Any electrical experts out there?

[jgeorge]

I just replaced the engine in my 88GW with a rebuilt from Advance Auto Parts. While I had everything out I did the TFI upgrade (cap and coil--both MSD). When I tried to turn start up the new engine it turned over fine but I couldn't get any any spark from the coil. The coil got very hot. Also, my resisance wire became very hot and so did the bowl vent solenoid and the carb solenoid (idle compensator). These all get hot even when I simply turn the key to the "On" position and don't even try to turn the engine over ("Start" position). I checked the battery, replaced the battery cables (kind of old), and checked the entire wire harness for grounds and opens and found none. I checked the resistance wire and it meets the specs listed in the service manual. I bought another coil and it does the same thing. When I did the TFI conversion I changed the coil connector and I'm sure I got the polarity correct. My electrical tester shows good continuity between in all the coil circuits. Does anyone have any suggestions? I'm not the smartest guy when it comes to electrical problems and could sure use some help. Thanks.

Jeff

[AJ Johnson]

double and triple check that you put all your grounding wires on when you swapped engines... sounds almost exactly the prob I had in a yota.. if in doubt, add a couple of grounds from the engine to the frame..if nothing else,give it a shot. you can never be grounded too much electrical wise

[Wesdog]

If the coil is getting hot when you turn the key to ON then I would suspect a fault on the negative side of the coil or internally. I believe the controller pulls the coil negative to ground to fire the coil. Shouldn't be doing that if the engine isn't rotating. Maybe a miswire, bad coil or bad controller? I'm answering this from memory so I could be confused.

Wesdog

http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[wagdriver]

There are two ground wires for the engine. One attaches under the A/C mount, this the negative lead from the battery to the engine. There is another from the frame to engine on the right motor mount. I would double check the wireing to the coil it sounds like you have the coil wired directly to 12V with nothing in between. The distributer has to be in the loop some where. ;)
Get a Haynes 50029 manual it has as good a wire schematics as can be found. ;)

[ July 27, 2003, 09:58 AM: Message edited by: wagdriver ]

[will e]

jgorge. You upgraded the cap and coil. DO you still have the original ignition box???
If you do, I can put a meter on my coil for comparison sake.

[Wesdog]

Originally posted by wagdriver:
...Get a Haynes 50029 manual it has as good a wire schematics as can be found. ;) Here's a link to wiring diagrams:

http://mysite.verizon.net/res00d4r/index.html

Wesdog
http://www.fullsizejeeps.com/jeeps/files/Misc-Pictures/wesdog_avitar1.jpg

[ July 27, 2003, 10:14 AM: Message edited by: Wesdog ]

[jgeorge]

Thanks to all for the quick replies:

Both grounds (engine to motor mount, battery to AC bracket) are good. I've got the wire diagrams (off IFSJA site) already and as far as I can tell, everything is in order. When I did the TFI upgrade I didn't change out the Ignition Control Module--still has the stock one in there. On the starter relay I have a green wire with white stripe (connected to the blade post labeled "F")that connects with the resistor wire (red-labeled "resistor wire") and a solid yellow wire at the same juncture. From there the yellow wire leads to the coil positive post (as I've got it wired right now). The resistor wire leads back through the harness to a juncture with a brown resistor wire (leads to the alternator) and two solid yellow wires (one leads to the bulkhead connector at the firewall and the other leads to the Duraspark box). The other wire that comes off the negative coil post is a green and white striped wire that leads directly to the Duraspark module. Did I misswire the connector for the coil when I did the TFI upgrade? I don't see how any of this is related to the circuit for the bowl vent solenoid and carb solenoid either. These are getting very hot as well and as far as I can tell by following the wire harness, they are not connected to the Duraspark module or the coil or the starter relay. They're both (along with the wire for the AC compressor--all these wires are solid orange) connected to the same wire that leads to the bulkhead connector at the firewall. How would I create additional grounds? Admitting I don't know much about electricity, it seems like I have a groundign problem somehwere. Again, thanks for all the replies and I'll take any additional advice anyone can offer.

Jeff

[jgeorge]

Could this be a problem with the ignition switch? Looking at the wiring diagrams, that appears to be one thing the coil, carb solenoid, and bowl vent solenoid have in common??? I'm getting desperate. I've spent the last 2 days trying to figure this out and I'm running out of ideas. Help!

[AJ Johnson]

i don't know about the other solutions, they are a little beyond my knowledge, but if you want to create another ground, find a bolt on your engine and get a wiring connector that the bolt can go through and install it, then bolt the other connector to the frame

[Joe Guilbeau]

The negative side of the Ignition Coil is supposed to be opened and closed to generate the collasping magnetic field inside the primary windings of the coil so that the secondary (1:100) will step up the voltage to be distributed by the (distributor), and sent on to the spark plugs via the rotor.

If the coil getting "too hot" (how did you diagnose this?), then that is an indication that there is too much current flowing through the primary side of the coil.

Check the wiring to the coil again.

[Max Power]

If this was the stock setup I'd say its the magnetic pickup not triggering the coil to spark.

[wagdriver]

Look in the conversion articles again I think there were some optional mods for the duraspark system. I don't remember them of the top of my head.