HELP: Cranks but no start

n2bimmer · Post by **n2bimmer** » Wed Sep 14, 2016 11:54 pm

Hey gang, im reaching out here in hopes of getting some help. My Euro 81 628csi wont start. Im getting fuel, but doesnt seems to have spark. i just replace the distributor cap and rotor, but still no good. Full story can be seen here.

http://www.bimmerforums.com/forum/showt ... t=no+start
http://www.bimmerforums.com/forum/showt ... ntrol-unit

Thanks for looking.

wmmag · Post by **wmmag** » Thu Sep 15, 2016 12:48 am

A long shot, but is there an alarm system in the car? It could be self-activating and blocking the spark.

n2bimmer · Post by **n2bimmer** » Thu Sep 15, 2016 12:52 am

wmmag wrote:A long shot, but is there an alarm system in the car? It could be self-activating and blocking the spark.

I believe there is some device under the steering column but its always been there

T.Hanson · Post by **T.Hanson** » Thu Sep 15, 2016 10:29 am

I can't help myself. Wanting to be helpful I read the posts from the link. To discover, once again , I am not, and never will be, a true inside E12, E24 advisor for problem solutions.

I don't speak acronym.

Qwodracer · Post by **Qwodracer** » Thu Sep 15, 2016 12:27 pm

Did you check the double relay? http://www.firstfives.org/faq/ljet/combo_fix.html

Very good read, and from your other posts you have been chasing fuel, not spark. Just pull the covers off and look for broken solder joints.

One thing that happened on my car, is the tachometer terminals loosened up from the housing, and were creating a short to ground in the ignition circuit, so in turn, no spark. (Was very frustrating to figure out) and I'm not sure if it's common or not... my fix was to tape off the wires and drive without a tach for now.

You said you change cap rotor and wires, well what about the coil? Cheap (performance muscle car) ones at autozone will work, you just have to get a new clamp, so they are properly grounded. I have replaced many Bosch coils through the years, and they have died in many odd, and different ways. Missing when cold, missing when hot, missing at low rpm, missing at high rpm.. lol there is no pre determined way for a coil to fail, until they get soo bad they don't work at all anymore.

If you want to test spark, get a timing light, cheap ones at autozone are 35$ and do rpm, you can "cheat" and put it on the coil wire and your rpm SHOULD read 6 times more than normal.. soo if you're cranking at 150rpm, it will read 800rpm. If it's less or it's fluctuating, then it's missing some of the time.

n2bimmer · Post by **n2bimmer** » Thu Sep 15, 2016 1:59 pm

I did check my combo relay, but ill check it again, i do have two but ill look over it again.

The wires look pretty good, they look fairly new, so the previous owner may have replaced it not to long ago.

That's interesting about the tachometer terminal. I may look into that.

Thanks

Im going to get a spark plug and check for spark on the wires and coil.

RonDwyer · Post by **RonDwyer** » Sat Sep 17, 2016 11:49 am

Run a known hot wire to the coil and disconnect everything else. My 10 foot alligator clip jumper is the most useful troubleshooting tool I own.

Do you smell gas in the exhaust?

If you put a tiny shot of ether in the intake, does it make any attempt to start?

Sometimes bypassing stuff can help identify the fault

RonDwyer · Post by **RonDwyer** » Sat Sep 17, 2016 11:54 am

And get rid of the alarm.
Reconnect spliced wires.
Disconnect power taps
Disconnect ground taps.
Remove the siren and its leads.
Ignore most sensors and LED warning lights on doors.
Take out as much leftover butchered stereo wiring as you can find.
Same for any alarm wires. Tiny 2-lead wires.

It's actually quite easy to remove an alarm. Get rid of everything that is not OEM.

n2bimmer · Post by **n2bimmer** » Mon Sep 19, 2016 12:50 pm

The problem has been found and solved, thanks to Ralph over at big coupe i was able to borrow a ignition module to test out. Swapped out the unit and it fired up right away. I opened up the unit that was installed in my car and there was aluminum oxidation and water in the box, im not sure how the water got in there, but based on the oxidation it was probably there for some time.

This is what is looked like, the chip was covered with silicone, it had appeared that the unit was rebuilt at one point, and whoever rebuilt it poured silicone all over to protect the unit,. This picture shows the unit with the silicone peeled away. Now im wondering if i can find a replacement chip somewhere?

http://i63.tinypic.com/143907.jpg

RonDwyer · Post by **RonDwyer** » Wed Sep 21, 2016 8:53 pm

I always recommend everybody to always get rid of any car alarm before it faults on you at an inopportune moment. A remote kill switch is much more effective. Taking the rotor with you is just as good at theft prevention.