m20b20 L-jet starting issues
Posted: Dec 27, 2024 8:32 PM
Hello all, I have been lurking the forum for some time in the process of fixing my 520i L-Jet and have finally come upon an issue I cant find the answer to.
Basically when I turn the key to start the car everying happens as normal, idiot lights come on, fuel pump primes and car starts as normal. The issue I face is that when the key returns to the run position the car stalls, lights stay on and all systems still have power but the car ceases to run. I had recently sone some work in the fuse-box reparing a loose connection and though I had maybe bumped something else loose but I cant find any system that isnt getting power. Checked injectors, fuel pump, main-power/fp relay, coil and distributor. I dont beleive there is a break in any of the circiuts, which is backed up by the fact that when I hold the key just out of the starter position I can get the car to idle/rev. Can't find a reason that the ignition switch is bad as all positions of the switch send 12v when selected.
This led me to believe that maybe the one of the sensors that the ecu references when in the idle loop is bad. I thought that may cause the ecu to fall on its face when car is in run position but cant find any evidence to support that. Bentley manual unfortunatly does not cover the Australian delivered m20b20 models but I do have the haynes manual covering this specific model just forget it when going home to fix the car
. I pulled the sensor connected to the side of the distributor which I beleive is the reference sensor (correct if wrong) but car failed to fire when starting telling me that its fine. Next step is to test the ecu, have purchased a second hand ecu just waiting on it to arrive to see if that fixes the problem.
(I did notice there was an extremely similar thread covering almost exactly the same issue but the answer was never posted
)
Basically when I turn the key to start the car everying happens as normal, idiot lights come on, fuel pump primes and car starts as normal. The issue I face is that when the key returns to the run position the car stalls, lights stay on and all systems still have power but the car ceases to run. I had recently sone some work in the fuse-box reparing a loose connection and though I had maybe bumped something else loose but I cant find any system that isnt getting power. Checked injectors, fuel pump, main-power/fp relay, coil and distributor. I dont beleive there is a break in any of the circiuts, which is backed up by the fact that when I hold the key just out of the starter position I can get the car to idle/rev. Can't find a reason that the ignition switch is bad as all positions of the switch send 12v when selected.
This led me to believe that maybe the one of the sensors that the ecu references when in the idle loop is bad. I thought that may cause the ecu to fall on its face when car is in run position but cant find any evidence to support that. Bentley manual unfortunatly does not cover the Australian delivered m20b20 models but I do have the haynes manual covering this specific model just forget it when going home to fix the car
. I pulled the sensor connected to the side of the distributor which I beleive is the reference sensor (correct if wrong) but car failed to fire when starting telling me that its fine. Next step is to test the ecu, have purchased a second hand ecu just waiting on it to arrive to see if that fixes the problem. (I did notice there was an extremely similar thread covering almost exactly the same issue but the answer was never posted
)