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cranking, no start--solved--fuse #3 intake cam sensor wire

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38K views 10 replies 6 participants last post by  J252  
#1 · (Edited)
Cribs--cam position sensor wire was kinked and blowing secret fuse #3 in the fuse pack in e-box. Took a while to figure out as it wasn't throwing a code.

HTH someone someday.

Magic fuse #3--powers 9 different things!

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For the record:


Cranking no starting...turned out to be intake cam sensor...in an odd way.

3 miles after filling up I stopped. 10 mins. later wouldn't start. It cranked great.

After checking fuses and fuel pump relay, I gave up and towed it to the shop.

They started checking the basics. I wasn't getting power to the fuel pump, but they could jump it and it started.

They tested the relay; it was fine too, even though I swapped fuel with horn relay, you never know.

At first, they were thinking crank position sensor, and in testing it, the signal from it wasn't right.

Last night I read a post from Cyberkaa and brought the info about secret fuse #3 in the fuse pack this a.m.

It was blown. Replaced it, it blew right away. So, they replaced that fuse with a resettable 20 amp fuse so we could test easily.

I started unplugging all the relays and sensors on that fuse; Enoc and Sal said they thought a power to ground or kinked/damaged wire issue. That sensors and relays wouldn't draw enough to blow a 20 amp fuse. Every relay/sensor I disconnected--every one blew. Fuel pump, AC compressor I couldn't find anywhere, Fuel tank leak detection, therm, crank position sensor. Then finally, the intake cam position sensor. Fuse didn't blow!

Turns out that the wire from the sensor was kinked.

There was a moment where I was this close to crying when Enoc said to look at every wire coming from that fuse. I'm thinking miles of wire that anywhere could have rubbed open and be touching metal.

6 hours today and probably the same yesterday...taking things apart, etc.

I award 40% credit to Kalim; 40% to IMG; and I take 20% for finding Kalim's thread and ripping everything in the car apart to get to things to test.

No cam position sensor code came up at all...every other code came up though. Interesting...next time I'll remember that a lack of a code from something that should register, points to an issue.
 
#6 · (Edited)
No I searched; no smart phone, just a PC at places I was at. I'd borrow online time, go out and play with car some more. Also, oddly, at all other keyboards, I don't seem to think so well!

Anyway, I got to the relays finally--relay is fine, fuse is fine, we can get pump going by powering it directly. Something is stopping power getting to the relay--exploring that now. I'm at my shop, so will get codes soon to see whether something like cam sensor is cutting off power to the relay.

Any random guesses on what might cause fuel pump relay not to get power?
 
#7 · (Edited)
Guys, thanks to those who responded earlier today.

I finally got the the relays...the fuse panel wasn't coming out on one side, so got the tip from a SA at JMK to just remove glovebox...easy to get to relays at that point! Relay swap didn't work.

Towed to shop where we learned fuse good, relay good, pump spins when power is supplied directly.

I just read a great post by the great Cyberkaa...in the hundreds of posts I'd read, his was the one that covered more than just fuse and relay.

http://forum.e46fanatics.com/showthread.php?t=828901&highlight=crankshaft+position+sensor

His post lead me to think about the fuse in the e-box, because I was getting codes for weird things--AC compressor relay, crank position sensor, fuel pump relay, Leakage diagnosis pump, SAP relay, and therm--not all the things covered by that fuse, but enough to make me wonder about that one #3 fuse.

My mechanic saw that the crankshaft position sensor wasn't working properly...that might be because of the fuse, might be its failure caused the fuse to blow. Maybe the fuel pump spins, but is still bad and blowing the fuse?

The search will continue tomorrow...wanted to document this while it's fresh in case it helps someone someday.

In the meanwhile, one other odd thing...we found a little bit of oil underneath one of the multipin plugs in the e-box. My mechanic has seen oil travel within a wire from a sensor--an oil pressure sensor he thinks. Odd; I've never heard of that before, but since this sensor is the only one that takes oil into it, it's pushing oil up the wire...it's only underneath that plug in the e-box; no where else.

I'll update when I'm running again. I thought my car was magical...turns out it's just a BMW. Damn!
 
#11 · (Edited)
Thanks!

HTH someone someday
Yup, me today! Thank you so much for this thread...

I have been fighting an aggravating intermittent short that would blow that 20A fuse. The worst part is that whenever I got it towed home and went to work on it, the fuse wouldn't blow, so I could never get it traced.

The car did not throw a code.

After reading this, I figure why not try the long shot and remove the sensor. Turns out there was a location about 5" down from the wire where it got pinched between some hard pipes below the intake (coolant/heater?). With the sensor out of the car and my trusty DMM, i could pinpoint the the spot where if I bent the wire I would get a short. Sure enough, when I cut open the sheath the red and black wires have frayed insulation, and bare wires.

Since it was red and black (+12V and ground) that shorted together, the 20A fuse would blow and the car would die before it got a chance to throw a code. Had I been luckier and it was green (signal) that shorted with either red or black, I would have got a handy code which would have made my quest a lot easier.

Anyhow, I didn't have a spare sensor on hand, so I cut and repaired the sensor wire. So far so good.....