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Does the e90 325i Fuel Pump prime?

2368 Views 5 Replies 5 Participants Last post by  Shibbydiggle
Trying to resolve a problem on my car, e90 n52 218hp, some of you might have seen any of my posts on here before -
So I'm on to testing the fuel pump, and I noticed it doesn't prime (turn on before the engine actually starts) at 1st or 2nd stage position ignition (fob pressed, Start button pressed). Runs at about 10.9 to 11.8 volts once the engine is running, but with the fob in the slot and / or the start button engaged (without depressing the clutch) the fuel pump DOES NOT turn on. Now I know some cars' fuel pumps do not "prime", but from the information i found on this subject, I think this car's pump should prime for 3 to 5 seconds.
Anyone have any concrete information I can go on?
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I realize this is an old post, but did you ever find an answer?
Welcome to the Forum!
SOME of us try NOT to give new members a hard time, or refuse to answer unless you've tried to use the Forum Search, so please don't hesitate to ASK whatever question YOU have. :)

Answer to WHICH question/Issue? OP in this thread was "last seen" on this Forum 9 months ago. In this thread, he had questions about When & How Long the Fuel Pump "Primes" on 325i E90 of unstated build date, almost certainly NOT to specs of vehicles sold in US (such as YOURS?)

He MAY have been relying on INPA to tell him if the fuel pump runs/primes BEFORE the Starter is cranked. It is NOT clear to me HOW he was trying to determine IF & WHEN fuel pump ran/primed. Since you have to have Ignition ON to connect INPA to EKPS Fuel Pump Module, in order to read Pump RPM, that means you have to open the door, get in vehicle, hook up INPA, and press START to activate Ignition.

On my 3/2007 328xi, the Fuel Pump "Primes" (Audibly ;-) when I open the door, if vehicle was NOT locked, but has entered Sleep Mode. So by the time you get INPA, or any other Diagnostic Software or Scan Tool that can read Live Data in EKPS setup and ignition ON, the pump has primed and shut off (~ one second on mine).

Another question he asked was whether 600 kPa (~ 72.5 PSIG) was adequate pressure. The answer to that question is YES. That is proper Fuel Rail Pressure for N52K engine. His "Implied" question in his second post was whether it was proper for INPA to display SAME pressure (600 kPa) at ALL times. AFAIK, the N52K as used in the 328i/xi has NO LPFP Pressure Sensor, and the INPA "pressure" value is calculated from RPM, or simply displayed at all times Pump is running. The N52 DOES have a Schrader valve on the Fuel Rail, to which a mechanical pressure Gauge can be connected to get actual Rail Pressure.

Why not identify YOUR vehicle, by model, engine, build month/year, and then state YOUR issue or question? THEN you might actually get a response to whatever question YOU have.
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