Fuel Pump or Relay?

[Pierre]

My 96, which is soon getting an S52 transplant, lost its pump. I pulled the one out of my M3 donor and compared. They look the same, the color is different (ti is green, M3 is blue) and the connectors are different but everything else is identical. I cut the connectors out of the M3 and spliced them in the ti.
It works.
I may never know why BMW built different pumps if they are indeed the same. At least I do know that if there is a difference, with the S52 eventually installed, the pump in the car now will be correct one for that motor.

[pdxmotorhead]

They operate at the same pressure, but usually bosch pumps are rated in volume@pressure, so the M3 pump is capable of sustaining full fuel pressure at higher volume. Sounds like your in the zone

Dave

[btbiii]

I cannot start a 96 318ti. I did not hear fuel pump coming on, so I checked for voltage to plugs. Which one is fuel sensor and which one is for pump? I have a Yellow and a Gray? I went into fuse panel, and there are only 2 relays where normally E36's have 3 . Position 1 has NO relay or socket. Usually position 2 is the DME, can I assume position 2 is the fuel pump and position 3 is the DME? Thanks for any help anyone can give.

[Pierre]

The pump will only run during cranking and and keep running after the engine starts. The pump does not run with the engine in the on position.
To test the pump. you have to override the relay or apply 12 volts directly to the pump. The Bentley manual has a detailed description on how to test the pump.

[btbiii]

Pierre,
Thank you for response. I can get the voltage to the fuel pump by jumping it out. My issue-EVEN with cranking there is only 5.5 volts going to fuel pump relay. I checked DME relay and it has 12 volts. So somewhere I am not getting enough voltage to bring in fuel pump relay. Any help or ideas would be greatly appreciated. Thanks again

[applefan]

Originally Posted by btbiii

Pierre,
Thank you for response. I can get the voltage to the fuel pump by jumping it out. My issue-EVEN with cranking there is only 5.5 volts going to fuel pump relay. I checked DME relay and it has 12 volts. So somewhere I am not getting enough voltage to bring in fuel pump relay. Any help or ideas would be greatly appreciated. Thanks again

5.5 volts with the pump connected or disconnected?
If pump is a suspect, I would disconnect the pump and measure the voltage

[btbiii]

Voltage was measure with fuel pump relay unplugged by placing a volt meter across fuel pump relay coil receptacle tabs outside fuse panel. If I connect negative lead to chasis and positive to fuel pump relay coil receptacle I get 12v. I discovered the negative wire for fuel pump relay goes back to the DME box. I also discovered I have NO voltage to spark plugs and I am not communicating with the OBD port. Could it be crank sensor or DME unit? Thanks again.

[yoda]

OK... this thread has what I'm going through, with the exception that when I crank my car it does run a bit with problems and it shuts off. If I give it gas it does pick up a bit but it it won't go FT, feels like choke (not getting enough) and when I let go of the gas it sputters and dies...

Any ideas?

[BMW_Hatchback]

Check codes, even if there is no CEL, check and report back.

Not sure what your FI setup is, but for most cars I would check out vacuum, especially in the back near the firewall (the Y)

[yoda]

Originally Posted by BMW_Hatchback

Check codes, even if there is no CEL, check and report back.

Not sure what your FI setup is, but for most cars I would check out vacuum, especially in the back near the firewall (the Y)

My CEL has been on since the I swapped the diff giving me a speed sensor code... so I couldn't tell you if it just came on. I can't even take the car out to a shop (it won't make it). I've changed fuel filter, spark plugs, dropped a bottle of fuel injector cleaner in the tank... about to go buy the relays to see if that does something.

[BMW_Hatchback]

I think you're doing it wrong. Throwing parts at the car is usually a bad idea. Go to advanced auto and get a code reader for rental

[yoda]

I'll try to do that....THX

[Bluebimma]

You don't need any relays if its actually running. You can remove the fuel relay, run a jumper wire, and that'll tell you if the relay itself is bad. Since you're boosted, I'd check for vac leaks, the maf sensor, and grounds. Also, check the cel, there may be more info beyond your vss.

[yoda]

Originally Posted by Bluebimma

You don't need any relays if its actually running. You can remove the fuel relay, run a jumper wire, and that'll tell you if the relay itself is bad. Since you're boosted, I'd check for vac leaks, the maf sensor, and grounds. Also, check the cel, there may be more info beyond your vss.

The car sporadicly will turn over and run smooth only to have it bog down under semi heavy throttle load... and then it goes back to not running.

[Bluebimma]

Have you checked your fuel pressure at all?