E28 crank- no start, electrics don’t work.

[Jadengyenes]

Having an issue where my 87 535 cranks but won’t start, something’s significant as well is the electrics like the windows won’t roll up, gas gauge doesn’t go up when I turn key, and ac doesn’t blow. Very weird,
We tried resoldering some weak points on the ecu, we’ve replaced main and fuel pump relay, outside fuel pump and still nothing, any help would seriously be appreciated!! 🫶
I’m thinking ignition switch but when I jumped the starter thru the diagnostic port it still didn’t start

Thank you!

[Fedaykin528e]

If it were me I would start checking chassis grounds including the one under the dash. Someone else on here probably knows exactly what it is though!

[Blue Shadow]

assuming you have compression
It cranks
does it get gas
does it get spark
I'd look at those two. you can check gas by wet plugs and spark by getting a spark plug wire to short through a screwdriver to a ground in the engine compartment where you can see it.

The OBC relay box stops spark and probably gas.


so you have the electrical manuals for your car?

www.e38.org/e28 middle of the left column or that wedphones site others link.

[Mike W.]

Spending a couple of minutes looking at things, a few thoughts. Check the plug that goes into the side of the fusebox. Make sure it's tight and not corroded. Next, what exactly does and does not work? Everything but the windows and cluster, or pretty much nothing? Does it crank with the key or just with the diag port?