A couple of months ago my 635 suffered a very brief loss of power. A couple of days ago, the problem reoccurred and the car stopped. After a short wait, it re-started but would run only for a short distance - before a final halt!
The problem turned out to be a faulty fuel pump relay (located just in front of the fuse box) - ?4.73.
Might help someone with similar problems.
JohnP
FUEL PUMP RELAY
Moderators: GRNSHRK, ron, bfons
Fuel relay
Remove relay and give contacts a good squirt of contact cleaner then work the relay into the socket a few times.Normally cures it.It is worth doing this to all electrical connections throughout the car.It's amazing the difference.
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dobleo7
Re: Hmm,
Hello there....just a quick question: I am unable to see the diagram you posted of the exact location of the fuel pump relay. There are three relays located in front of the fuse box and I was wondering if you could send the pic indicating which one of those would be the nasty culprit of my no start condition. THanksKC Ron Carter wrote:Here is a diagram for the lurkers to show the issue.
Later,
sean
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KC Ron Carter
Locating the fuel pump relay
OK, the relay location can be moved.
The best method of locating the fuel relay is by looking at the color coding of the wires on the bottom of connector.
Fuel pump relay uses 4 each wires
30.Red= Power in from battery 1.5 in size the largest of the wires
86.Red/White= Power from main relay
85.Brown/Green = Control in the ECU pin 20
87.Green/ Violet = Power to fuse 11 and o2 sensor relay
Main Relay uses 5 each wires
30.Red = Power in from battery 1.5 in size the largest of the wires
86.Green = In from the OBC relay
85.Brown = Ground
87.Blue/Red = Pin 35 on ECU ignition power
87.Red/White = Power to injectors and to fuel pump relay
The o2 sensor uses 4 wires
30.Green/Yellow = Power from fuse 9
87.Green/Violet = Power from fuel pump relay
85.Gray/Brown = Pin 31 on ECU for control
86.Green/Blue = Power to o2 sensor
Here is a picture, not very good or accurate.
Later,
The best method of locating the fuel relay is by looking at the color coding of the wires on the bottom of connector.
Fuel pump relay uses 4 each wires
30.Red= Power in from battery 1.5 in size the largest of the wires
86.Red/White= Power from main relay
85.Brown/Green = Control in the ECU pin 20
87.Green/ Violet = Power to fuse 11 and o2 sensor relay
Main Relay uses 5 each wires
30.Red = Power in from battery 1.5 in size the largest of the wires
86.Green = In from the OBC relay
85.Brown = Ground
87.Blue/Red = Pin 35 on ECU ignition power
87.Red/White = Power to injectors and to fuel pump relay
The o2 sensor uses 4 wires
30.Green/Yellow = Power from fuse 9
87.Green/Violet = Power from fuel pump relay
85.Gray/Brown = Pin 31 on ECU for control
86.Green/Blue = Power to o2 sensor
Here is a picture, not very good or accurate.
Later,
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Chris Wright
KC Ron,
What year is your written discription referring to?
If you switch the two descriptions for pin 86 and 87 on the O2 Sensor, your written description matches my '87 wiring diagram exactly.
What year car is the pictured diagram for?
Where did you find this diagram? I have one like it for an '87 that I got out of a Mitchells Manual. i was wondering if there was another source out there for wiring diagrams like this. As opposed to the BMW style like the ones that are online.
What year is your written discription referring to?
If you switch the two descriptions for pin 86 and 87 on the O2 Sensor, your written description matches my '87 wiring diagram exactly.
What year car is the pictured diagram for?
Where did you find this diagram? I have one like it for an '87 that I got out of a Mitchells Manual. i was wondering if there was another source out there for wiring diagrams like this. As opposed to the BMW style like the ones that are online.
Just as an additional to the above;
The diagram for the main relay is, as an electrical drawing, correct where it shows two outputs (both labelled 87) from one contact arm in the relay; however, this is not physically correct - inside the relay there are TWO contacts, one for each 87 terminal, and sometimes, just sometimes, those contacts will wear or deteriorate and only one of the contacts will make, giving you dashboard lights, ability to turn the engine over and.......no power to the motronic and no starting
Please don't ask me how I know - my therapist says i'm still recovering and it's best not to drag it up too often.
Moral - check power at BOTH 87 terminals at the bottom of the relay
HTH someone
Sharkfan
The diagram for the main relay is, as an electrical drawing, correct where it shows two outputs (both labelled 87) from one contact arm in the relay; however, this is not physically correct - inside the relay there are TWO contacts, one for each 87 terminal, and sometimes, just sometimes, those contacts will wear or deteriorate and only one of the contacts will make, giving you dashboard lights, ability to turn the engine over and.......no power to the motronic and no starting
Please don't ask me how I know - my therapist says i'm still recovering and it's best not to drag it up too often.
Moral - check power at BOTH 87 terminals at the bottom of the relay
HTH someone
Sharkfan
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Lymond