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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > M Series > E46 M3 (2001-2006)

E46 M3 (2001-2006)

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  #1  
Old 10-21-2013, 08:19 AM
JayMac JayMac is offline
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Location: Virignia
 
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Mein Auto: what ever starts
S54 electrical

When you turn the key to the run position you should hear the throttle bodies cycle. If you do not is it an indication of a blown fuse? These are in the 5 pack correct?

I swapped in a S54 and took it for a shake down run. Nothing over 4 grand or 50 mph as I was bedding in some new pads also. Car has started and run fine for the last 6 months. After the first run yesterday it would not crank. Popped the clutch and it ran fine. Now when I turn the key the starter will turn but no fire. Fuel pump is manual and I can hear it running. I do not think the throttles cycle when the key comes on so I do not think they are getting power. Will start with all of the grounds and the fuse in the five pack. Any other suggestions or help is greatly appreciated. Have Bentley and wiring diagrams. I hate electrical.
Jay
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  #2  
Old 10-21-2013, 11:38 AM
JayMac JayMac is offline
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Mein Auto: what ever starts
Okay A little more research and some testing revealed a blown fuse. 20 amp in the middle of the 5 pack here.


This powers the DME relay so I though I am making progress. Still have no cycle on the fuel intake when I power up. From the e46 Bentley on page 130-5 I am testing the ecu relay. I have power up to relay and when I plug in relay I have power out on ground but no power out of the two red wires. I pulled the relay and tried it in my M3 and the car started so I know the relay is good. I think this is some kind of ground short issue. I do not get power in the two other wires that should now have power if the relay is closed. If I understand the relay correctly when the relay closes it should send power out on the two other read wires connected to pin(s) 87 on the relay. I don't get any power there. I guess it could be that the base for the relay is fried also. Any ideas are appreciated but i will sort through this slowly.
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Old 10-21-2013, 02:33 PM
JayMac JayMac is offline
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Mein Auto: what ever starts
Think the ecu is fried. Not sure how as engine has run for 10 to 15 minutes at a time on multiple occasions. Plugged in my other ecu form the M3 and the throttle bodies cycled. Not a good sign. Oh well $hit happens back to the drawing board and wallet.
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Old 11-18-2013, 07:15 AM
JayMac JayMac is offline
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Mein Auto: what ever starts
Solved this issue yesterday. Fired the ecu. Question was how? Everyone I spoke with was leaning to I wired something in the swap wrong. The answer turned out to be yes and no.
Symptoms were as follows:
Engine has run for 6 months in garage as wired.
Engine was run long enough to bring oil up to 160 degrees to check mechanical gauges (@10 min) on 4 or 5 occasions. The last the day prior to the failure.
Took car out for a test drive, about 4 miles nothing over 4k on the tach.
Son went to do the same and the starter just clicked, like bad starter or low battery. Battery was always on battery tender when in the garage.
Push started the car and son drove the same loop.
Go to start the car and nothing. No starter, no cycle of the s54 throttle bodies.

Tried to figure out what happened and whey I had no power to the starter. Pinned out the B+ terminal and one of the post was dead. This was the culprit.
When I hooked up the B+ cables I put the starter on the post that has your secondary wire. If you look at your positive battery cable there is a small wire along side the thick one. This has an 80 amp fuse built into it. Buy me screwing that up I did tow things. Starter amps were now being drawn through an 80 amp fuse. You crank at around 180 with the initial spike to be about 300. This was not enough to blow the fuse since it was short bursts and did not blow the fuse. Anyone see where this is going yet?

You can charge any 12 volt car system from anywhere you can get access to a ground and a 12 supply. As a result you can do it through your cigarette lighter or even a usb port if you needed to. The caveat is the amps you are charging at. So you can't jam 20 amps through a system that has a 5 amp fuse or something even smaller. As a result if you ever use the cig lighter use something like 1 amp or less and just be patient. Just think of amps as pressure.

So we proceed. As part of my build I put an under drive pulley on the alternator. Just idling or slightly higher in the garage was not going to do much but the bomb was already ticking. Your alternator shoves voltage back into the system. As my rpms in the test drive come up so will l the amps. Alt equals 120 amps, fused for 80 amps because I hooked the starter to the wrong post. So we know are up to 4k rpms and we generate enough pressure to blow the 80 fuse on the small b+ line. THIS IS WHAT KNOCKED OUT THE STARTER. HAD I STOPPED THERE THE ECU WOULD NOT HAVE BEEN FRIED.


With the engine running due to the push start we now have power and think we are okay. Nope. The system is not seeing any volts from the alternator since this fuse has been blow. As such I am running off the battery and the ecu sees volts dropping. As a result the alternator starts shoving out more an more volts at 120 amps. Remember pressure? Remember any 12 source to recharge. So I am now pushing huge volts and amps backwards through the 12 volt side of the ecu. Not a good idea. As a result we are eating fried ecu for supper here but the issue has been solved and the car runs great.

For those of you wondering we did pin out all of the other wires to make sure nothing else was shorted out. We did this first as we thought that maybe the harness work left something out that would have done this. The guy helping me is a firm believer that **** does not just happen and wanted to find the issue. We were ready to plug the new ecu in but still could not figure out why the first went. I then mentioned the b+ issue that I have changed already and it led us to the 80 amp fuse that would be buried in your trunk. Cut back the tape, found it blown and the rest of the puzzle just fell into place.

Here is a little toast to go with that:


Last edited by JayMac; 11-18-2013 at 07:35 AM.
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