Danified

So my tach wasn't working so I hooked up a aftermarket tach to that little female connecter that is the suppose to be the tach diagnostic port and I still get nothing. So Then I pulled off both the wires going to my spark plugs on the trailing side and my car didn't run any differently at idle. Shouldn't it?

So before I go blow money on new igniters I want to check the wiring. Does anybody have a good resource on what voltage or ohms each plug should have and what should be pluged into what?

I can take pics if that would help...

Thanks in advance!

Dan

LorenzoAir

Hi
When you pulled the plug wires did you check to see if they had spark. I think that would be the easy check first. If no spark then it would be time to dig deeper.

Did you try hooking the tach directly to your coil to see if that worked? Just some thoughts

Loren

Danified

My method for checking for spark was inconclusive because I didn't find spark on any of the plugs. I guess I should go get a spark plug tester.

How would I hook the tach directly to the coil without frying it?

HAILERS

You download the factory service manual from this site. See FAQ thread.

You just download the Fuel and Emissions section. You look at page 4A-30 and the next two pages. On those pages is the input/output of the trail coil assy to/from the ECU. You look at the pinout of the ECU plug, looking at the wire side of the ECU plug.

No tach equals no spark at the trail coils assy. The trail coil assy will cutoff if the ECU sees certain conditions. Like a very low battery. I forget what else.

Trail coils add very little to the performance of the engine. Pull them off at idle and you won't notice a thing has happened. Effects starting little to nothing at all. Helps clean up emissions is it's role in life on the whole.

Make sure both elect plugs are on the coil assy. Look to see if there is batt voltage on the BLACK/YELLOW wire. If that is there, go to the FSM.

Check out your aftermarket tach by connecting it up the LEAD coil assy's black bullet connector, to see if it works there. Should if your car is starting up and running just off lead plugs.

Danified

Awesome!!! Thanks you for that very very useful info. For some reason I was looking in the "Engine Electrical" Section... Silly me...

Darn though... I was hoping that was why my engine wasn't running as smooth as I would like it to.

Danified

I tried that and I still get nothing. Can put a jumper wire between the black bullet connector and the blue/yellow one to make the dash tach work?

HAILERS

Never crossed my mind to do that. It seems it could work. I don't see it harming anything. Tell you what, I'd remove the elect plugs from the Trail coil assy prior to doing so. Not the sparkplug wires, but the electrical plugs. Then jumper a wire b/t bullet connectors.

Write back on how that worked out. I'm even tempted to try that out on my 86na (hardly ever driven car), just to see if that works or not.

HAILERS

I just went out to the 86na. I pulled the two white elect plugs off the trail coil assy for safety reasons. Then jumpered the two black bullet connectors. Tach worked just fine.

I've had the tach/trail coil fail on me only twice in the past. Both times was after having to jumper the battery. I remember noticing the lack of tach after I'd been driving a couple of miles. So instinct somehow told me to turn the engine/key off while driving and then key back ON and dumped the clutch. Engine started and tach then worked. I attributed the lack of tack due to the ECU killing the trail signal because of a low battery. It's written somewhere that the ECU can do this....kill the trail coil assy only. Training Manual I think, that is online somewhere.

HAILERS

Sometime I'd fix the problem with the trail coil assy. The wires from the coil assy to the large plug on the ECU have no connections inbetween. Usually you can get a trail coil assy from the wreckers for less than twenty bucks. I'd check the continuity of the wires b/t the coil assy and the ECU large plug prior to buying a used one. OR check the wires with a voltmeter by backprobing the wires at the ECU plug while the engine is idling and compare it with the jpgs I attached.

chibikougan

iTrader: (4)

I have a trailing coil if you want to try it. You can pick it up on Friday Saturday. Or you can just bring er by the shop. I will be there.

Danified

That would be awesome! Where/what is your shop? When is the best time to stop on by?

Danified

I checked the voltage coming from the black/yellow wire with the ignition on and it does have 12v. I also checked the voltage of that black wire on the lead coils and it has 12v when the car is running. I plugged my tach into that and it still doesn't work. The wiring diagram for the tach says to plug it into the - side of the coil. Wouldn't that just be the chasse?

Also... someone (aka: not me) has wired the radiator fan to run whenever the key is on so I wonder if that is putting a load on the battery and then the ecu thinks the battery is low so it doesn't power the Trailing igniter? Could I just put a battery charger on the battery and then start it to keep the ECU from turning off the Trailing Igniter?

Danified

Hailers I appreciate all the help but what is up with the digital pictures of your monitor?

Try this... Hit that button on your keyboard that says "PrtScn". Hold down the windows key and hit "R". Then type "mspaint" and hit the Enter key. Then hold down "Ctrl" and hit "V". Then edit it or save it or do what you want with it. Try it, it might save you some time.

Thanks again for your help.

Dan

HAILERS

Does your stock tach work if you get a piece of ordinary wire and jumper the two bullet connectors? Like I did in post #8 above???

I never had a aftermarket tach. I just use a Fluke 88 with a clamp adaptor that goes over a plug wire or use the Fluke connected to the bullet connector and put it on RPM's.

What's the name of the aftermarket tach?

By the way, the stock coil assy's ignitor gets its ground from the base of the coil assy unit mating with the chassis. If it sits on a piece of wood/rubber/you name it, the coil assy won't work. Then again, of the three nuts that hold it to the chassis, only one could do the job.

You could start the car cold and have the elect fan disconnected, just to find out if that is causing a problem. You'd find out before the engine gets too hot.

Danified

The tach is just a generic JDM tach that has a selector switch for 8 - 4 cyclinder motors which I was told would work with a rotory. But I guess not...

I tried unpluging the main harness from the trailing igniter and jumpered the two tach connectors and it did make my tach work.

I tried starting the car with the fan unpluged and the trailing igniter still didn't work.

HAILERS

That was very, very helpful. Thank you for the information. I was clueless about that.

Danified

So I bought a trailing coil and igniter off ebay and hooked it up. Now the tach works but when the motor is under a load it sounds like it's only running on one rotor. Almost like it's grounding out somehow. If I unplug the two connectors for it then it runs fine again. What would cause that?

HAILERS

Sounds like the trail spark plug wires are crossed up.

Danified

Hailers you are a genius! I hooked them up correctly on the trailing coil but they were backwards on the block. Car accelerates much smoother now.

Thanks again for all your help!