85 Finally stops running ... again
 

After a week of running perfectly again it finally wont start and looks like its permanent(so to speak) this time. Time to solve the intermittant start issue. After borrowing JJ's DME and relay last night I have ruled that out. Next step found...
No spark at plugs because no current at coil... that seems to be the issue. With key on no voltage showing at either post on coil. Does that just leave only no power from the key as the lone possibility?
Not being a big electrical guy and only barely able to use a voltmeter,does anyone have any suggestions . Help appreciated. thanks Doug

Could be the ignition switch.
Also check the 14 pin connector.
Is the starter working....... just won't start?

It turns over fast but no spark at wires and no power to coil. Fuel pump working and idle control valve buzzing. Working DME and relay tried.

It turns over fast but no spark at wires and no power to coil. Fuel pump working and idle control valve buzzing. Known working DME and relay tried.
CHT sensor, crank position sensors ,wires,cap,coil ect everything new. Plug behind key nearly new. Starting problem intermittent but increased frequency over one year and now permanent.

Is the DME relay clicking when ignition is turned on? If yes, good....if no, replace it

Does it continue to click while cranking? If yes, no good. It is a switched power short likely at the fue box.

Hi Bob Just checked, the DME relay clicks only when on and off, not while turning engine over. Have tried a known working relay and DME.

Then check volatage on the 14 pin connector in the engine bay. There are a couple of schmatics on the list.

Just had this problem and it was due to a wire that leas up to the me came undone. Really simple solution that got overlooked. Its probably not your answer but you never know

Joe Bob I see the diagram but where am I checking for power?
Nkotselas I can't make out your suggestion? thanks all Doug

Disconnect the DME and turn the ignition to ON. Then measure at the coil. It needs to show +12V on both sides. If not trace the black wire from the coil all the way back to the fuse panel in the front lugage compartment. The wire comes through the main harness to the relay panel. There is a connector facing the fire wall if I am not mistaken (there is one on the earlier cars). You might have to take the relay panel off to get to it. From there it goes to the coil. It does not show up on the 14-pin connector since there is no need for terminal 15 on the engine itself. The injectors are powered by the DME harness from the DME relay.

Ingo

So after taking a short tutorial on line I figured out how to properly use the multimeter and I do have 12 volts to both sides of the coil with the key on . Sorry about that...new to electrical diagnosis.

To review
has been an intermittent problem now full time
Turns over fast but no ignition
No spark at plugs
12 volts at coil both sides key on
Tried known good DME and relay
vibration at ICV
New position sensors
tick on and tick off at DME relay
fuel pump working

Any other suggestions? thanks Doug

Well....you've checked pretty much all of it.

My suggestion is to question your methodology.

How did you check for spark?

The fuel pump is running.....have you given the intake a shot of ether/quick start?

A cough when a shot is given while cranking (2 people required) tells you two things, you have spark and it's a fuel issue. No cough...it's spark.

Have you pulled a plug and taken a read?

I just went thru the same drill/problem on my 84, check the troubleshooting electrical section and measure the resistance of the speed and crank position reference sensors. If it is not per the resistance in the Bentley manual thats your problem. I found them on line for $55 each from a BMW parts place in NH.

Bad coil

I pulled a plug, put in a spare and no spark, tried spraying ether under ICV and no cough. Just tried known good coil. Speed and Crank sensors are new 1000 miles ago and carefully put in when engine was out. Could still be them but running out of ideas.Dont have a occilliscope to check them. Thanks for your help Doug

To review
has been an intermittent problem now full time
Turns over fast but no ignition
No spark at plugs
12 volts at coil both sides key on
Tried known good DME and relay
vibration at ICV
New position sensors
tick on and tick off at DME relay
fuel pump working
smell fuel in tailpipe
tried known good coil

Check your rotor and cap.

Rotor and cap new Pete but double checked and ok. Starting to wonder if new reference /position sensors might be defective after only a year. All cables and attachments appear fine .

It appears (after grounding removed green wire from coil and grounding top of coil output) that my green wire to coil is not pulsing hence no spark. Does that lead me back to speed sensors knowing that my DME and relay are good?