• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Improving the Renix crank time

TiRod

NAXJA Forum User
Location
SW MO
If you have a Renix XJ, you know about the cranking the system requires to get a signal before it will start. For some, this seems to be a lot longer than it should. The RENIX computer has to see 300 RPM for a few cycles to pick up a valid signal from the sensors, so it seems. Try the following to at least shorten the amount of time it takes.

First, go overkill with the cranking amps. I recently switched from a group 58 with 500 CCA to an AGM group 34/78 with 800. It's about the biggest that will fit the stock tray. Once in, my crank times have reduced by a third and the "ear tachometer" tells me the thing is spinning much faster. It's apparently taking the same amount of rotations - but less time to do it.

A good starter is necessary, and good clean cables to pass power to and from help, too. Voltage drop losses on the notoriously small, undersized, and now corroded 19 year old cables just eat up the available power. Don't forget a good clean ground connection. I can't reasonably accept anyone whining about starting problems when they won't change the cables. Probably like a lot of older owners, we just don't want to help when that advice is ignored.

An appropriately maintained tune up helps, too. Renix systems can fire some cheap plugs for a long time, but you do have to have decent ones. Lots of posters favor NGK V-powers or Champion Truck plugs, but one thing is sure - it's not necessary to have more expensive ones.

By attacking the problem with abundant power and fewer obstacles to keep the computer from waiting for a signal, I've gotten to a point where it starts as fast as my son's 99, if not faster. Just science out where the constraints can be and enjoy your newfound seconds of freedom. Or at least, get moving.
 
I agree that the cranking time can be shortened. My 90 has to crank away for a few seconds before it starts and it needs all of these upgrades but my last jeep was an 89 and it never did this. It always started on the first or second turn.
 
Don't forget to clean up the ground between the cylinder head and the firewall. All of the sensors ground to the engine, but the ECU is mounted near your left knee inside the cabin, and the firewall strap is the only ground for the chassis.

Replace the firewall ground straip and/or provide an auxiliary ground between the battery and the chassis, and you'll see cranking times drop as well. And, make sure the starter motor-to-engine block contact is nice and clean as well, since the starter motor grounds through the nose housing (I also replace the black oxide screws with plated - black oxide just isn't as good a conductor as zinc plating.)
 
Back
Top