If it kept running when he was spraying WD-40 down the intake, it seems like you are not getting fuel to the injectors or the injectors are not opening. I would check the relays as you mentioned, but would also check fuel pressure at the rail. If your pressure isn't where it should be, quite possibly a dead or dying fuel pump, since you mention that the filter is fine.

If you have fuel pressure, then communication to the injectors isn't working since you aren't getting any fire. Unfortunately, to diagnose this part you need something that will communicate with the car and see what errors are happening.

Sorry, I don't have a diesel, though I know the mechanics, it's nearly impossible for me to provide any more guidance. I'm not sure of all of the specifics of the BMW diesel. Hopefully, some of the diesel guru's will be able to chime in for you.

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'01 740i Sport MKIV, Quad Brake Lights, Bi-Xenon retrofit, HID Fogs Dinan 7 Struts, Springs, camber plates, Intake, MAF, CAI, Throttle Body, NBT Retrofit, Strong Strut


'99 318ti Titanium Silver; '97 318ti Boston Green; '13 X5 3.5i Saphire Black Metallic
'84 633csi Black (sold); '88 325iC Black (sold); '97 740iL Black(sold); '01 740iS Black (sold);'97 318ti White (sold); '08 X5 4.8i Titanium Silver (sold); '96 318ti Alaska Blue (sold)