1990 US M3...No Spark

[erikm54life]

Hi all !

I'm much more of a lurker and searcher than a poster but my situation has reached a point where I'm constantly scratching my hairless head !

Let me provide some background to my "No Spark"situation......

In December I had an issue with my water pump and parked the car for 3 months. I purchased the water pump, installed it myself and then the car refused to start ! Figuring that it was the fuel pumps, and I had a new Walbro at hand for the double to single swap, I swapped the pump. The car ran perfectly prior to my water pump issues.....oh yes, on some days if I switched the car off and attempted to start it immediately it wouldn't start unless I waited for roughly 10 minutes. Figured this was a fuel pump issue as it seemed to bog down a bit over 190kmh

Personal issues, work with constant travel prevented me from working on my car....this was about a 4 month period. Fast forward to last week and I resumed work on the M3.

This is where I am currently.....There is no spark from the coil but the fuel delivery from the pump is ok. I've checked the fusible link in the trunk....i even took it apart just to make sure the fault wasn't from there. Also checked the OBC relay, jumpered the 2 green wires still no spark. I changed the coil as I had a new one in my store and no difference...there's voltage at the coil but no spark. I changed the ground strap near the expansion tank too

The only areas left seem to be the ECU and the sensors on the bellhousing. I removed the 2 sensors and cleaned them but still no change....I''ve read that though they may pass an ohm reading check they still may not be functional.

As I'm resident in Lagos I don't have the luxury of going to a parts store to buy parts for this car....ordering from the US isn't an issue...its just the time. I've gone through almost all the "no Start" threads here and I'm just hoping it isn't the ECU.

Can you wonderful people point me in the right direction ?

Cheers,

Erik

[Dave @nz]

Hi Erik,
I take it you have been checking for no spark at the coil tower, just seems strange that the fuel pumps are working with no spark .
Good thing to try is bridge or replace the DME relay behind the plastic panel at the coolant tank and try starting.

This year I was chasing intermittent hard starting then non starting issue, followed the power supply from the trunk tested the OBC relay ended up being the DME relay faulty. I replaced the original DME relay in 2013 because I read they can cause problems didn’t expect problems from the replacement one.

[erikm54life]

Thanks Dave !

The relays in my car behind the plastic panel also behind the expansion tank seem to be a different colour than what I see here. When I'm home at night I'll take a picture of them.


The fuel relay must be fine as I have fuel.... disconnected the hose to the fuel filter and cranked and fuel was pumped with good pressure.

I have a new DME relay......I assume the one in the middle.....swapped it and same result....no spark.
The first relay from the left (Black and bigger than the others on my car) is for what ?

I had a E30 325i back in 1999 and seem to have forgotten most of my E30 troubleshooting skills......on my E34 M5 I easily disassemble anything on the car but I guess this is the price I pay for not bonding with such a beautiful piece of engineering !!

[Chris W]

The bigger, black relay should be the evaporative purge valve relay. That won't affect the ignition system.

[erikm54life]

The bigger, black relay should be the evaporative purge valve relay. That won't affect the ignition system.

Chris thanks.

Figured it would be something like that.

[Dave @nz]

Just to confirm you are cranking it over and no spark at all from the coil, checked by having a jump lead from the coil tower to the chassi.

Next I would follow this post sounds like exactly same symptoms.
https://s14net.vbulletin.net/forum/s...spark-no-start

[erikm54life]

Dave thanks!

I read through the thread previously......wanted to exhaust all the usual suspects before I crack open my DME.

Tomorrow morning I'll go through some of the test procedures entailed that I didn't do and report back.

[erikm54life]

Come to think of it...though I have fuel delivery from the fuel pump I don't think the fuel is being delivered to the engine.....i.e....injectors aren't firing !

After cranking the car several times I see no sign of fuel on the plugs ! I'm going to have to attack the troubleshooting matrix systematically and report back !

[hesnotthemessiah]

I have exactly the same problem, I thought it was the fuel pump......had an auto electrician visit today, he checked everything.....turned out it was the fuel pump as suspected.

[erikm54life]

In my case the fuel pump is brand new and it pumps fuel but the injectors aren't active and no spark.

Haven't had any spare time due to "back to school" duties for my kids......but I'll resume troubleshooting on Sunday.

[hesnotthemessiah]

Hope you get it sorted......I guess I was lucky, straitforward to solve. A pain in the b*tt when one has to go through pretty much the entire system to get to the bottom of the problem. I think the only reason my fuel pump packed in was because it had been sat there idle for over seven months while the whole car had a nut and bolt rebuild....

Good luck.

[hesnotthemessiah]

UPDATE......After all the assurances that my problem was the fuel pump.....turns out it's not! It is definitely electrical (errrr.....maybe)....

My car is now off to it's third port of call.....and again on the back of a truck...:-( It is off to a reputable Auto Electrician company who assure me they can sort it.....

I think it maybe a relay behind the dash or maybe the immobiliser.....

The pump is working....I attached a battery to it and it definitely primes....but no fuel gets through to the engine.....?

After all the work I've had done (engine rebuild etc) I think maybe they squished a wire or broke a wire or blew a relay......(not sure which obviously) but......

My saga continues.....Hope you got your's sorted?

[hesnotthemessiah]

Update....Update....

After a thorough diagnosis....turns out it was the CPU

A capacitor had blown and there were some dry joints as well.

All good now though :-)

[hesnotthemessiah]

D’oh....! ECU....not CPU.

I’m such a dumb a** sometimes.

[Dave @nz]

Good to hear you have it up and running, ECU problem sorted and good to go.