1995 525iT won't crank or start

[ZeroHeadroom]

1995 525iT (build date 9/94) will not crank, will not start. Battery is fine, everything else works on the car. This happened several weeks ago when I was downtown. I tried to troubleshoot it but the weather was a total downpour and after a week I had the car towed to my house. One of those deals where they slide the tow bar under the rear tires tie it down and lift it up.

A week later I went out and tried to start it again and it fired right up. I immediately drove it into my shop. Stomp test has never worked on this car. My Peake tester shows no error codes. Can’t find any blown fuses. Failed to figure it out and it started every time I tried, so I finally said screw it and started driving it,

A couple of weeks later I parked outside the garage and the next day it wouldn’t crank or start. I was so ticked off that I let it sit for a week or two. Jumped back in and it started right up with my having not touched it in between.

It’s back in the shop and I don’t have a clue what to do next. I tried to check the starter relay but I have no idea where it is and the Bentley manual is no help. It shows two photos of front power distribution boxes but neither one is the same as mine.

Help !

[632 Regal]

Definitely a connection or ground issue. I would probably start with loosening the ground bolts, cleaning and re-tightening. Something is very marginal so you might not even see an issue but loosening and tightening connections might be the fix. I use Deoxit D5 for everything electrical, good stuff. I doubt you will have any codes for a freak issue like this though.

Afterthought... does you car have an immobilizer with the alarm thing? I had an E31 8 series with issues it would crank but not fire. Took 3 months to cut the anti theft wire and was good. Perhaps if you have an anti theft security system it's causing the no crank issue?

[Rustam]

It shows two photos of front power distribution boxes but neither one is the same as mine.

Help !


And, why didnt you provide a picture of what you actually have , to give traction to own request for help? What does it look like? Not sure if you're looking at same box.

The Bentley manual does indeed show two pictures, however in both cases the relay is practically in same place. Stick the ohm meter to the power feeding socket, the other lead to battery "+", then turn the key to "start" - observe a change in resistance from infinite to continuity. Keep repeating till the correct socket is found - that is the place of the starter relay.

Alternatively: look at the wiring diagram. Note the wire color code. Pull out sockets in the relay box and match the wire colors - that is your starter relay. Use flat long screwdriver.

The relay is not the end of things. The contacts on the starter see "elements " and may easily get corroded, or the nuts could get loose. This may easily be exacerbated by rainy conditions. Make sure the starter nuts are securing the wires well. The car is 25 years old - get the wiring diagram and trace all wires with a continuity meter.

[genphreak]

It's a late M50 e34, so likely has the wide grille and later security fitted to placate the insurance industry. You can tell from the key as it involves their very reliable transponder key (aerial and rolling code module in the dash), and DWA protection under the rear seat. It could have an old alarm module back there too which integrated with the DWA to cause key and fuel cut-out through the same signal to the DWA unit. However all e34s, especially tourings, can suffer from water ingress from A, B and C pillar sunroof drains. If any are blocked, rain water spills out of the sunroof drains, then secretly runs down inside the pilars and floods the floor-pan, under the carpet.

Afterwards, a musty smell inside the car indicates this is a thing, and if the smell is strong, the problem is large. e34 can carry 40 litres of water in the thick foam under the carpets. If you have the big factory mats, you won't even notice.

But the water will cause oxidation under the general module and rear power distribution box, just pull the rear seat and use a 10mm spanner to undo the black plastic frame and lift the modules and the relays up. If you can feel dampness under it with your fingers... clear the leaves and stuff from the drain openings using a vacuum cleaner and a 5' piece of garden hose taped to the end, that way it's easy to suck the rubbish around the drain openings as well as any leaves and things that has made it to the back of the sunroof cassette (esp. the C pillar drains in each corner)

If it has water under the carpet in the front and rear foot-wells, just pop up the floor drains from underneath, so it can drip out. Leave the windows open for a while somewhere it won't get rained on, ideally in the sun so it will evaporate out in the heat of the day.

If not that, check the ECU relay and fuse, in the engine e-box- and the main 50 and 80A inline fuses in the red chassis cabling near the battery, usually shrink wrapped to prevent shorting. At age these fuses suffer from corrosion and micro fractures that can allow them to work sometimes, and not others (ie intermittent temperature or use-related failures).

Checking involves removal of the wrap, replacement, and diligently re-shrinking with new wrap. I do 2 layers. Just whatever you do don't just using tape- remember one short will likely cause a fire and burn the entire car.