e39 525d fuel pump issue

[kildangan_kid]

The car also developed a bit of a strange problem recently. Regardless if the car has being running or being started from dead cold. The in tank pump sounds as if it is sucking air, almost like its out of diesel, even though it had a 3/4 tank of fuel. I turn the ignition on and the pump continues to suck air until near the end of its cycle. Just as its nearly done i can hear it operating as it should. i still have to flick the ignition at least 2 more times or it just wont start.
Also if i leave the ignition and let the pumps finish and wait a couple of seconds, i can hear air rushing back into the tank from what i can only imagine is the line to the inline pump. I had already changed the lift pump for a brand new unit in October which worked fine from the word go. I even took it back out on Sunday, there was no rattles from it and was in good working order. The filter wasn't blocked. There was no excess dirt etc in the tank. I checked the tank for leaks, as did with the inline pump and fuel lines, everything was A1. Once the car starts there is full power, climbs up and down the revs fine and idles fine. I had also changed the fuel filter the week previous. I'm pretty stumped, and it is extremely f**king annoying at this stage..

If anyone could shed some light on this or give me some advice I would really appreciate it.

Adam

[GERMANIKS]

The car also developed a bit of a strange problem recently. Regardless if the car has being running or being started from dead cold. The in tank pump sounds as if it is sucking air, almost like its out of diesel, even though it had a 3/4 tank of fuel. I turn the ignition on and the pump continues to suck air until near the end of its cycle. Just as its nearly done i can hear it operating as it should. i still have to flick the ignition at least 2 more times or it just wont start.
Also if i leave the ignition and let the pumps finish and wait a couple of seconds, i can hear air rushing back into the tank from what i can only imagine is the line to the inline pump. I had already changed the lift pump for a brand new unit in October which worked fine from the word go. I even took it back out on Sunday, there was no rattles from it and was in good working order. The filter wasn't blocked. There was no excess dirt etc in the tank. I checked the tank for leaks, as did with the inline pump and fuel lines, everything was A1. Once the car starts there is full power, climbs up and down the revs fine and idles fine. I had also changed the fuel filter the week previous. I'm pretty stumped, and it is extremely f**king annoying at this stage..

If anyone could shed some light on this or give me some advice I would really appreciate it.

Adam

Could be relay, assuming your new fuel pump is working fine. Seen faulty relays doing strange things like that. 20 euros from BMW. I assume yours is a post 2001 car, in that case, relay is under the glovebox. Green one close to the body module (Big white module with 3 plugs)

You could actually swap your relay with rear windscreen defrost one which is located in the trunk (Top right green one). Just temporally to see if that is doing any good.

[kildangan_kid]

Thank you for your reply.

Took it for a good run to swords on Wednesday, 250 mile round trip. Since then the problem has disappeared. Very strange. It was left lying up Thursday and friday, and started perfect this morning. Now I'm even more confused..