Fuel pump frolics....just need a little guidance please

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shonky
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Tue Aug 24, 2010 7:36 pm

My 325i has always started on the button until today when it would turn over but wouldnt fire.

I popped the rubber tube off the fuel rail and turned the engine over but no fuel came out leading me to believe that there is a fuel supply fault.

So after being RAC'd home I had a closer look......It seems that the Fuel pump relay wasnt clicking when the ignition is turned on (is that how its meant to work? )

There seems to be voltage present at the base of the relay when the ignition is turned on and it alters when turned off again

On my car there are two orange relays there and swapping them over still shows the same thing

Any advice on what to look at next would be appreciated ( I have done a search but wasnt satisfied that the questions were related to my problem )

Thanks
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shonky
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Wed Aug 25, 2010 12:52 pm

Just done a little more digging on this.....

Today I have had another look after taking on board what has already been said in various posts.....

I checked the voltage at the two connections above the fuel pump and they are showing 7V when the ignition is on and drop to 0V when the key is removed

pulling the orange relay in the engine compartment out when the ignition is on makes no difference to the voltage

Does this mean that the fuel pump is not working and the rest of the circuit is OK?

Also is there a special tool needed to remove the fuel pump?

Thanks for any help :)
daimlerman
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Wed Aug 25, 2010 6:27 pm

Fuel pump is switched on by the engine ECU when it is told that the engine is cranking,this is a safety device so that the fuel pump does not continue to supply fuel after an accident in which the fuel line is split,so you need to discover if the fuel pump is being told to switch on.

Usual way of doing this is to wire a bulb across the fuel pump terminals,if the bulb lights,power is reaching the pump.

Fuel pump hides under the rear seat base,there's a black access hatch,but you must remove the sender unit(8mm bolts)first,so you can get the thing out of the tank.

You can 'prove' the fuel pump and circuit by bridging two terminals on the fuel pump relay,cannot remember(due to my incedible age)what the numbers on the relay are,but the fuel pump feed is green/violet and the feed will be red with a tracer!

Hope this helps...
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bpowell555
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Wed Aug 25, 2010 10:02 pm

I did this a couple of weeks ago. The fuel pump is dead if there is no continuity between its poles when the power is disconnected. I strongly suspected my pump was dead - swapped the relays over like you did and prayed the power/loom was still working - so bought a replacement part.

There was continuity between the poles on the new part and not on the old so the old was fooked.

Had a right laugh swapping it out errrr. Boiling hot weekend and I'd just brimmed the tank - failed in the fuel station. Luvverly petrol swilling about everywhere :)

The old pump twists out - remember to replace the seal!

I reckon to twist the new one in get two vice grips and grab hold of the top edge either side and twist it round in and tight. I found I couldn't get traction on it otherwise without fearing damaging the fuel exit pipe.

Also beware replacing VDO with OEM. I had to grind back the fuel level sender and chisel off some of the plastic surround to get it to fit - again lots more fun when the tank is full. Beware the bolts are just spot welded on so don't torque too tight. Just a light hand tightening.

Cheers!

:cool:
1990 325i touring
She's a minter! Best 3 years of my life - bye bye baby :D
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shonky
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Wed Aug 25, 2010 10:42 pm

Superb info guys...thanks

Ill take a look when it stops raining!
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shonky
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Sat Aug 28, 2010 4:05 pm

Sorted now......New Bosch fuel pump cartridge from ECP and an hours work.......quite impressed with myself really as this seemed like a daunting prospect.

I didnt need a vice grip or special tool to get it back in......I used my bare hands to twist it back in........

Damn...im strong!
daimlerman
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Sat Aug 28, 2010 4:43 pm

Hope you fitted a nice new rubber sealing ring....
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shonky
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Sat Aug 28, 2010 4:50 pm

daimlerman wrote:Hope you fitted a nice new rubber sealing ring....
I did!........the original didnt look to bad to be honest!
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