fuel delivery 735il

[perrin]

Hi there, My user name is Perrin I am in Sydney, Australia, so far I have just viewed The various threads and replies, some funny, some serious. (life’s like that).Introduction is now complete, Now I need some H.E.L.P.I drive a 735il with 340,000Kms on the dial, I appear toHave an erratic fuel delivery that seems to be baffling theNon BMW experts.On driving on a hot day and stopping for about 10 minutesAt restart engine appears to have a flat spot as I start to move, the Further I depress the pedal the worse it gets, I have found thatIf I back of the pedal and press down very lightly fuel appearsTo flow again, The same happens at traffic light stops and alsoIf I increase pedal pressure going up hills, it is more prevalentIf the fuel level is down to a quarter.Has any member had similar problems or perhaps know what my Problem may be? (That is besides owning a 735il)

 

[pussy]

hi..

having problems on your car..

listed below are some of the systoms that you can try.

1. do a test like this... look for the fuel hose that return to the tank after the FUEL REGULATOR . bend it or grip it to stop the fuel..do this engine running . if the rpm goes high, than it's your fuel regulator dying or can't hold the pressure.

2. check for the ignition coil, only one next to the ecu box. very hot, than got problem... change it.

3. check also for the FUEL PUMP pressure, below than 3.5 bar, need to change the pump.

4. check also the FILTER unit, could be clog.

5. check the fuel delivery lines or hoses, could be old hoses, or clog aluminum lines due to petrol varnish..

6. check if the THROTTLE POSITION SENSOR SWITCH next to the throttle body is working, with the 'click' sound on when the throttle open.

Last of all, it could be the DARNED AIR FLOW METER !!....check that last, cos it's expensive..


best of luck ..

regards.

 

[perrin]

Hello Pussy,
Many thanks for speedy reply, I will go through your checklist and hopefully fix or at least Know my problem.
I report back on my findings.
Kindest ,Perrin

 

[perrin]

Hello again members,
My fuel delivery problem is now solved, I went through Pussy’s check list,
1. Return fuel hose grip/squeeze test.
Result, no difference to rpm, so fuel regulator appeared ok.
Also disconnected small diameter hose on regulator to see if any fuel
Getting past the diaphragm, no sign of fuel, appeared ok.
2.Check ignition coil for very hot.
Result, coil not very hot, so coil appeared ok.
3.Check fuel pump pressure to 3.5 bar.
Result, disconnected return to apply test, found NO evidence of fuel at all
In return line, removed regulator, physically tested flow with compressed
Air and found regulator working ok.
4. Check air filter,
Result clean, no problem.
5. Check fuel delivery lines for blockage.
Result, Did not do fuel line check but blew through return line, engine to tank
Found clear.
6. Check Throttle position sensor.
Result, could NOT hear it clicking, so suspected this was possible problem.
Had an analyser check, found throttle sensor was OK.
WHAT NEXT?
Based on the information I had gained from PUSSY’s list , I decided that it was possible
That the fuel pump, whilst still apparently working enough to run the engine, albeit sadly,
was not giving enough pressure to open the regulator diaphragm, maybe the reason for no
fuel in the return lines. I had already suspected the fuel pump and had one on hand. So I
Drained the tank and removed the pump, What I found amazed me that the car had run at all,
The body of the pump had almost split in two, so whilst it was still pumping some fuel to
the engine, half the fuel was pumping out through the split back into the tank.
To finalize my story, The new pump was fitted and I was restored to full BMW power again.
THANKS AGAIN PUSSY
Kindest regards
Perrin (Australia)