'85 535i not starting

have new starter new battery new alternator.Car sounds strong when starting but haws trouble kicking over. I turn car power on and fuel gage goes up.
Try to turn car on, fuel gage goes down,eventually the fuel gage will rise again after trying top start the car a couple of times and that is when the car finally starts. When running car is very strong and dependiable. Please help with what could be wrong
Thanks, Skunkman
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Hello,
Sometimes additional symtoms like you fuel guage can be misleading, but it is possible the your key switch is failing. The key switch must send a start signal to the ecu as well as the starter.
Starting issues can be caused by- (I can help you will these.) *Worn distributor cap center electrode. Extremely soiled throttle body. *Inoperative Cold-start switch. Inoperative Cold-start injector. *Weak crank sensor/dirty wires. Throttle switch failed or in need of adjustment. *Failing ecu water temp sensor. Failing thermistor in the AFM. *Worn AFM resistor matrix. (fixable)
Cheers, Blake
If you want to gain a greater understanding of your car then check for things at the ecu. Two guys can rip through these tests. Sinking ground Sourcing= Voltage
Start signal voltage (source) at pin 4. (Key in start position) Power (source) to ECU at pin 5 in start and run positions. Pin 18 should always be powered. pins 14 and 15 are sinking (ground) outputs for the injectors. Pin 34 sinks to idle valve. (Close) Pin 35 sinks to idle valve. (Open) Pin 20 sinks to fuel pump relay. Pin 1 sinks to ign coil. (Fires Coil) Pin 2 sinks throttle closed. Pin 3 sinks wide open throttle. On manual transmissions - if grounding pins 10 and 28 start the car then you have a bad jumper wire in your harness. On automatics- If grounding pin 28 starts car; bad transmission switch.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.