M60 Won't start (Still)

[BIGRED]

Hello all,

I posted in the E34 area and while there has been replies, to this point in time I am still hunting for the source of my troubles. Car is a 94 530it. I have owned it for a short while, it has 148,000 miles on it and I have no paper history.

History
Once purchased I had a rebuilt transmission put in it and a major service. The car ran really nice. I was out and about, floored it and it downshifted as it should have. There was a stumble the check engine light came on ran much rougher and then died. Re-start attempts within minutes of this event at best showed it trying but would not start.

Condition at time of event
1/2 tank of fuel
No blown fuses
Code was thrown Oxygen sensor #1

Tests performed thus far
Checked and swapped Fuel Pump relay - Both appear to be working fine.
Ran pump before regulator - Fuel was coming out
Put pressure tester at tank - 25 psi (with motor cranking)
Pulled pump and ran it using another battery source - Huge difference in liquid flow

Checked voltage at both fuel pump and main relays - The problem seems to point to something in this area or the oxygen sensors.

With the engine cranking at times there is no voltage at the plug to the pump.

Jumping the fuel pump relay socket (ignition on) does nothing. No power to the plug and or the pump does not pump.

There is a green wire with a violet stripe that should be hot but is not. Tracing it around in circles brings me to 2 green wires to which it is joined. The green wires head to the oxygen sensors.

It "feels" like the oxygen sensor has the fuel pump shut down. I did read when cool, they oxygen sensors have no impact on fuel control until it warms up.

I am fairly certain that is I power my fuel pump directly from the battery, the car will start (assuming there isn't some other control o prevent this).

So.....

I am not sure what my problem is.

Any help will relay be appreciated. I live in quite a remote area and no way is there a mechanic around that has BMW experience.


Thanks in advance!
Don

[632 Regal]

Hi Don,

the O2 sensors wont shut the pump off, sounds like a voltage issue from what you wrote. Im guessing the fiuel filters are fresh and with batt voltage your getting upwards #45 lbs pressure. This will zero it down a bit before you ransack the electrical system which runs miles long.

Double check voltage with key on with engine not running, then with direct 12 volts. if both pull the same pressure at the pump measure at the manifold, could be FP regulator or other nonsence.

Zero this in and we can go from there.

[winfred]

if all you get is 25psi of fuel pressure something is screwed, sounds like the pump to me without getting my hands dirty, should shoot over 75 if you pinch the return line when jumping the fp relay 30 is the power 87 is the power out to the pump, connect those two, 85 and 86 are the triggering wires one should go hot with the key and the computer grounds the other to turn on the pump if i remember right, if you have 3 relays 2 4 pins and a 5 pin the 5 pin is the main and the 4s are fp and 02, if it has 2 relays (like a 535) the 4 pin does the 02 and fp, if the fp relay doesn't power up while you are cranking see if you have spark by pulling a coil and sticking a screwdriver in like a plug and hold it about 1/8" from a good ground (you can get zapped if you are a better ground!). the 02 has nothing to do with starting

[632 Regal]

I like good burgers, get that at IHOP?

[BIGRED]

Thanks for the replies.

Knowing it can't be the OS2's is a BIG HELP!

I want to run my tests over one more time to make sure I have done it correctly, however I am almost sure that I have an electrical problem. In one test I pulled the electrical connector to the pump with the engine being cranked, there was no voltage at the plug end.

Is it reasonable to bypass the entire electrical system and power the fuel pump from another battery source and then.

1. Take pressure readings
2. Try to start the car?


OR will I muck up something new?

[winfred]

you can power the fuel pump by jumping 87 to 30 at the relay, with the key on 30 should be hot, if it's not the main relay may be dead, just look at the bottom of the relay for which pin is which #

[BIGRED]

you can power the fuel pump by jumping 87 to 30 at the relay, with the key on 30 should be hot, if it's not the main relay may be dead, just look at the bottom of the relay for which pin is which #

Assuming (I will re-test) that 30 is not hot with the key on. That points to the main relay as the source of the problem for the FP Relay? Is there a way to test the main relay and socket to confirm that is the source of the problem? AND that the source of the problem isn't further upstream, before the main relay?

Thank you for the help!

[Ross]

It sounds like you are jumping the wrong relay. The grn/vio wire that splits into two grn ones is for the O2 sensor heaters.
The fp relay will have a brn/grn wire to term #4(85 on the relay), the O2 relay has brn/blu at that position.
You have checked for spark, right?

[BIGRED]

I have not yet checked the ignition side yet. I am working on diagnosing fuel first. I have 25 psi at the pump and or at times no power to the pump. The question why?

I will check and see where the grn/vio wire goes (to get it fresh in memory)

[winfred]

the main relay gets it's power from the battery, it's 30 should be hot all of the time, the fp and 02 relays get their power from the main relay