originally Posted by Mastermixlee

Found two wires had fused together near the resister next to the coil packs.

How the hell has that happened? Could you post a pic of what happened please?

[Mastermixlee]

Actually haven't got a picture of what happened. Completely slipped my mind to take a picture at the time as I was so stressed with trying to sort it out lol I'm guessing it was just from rubbing together with vibration of the engine. If you remove the engine cover there's the spark plug/coil packs located along the left side, and there's a little resistor held in a purpose made clip/bracket just to the left of them. The resistor was still in the bracket but the wires were melted together further up. I'm guessing they wore down over time, and then when I went to crank the engine it just went through the final bit of sheathing and sparked, which then melted the rest of it and fused the wires together. Seems I'm the only one this has happened to but at least it's on here now and may help someone else :-)