Moderator: martauto
all was good apart from i realised that the fuel pump runs constantly once the ignition is turned on. is this correct ? i am sure it normally primes then runs constantly once the engine is running ? if this is correct how does the pump know it has primed has it got some sort of pressure sensor or is it done on a timer ? any help would be great as the last thing before its out the garage ! 
thanks ! Yes i have the two relays and have found the fuel pump relay with the green and purple wire but what do i need to do with that, there is no problem with the relay ? i assume the fuel pump should only prime at first yes ? then run constantly when engine is on ? mine just runs all the time with ignition no prime function, is this normal ? thanksBrianmoooore wrote:Your M52 engine loom should have three relays on it. One of these has five pins and the other two have four. One of the four pin relays will have a green/purple wire connected to pin 87 of its socket. This is the power feed (via a fuse) to the fuel pump.
Running your fuel pump directly from the ignition switch, or via a separate switch makes your car technically unroadworthy, since it will contravene construction and use regulations. It is also potentially dangerous.
Only becomes a problem when some plod you have annoyed is looking for something to throw at you, or an insurance company is looking for a way out of a claim.
in that case i am beginning to think there is an issue with my ecu as it is all wired up correctly and i can not see why the fuel pump would be running constantly unless getting the signal from the ecu, very fed up now thinking of just driving it as is !Brianmoooore wrote:The green/purple wire should go to fuse 11 in the fusebox, via pin 13 of the C101 engine loom plug and socket, and from the fuse, a green/purple wire goes to the fuel pump.
The fuel pump relay should pull in, under the control of the engine ECU, putting 12 volts + on pin 87 of the relay and the green/purple wire, when, and only when, the ECU decides that the pump should prime and when the engine's crankshaft is rotating.
Pin 87 of the pump relay should be the only source of power for the fuel pump.
in that case i am beginning to think there is an issue with my ecu as it is all wired up correctly and i can not see why the fuel pump would be running constantly unless getting the signal from the ecu, very fed up now thinking of just driving it as is !Brianmoooore wrote:The green/purple wire should go to fuse 11 in the fusebox, via pin 13 of the C101 engine loom plug and socket, and from the fuse, a green/purple wire goes to the fuel pump.
The fuel pump relay should pull in, under the control of the engine ECU, putting 12 volts + on pin 87 of the relay and the green/purple wire, when, and only when, the ECU decides that the pump should prime and when the engine's crankshaft is rotating.
Pin 87 of the pump relay should be the only source of power for the fuel pump.
I think that's whats happened. One is always live then goes earth and the other is earth the goes live. Once the engine turns over. I have to look at mine to remember.Brianmoooore wrote:Wrong type of relay fitted is one possibility.
The four pins should be 85,86, 87 and 30. Look under the relay's socket, and list the colours of the wire(s) going to each pin.
thanks allot for your help i will have a look mid week, what fuel pressure should the rail be running even if i clamp the return line briefly the pump doesn't stop running so i don't this the pump has a pressure cut off, so the prime is just done on a timer right ?drakesmith wrote:I think you got the relays wrong wiring wrong. Sure one switches from earth to live once the engine starts. Check your ignition switch. You my just may have a fuel pump issue. Once its primed it should shut off. Check you fuel pressure at the rail?
See if that holds bar
right so been out there tonight having a go over things.Brianmoooore wrote:No pressure sensor involved, so this cannot be caused by a duff one or duff pump
Pressure in the rail should be whatever is marked on the side of the fuel pressure regulator less the partial vacuum in the inlet plenum. The partial vacuum will be 1/2 a bar or so at idle and close to 0 at WOT.
right so been out there tonight having a go over things.Brianmoooore wrote:No pressure sensor involved, so this cannot be caused by a duff one or duff pump
Pressure in the rail should be whatever is marked on the side of the fuel pressure regulator less the partial vacuum in the inlet plenum. The partial vacuum will be 1/2 a bar or so at idle and close to 0 at WOT.
thanks i understand the pins allot better now! i have re-looked at the voltages and the only time i am getting 12v at pin 85 of fuel relay is for about three seconds after the ignition is switched OFFBrianmoooore wrote:Both the above sets of results are correct, except for 0 volts on 85 with the ignition on, which leads to 12 volts on 87.
30 is connected directly to battery +, so is always 12 volts. 86 is fed from 87 of the DME relay, which is switched on by the ECU when the ignition is turned on, so is 0 volts with the ignition off, and 12 volts with the ignition on. 87 is the relay output to the fuel pump, so 0 volts with the pump off, and 12 volts + with the pump running.
85 is the control pin, and is earthed (0 volts) by the ECU to make the pump run. 85 should briefly drop to 0 when the ignition is turned on, before returning to 12 volts until the crankshaft is rotated.
Disconnect the ECU, pull out the DME relay, use a wire link to connect 30 to whichever 87 gives 12 volts+ at 86 of the pump relay, then turn the ignition on.
The pump should not run, and 85 of the pump relay should be at 12 volts.
If this happens, it looks like your ECU is faulty, probably with the pump control output device gone short circuit.
If the pump still runs, then the brown/green wire from 85 of the relay to pin 69 of the EU is shorted to earth somewhere.
i have tried to understand your instructions on what to do with link wires and things but i think i am out of my depth and don't want to kill something ! time to get someone too look at it i guess $$$ will probably take them 2 minutes ! i am sorry i mean pin 85 ! i have edited my last postBrianmoooore wrote:Nothing you can kill with the ECU unplugged.
Your previous post says you have 12 volts on pin 30 with the ignition on or off, which is correct, as it's connected directly to the battery.
That makes it unlikely that it's a wiring fault shorting to earth, and more likely that it's an ECU fault.Lyne30318 wrote:the only time i am getting 12v at pin 85 of fuel relay is for about three seconds after the ignition is switched OFF
Brianmoooore wrote:That makes it unlikely that it's a wiring fault shorting to earth, and more likely that it's an ECU fault.Lyne30318 wrote:the only time i am getting 12v at pin 85 of fuel relay is for about three seconds after the ignition is switched OFF
Pull out the pump relay, and check if this three second voltage is on 85 or 86
i know its hard to say when your not looking at the issue yourself but from this information do you reckon its worth ordering another ecu and trying that ?Brianmoooore wrote:The 12 volts must be from a delay in the DME relay switching off after the ignition is turned off
the ecu has an news delBrianmoooore wrote:It would be worth borrowing one, but don't forget, it needs the matching EWS box and key chip.
there is no issue with the news the car runs, and the loudness off the pump is also not the problem its that it always runs with ignition no 'prime' function controlled by the ecudrakesmith wrote:I think some simple is a miss. The ews only kills the spark. Wrong or right? ?
You might just have loud pump my mates touring pump was aways loud when low on fuel.
Are 318i pump different from 325i?
over the last few days (haven't touched the car) it has began working correctly on its own every time i try it, that leads me to think it is defiantly the ecu playing up! i will get the conversion completely finished for now and hope it stays working, can easily swap out the ecu at a later date! is this an issue you have seen caused by the ecu before ?DanThe wrote:Have you tried a different ECU yet?