Author Topic: Why does my fuel pump shut itself off **8/10 update**  (Read 6327 times)

VegasKyle

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Why does my fuel pump shut itself off?
« Reply #15 on: July 05, 2011, 06:09:28 PM »
Quote from: DesktopDave;105087
LOL, caught me editing that last post...

I'm wondering if the jacket of your CPS is broken...if the DME loses that signal it shuts the pump off.  Annoyingly, the stomp test will give a 1444 (all clear).  Maybe the heat is stretching a jacket break?  Or the CPS is really dirty?  Mine stopped once just because it was coated with oil & rust.


The stomp test gave me the all clear 1444 too. Feeling around the CPS left me with a glove covered in grime so I'm going to clean it up as bes I can and go from there.

DesktopDave

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Why does my fuel pump shut itself off?
« Reply #16 on: July 05, 2011, 06:16:11 PM »
Quick & easy fixes are always the best place to start!

Let us know how it goes.
'08 Karmesinrot 128i 6MT
'86 Zinnoberrot 635CSi (M30B32/G265/3.46 torsen LSD)

Sold: '97 Montrealblau 318iS, '91 Brilliantrot 318i, '91 Brilliantrot 318iS

VegasKyle

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Why does my fuel pump shut itself off?
« Reply #17 on: August 05, 2011, 12:16:17 AM »
I just wanted to give an update.

I cleaned the crank position sensor with some engine degreaser and haven't had a problem.  I driven the car in similar conditions and temps and it's been fine.

Thanks to everyone who helped.

DesktopDave

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Why does my fuel pump shut itself off?
« Reply #18 on: August 07, 2011, 09:51:00 AM »
Excellent.  I had the same problem with mine when I bought it.  So I messed with it for a day or so, once I cleaned the sensor thoroughly it fired right up.  It was covered... caked-up with oil and rust.

So my crackpot theory is that rust on the sensor tends to interfere with the CPS signal.  I pulled mine off the motor to bench test it (and that's not easy as the A/C mount must come off to do this) - take care when putting the CPS back that it's as close as possible to the crank wheel.  Any bits of rust or gunk might push it too far away.
'08 Karmesinrot 128i 6MT
'86 Zinnoberrot 635CSi (M30B32/G265/3.46 torsen LSD)

Sold: '97 Montrealblau 318iS, '91 Brilliantrot 318i, '91 Brilliantrot 318iS

VegasKyle

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Why does my fuel pump shut itself off?
« Reply #19 on: August 10, 2011, 08:56:06 PM »
I HAVE ANOTHER UPDATE

I was driving home today and the car died just as it had before. I tried to start it a couple times with no luck.  However, this time I was ready with a multi meeter and a jump wire.  The first thing I did was pull the fuel pump relay and stuck the wire in #30 & #87.  I instantly could hear something come to life (fuel rail?) got in the car and it started right up.  I shut it off and put the relay back in just to see what it would do and it started right up.  I was only about 1 mile away from home so I set off.  It died again about 100y from the house.  I pulled the relay again and noticed it was almost too hot to hold (the pins were too hot to touch) I put the jump wire in again and could hear the same noise and it started right up.

So am I now safe to assume the fuel pump relay is the culprit?

If so should I replace all the relays while I'm at it?  No sense in ordering just the one if the others may be going out soon too.

VegasKyle

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Why does my fuel pump shut itself off?
« Reply #20 on: August 10, 2011, 08:59:50 PM »
Quote from: DesktopDave;105981
I pulled mine off the motor to bench test it (and that's not easy as the A/C mount must come off to do this) .


No kidding! The A/C mount was the worst part about changing the timing chain, by far. If you remember I had to do it twice because a piece of the guide binging up the crank sprocket.  If I didn't live on the surface of the sun I would have ripped out the whole AC.