BimmerFest BMW Forum banner

No fuel and no Spark 98 540i Crank sensor?

5914 Views 15 Replies 3 Participants Last post by  neonphire8604
I just finished a motor swap on my 98 540i. I installed a JB race flywheel and I think it broke the crank position sensor. The thing is I cant tell if tone wheel is what broke it or if I broke it unintentionally while trying to remove it to examine it. I am a Honda Technician, not a do it yourself-er and am pretty sure I didn't break it but I know how brittle old plastic can be. Has anyone tried to replace the crank sensor and broke it in the process? Either way its broken so I bought a new one.

Would a broken Crank sensor cause the PCM to not energize the fuel pump relay on one of these cars? If it was a Honda I would say no. Its my first BMW so I simply do not know. The alarm was going off sporadically when trying to crank it, I attributed this to my weak battery but is that wrong? does the alarm module communicate with the immobilizer? no fuel and no spark makes me think of all sorts of horrible immobilizer issues and factory scan tools. This car did sit dead for about 3 years so could I have a module coding issue?

I bought the car with the engine pretty much removed from it so I had to figure out for myself where all the plugs went but that was easy so I doubt I have an issue their.

Yes the fuel pump and fuel pump relay work because I know someone is going to ask me that. Does anyone have any suggestions for me?
1 - 16 of 16 Posts
That's one purpose of the crank sensor, to inhibit the operation of the fuel pump and ignition. It also sends data to the ECU to detect misfires.
so the pcm needs to see a crank signal to energize the relay?
Yep. Make sure that the gap between the flywheel pulse generator and the sensor is 0.55 mm.
is there a shim kit i should get or something?
Yes there is a shim kit. There is also a range the crank sensor needs to be from the flywheel check the online TIS database for the actual gap size.
is there a shim kit i should get or something?
But there is quite a large range I can't look it up on my phone but the tolerance on the number you gave is something like 0.55 +/- 0.2 mm...
What I said.
you are correct on the .55+/- .2, I just read about how to adjust for clearance on TIS.

Let me get something straight though, so when I am KOEO the fuel pump does not prime the fuel rail for 2-3 seconds like on a normal car? The crank sensor is indeed a magnetic pick up type and not a hell effect right? If this is the case how does the PCM know its at fault before it cranks and generates ac voltage? I know certain domestic vehicles will see proper hall effect voltage to start the pump but this is because the PCM supplies a reference and most likely a ground.

do these cars not prime the rail prior to KOEC? Mitchel has been less then helpful with circuit operations, i'll try all data tomorrow.

BTW if just because I have no posts on this forum it does not mean that I am new to using forums, it just shows I can search well... My unfamiliarity with German cars is really beating me over the head right now. I just hope this thing is a monster
The E39 ECU does indeed run the pump for about 2 secs when the key is placed in position 2.
a crank sensor is not needed for that to happen... I must have another problem right?
Are there any BMW tech's who can give me some input? Can a bad crank sensor truly be the cause for the ecu not to even prime the fuel rail?
The crank sensor can only do something when flywheel is rotating. No the crank sensor can not prevent the pump from priming...it can cut it off but only after it gets bad readings.

Check the relay for the pump...verify you are not getting pressure. Either attach a gauge or just detach the hose on the rail and put the hose into a bottle to collect the fuel. Then turn key. With gauge obviously you will see pressure if good. With the bottle trick you will see gas pumped in. This should really confirm no fuel pressure.

Detach the relay and perform a check on it apply 12v to switch and you should hear it click on and off. Also measure resistance should be high impedance when open and low when closed. Check online for a good test video. Replace this relay if it failed...if not maybe your pump is no good.
By the way after a motor swap I would just replace the crank sensor anyways. It is a magnet and too bad of an impact could demagnetize it.
Thanks for the response but like I stated in my first post I have already verified the operation of both the fuel pump and relay... I disconnected the lines and the fuel rail was empty so I put them in a bottle, used a jumper lead and back probed 85 on the fuel pump relay to apply ground and wallah I had fuel pressure and volume.... The issue lies with the ECM not applying a ground to energizing the relay... I do not know why this is happening.
Well it runs now! I guess the computer won't even try and prime the fuel system once the crank code is set. It seems like I have no other issues, the cel went off after a few key cycles. Next thing to do is test drive it!
1 - 16 of 16 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top