Alright so I'm still fairly new to the whole XJ experience. My '90 takes a good 3-6 seconds to turn over before it starts. does anyone have any suggestions other than carb cleaner and replacing my air filter?

 

that normal for renix era 87 thru 90 dont sweat it read up on renix xjs there different from 91 and up.

 

okay thanks. do you know of any specific articles or what not?

 

Thats not to bad. Try a tune up spark plugs wires rotors. Clean off all the build up under the rotor and distributor clean up all the build up on your grounds. And run threw a carb cleaner. That should help abit but xjs never really fire up in one turn over.

 

Yep, Renix-era XJs don't turn over right away. Replacing your CPS (crank position sensor) may help a little, along with the other advice regarding general maintenance but, for the most part, you should expect between two and four seconds of cranking before she fires.

Any other problems? Failure to start when warm? Stalling? "Misfires"? If everything else checks out then I'd just follow the advice above and perform routine maintenance/tune-up and have fun.

 

You have a Renix XJ (87-90) By design, the engine is not going to fire until the computer (ECU) gets a signal from the crankshaft position sensor and measures that signal to indicate that 300 rpms while cranking has been met/exceeded.

Somewhat extended crank times should be considered a “characteristic” of your engine, rather than a problem.

You can upgrade the battery and battery cables--at least 4 ga., 2 ga. better--and buy a high-torque starter.

Be sure that all grounds are good. Remove them and freshen them. You cannot tell if the grounds are electrically good by looking at them! Renix vehicles are very sensitive to ground issues.

Your CPS can be a bit weak, too. Unplug it and probe the two wires with your meter set on AC volts. You should get .5 as a reading. Anything down around .35 will cause long crank times and possible intermittent no-starts.

Other than that, performing basic tune-ups on a regular basis is important, (plugs, wires, cap, rotor, fuel filter) The importance of fresh secondary ignition (tune up parts) cannot be overstated.

Good luck!

 

This will help, as will making sure the tune-up parts are fresh and cleaning the throttle body as suggested.

Renix Ground Refreshing
The Renix era XJs and MJs were built with an under-engineered grounding system for the engine/transmission electronics. One problem in particular involves the multiple ground connection at the engine dipstick tube stud. A poor ground here can cause a multitude of driveabililty issues, wasted time, and wasted money replacing unnecessary components.
The components grounding at the dipstick tube stud are:
Distributor Sync Sensor, TCU main ground, TCU "Shift Point Logic", Ignition control Module, Injectors, ECU main ground which other engine sensors ground through, Oxygen sensor, Knock Sensor, Cruise Control, and Transmission Sync signal. All extremely important stuff.
The factory was aware of the issues with this ground point and addressed it by suggesting the following:
Remove the nut holding the wire terminals to the stud. Verify that the stud is indeed tightened securely into the block. Scrape any and all paint from the stud’s mounting surface where the wires will attach. Must be clean, shiny and free of any oil, grease, or paint.
Inspect the wire terminals. Check to see that none of the terminals are crimped over wire insulation instead of bare wire. Be sure the crimps are tight. It wouldn’t hurt to re-crimp them just as a matter of course. Sand and polish the wire terminals until clean and shiny on both sides. Reinstall all the wires to the stud and tighten the nut down securely.
While you’re in that general area, locate the battery negative cable which is fastened to the engine block just forward of the dipstick stud. Remove the bolt, scrape the block to bare metal, clean and polish the cable terminal, and reattach securely.
Another area where the grounding system on Renix era Jeeps was lacking is the engine to chassis ground. There is a braided cable from the back of the cylinder head that also attaches to the driver’s side of the firewall. This cable is undersized for it’s intended use and subject to corrosion and poor connections at each end.
First off, remove the cable end from the firewall using a 15mm wrench or socket. Scrape the paint off down to bare metal and clean the wire terminal. Reattach securely.
Remove the other end of the cable from the rear of the head using a 3’4" socket. Clean all the oil, paint and crud from the stud. Clean the wire terminal of the cable and reattach securely.
A suggestion regarding the braided cable:
I prefer to add a #4 Gauge cable from the firewall to a bolt on the rear of the intake manifold, either to a heat shield bolt or fuel rail bolt. A cable about 18" long with a 3/8" lug on each end works great and you can get one at any parts store already made up. Napa has them as part number 781116.
A further improvement to the grounding system can be made using a #4 cable, about 10" long with 3/8" terminals at each end. Attach one end of this cable to the negative battery bolt and the other end under the closest 10mm headed bolt on the radiator support just forward of the battery. Napa part number 781115.
　
　
If you want to upgrade your grounds and battery cables in general, contact Jon at www.kelleyswip.com. He makes an incredible cable upgrade for a very reasonable price.
　
Revised 11-28-2011