FAQ
TL;DR: After replacing the BMW E46 320d fuel pump, bleed by cracking injector lines and following the 1‑3‑4‑2 firing order; "Loosen the injection tubes" to speed venting. For DIYers fixing no‑starts after pump work. [Elektroda, żałosna udręka, #17029904]
Why it matters: It helps E46 320d owners quickly restore fuel delivery and avoid needless cranking after pump replacement.
Quick Facts
- Prefill the new fuel filter with diesel (often called “ON”) to make bleeding easier. [Elektroda, kristoferson22, post #17020856]
- If the in‑tank pump stopped, the system can be sucked dry, making priming difficult. [Elektroda, kristoferson22, post #17023790]
- Key‑cycling the ignition several times will fill the system only if the in‑tank pump works. [Elektroda, lato8, post #17024518]
- If the pump runs yet the engine still won’t start, look for faults elsewhere. [Elektroda, lato8, post #17029741]
- A damaged pump controller or stored ECU errors can prevent the in‑tank pump from running. [Elektroda, naprawa-pomp.com, post #17593831]
Do I need to bleed the fuel system after replacing the pump on an E46 320d?
Yes. The forum guidance is to replace the fuel filter at the same time and prefill it with diesel to ease bleeding. This shortens cranking and helps the high‑pressure pump receive fuel quickly. [Elektroda, kristoferson22, post #17020856]
How can I prime the system without special tools?
If the in‑tank pump works, cycle the ignition several times to position II. That primes the lines and filter. Then try starting. If the pump is silent, address power or the pump first. [Elektroda, lato8, post #17024518]
Why won’t it prime if the in‑tank pump failed?
A failed tank pump can empty the feed lines. The engine‑mounted pump then struggles to draw fuel, so bleeding becomes slow and difficult until you restore supply. [Elektroda, kristoferson22, post #17023790]
How do I bleed through the injector lines without a scanner?
Use the injector‑line method: 1. Slightly loosen injector pipe nuts. 2. Crank; when one overflows, tighten it and move to the next, following 1‑3‑4‑2. 3. Continue until it fires. “Loosen the injection tubes” to speed venting. [Elektroda, żałosna udręka, #17029904]
What is the firing order for the BMW 320d (M47)?
The cited procedure uses 1‑3‑4‑2. This sequence ensures each injector gets bled as its cylinder reaches injection during cranking. "1342 order." [Elektroda, żałosna udręka, #17029904]
Should I prefill the fuel filter when swapping the pump?
Yes. Prefilling the new diesel filter reduces air in the circuit and makes bleeding easier after pump replacement. It’s a recommended time to change the filter anyway. [Elektroda, kristoferson22, post #17020856]
The pump runs, but the car still won’t start—what next?
If the pump operates continuously and you still have a no‑start, the fault lies elsewhere. Check for injection, rail pressure, or other engine management issues. [Elektroda, lato8, post #17029741]
Can I power the in‑tank pump directly to test it?
For diagnosis, you can briefly power the in‑tank pump and attempt a start. Do this only short‑term to confirm supply, then fix the root cause. [Elektroda, lato8, post #17028356]
Is there a fuse I can jump to run the pump on an E46?
One poster corrected themselves: there isn’t a simple fuse‑jump method noted; the E46 uses ignition‑switch control for pump operation. Use normal key‑on sequencing. [Elektroda, żałosna udręka, #17031358]
My pump won’t run at key‑on; could ECU faults be the reason?
Yes. “If the pump controller is damaged, if the computer catches any errors, the pump in the tank may not work.” Scan and repair before further cranking. [Elektroda, naprawa-pomp.com, post #17593831]
Should I always hear the pump at key‑on?
Not always. An edge case noted: on some cars (other brand), with more than half a tank, the primary pump may not run at key‑on. Absence of sound isn’t definitive. [Elektroda, naprawa-pomp.com, post #17593831]
Will excessive cranking damage or stall the VP pump during bleeding?
Avoid long cranking. As warned, excessive spinning wastes time and “the VP pump may not release.” Use the injector‑line bleed with the 1‑3‑4‑2 order. [Elektroda, żałosna udręka, #17029904]
