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Discussion Starter #1
Alternator seized on daughters 2001 X5 3.0. I charged the battery, removed the drive belts just to make sure car would start. Engine turns over but will not fire. Does the ECU/DME require current to flow thru a "working" alternator in order for engine to fire?
 

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You should be able to start using a host car and jumpers. If you get repeated hard start I would look into fuel supply just changed wife's FPR and things are much better. Oddly still starts a little harder than my car.
 

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Discussion Starter #4 (Edited)
You should be able to start using a host car and jumpers. If you get repeated hard start I would look into fuel supply just changed wife's FPR and things are much better. Oddly still starts a little harder than my car.
Thanks, Before I tried to start, I charged the battery back up to 100%, and verified approx 50lbs of Fuel Pressure with Ign on, and engine would not fire. Thats what stumped me, Good Battery and good Fuel pressure, but engine would not start, then I could not remember if the car would actually run without an alternator, thinking maybe the DME picked up a signal from the Alt, or required current going thru the ALt before it would send current to the Coils.

Turns out that was not the case, for some reason it was just difficult to start even though the battery was 100% and the motor was spinning over with Fuel Pressure and spark. I finally got it to fire and now runs just fine without the Alt. I should be good to go after I install a new alt.
 

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I had very similar symptoms. Check your fuel pressure after sitting over night. It should be on the order of 25#. If not the FPR needs a fix (not necessary replacement)


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Discussion Starter #6
I had very similar symptoms. Check your fuel pressure after sitting over night. It should be on the order of 25#. If not the FPR needs a fix (not necessary replacement)


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See my post above, my FP was around 50lbs, which is in spec. Car was still difficult to start. Once I got it started, it now starts normal.
 

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I saw that. Mine was also perfectly fine once running but had very hard starts after long pauses in use. This continued until I replaced the FPR.

When I did that I did an autopsy that showed most likely the FPR was perfectly fine but the o-ring between inlet and outlet was shot bypassing the FPR. I have no idea how that affected starting so much but never had a hard start since.

To determine if your FPR or fuel pump check valve is shot, check the fuel pressure after an over night wait. (leave the pressure gauge on over night).

Before replacing, I lost most pressure in 3 hours and overnight was zero. After replacing the pressure was 25 after 18 hours.

It took 100 seconds of cranking after a month sitting to finally start and that was with gauge showing about 48 psi (but was bouncing from 47-49).
 

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Discussion Starter #8 (Edited)
Thanks for the info, but my FPR was always 50lbs prior to starting, even when I had the hard start, so I don't think my issue was due to FPR, as it was in spec before and after. My guess is plugs were a bit fouled due to the increased throttle that was required to keep the engine running to over come the belt drag from the seized Alt as my daughter tried to find a safe place to pull the car over. She was able to restart after pulling over as I was diagnosing over the phone, but told me the car required a lot of throttle just to idle. After towing it home, Once I got it started, blew a bit of smoke out the exhaust then immediately cleared and has run fine since. I've had FPR issues before in other cars, leaking injects etc etc, but this car has not exhibited the same/consistent symptoms of Hard to start after sitting. Those I could read a drop in FPR after sitting over night, or smell the gas due to leaking injectors. I don't have any of those with this, as it now starts fine after sitting 24-48hrs.

I'll definitely keep the Reg "o-rings" in mind, as you just never know.
 

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My gas pressure always read to spec except that it wouldn't hold pressure.

You are on to something as I'm a little over due for some infector cleaner myself and wife's car still starts harder than mine but no longer concerning. I'm just saying if you have a fuel pressure gauge there is one way to confirm the FPR is not leaking back to the tank
 
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