Help! Ignition problem. TFI upgrade.

[Dan]

First of all: Thanks to all that helped me with my timing chain replacement problems. That timing chain was looser than a ....<fill in the blank>. She's back running, but barely (about the same as before the timing chain replacement). I was thinking ignition problem or vaccuum leak.

The coil looked to be ancient (probably original), so I checked the resistance of the primary, and secondary terminals per my Haynes manual and it showed it to be a little out of specs. Great time to do TFI upgrade! (Thanks go out to IRBOB for all the info and pictures on his website and also thanks for this site's tech info)

Get all the parts, masterfully craft a bracket to hold the new coil, hook it all up, and turn the key. Won't start...

I checked the voltage going to the coil and it is only showing about 3.75V (Maybe I should have checked that when my old coil was in - could have very well been the source of my problems). I checked the voltage coming off the starter relay (on the "I" terminal) and it shows about the same: 3.8V or so. Battery shows 12+V. Shouldn't the starter relay show 12V too? Haynes doesn't show any diagnostic tests for the starter relay. Probably because they are a dime-a-dozen at the parts store. Am I right in thinking that I need to replace this?

Thanks all. Off to bed.

[ July 28, 2002, 12:33 PM: Message edited by: Dan ]

[Heimeken]

Dan, I believe your voltage should be around 10 volts after the relay to the coil. Just checked mine yesterday. The TFI coil needs 7 to 10 if I recall correctly. You may want to replace the relay, but I'm thinking you may have something else not hooked up right. It took me a couple of rounds.

[Dan]

Dan, I believe your voltage should be around 10 volts after the relay to the coil. Is that measuring at the coil or at the starter relay? Shouldn't the relay measure 12?

[Dan]

OK. Update.

When I unplug the wiring harness on the coil, the voltage on the starter relay jumps back up to normal 12V. Also if I test the voltage on the wiring harness while unplugged, I get 12V. As soon as I plug it in to the coil, it goes to 3V again. I checked all of the grounds and they all tested OK. I double checked to see if polarity is crossed, and that's OK. The coil resistance on the primary and secondary terminals is OK (to eliminate possible bad coil). Must be something in my wiring or maybe ignition module?

[ July 28, 2002, 02:02 PM: Message edited by: Dan ]

[shadowfax101]

That could be the ignition mod. When I have mine unpluged I get 12 volts to the coil. When I plug in the ignition mod it drops to about 9 or so. If you unplug your ignition mod and all the other parts are good you should get 12. If you unplug it and you still get less than 12 check the reley and your wires. I ended up doing about a month of extra work to mine due to a bad wire about 6 inches back from the coil.

[Dan]

Well...I don't understand. For some reason, she just started right up and is running better than she ever has. I took off a spark plug wire to see what kind of spark the coil was generating and I noticed when it was off that the engine was wanting to start up. So I plugged the wire back on to the spark plug and she fired up immediately. I'm still only getting about 4V with the key in the On position and the engine off, but when I check it when the engine is running, I'm getting over 10V which should be plenty for the coil. I'm thrilled that it is running and the TFI is giving it great power. Throttle response is immediate. Now I can fine tune and see if I can track down the wiring malady later.

The truck has been sitting basically since November and it sure is nice to get her going again. Thanks all.