Timing Light and Tach Questions
 

I just installed a Crane XR700 optical ignition system in my stock '74 2.0. Also put in a new Crane coil (PS20), ballast resistor, rotor and spark plugs. Now I'm trying to get the system properly timed, and I'm running into problems.

Got the distributor adjusted to the point where the engine is idling nicely. I hooked up my Sears inductive timing light and Sears tach meter, and then the fun started (or should I say continued).

The car's dash tachometer does not rise above 1K, no matter how fast I rev the engine. The Sears tach seems to hover around 400. The timing light doesn't flash at all.

The timing light has the inductive pick-up around the plug wire for #1, the red lead clipped to the "+" battery post and the black lead clipped to the "-" post. Pulled the trigger, and ... nothing! I hooked it up to my wife's Caravan, and it worked like a charm. I re-did the connections numerous times. Moved the pick-up close to the plug,to the opposite end, to other plug wires ... nada.

The Sears tach is connected to the "-" post of the coil and to chassis ground.

The dash tachometer has always been a little flaky. It would work fine until I turned on the headlights (hadn't had a chance to get into that yet)but otherwise gave me no problems.

Does anyone have any ideas regarding either issue? I would sure appreciate any suggestions.

Thanks, guys>

Howard

Does the tach/dwell meter get hooked to (-) and ground, or to coil (-) and battery (+)?

My Sears timing light is a bit finicky about the inductive pickup. You sometimes have to fiddle with the angle that the plug wire takes through the clip-on lead. Try fiddling with it with the trigger held down and see if you can get it to light off.

--DD

Dave:

According to the instruction sheet for the dwell/tach meter, when using the tachometer function, the green lead clips to the "-" terminal on the ignition coil, and the black lead gets clipped to vehicle ground.

I'll try to move the inductive pick-up around while holding in the timing light trigger, and will let you know what happens.

Thanks for your response.

Howard

Just went out to the garage and started the car. I moved the inductive pick-up all around ... nothing. I put the pick-up on the center cable on the distributor cap, and PRESTO. My only issue with this is that I don't really know what this is reading. Can I use this signal to set my timing? I looked into the fan housing hole, and my 27 btdc mark is in view, which means that it's sync with something.

As for the tach ... I've got to do some further checking out.

Thanks again,
Howard

SmileWavy

What you're checking when you put the tach on the center coil wire is every spark. So you will probably see a mish-mash of four images, only one of which will have the timing mark in (or near) it. It sounds like that is good enough to let you set the timing.

Are you getting a spark on the #1 cylinders? If so, then keep monkeying with the clip-on lead until you get a reading...

Not sure on the tach. Try disconnecting the stock tach when using the Sears one. That will eliminate one possible source of problems.

--DD

OK, here are the most recent developments. I disconnected the dash tach wire, but the dwell/tach still gives me somewhere around 100-200 no matter how fast the engine revs.

I called the tech support line at Crane to see what they could tell me. The guy said to put a 10K 1/2 watt resistor in between the "-" coil terminal and the black/purple tach wire. I soldered connectors onto the resistor and covered it with heat shrink tubing (nice job, IISSM. Same *****.

Has anyone else had tach problems after installing a Crane XR700 ignition? If so, were you able to correct them?

Thanks for trying to help.

Howard

:confused:

Regarding the timing light, is it possible that your plug wires have some sort of emi shielding that your coil wire or your Caravan wires don't have?

I know that's a strech and doesn't solve your other issues, but it's $.02 worth!:)

--Case...

I'd give a try on connecting the timming light on either #2, 3 or 4. Could be that #1 isn't firing?

HTH

Marc-André

First ----- Thanks for the responses.

Second --- The plug wires could be shielded, but since they're a set, I would think that the center (common) wire would also be shielded. The pick-up works fine when connected to this one. Marc-Andre, unfortunately the #2, #3 and #4 wires dont give me any signals either.

Finally --- I called the tech support desk at Crane again, and the guy suggested that I increase my plug gap to .045" because the smaller gap may not be allowing the tach enough time to see the pulse. I didn't understand it, but I did it, and the car seems to run ok, but still no tach.

Even though the answer probably won't cure my tachometer issue, does anyone know what determines the proper spark plug gap for a given ignition system? I know that because I "upgraded" my system there should be more voltage to allow the spark to jump across a wider gap, but going from .028" to .045" is a 60% increase. Are spark plug gap dimensions really so arbitrary?

Thanks again for any responses.

Howard

.045 sounds about right for a CD unit and a high outout coil.