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  #1  
Old 01-17-2025, 01:18 PM
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Fuel pump replaced but...hard starting

The first super-cold day (29 degrees) about 10 days ago my ride wouldn't start in the morning. I had 1/4 tank of gas. I messed with my Foxwell and activated the Fuel pump a few times and then it turned over and ran perfectly. I filled the tank all the way up per some suggestions here.

It happened again the next day, so I figured the fuel pump was 'failing slowly' like AndrewWynn often talks about. So I replaced the fuel pump with a Pierburg from RockAuto.

Lo and behold, yesterday morning it did the same thing. I have to let the pump prime fully before attempting a start. It works fine like that. If I don't turn the key to accessory and I just slam the key all the way to start on the first start of the day, it will turn over and over and over. No start. Then I just turn the key OFF, back to Accessory, wait for it to prime...and no problems.

I did have a few codes on the Foxwell regarding fuel trim, ignition switch and oil pressure sensor. I reset those and they haven't come back on. They probably will in a few days though. I have seen them before but the car runs perfectly other than a chronic low idle.

My next suspect was the siphon jet pump, but my fuel level reads fine all they way down and the problem occurs both with a full tank or 1/4.

Would love some help troubleshooting! Thanks guys!
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2005 X5 3.0i - 71k mi (9.2018) -> 81k (9.19) -> 100k 9.21
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  #2  
Old 01-18-2025, 05:32 PM
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Is it cranking but not starting? If so, my recent thread where I tracked down my similar issue might be of some help. I was having trouble starting on the first start of the day in cold weather. I went through a battery of tests before finally trying a new fuel pump relay and that was the problem. Hope it helps:

https://xoutpost.com/bmw-sav-forums/...art-issue.html
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  #3  
Old 01-18-2025, 11:27 PM
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Fuel pump replaced but...hard starting

Check fuel pressure after it's off for overnight.

If the pressure is less than about 30 psi most likely the fuel pressure regulator. Siphon jet won't cause starting issues just running out of fuel
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Last edited by andrewwynn; 01-19-2025 at 10:11 AM.
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  #4  
Old 01-20-2025, 04:57 AM
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80% improvement when I experienced a similar problem....use a fully charged battery when starting.
Short trips around town?
Battery 3 yrs or older?
Has the alternator been replaced recently?


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  #5  
Old 01-20-2025, 05:25 PM
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Quote:
Originally Posted by RenaissanceMan View Post
Is it cranking but not starting? If so, my recent thread where I tracked down my similar issue might be of some help. I was having trouble starting on the first start of the day in cold weather. I went through a battery of tests before finally trying a new fuel pump relay and that was the problem. Hope it helps:

https://xoutpost.com/bmw-sav-forums/...art-issue.html

That's actually a good point about the relay. Since I already replaced the pump, that might be a good place to look. I was going to say that my battery is basically new but it is 4.5 years old. Got it from AAA. 94 AGM.

The thing will crank forever though. I can't imagine it's the battery. But who knows. I'll go thru your thread and check it out!
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2005 X5 3.0i - 71k mi (9.2018) -> 81k (9.19) -> 100k 9.21
---------------------------------------------------------------------
SOLD : ( 2003 X5 3.0 - 177k mi (9.2018) -> 186k (9.19) -> 205k (9.21)
SOLD : ( 1997 328is Coupe - Hellrot Red
SOLD : ( 1988 528e w/ Bullseye s256 / MS2 Extra / GC Coilovers / Yukon Coils ~ 300+ HP
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Old 01-21-2025, 03:37 AM
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If you've never charged that 4.5 year old battery then yes it will start the car but, it has lost life.And it will show itself in the cold temps. The BMW car calls for a great deal of power from a battery.
My experience, I'm just learning that the ecm prioritizes the many electrical components in the car and feeds accordingly.
simple example...I've tracked that my garage door opener functions poorly on a less than fully charged battery.
Just the same with the mirrors, wipers and yes with the starter!
A poorly charged battery can and will burnout a starter prematurely. I equally suspect that goes for the spark plugs, coil packs etc...
I've learned any battery supplying a BMW car's power should be charged to the fullest once a week especially if it's 4.5 years. Newtis reports once every 6 weeks if I remember correctly. Lots of things I was not aware of concerning the battery, BMW relationship. I now place a charger on my cars every weekend. Especially, if the car had sat for over a week dormant!
I am coming to the revelation that just as fervent as we BMW owners are about choosing the oil and changing it. Just as well we need to be for changing and charging the car's battery!

See this post...
https://www.xoutpost.com/showthread.php?p=1242130

Some great comments and perspectives from others about the subject of battery/BMW relationship.

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Last edited by getty150; 01-21-2025 at 03:57 AM.
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  #7  
Old 01-21-2025, 07:48 AM
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I'm the same way. Anytime I have it in the driveway, I try to put charger on it. Especially if I have the hood up.
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  #8  
Old 01-21-2025, 08:49 AM
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A1

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  #9  
Old 01-23-2025, 11:39 AM
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So I went to Costco and got a new battery. Great prices there on Interstate batteries btw. I think the old one is probably find but for $175 to replace...better safe than sorry.

Unfortunately, same issue happened this morning in 23 degree weather.

Engine turns over and over. Crank.

When it's failing like this and I put the key in the accessory position, I can hear the fuel pump relay click but don't hear the fuel pump...until after the first successful crank. Then i hear it every time and the motor starts every time for the rest of the day.

Then I hooked up the Foxwell, activated the fuel pump relay a few times...and boom, it cranks. It does usually take 2-3 activations with the Foxwell for it to turn over. No problems after that. Everything works normally.

I suppose the relay could be in the process of failing but I just don't know.

My codes have come back though.

E3 and E4: DME Fuel trim bank 1 and 2, permissible range exceeded. I'm guessing I must have a tiny vacuum leak that will need to be professionally smoke tested.
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2005 X5 3.0i - 71k mi (9.2018) -> 81k (9.19) -> 100k 9.21
---------------------------------------------------------------------
SOLD : ( 2003 X5 3.0 - 177k mi (9.2018) -> 186k (9.19) -> 205k (9.21)
SOLD : ( 1997 328is Coupe - Hellrot Red
SOLD : ( 1988 528e w/ Bullseye s256 / MS2 Extra / GC Coilovers / Yukon Coils ~ 300+ HP
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  #10  
Old 01-23-2025, 11:55 AM
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Quote:
Originally Posted by Russianblue View Post

Then I hooked up the Foxwell, activated the fuel pump relay a few times...and boom, it cranks. It does usually take 2-3 activations with the Foxwell for it to turn over. No problems after that. Everything works normally.

I suppose the relay could be in the process of failing but I just don't know.


IMHO your symptoms never suggested the problem was your battery. In my case, what made me suspicious of my fuel pump relay was that:

- with it jumpered, fuel pump worked and the measured fuel pressure was at spec so it wasn’t the pump
- only happened intermittently when temps outside were super low
- removing and reinstalling relay would result in successful start
- engine wasn’t getting fuel when I had the no start condition

A new relay was super cheap ($10?) and a worthwhile test and ultimately ended up solving the problem. You should try that next to eliminate that from the list.


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