Starter Relay works intermittent

[EnanoGee]

So when I drive around and leave my car for 30 mins, try to crank, nothing happens. Just dash lights come one and all electronics are fine. I found that the starter relay was the problem and bought a new one now everything works back to normal. Or so I thought. The new relay I bought does the same thing now after driving around for a few days. I came back to my car and tried but it wouldnt turn over. So again I switched relays in that exact moment when it wouldnt crank at all and behold it did. I can replicate that consistently when the car doesnt want to crank. Just switch relays.
Any idea whats causing this annoying issue? Just recently replaced battery, chassis to ground, checked for voltage drops. Nothing looks out of the ordinary. Any guidance on what to do next would be great.

[cheffy30]

part out.

[nando]

There's no 'starter relay'. The ignition switch is wired straight to the starter solenoid. The relay you replaced is probably the unloader relay, which just turns off accessories & hvac so the starter can have the full power of the battery.

Probably just a bad ignition switch or even the starter itself.

[EnanoGee]

There's no 'starter relay'. The ignition switch is wired straight to the starter solenoid. The relay you replaced is probably the unloader relay, which just turns off accessories & hvac so the starter can have the full power of the battery.

Probably just a bad ignition switch or even the starter itself.

The unloader relay is in the fuse box correct? This relay which I believe is the starter relay is located under my dash. Its the same orange relay as the ones for the fuel pump that are next to the main relay. I unplugged this relay while cranking (probably terrible I know lol) and the starter stopped rotating). It may just be an auto thing. But ive confirmed that its not the relay at fault. The ignition wire that is supposed to get 12v when i turn the key gets >1v when it wont crank. I measured this at the starter with my volt meter. I do get a steady 12v to the starter. But if I do wait long enough (lets say about 30 mins- 1 hours) it cranks and starts fine. Thats the annoying part. Starter will work consistently if i turn it over a couple times when i first start to drive.

[nando]

Well, auto or not - there's no relay tied between the ignition switch and the starter. There is a start interlock of course (so it has to be in D or N to start), but the wiring is actually the same except for an extra harness added for the AT cars.

[EnanoGee]

Well, auto or not - there's no relay tied between the ignition switch and the starter. There is a start interlock of course (so it has to be in D or N to start), but the wiring is actually the same except for an extra harness added for the AT cars.

https://youtu.be/WDLxV92bDXI

I recorded this a few days ago but now that youve pointed that out, this must be some kind of 3rd party thing done by one of the PO? Idk but ive driven and started the car fine for over a year and this is the only problem its ever really gave me.

[nando]

http://wedophones.com/BMWManualsLead.htm

download the ETM for your car, troubleshoot as neccesary.

I mean, technically it is a relay on the auto, but it's controlled by the shift mechanism - not the ignition switch.

[TobyB]

uneeda starter.

The integral solenoid's worn and binding.

t
carries a gallon of water for this sort of thing

[EnanoGee]

So on auto trans, that is the starter relay which also connects to Fuse 10. I get 12v out from the relay, so the relay is obv not the problem. Now when I measure the voltage when turning the key (back probing the BLK/YLW wire that connects to the solenoid from the relay) I get 10V to the wire. Is that much of a drop not getting the starter to turn over? The starter reads no significant amount of resistance. Fuse 10, has atleast 7OHMS of resistant, measured by taking out the fuse. Could this be the reason?

[EnanoGee]

So after jumping around from place to place with my multimeter, I get 12V when jumping the pins on the diagnostic plug (measured at DP) but I dont get 12V from the wire that goes from the top post of the starter to the unloader relay. It stays around .5V and gradually goes up over time until it finally cranks and turns over. Is this a heat soak problem @ the unloader? Because 10/10 times it will always crank on a cold start.

[nando]

The unloader relay just shuts down everything else (HVAC, lights) so the starter gets full power. It doesn't energize the starter, but is triggered when the starter is energized.

[EnanoGee]

So interesting thing happened yesterday. Pretty hot here in SF yesterday and when i was getting off work my car was doing the same thing (not cranking) since it was so hot outside which leads me to believe it is a heat soak problem. Luckily i got a jump start from a friend at work. Before that though, I measured 12V at the C101 port that goes to the starter, but the starter post was only getting ~6V and rising as temps settled.

[ForcedFirebird]

There is a starter relay under the dash and interrupts the voltage to the starter when not in park or neutral. When people tie the wires under the shifter instead of removing the automatic wiring loop, then it is very difficult to diagnose a manual swapped car (ask me how I know lol).

More than likely the female spade connectors in the relay holder have burnt spots on them, you probably could have just jiggled the relay to get it to start again. If you have an electrical pin removal tool, it's a pretty easy thing to replace (or could buy a relay holder from the auto parts store and splice/crimp it in).

Youtube-university link lol: https://www.youtube.com/watch?v=WDLxV92bDXI

[EnanoGee]

Hmm I tried to swap relays like I usually do and that didnt let it crank, I had to get a jump start. The thing is I measured the voltage through the C241(BLK/YLW connector that leaves the relay under the dash and goes to the starter) and got 12.4V. This is with the connector disconnected. While connected I got around ~10V. I'll see what I can do about the connection as stated, but Ive def cleaned every wire connected to the starte just in case

[lukeADE335i]

If you're not worried about whether the car tries to start if it's not in park, you could bypass the starter relay like we do for manual swaps?

I had the same issue as you after a manual swap, and just replaced the whole wire from the steering column to the starter and have never had a problem since. That circuit can be a pain to diagnose. I did this after I'd replaced the starter, so I knew it was good.

Here's my post on it:

https://www.r3vlimited.com/board/showpost.php?p=4583050&postcount=46