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-   -   Fuel Pump or Relay? (http://www.318ti.org/forum/showthread.php?t=32615)

juan.manjarres 01-24-2011 01:42 AM

Fuel Pump or Relay?
 
hey guys,

Today I went for a drive and then came to a shop and turned off the car. After about 20 minutes I went back to the car and tried to start only to find my car sputtering and with no response to the throttle. I then kept on trying to start the car and it would start up and sputter with again no response to throttle position. Now it cranks but does not start. I replaced the camshaft position sensor and it also did not start. I now am testing the voltage to the fuel pump and it is measuring 10.6V when cranking the car. Is this a faulty relay? or is this the correct voltage to the pump? When I turn the ignition on there is no reading to the pump only when I crank the engine will it receive a voltage reading. Any help here would be greatly appreciated, thanks guys!

1996 328ti 01-24-2011 03:32 AM

You can swap the relay with another one I think, but most likely it's the pump.

Pierre 01-24-2011 06:15 AM

I am having a similar problem
 
The car won't start and I suspected a fuel issue. I tried the the relay bypass method but the Bentley manual does not match my 96 automatic. (I have no relay in location #1. I only have two relays there, not three as per Bentley.)
I pressed on the schrader valve on the fuel rail and got nothing. I suspect the fuel pump is not running. But is it the pump itself or the relay? Which one is the relay?
I guess I can test if I have voltage at the pump during cranking. If I do, I know it's the pump. If not...
Does anyone know which relay goes to the fuel pump on a 96 automatic? (Soon to be an S52 5-speed but not yet.)

juan.manjarres 01-24-2011 06:20 AM

I have the same setup as you. The fuel relay is the one in the middle or in our case the one on the left and the second one is the dme relay. Both work together so to test out the relays you would have to replace them both. Check the green and violet wire at the fuel pump and you should be getting 12v while cranking. Let me know what happens.

Bluebimma 01-24-2011 02:52 PM

If youre unsure what relay is your fuel pump relay, you use a screw driver to unlock the socket from the fuse box and look at the colors. Get your schematic for your exact year and look for the fuel pump on the schematic. Once found, itll tell you the colors of the fuel pump relay socket, if they dont match, try the other sockets. Once found, you can use a jumper (piece of small length wire with both ends exposed) and jump the leads for power in and power out. This will complete the circuit to your fuel pump. It will activate whether the car is on, off, or even if the key is in the ignition. If it works, the pump is not at fault, If it doesnt, check the fuel pump fuse. If good, go to the pump and hit it lightly with a mallet or rubber hammer, you dont want to damage if its good. If it turns on, then your pump is going out and you need to get a new one.

juan.manjarres 01-24-2011 03:40 PM

Well I would go and replace the fuel pump but I want to rule out a relay problem. I need to know if the pump should be seing exactly 12V or if its ok to see 10V. When I test the the plug at the pump it only shows 10V when I crank the car.

Bluebimma 01-24-2011 03:50 PM

When i tested mine, i got 10.4

juan.manjarres 01-24-2011 03:59 PM

Now I'm just confused. Should it be receiving 10v on crank? I'm not sire if it's the relays or the pump.

Pierre 01-24-2011 05:08 PM

Relay or pump? voltage
 
During cranking, you will most likely get lower voltage to the pump because the starter is sucking up all the juice from your battery. A bad relay will give you no voltage.
You can also jump the relay terminals to test the pump as described above. Take the relay out (I found out it's the left relay on the 2-relay setup, the right one os the DME relay, both green) and with the ignition on, use a jumper wire between terminal 30 and 87. (6 and 9 clock positions if you're standing next to the fuse box) You should be able to hear the pump turn on and buzz. You will also get 12V to the pump terminals. If you have the voltage and no buzzing, the pump is bad and needs to be replaced.

318_mzk2 01-24-2011 05:35 PM

I just had the same issue on the car I'm doing a moto swap too.. Car drive fine and went to start it after.a While and no fuel

juan.manjarres 01-24-2011 09:06 PM

K ruled out the relay. Now off to buy a fuel pump. Just found someone locally selling one off of an e36 325i with the M52 engine. According to the turner motorsport website will work. It is the fuel pump that is blue in color and I believe it is a VDO unit. Does anyone know if this will work?

Pierre 01-25-2011 01:58 AM

It may not
 
The M42/M44 pump as well as the M50/S50 pump put out 43.5 psi. The M52/S52 pump puts out 51 psi.
There may be fitment issues too. The ti pump has a unique part number. It may work but you may have depth issues, and fuel gauge reading errors.

Bluebimma 01-25-2011 02:01 AM

Thy put out the same fuel numbers, the fpr changes the pressure at or before the rail depending on the engine.

Pierre 01-25-2011 03:24 AM

I am not convinced
 
Fuel pressure and volume are different between the pumps. Part numbers are also different.
It makes no sense that BMW would produce a separate pump with different specs for no apparent reason. And the ti pump, while putting out the same pressure and volume as the M50/S50 pump, has a different part number. I plan to do a side-by-side physical comparison of the two but I suspect a different depth of the tank the main reason for the difference.

Bluebimma 01-25-2011 04:45 AM

All the e36s use the same replace pump, the unit itself, not their housings and such. The differences are whether theyre the passenger side with pump and sending unit, the drivers sending unit, and the other variable of whether they have one or two lines that go between the tank sides. They all pump the same volume of fluid prior to the FPR which changes the pressure for the rail. For OBDI engines, its regulated at the rail, the OBDII FPR is underneath the drivers side floor and is changed to the required psi before it even reaches the fuel lines to go to the rail.

The only other possible discrepancy for parts numbers would be the strainer. The actual size of the pumps are the exact same as well as their guts, all OE VDO, thus, no volume increase nor decrease.

Here are the direct replacement pumps for the e36.

Bosch
http://www.rockauto.com/catalog/moreinfo.php?pk=976817

Delphi
http://www.rockauto.com/catalog/moreinfo.php?pk=1114515

Beck/Arnley
http://www.rockauto.com/catalog/moreinfo.php?pk=1997944

Airtex With OEM VDO pump
http://www.rockauto.com/catalog/moreinfo.php?pk=59972

Youll also notice that the bosch unit is a replacement for 93-2005, m42-S52-M54.


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