Weak/occasionally no spark problem....

ukmercman · Post by **ukmercman** » Wed Sep 03, 2014 7:26 pm

Hi all.

Had megajolt on my 1989 190e 16v for around 18months. Had it mapped at a rolling road to set up (along with my 48dcoe webers) and been good as gold ever since.

Use the car at weekends mostly. Last weekend - running like a champ. This weekend - start it and lumpy on idle almost like missing. Revs up OK but still coughing/spluttering. Bogs and loses power under load.

Pull plug 1 to check - very weak spark. Pull rest of them - same. Very weak spark and occasionally it looks like its missing a spark altogether. This seems random - sometimes they all spark weakly. Sometimes one looks like it drops away and returns. This is when cranking engine with all plugs removed from engine but plugs still attached to leads.

So, checked:

Trigger wheel all good and static timing correct.
VR sensor, gap (1mm) and bracket all good (although I bought a new VR sensor from triggerwheels and switched between them just in case - no change)
Thought coil pack might be on way out so got a brand new one from triggerwheels - no change
Checked all fuses and earths - all good.
Visually checked shielded lead for VR sensor - all good.

Problem still there if I unplug the megajolt ECU.
Timing still works - revving engine with light attached shows advance.

So - given that it was in perfect health last week and I've not touched it - any ideas? Am assuming an EDIS/component fault as problem persists with MJ unplugged?

Could it be the EDIS module itself - do they go funny?

Many thanks for any pointers, its driving me mad!

Steve

ukmercman · Post by **ukmercman** » Sat Sep 06, 2014 5:04 pm

anyone?

swapped out the EDIS module today - still got the weak spark problem.

set the sensor gap at 1mm, still got the problem...

HELP!

Thanks.

ukmercman · Post by **ukmercman** » Sat Sep 06, 2014 5:34 pm

Just replaced the shielded wire from the EDIS module to the VR sensor. No change.

So that's:

swapped VR sensor (around 2 weeks ago, car has run since then with no problems). Tried swapping in old one too.
brand new coil pack.
swapped EDIS module.

that's the entire EDIS system swapped and the problem is still there - was fine last time I drove it???

Alex B · Post by **Alex B** » Sat Sep 06, 2014 7:37 pm

How about the earthing of the engine block? No problems with corrosion at the earthing points?

Alex

Warning634 · Post by **Warning634** » Fri Sep 26, 2014 8:23 pm

hey there

i seem to be having exactly the same problems with my set in my mini.

check out the clips i have posted of the spark, can u tell me if yours is doing the same? its in the q&a section.

im pulling my hair out as well, as i have event in 2 weeks time andi cant get my motor to run 100%

if you figure it out please let me know

thanks

kevin

Post by **brentp** » Sun Sep 28, 2014 6:26 pm

Always good to re-check voltages as part of a verification. Especially system voltage while the engine is running (or attempting to run).

These checks will be helpful:
http://www.autosportlabs.net/MJLJ_V4_ve ... tion_Steps

Keep us posted on what you find out

ukmercman · Post by **ukmercman** » Mon Oct 06, 2014 4:55 pm

Some good news and bad....

I was tinkering on the driveway a few weeks ago and by chance, as it was getting dark, I noticed one of my ignition leads was arcing out! I decided to go the whole hog and got a custom set of leads made up by Magnacor as I assumed this must be the cause of the problem. £90 and 3 days later they arrive.

I promptly fitted them and was surprised to notice hardly any change. I decided to install a new set of plugs - just in case. New plugs fitted and problem instantly goes! All good, car ran smooth and strong. Subsequently did around 160 miles over the last week or so - ran beautifully.

So. Get in the car on Sunday to do to a show - got around 45 miles up the road and the problem seems to have reappeared!! Not quite as severe but had to really limp the car home with barely any throttle.

I'm now wondering if it could be a problem with the plugs? My local Merc specialist recommendeds NGK BP6EF S plugs for my engine - obviously, this would be for a standard ignition set up of coil and distributor. Should I be running a different plug with a coilpack/carb set up over the original fuel injected, distributor set up?

So, to confirm - I have:
Swapped the EDIS module for a spare
Checked all earths
Checked all powers
Brand new VR sensor
Brand new leads
Brand new plugs
Brand new vr sensor lead + plug
Brand new coilpack.
Only thing that seemed to 100% sort it last time was plugs.
Did around 150 miles and problem is back...

Anyone.....?

Thanks.

Post by **brentp** » Mon Oct 06, 2014 5:02 pm

Hi ukmercman,

thanks for the follow up. What do your plugs look like after the drive? are the clean or fouled?

ukmercman · Post by **ukmercman** » Mon Oct 06, 2014 5:06 pm

brentp wrote:Hi ukmercman,

thanks for the follow up. What do your plugs look like after the drive? are the clean or fouled?

pretty sooty......don't seem wet.

FYI: car is running 48dcoe Webers.....a little sooty is common!

Post by **brentp** » Mon Oct 06, 2014 5:07 pm

If your problems go away with fresh or cleaned plugs, then I would suspect carbon fouling. Maybe you're running a bit too rich?

ukmercman · Post by **ukmercman** » Mon Oct 06, 2014 5:33 pm

will shove another set of new plugs in, see what happens and report back!

thanks for your help