So I've been trobleshooting an issue I'm having with the tachometer - it basically doubles in speed after 16-1800 rpm - all the way up to 8K.

I tested the leading coils resistance, and both spec'd out at .5 ohms. Next I busted out the 15 dollar special timing light from HF, and noticed that I'm getting strong spark from L1, L2, and T2. T1 seems very erratic, relative to the other 3.

I disconnected the plug wires (all are new NGK), and both wires spec'd out about the same, with the 2 inch longer (T2) one coming in at about 5.4K ohms. The T1 was about 4.9K ohms. I checked for spark from T1 by laying a screwdriver on T1s end, and was getting spark.

When I first disconnected T1, I noticed a powdery white/yellow crust on the plug wire end (the metal). After wiping it off, I took the compressor and blew some air into the coil... dust everywhere. After the dust subsided, I hooked the wires back up and started the car... still couldn't pick anything up on T1. All others were good.

Is the coil or ignitor dying or dead? If it produces a spark without the cable on it, does it just not have enough juice to push through the resistance of the cable?

Thanks in advance!

 

The one thing I forgot to check (leaving the cable attached to the coil, and placing the engine side near a ground) just turned out ok. So the spark is making it to the plug, but I cant pick this particular one up with a timing light... the one with all of the crust inside of the coil (coincidence?)....

I dont get it.

 

One of the local 7club guys is going to let me borrow a spare trailing coil and his timing light! Will report back later!

 

swapped coils, and timing light.... same issue. I think this is a standalone issue.

 

the trailing has 2 separate ignition circuits, i don't recall which the tach gets its signal from but that may give you a hint that one of your ignition trigger circuits is not sending a clean signal from your ECU.

first however i would replace the trailing spark plugs, or at least swap the 2 trailings and see if the problem follows the plug you swapped.

 

thought about doing that last night.... but since you reminded me, I just went out and did it. No change

This is killing me! The megasquirt connects to the red and the white wires on the trailing coil. The middle LED on the ECU is the only one that flashes... that must be T2.

 

update...

whenever either the T1 or T2 coil is plugged into the T1 spark plug, I get nothing across the timing light. Both coils will fire to the T2 plug.

I just bought brand new spark plugs to try and figure this out... still doing it.

I'm giving up... this is beyond me.

 

a couple minutes ago I removed the cable from the T1 plug, and laid the cable end near enough the plug to where I could see a spark jumping... I saw the spark jumping. When I looked at the coils, I was getting a spark between the T1 and T2 coils as well.

 

something about the tach select signal is bugging me... but I'm skeptical. If tach select isn't functioning, only 1 coil would fire. Both coils fire in this case... but neither to T1.

 

did you try swapping the plug wires as well?

 

yep

 

after reading the assembly guide for the MS2, I realized that I skipped step 65 almost in its entirety. I have the question in the appropriate section for an answer. If anyone here knows the answer... feel free to chime in here or in the MS section.

 

HAH! got it. Like I said... the wiring was least likely.

The IAC2A/2B leads were swapped when jumped to the LEDs. I even thought about just swapping the 2 wires going to the trailing coil, which would have effectively done the same thing.

On another note... my friggin TACHOMETER IS FULLY FUNCTIONAL!!! everything is working! tuning time!

Ben, thanks for being a sounding board!

 

Sorry, had to laugh. I've been there several times. I installed my first MS when I was 16.

 

the ignition is the easiest to screw up, as it's usually last to be assembled. just pace yourself when working with electronics and don't try to jump steps ahead.

 

yeahhhhh buddy... thats what I get for working on it until 6am one night!