I have a 1988 BMW 535si. I am trying to diagnose a problem where the engine will turn over and surge for a second and then die. I believe that it has to do with the fuel pump relay. Problem is that I can’t get a straight answer from the dealer as to which relay that is. The owner’s manual diagram does not include the relays in it and the parts houses don’t have that information either. Talk about forced dealership dependency! Can anyone help me with identifying which of the relays in this picture is the one? This picture is taken from the front of the vehicle. There are three relays outside the box on the left, three on the outside of the box on the right (covered with rubber shields so they are not that obvious) and the ones in the box. I was told by the dealer that the MAIN relay is white, the FULE one is orange or blue and that if they had been replaced they would most likely be light green. Also told that if I wanted to take the fuse box out to look for the purple wire as that indicates fuel and is going to the fuel relay.
The lid on the fuse box identifies the relays on the inside and doesn't mention a fuel pump relay, so I am assuming that the relay I am looking for is one of the 6 relays on the outside of the box.
Looking at your pic-the main relay is the 1st on the left corner and the fuel pump relay is above it
January, 30, 2012 AT 10:26 PM
Thank you very much. You are an angle!
January, 30, 2012 AT 10:31 PM
To rasmataz, In addition to saying thanks, I want you to know that even though I can't return the favor you have so graciously done for me, I will repay your kindness to someone else that I meet along the way and tell them it's because of your kindness helping me. God bless. Ken
January, 31, 2012 AT 12:20 AM
Your welcome and thank you for the kind words-your appreciation is good enough and TY for using 2carpros -God Bless
February, 1, 2012 AT 6:25 PM
Regarding the 535is question I posted before. Located and tested the relay (thanks to your diagaram) and it tests fine. The fuel pressure holds stead at 38psi and when car dies/turned off, it still holds 38 psi in the rail.
The ground from the relay is open until the car starts and then it closes. When the ground opens the car dies. But the fuel pressure is maintained at 38 psi indicating that there is a closing switch to ground further down stream. This also indicates to me that the fuel system is not an issue and also the fule pump relay is not the culprit either.
What switches the ground from the fule pump relay to the actual ground further down stream? Is that the computer, another relay or is it possible that the computer is not grounded properly?
BTW, where is the computer located?
Thanks for your reply.
February, 1, 2012 AT 7:59 PM
Brain box is at under left side of dash-
Could be a ground issue, double check computer ground and also the computer might not be grounding the fuel pump relay to transfer power to the fuel pump