No crank no start issue

8BIKER1

MEMBER
1998 BMW 528
2.8L
6 CYL
2WD
AUTOMATIC
119,000 MILES

The car is been having some electrical problems such as; the radio turns off and instantly the brake lights turn on. Also once in a while it’s got electric tilt steering wheel it was just tilted all the way up as you’re driving. So today I pulled the four relays out by the battery in the trunk and the terminals looked kind of corroded so I sanded them a little bit and clean them up. I put them back in and the car won’t start all the lights come on, the dash lights came on, the radio comes on, the windows go up, but the engine doesn’t turn over. Can you tell me what I did and how I can fix it? Do you think maybe I messed up the alarm system? I’m stuck out here right now and I need to start my car.

Friday, June 11th, 2021 AT 11:45 AM

1 Reply

JACOBANDNICKOLAS

MECHANIC
110,101 POSTS

Hi,

Is the security light flashing or staying on? Are the only relays removed in the trunk?
I'm asking because the starter is controlled by the engine control module relay.

If you look at pics 1 and 2 below, that is a wiring schematic for power to that relay. Check the two fuses to see if one is bad. In addition to checking the fuses, make sure there is power to and from them. Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Next, in the trunk, one of the relays is called an unloader relay. Its purpose is to remove power from other relays while the starter is engaged. Remove it and check it to make sure none of the pins are pushed in and it is fully seated. Also, here is a link that explains how to test a relay:

https://www.2c7
arpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

Also, we need to check several fuses. If you look at pics 3, 4, 5, and 6, they are the power distribution schematics. I highlighted everywhere the unloader relay receives power. You will need to check these fuses as well.

When you look at the power distribution pics, the fuse numbers and fuse panel number is indicated. For some reason, my manual doesn't supply a legend for me to show fuse specific location.

Let me know what you find. Also, if you look at the very last pic, I included a pic of the unloader relay in the trunk so you can locate it easier. Note that it does indicate terminal R. So, pay special attention to fuse 43 in fuse panel 1.

Take care,

Joe

See pics below.

Images (Click to make bigger)