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Long Crank Period

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Old 02-16-2012, 04:11 PM
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Default Long Crank Period

Sometimes when I go to start my 89 4.0 it takes a while to turn over. It cranks and cranks for sometimes 6 seconds or more before it starts. Other times it cranks for maybe 3 or 4 and starts right up. It takes a little longer when its cold to start, like normal, but I feel like it almost wont turn over on some mornings. Usually it only starts good if its been running for a while already and its warm. any thoughts on this? Also, my lights all dim out a good amount when I crank it. Im thinkin it could be the alternator or the battery.
Old 02-16-2012, 06:44 PM
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have you tried turning it to the on position for 20-30 seconds before starting it? probably doesn't even need to be that long.
Old 02-16-2012, 06:47 PM
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Sounds to be the battery. Have it load tested and also clean your grounds up. The Renix grounds are horrible and cause alot of havoc
Old 02-16-2012, 09:56 PM
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Check your CPS output. It may be weak and ready to fail. as already suggested, refresh your grounds. Cheap and easy. Here's everything you need to do both.

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


Renix CPS Testing and Adjusting
 
 
Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.
 
Revised 11-29-2011



Old 02-16-2012, 11:02 PM
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Getting all 4 surfaces on the battery connections shiny is important. That crust of gray oxidization might look OK but it can a make a decent insulator!

A test, (sort of mentioned). When you turn the key to on, the pump will run one or two seconds. That might, or might not bring it up to pressure. Try that two or three times then start it. If it's way better, you are loosing pressure somewhere. If you have the stock injectors, you might well benefit with a change.

A sign an injector is leaking is if you do the same procedure warm, and it misses a bit when you first start it. A cylinder or two was flooded.
Old 02-16-2012, 11:51 PM
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Originally Posted by cruiser54
Check your CPS output. It may be weak and ready to fail. as already suggested, refresh your grounds. Cheap and easy. Here's everything you need to do both.

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

Renix CPS Testing and Adjusting


Renix CPSs have to put out a strong enough signal to the ECU so that it will provide spark.
Most tests for the CPS suggest checking it for an ohms value. This is unreliable and can cause some wasted time and aggravation in your diagnosis of a no-start issue as the CPS will test good when in fact it is bad.
The problem with the ohms test is you can have the correct amount of resistance through the CPS but it isn’t generating enough voltage to trigger the ECU to provide spark.
Unplug the harness connector from the CPS. Using your voltmeter set on AC volts and probing both wires in the connector going to the CPS, crank the engine over. It won’t start with the CPS disconnected.
You should get a reading of .5 AC volts.
If you are down in the .35 AC volts range or lower on your meter reading, you can have intermittent crank/no-start conditions from your Renix Jeep. Some NEW CPSs (from the big box parts stores) have registered only .2 AC volts while reading the proper resistance!! That’s a definite no-start condition. Best to buy your CPS from Napa or the dealer.
Sometimes on a manual transmission equipped Renix Jeep there is an accumulation of debris on the tip of the CPS. It’s worn off clutch material and since the CPS is a magnet, the metal sticks to the tip of the CPS causing a reduced voltage signal. You MAY get by with cleaning the tip of the CPS off.
A little trick for increasing the output of your CPS is to drill out it’s mounting holes with the first drill bit that just won’t fit through the original holes. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.

Revised 11-29-2011

I wanna copy your post here and quote you when I use it in the future if I may. I went searching before and couldn't find this to post for him
Old 02-16-2012, 11:56 PM
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5 secs is about normal for renix.
Old 02-17-2012, 05:29 AM
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Originally Posted by sycoglitch
I wanna copy your post here and quote you when I use it in the future if I may. I went searching before and couldn't find this to post for him

Sure. Go ahead. Yes, the Renix cranks longer than most vehicles.

But, there is room for some improvement. And in searching for that improvement, we get to see if our CPS is weak and get the opportunity to make much needed improvements on our underengineered grounding system which will reduce the number of failures and performance issues in the future. It's time well spent, hurts nothing, and has great potential for gain along with better familiarizing some with their Jeeps.
Old 02-17-2012, 07:21 AM
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Broken; With a new CPS @ over 1/2 a volt, (AC), and the 703's, now more like 2 seconds is the new norm!

Syco, You might as well have this as well, (another of Cruiser's).

Renix Jeep C101 Connector Refreshing
 
The C101 connector on 1987 and 1988 Renix Jeeps was a source of electrical resistance when the vehicles were new. So much so that the factory eliminated this connector in the 1989 and 1990 models. The factory recommended cleaning this connector to insure the proper voltage and ground signals between the ECU and the fuel injection sensors. We can only imagine how this connector has become a larger source of voltage loss and increased resistance over a period of almost 25 years. The C101 connector needs to be cleaned at least once in the lifetime of your vehicle. Chances are it’s never been done before.

Almost every critical signal between the engine sensors, injectors, and the ECU travel the path through the C101.
The C101 is located on the driver’s side firewall above and behind the brake booster. It is held together with a single bolt in it’s center. To get the connectors apart, simply remove the bolt and pull the halves apart. You will find the connector is packed with a black tar like substance which has hardened over time.
Take a pocket screwdriver or the like and scrape out all the tar crap you can. Follow up by spraying out both connector halves with brake cleaner and then swabbing out the remainder of the tar. Repeat this procedure until the tar is totally removed. This may require 3 or more repetitions. Wipe out the connectors after spraying with a soft cloth.
If you have a small pick or dental tool tweak the female connectors on the one side so they grab the pins on the opposite side a bit tighter. Apply a true dielectric grease, not the stuff that came with your brake pads, to the connection and bolt it back together.
 
 
Revised 11-29-2011
Old 02-17-2012, 07:34 AM
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not sure if this is applicable? but the first thing that popped into my mind, was fuel pump not energizing when key is turned? & energizing after cranking & building oil pressure which allows the pump to energige on the running circuit.

the fuel pressure bleeding down in evenings or after not being driven in a while, explains the hard starting, & when warm it cranks since pressure is still available to crank.

anyway, not sure this applys here, not I am not a Jeep tech, but I have been around the automotive scene for 30 years. not sure where cranking circuit versus running circuit may be, but it may be worth looking into, but check to see if pump energizes when you turn the key. or if you have fuel pressure when cold after you turn key, before you crank.
Old 02-17-2012, 07:36 AM
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Renix ECU does not give spark until it sees about 300 RPM cranking speed.
They don't just wick off like the later Jeeps. but, as stated above, there is room for improvement in the ground system and CPS output voltage.
Old 02-17-2012, 08:05 AM
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Does Renix have an ASD relay?
Old 02-17-2012, 11:22 PM
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Thanks everyone, ill check all that. I think I might just need a new battery soon though. How long would it take to overhaul all the grounds? I might do it tomorrow because I'll be workin on a new sound system anyway.
Old 02-17-2012, 11:53 PM
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Originally Posted by cruiser54
Renix ECU does not give spark until it sees about 300 RPM cranking speed.
This.

ALWAYS keep this in mind.
The quicker you get it to 300 rpm, the faster itll start.
Old 02-18-2012, 05:51 AM
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Originally Posted by XJ.89.Limited
Thanks everyone, ill check all that. I think I might just need a new battery soon though. How long would it take to overhaul all the grounds? I might do it tomorrow because I'll be workin on a new sound system anyway.
Under an hour. Some of the best time you'll ever spend. Add the cables per the write-up for about $20 or less. More valuable than a sound system......


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