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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Wed, May-22-2019, 01:05:00 PM   #1
JoeCap
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Default Crank no start, fuel pump and possible relay issue. Need help!

Anyone good with E46 M3 fuel pump and relay issues?? My car (2001 M3 coupe with 156k miles) lost power and died. At first it would start and die immediately. Now it just cranks. I have it narrowed down to the fuel pump and relay.

I cannot hear the fuel pump kicking on during the prime cycle.

I checked the #54 fuse in the glove box and the the middle fuse in the DME box under the hood, both are good.

I checked the voltage at the pump. With the car off, no key in the ignition, I have between 4-5 volts at the pump connector. Should there be any voltage at the pump with the car off and no key in the ignition?? I figured it should be zero volts until I go to turn the key.

When I turn the key to position 2, it spikes to 12.6 volts as it should for a second or two. And then returns back to the 4-5 volts.

So should I have 0 volts at the pump connector with no key in the ignition? Or is the 4-5 volts normal?

Iím trying to determine if I need to replace just the pump, or the pump and the relay.

Thanks so much for your help!
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Old Wed, May-22-2019, 01:08:14 PM   #2
ftapache
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Default Re: Crank no start, fuel pump and possible relay issue. Need help!

How old is the battery?

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Old Wed, May-22-2019, 01:15:25 PM   #3
JoeCap
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Default Re: Crank no start, fuel pump and possible relay issue. Need help!

Don’t know how old the battery is, just bought the car a few months ago. But the battery tests fine. Before my last fill up I let the fuel level get super low, so I have a feeling that screwed up the pump.

The new pump is on the way, I’m just not sure if I should replace the fuel pump relay in the trunk as well. It behaves normally during and after the prime cycle (based on the voltage at the connector). But before the prime cycle I just don’t know if it should have 0volts or the 4-5 volts that I’m showing at the fuel pump connector.
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Old Wed, May-22-2019, 06:11:48 PM   #4
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Default Re: Crank no start, fuel pump and possible relay issue. Need help!

Quote:
Originally Posted by JoeCap View Post
Before my last fill up I let the fuel level get super low, so I have a feeling that screwed up the pump.
Low tank should not kill the pump.


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Originally Posted by JoeCap View Post
When I turn the key to position 2, it spikes to 12.6 volts as it should for a second or two. And then returns back to the 4-5 volts.

I just don’t know if it should have 0volts or the 4-5 volts that I’m showing at the fuel pump connector.
With 12.6V at the pump and you didn't hear the pump running then it's bad.

Re to the 4 or 5V at the pump with key off, measure again from the connector pin2 to a good clean chassis ground instead of to pin1. If it still shows floating 4 or 5V then definitely the pump motor is bad with open connection (worn brushes???). The reason it might have 4 or 5V because this is a FET replay and not a mechanical point breaker contact relay. A FET has output floating voltage without a load on it in its OFF state.
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Old Thu, May-23-2019, 11:11:11 PM   #5
JoeCap
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Default Re: Crank no start, fuel pump and possible relay issue. Need help!

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Originally Posted by sapote View Post
Low tank should not kill the pump.




With 12.6V at the pump and you didn't hear the pump running then it's bad.

Re to the 4 or 5V at the pump with key off, measure again from the connector pin2 to a good clean chassis ground instead of to pin1. If it still shows floating 4 or 5V then definitely the pump motor is bad with open connection (worn brushes???). The reason it might have 4 or 5V because this is a FET replay and not a mechanical point breaker contact relay. A FET has output floating voltage without a load on it in its OFF state.

Thank you sir! Thatís what I was looking for.

New pump is in and weíre back up and running. The relay seems fine.
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Discussing Crank no start, fuel pump and possible relay issue. Need help! in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)