93 E34 525i - Fuelling issues

[E34DRZ]

Hi guys, first post here having had several similar hits here from google but never quite the same issues.

Basically, the oil pump went bye-bye and took the cam chain with it, turning my engine to scrap - not a problem, I sourced another M50TU engine from a 1996 325i Coupe (definitely the same engine bar the sump and oil pickup, which I have swapped).

Got the engine in and connected up etc and went to crank it - it turned and turned but didn't fire. Thinking I might have got the fuel lines backwards, I whipped them off and there was absolutely no fuel in the lines at all (when the fuel pump was quite obviously fine beforehand).

I checked the relay, it seems fine and I have bridged posts 30 and 87 and still the fuel pump will not run. I get voltage to the connectors under the relay but I don't appear to get any voltage at all to fuse 23 or to the connector on the pump in the boot.

What am I missing here?

[whiskychaser]

A fault in the circuit can drag the voltage down so it 'looks' like you dont have any power. More likely its an open circuit due to a bad connection. First job has got to be to pull the relay and check for continuity between the relay slots and fuse 23. Or has it got a high resistance or go to ground? Then from the other side of fuse 23 to the pump. HTH

[E34DRZ]

It gets a bit stranger...

I've got the pump to pump now, one of those things where you go back to something and it just works first time. That was with a cable bridging pins 30 and 87 on the relay connector block.

Tried to start the engine with that cable in place (so I knew it was getting fuel) and it refused to go, not even trying. Put the relay back in and exactly the same.

Pulled a spark plug and tried it against the block and there was no spark, nothing at all.

Could the fact that I moved the toothed wheel (that the crank position sensor reads from?) from my old '93 engine to this 96 engine be the problem here? I have looked on RealOEM and the part numbers are the same but they do look physically different laid next to each other.

Its going to be a bit of a PITA to swap it over so I'd rather know beforehand if its likely to be something else...

[whiskychaser]

Try testing the crank position sensor or stick the 'old' one in. If the CPS is duff the pump wont run and you wont get spark either. As the CPS picks its signal from that pulley, its logical to assume that if that's not compatible the result will be the same - no go.

[Dave M]

It gets a bit stranger...

I've got the pump to pump now, one of those things where you go back to something and it just works first time. That was with a cable bridging pins 30 and 87 on the relay connector block.

Tried to start the engine with that cable in place (so I knew it was getting fuel) and it refused to go, not even trying. Put the relay back in and exactly the same.

Pulled a spark plug and tried it against the block and there was no spark, nothing at all.

Could the fact that I moved the toothed wheel (that the crank position sensor reads from?) from my old '93 engine to this 96 engine be the problem here? I have looked on RealOEM and the part numbers are the same but they do look physically different laid next to each other.

Its going to be a bit of a PITA to swap it over so I'd rather know beforehand if its likely to be something else...


Out of interest, why swap the cam wheelies??

Did you remove timing chains, mess with timing at all?

Did you move the tag or "impluse wheel" that fits behind the intake cam (#7 below)? I had a similar issue (no start) with my non-vanos when I put my tag on upside down. I felt quite brilliant after that one ;).

http://img.photobucket.com/albums/v11/dave_macisaac/2.png

[Mendozart]

Out of interest, why swap the cam wheelies??

Did you remove timing chains, mess with timing at all?

Did you move the tag or "impluse wheel" that fits behind the intake cam (#7 below)? I had a similar issue (no start) with my non-vanos when I put my tag on upside down. I felt quite brilliant after that one ;).

http://img.photobucket.com/albums/v11/dave_macisaac/2.png
I was so paranoid about something like that happening when disassembling, that I tie strapped everything together the way it came out.:D

[E34DRZ]

I didn't touch the timing chain or anything at the top of the engine at all, just the big crank pulley (swapped it over as it looked in better condition, but they do appear to be slightly different now I've had them side by side and had a close look).

An auto electrician came up and had a look at the car and reckons the cable to the CPS is faulty as it is leaking power to the screen of the cable, so I am going to swap that over.

I am wondering if I got the connectors under the inlet manifold connected up correctly. I dont have a pinout for the big round connector to be able to test that though... Everything seems to go to the right places but there are a couple that are the same length, so I'm not 100% sure...