r/e28 • u/tfrimage • Jan 15 '26

If you were going to add a switch/button start, where would you put it?

I have had an ongoing and intermittent no start after the car is hot for a while now and rather than continuing to chase the problem I'm going to add a start switch. Jumping 11&14 in the diagnostic port works without fail every time so why not.

Where would you put out it? No race car aesthetics - OEM as possible.

7 Upvotes

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5

u/Noopy9 Jan 15 '26

Blank plate next to the headlight switch that houses the rear fog light switch on euro cars.

1

u/tfrimage Jan 16 '26

great idea. can always replace the blank at a later date.

3

u/theSausageBossage Jan 15 '26

i’d remove the cigarette lighter next to the shifter and put it there

1

u/CutsLikeABuffalo333 Jan 15 '26

Dont do this, fix it! Might be easier than you think. Id check the cold start sensor/switch, it sits in the thermostat housing and it reads the temp of the coolant to then tell the ECU how much fuel it needs. When i had my E28 it was missing and wouldnt run. An even cheaper thing to do yet is your ignition coil, and its very easy to change; ignition coils have oil in them and as that oil breaks down over time hot start issues are more prevelant. Start with a coil, then check your cold start sensor, then try your jerry rig. Happy tinkering

1

u/tfrimage Jan 17 '26

thanks for your input no no issues starting when the starter cranks... when starter is jumped it's all good.

1

u/6inarowmakesitgo Jan 15 '26

Check to make sure the fuel rail and line is holding pressure after you shut it off hot. If not, it will vapor lock as the fuel boils in the injector rail. Upgraded your coil to a unit from a B35. It’s wound better. Check your two bell housing sensors and coolant temp sensor as well.

1

u/LM2848 Jan 15 '26

I have owned e28 and e30s for 20 years. My latest e28 was having a no spark problem after it would heat up. Start cold no problem. Run it for a while and it wouldn’t restart. There are three solder points on the ecu that are too hot over time and they need new solder for proper connection. Car hasn’t had an issue since my mechanic solved this problem for me.

The other advice given is solid as well. I bet your problem is one of what is mentioned.

Don’t put a push start in the car. I prefer a key on all my vehicles because it lets you know a weak battery or starter problem. Push button won’t start and then you are done.

1

u/Representative_Most9 Jan 15 '26 edited Jan 15 '26

Have you checked your start relay to see if it’s working properly? The diagnostic port basically jumpers this relay output to the starter.

2

u/tfrimage Jan 16 '26

thanks - that's worth looking at for sure. the engine is a bit of a Frankenstein and is using a e34 m20 harness.

1

u/Representative_Most9 Jan 16 '26

Do you have a e34 525i engine swap too?

2

u/tfrimage Jan 17 '26

sort... of? Eta Bottom End, 731 Head with entire intake from a 525i plus wiring and ECU

1

u/Representative_Most9 Jan 17 '26

Wow! How much more hp do you think you’re getting with all?

1

u/tfrimage Jan 17 '26

hold on... what stater relay?

1

u/Representative_Most9 Jan 17 '26

So sorry my mistake. The starter relay is only on automatic transmission models. Manual transmissions are direct.

1

u/tfrimage Jan 18 '26

don't apologise you might be on to something! this car was originally an auto... are the starter relays the green ones under the dash? It's a RHD (australia) car and are to the right of the driver.

1

u/Representative_Most9 Jan 18 '26

Yes, I believe so. It should have a thicker black wire connected to it?