funky stall/no start 02 4.4i

[Jroc]

So, the other day I was about a mile from the house and the x started misfiring under load, so I coasted it to a stop(it had about a quarter tank in it). It started back up, but it just misfired and died. On the next attempt, it would only run with my foot on the gas. Finally it wouldn't run at all, regardless of throttle input. I tried it with the maf unplugged, but that made no difference. I had it towed back to the house and began researching similar issues, here on this site. Previous experience had me thinking that it was probably a clogged fuel filter. I go outside to do a fuel pressure check at the rail and it starts up, runs fine, drives, with no misfires for about 10 minutes. I turn off the engine, to check the key-on rail pressure and its at about 15 pounds. Tried to start it again, but symptoms repeated and it wouldn't run. Rail pressure check returns a 9 pound reading. I relieve the pressure and it rises to 7, then to 4-5psi and has stayed there, with every subsequent check. Typically, I'd suspect the pump relay, pump or filter. I cant hear the pump turn on, but in retrospect I don't recall ever actually hearing it running, before. Also, the fact that it started the next day and ran perfectly for 10 minutes, is skewing my theories. Anyone have an experience like this one?

Update: fixed!

[Bianca98]

I agree that it sounds fuel related if you are getting low pressure. However, have you checked what your spark plugs look like? Perhaps you have some leaking VCGs and may fouling the plugs. I have had it happen to me which is the only reason I would tell you to check the plug condition.

[Jroc]

Well, all the gaskets above the h/gs are less than a year old, including the valley pan gaskets. The x never misfired once, before that day and doesn't burn any oil. Also, the low rail pressure pretty much rules out anything in the ignition system. I didn't mention this, but there's no cel lit.

[srmmmm]

Sounds like bad fuel pump. My wife's 325i did the same thing.

2002 X5 3.0 251,873 miles
2004 325i 112,700 miles

[Jroc]

Ok, so that's one vote for a pump. Thanks srmmmm

[Jroc]

Update: I changed the fuel filter yesterday, but the battery went dead from sitting, so I couldn't see if that solved the issue. I'll be charging the battery and trying to start it, later today(fingers crossed).

[Jroc]

Update: the x wouldn't run unless I had my foot to the floor and even then, it was barely idling. Rail pressure check returned a 12 psi reading, so with the filter/regulator out of the equation(it was the original and needed changing anyway) I'm moving on to the fuel pump. There's no fuel leaking anywhere, so the fuel pump must be giving up the ghost. Unless I've forgotten something major, there isn't any other component in the fuel system, that would cause a low-pressure condition at the rail.

[upallnight]

Originally Posted by Jroc

Ok, so that's one vote for a pump. Thanks srmmmm

You could have a bad transfer pump and even though the gauge register 1/4 tank, the fuel pump pickup side could be dry. Try dumping a couple of gallons of gas into the X and see what type of fuel pressure you have with key on. If this solve your problem you have a bad transfer pump.

[Jroc]

Originally Posted by upallnight

Make that two vote for a bad fuel pump.

Noted. I ordered a new Walbro last night. I figured; if I'm gonna replace it, I might as well upgrade. Will update with results, when it comes in

[Jroc]

Originally Posted by TiAgX5

To verify if this is a pump/filter/regulator issue you will need to hook up a fuel pressure gage ($20 at Harbor Freight) to the schraeder valve on the fuel rail and read rail pressure. With the key in the run position it should be 51 +/- 3 psi. and only take 2 or 3 seconds to reach that pressure (if it rises slowly you have a clogged filter or bad pump, see NOTE 1 below to identify). Next step, start the engine and let set at idle for 1 minute (high vacuum), pressure should now read 36 to 46 psi. Now disconnect vacuum line from pressure regulator to simulate full load, pressure must increase 6 to 10 psi.

NOTE 1; If pressure did not come up to 51 +/- 3psi, repeat test while gradually pinching return hose to fuel tank. Rapid rise in pressure reading at rail with each pinch verifies pressure regulator is bad. No rise in pressure verifies fuel pump is bad.

A $10 digital voltage indicator that plugs into your cigarette lighter will tell you the condition of your battery (turn key to run position (NOT start), voltage displayed should be over 12.5 volts). The condition of your alternator (start engine, wait 10 seconds and voltage displayed should be 13.7 to 14.7 volts).

Fixing a problem by throwing parts at your vehicle is expensive and frustrating. Diagnosis seems to be turning into a "lost art" not only in the DIYing area but the dealer/indy shops too......and to ALL DIYers, buy a Bentley Manual, it's all there in black and white and saves you from "I had that same issue that was fixed by "INSERT MY FIX HERE" responses". These will leave you with an empty wallet and broken vehicle, NO fun.

These vehicles are MUCH too complex to have issues resolved with the same part every time WITHOUT PROPER DIAGNOSIS. Only fools and neophites think in this manner.

Sorry for the rant, but this is a pet peeve of mine and it has been building up for over 15 years. Several BMW forums I have been a member of (E46Fan is a BIGGIE) have turned into fastest response is right and max post count is ALWAYS right (even though they hit that response count by going on once a week and responding to every thread with a "k".

The tool required to diagnose this issue cost less then 1/3 a tank of gas, why guess and throw part at the problem????

Borrowed from another thread, but this guy couldn't be more correct.