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Hi, Moses!

         How are you? can you please teach me how to  connect  or wire the tach. and speedometer in my zj , when i convert  the car to carb. and hei at first  everything is good , i have an  RPM indication and after  4 months its erratic  , sometimes  it will indicate other times not,same with my speedo. as you know  im using carburator and HEI.

Regards,

Mario Bedayo

Philippines

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Hi, Mario...You have eliminated the MPI/EFI fuel and spark management completely.  However, the OEM speedometer gets its signal from the transfer case speedometer drive and PCM.  The OEM tachometer requires a tach signal from the coil and PCM.

If both of these gauges are erratic, this could be trouble at the crankshaft position sensor, the PCM, the speedometer drive or the wiring for the tach and speedometer.  (I'm not clear where you sourced voltage for your aftermarket HEI distributor.)  The original wiring for the speedometer, the tach and the PCM need to function properly.

If all of these devices and the wiring are okay, the XJ Cherokee and Grand Cherokee do have issues with the connectors at the gauge panel.  This could be a source of trouble.  I discuss the XJ Cherokee issues and the repair at the magazine:  http://www.4wdmechanix.com/How-to-XJ-Cherokee-Erratic-Gauges-Fix?r=1

Usually, the gauge connector issue affects all of the gauges, including the speedometer and tachometer.  You could have a connector or wiring issue at the gauge panel.

A factory workshop manual (FSM) covers the wiring schematics for the tachometer, PCM and speedometer.  If you need to trace wiring circuits or fix the wiring, I suggest that you purchase a used copy of the Mopar FSM for your 1993 ZJ Grand Cherokee.  These print manuals come up at eBay, here is one current example for your specific Jeep:

http://www.ebay.com/itm/like/331594039394?lpid=82&chn=ps&ul_noapp=true

You may find these original FSM print manuals cheaper at other online used automotive book sources.  Also, here is one Google Search that turned up a download PDF of your 1993 Jeep Grand Cherokee FSM for only $7.95.  If this is a copy of the complete manual and legible, it should include everything related to your Jeep ZJ Grand Cherokee, including all wiring schematics and electrical troubleshooting details:

http://jeepfsm.com/jeep_grand_cherokee_factory_service_manuals.html

If you need to troubleshoot the wiring, gauges or any other electrical issues on your Grand Cherokee, invest in a FSM.

Moses 

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