Long story short, and I'll post all the details soon...
My tach needle in my 94 LT1 auto sits below zero when off. When turning the key on, it rises to zero, and it stays at zero with the engine running. I made several changes to the car, but the one that might be of importance here is that I installed a Delteq opti-direct ignition system, with the 4 coils. It looks like I plugged everything in. Has anyone experienced this with the Delteq? Thanks for any help you can give.

Darren

 

Any ideas?

HELP!

 

Did it happen imidiately after the delteq install?
-=Rick

 

Well, yes and no. This is the first time I fired it up after the delteq install, but I also installed a vortech supercharger and sorta replaced the motor, trans, rear, and some other stuff...

But everything is plugged in, and ground G108 is on tight (on the front of the block, below the passenger side head). Like I said, the motor starts and runs, just no response from the tach, other than jumping from dead bottom up to zero when turning the key on.

 

Is the opti still all plugged in?

I am thinking it's (the tach) getting power and ground to the tach because it moves up to 0 but not recieveing a Tach signal. which from the factory would be coming from the Opti.

Obviosly there was alot of harnesses un plugged and things distrubed, during the operation.

But then again the injectors are being fired off of a crank signal too. The PCM must be seeing an engine RPM signal. I am not familiar with how the delteq is interegrated into the system. What triggers the the tach signal for the ignition? The opti or an additional source?

-=Rick

 

The opti harness is still plugged in, and where it connects to the engine harness on the passenger side of the intake, the delteq system T's into it with factory style connectors. That T runs to the opti box (mounted where the coil used to be. The gray and black connectors of the stock coil are plugged into a connector that loops them together. The factory coil module connector plugs into the opti box, and two connectors from the opti box run to the 4 coils on the driver side valve cover. Then the plug wires run to each cylinder from the coil pack. And the engine has a brand new optispark on it. No check engine light on.

 

Another forum member is having the same problem after a Delteq installation. I suggest that you call Delteq. It is probably something simple.

 

Yeah, I went ahead and emailed Pete at Delteq last night. I guess I'll hear back from him tomorrow. I got out the shop manual, and I was checking the continuity of all of the wires, from the fuse to the coil connector, coil connector to coil module connector, tach filter to ground, etc., and I haven't been able to come up with anything yet. I want to check the white wire, from the tach filter to the connector on the firewall, but I would have to remove the battery and side panel to access it. I'll wait to see what Pete has to say Monday.

 

Well, I figured it out. I was looking on the Delteq website at work, showing a friend the system, and decided to show him the instruction manual. I quickly noticed some changes, like large color pictures, which were not in my manual. I purchased what must have been an early system, sometime last year. So, I was going through the manual, and there it was...on 92-94 corvettes...you must bypass the tach filter! It states to either cut the filter out and connect the 2 white wires, or to use another wire to jump the 2 white wires together. The filter changes the high voltage coil signal to a low voltage signal for the tachometer, but the delteq coil pack generates it's own low voltage tach signal, so the filter is not needed (and the tach won't work with both of them). So when I got home, I cut the white wires off the tach filter, stripped the ends, twisted them together, soldered them, and heat shrunk them. I then fired the car up, and guess what? My tach is working now! The problem is I couldn't find anything in my directions about this modification, as if they didn't know about it at the time. So, needless to say, I'm happy now.

Another note...the service asr light had come on too, and in the shop manual it shows the asr module gets a signal from the white wire after the tach filter. When I started it tonight, the service asr light stayed off.

 

Good Deal!
-=Rick

 

When I installed a MSD I had to "Bypass" the tach filter, but I never did put the white wires together, is that necessary? I cant remember, but are the white wires going in the filter then out, and you cut them then reconnect them , which just ByPasses the filter? Its been 7 years since I did the MSD, so bear with me.
I am awaiting the DELTEQ system, and mine is just cut, tach works fine right now.