murfanater

just when i got my jeep till now it has always started up really slow. not sure if its because its old or not but starts up slow. i have replaced the starter and the spark plugs and the wiring to both of these. So what i want to know is what to do next to improve starting time or will it always start up slow? thanks!

chill

I assume you mean excesive cranking before it fires. check spark, check fuel rail pressure. what plugs are you using? how are the wires? cap/rotor? battery, battery conections. battery cables. last one I worked on with starting problems I fixed by tightening the battery cables.

SurvivalHorror

My jeep has the same issues at times, but only when I rush to start her, when you turn your ignition to the power setting, it beeps about 6 times, wait for this to finish and the fuel rail will have time to properly pressurize.

Starts fine when i do this.

89Laredo

If you mean a long crank, that is normal for a renix.
If you mean slow crank, I would clean all electrical contacts in the starting circuit.

afdude

from my experience a 3-5 second crank time is normal for RENIX motors

cruiser54

Do this. It will improve the under-engineered electrical system of your Jeep. Costs less than $20 and takes under an hour to do.



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

murfanater

thanks crusier54 would you have ay pictures on step by step on how to do this would help greatly.

crbnfibr

crusier, you got that s. on speed dial : ) i love it

cruiser54

No pix but just go step by step and you'll be fine. It's worth it.

cruiser54

Yep. All stored in My Documents. I got tired of typing it each time someone needed it!!!

naturist

I have owned 2 jeeps and they both crank awhile to start.. lol just a jeep thing i spose

crbnfibr

if you dont have a haynes manual then you should get one cause it will make it much easier

cruiser54

I think the OP's issue is SLOW cranking which leads to even extra LONG crank times as on a Renix, the ECU must see around 300 RPM before spark and fuel are provided.

The ground refreshing/upgrade will help with that provided battery condition is good.

tjwalker

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 following cruiser54's recommendations above. 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!

SuperGlue

Like everyone else said, if your complaining about how long it starts thats just a Renix thing, 87-89 FI jeeps. I was always told it has to crank 6 times and get a reading from every cylinder before it can start but having to reach 300 rpms sounds reasonable also. Every jeep I have every seen with a 4.0 takes 3-6 seconds to start. If its just slow cranking, I agree with everyone else about checking your grounds. I let my Renix xj sit for a month in the snow once and when I came back couldnt get it to start. a few days of probing and headaches, replaced the starter, etc etc. Wound up being the grounds..