Wasted spark and rev counters - again........

[SECS]

Dave,

I would remove the filter and join the 2 wires together anyway as its only there to stop interference on AM radio so unless you listen to 5 live...bin it.

If the counter doesnt work properly after removal of the filter then the counter must be faulty IMO.

You will not see a connection between pin 3 and earth as it is provided via the ignition module through an internal diode and transistor to the ecu.

If it wasnt there, the car wouldnt run

This ground must NOT be connected to vehicle chassic or the battery negative as it will induce missfires.

[Dave_M]

Simon

Thanks - will bypass the filter.

I'm about confused about the different grounds (doesn't take much lol). In an earlier post you said I need to ensure both ignition amps need a good ground and to add a wire from the mounting plate for each amp to chassis (which I've done). However I noticed yesterday that there is a direct connection internally in the amp between the backplate and pin 3 - so surely by providing a good ground to chassis for the back plat I'm effectively tying the pin 3 (floating) ground to chassis/battery ground?

If bypassing the filter doesn't work I'll try to get hold of anothet RS2K rev counter.

Thanks
Dave

[SECS]

Dave,

Dont be confused about the grounds/earths, if the car runs they must be ok !

Adding extra ground wires to the heatsinks can cure wiring loom voltage drops which can affect the rev counter.
The heatsinks must be earthed but for most purposes a screw into teh bodywork is sufficient but I personally always beleive in bonding them with wires anyway.

Pin 3 on the ignition module supplies a "clean earth" to the ecu for the signal switcher back to the ignition module pin 6.

This may or may not be a direct connection internally to the ignition module depending on the manufacturer but either way it must not be connected to anything else under any circumstances other than pin 24 on the ecu.

This "clean earth" is needed because the ecu earth itself will see voltage changes due to the injectors drawing high currents and the wiring loom acting like a resistor resulting in the ecu earth RISING upto 1 volt above the vehicle chassis in the form of high speed pulses/spikes.
I.E. the high injector peak currents pass down the ecu earth wires.
You can only measure this properly with an oscilloscope.

1 volt doesnt sound much but if the switching control earth for the ignition module was not there, this would actually cause the coil to fire randomly as the signal switch point effectively changes with earth voltage fluctuations.
A seperate ignition module signal earth ensures this doesnt happen and is not connected to the ecu earth internally !

[Dave_M]

Just to resurrect this thread again as I still haven't managed to get the rev counter working. However I had a eureka moment yesterday whilst thinking about Simon's post about ensuring the ignition amp is properly grounded. My amps are mounted on a black anodised double amp mounting bracket - as sold by msd.. The anodising seems to act as an insulator so although I'd run an earthing wire to the heatsink plate, the amp still won't be earthed. Removed the mounting bracket and I've sanded away the anodising where the amp mounts, as well as where the plate attaches to the mounting pillars. Then ran out time so it will be tomorrow now before I find out if this cures the problem. I'll be very happy if this fixes it, but also very pissed off that the anodising has caused so much grief.

Will post the outcome........

Dave

[The Radman]

i wouldnt have thought it would make any diff myself,but fingers crossed for you

[Tore_TJ]

Tried the Crank sensor signal instead?

[Paul Cos]

I know you haven't fitted the MSD board. But I have put the instructions from when I put the waisted spark on mine. You never know if all else fails it might be worth a try

[RWD_cossie_wil]

I have a spare small turbo rev counter if you want to borrow it & see if it works with that, as it's set up for two coilpacks as standard?

[Dave_M]

Paul - thanks - but don't think that will work as the mod is to a BT rev counter - the msd baby board I believe provides an output which mimics the original feed to the rev counter.

Wil - cheers for the offer. I've tried 2 different rev counters - one from an RS2000 and one from a wasted spark cvh escort cabriolet - both (mal)function in exactly the same way and I reckon I'd have been pretty unlucky to source 2 dead rev counters!

I've got my fingers crossed for when I try it tomorrow!

Dave

[garet]

check rev counter wire, the signal comes from pin 21, you can run a fresh wire from pin 21 straight to the signal to your rev counter ...green wire it is as i remember...

[Dave_M]

Bugger - that didn't work. Even hooked an earth wire up direct from the heatsink to the battery as I still had 2 ohms resistance when earthed via the chassis.

Garet - think I'll try that next but I'm not going to be able to try that for another 3 weeks now as we're off on hols next weekend and I'm off out now for the rest of the day.

Dave

[rsdene]

My small turbo worked fine after fitting wasted spark, 2 days later no rev counter!!!!! Arrhh

[Dave_M]

From the wiring diagrams, the st rev counter takes its signal from the edis unit - from a separate pin which is specifically a drive signal for the rev counter. I suspect this is quite a different signal to tapping into the coil negative which will have some pretty big spikes in the signal and will be pretty "dirty" by comparison.

I'm pretty flummoxed at the moment - I've checked and double checked everything I can think of:

• I've (now) got a good earth connection from amp backplate to ground
• Checked resistance of wire from coil negative to back of rev counter (all good)
• Tried 2 different rev counters in case one was knackered
• Checked I'm getting >12v at the rev counter +ve

Starting to wish I hadn't bothered with wasted spark and just bunged a group A coil on instead!

Dave

[garet]

what about jumper on old connector.....

[Dave_M]

If that's the connector that used to go to the rev counter filter (can't tell from that pic) then I've completely removed the connector and joined the wires together.

Dave