antiquexj

Alright Ladies and Gent's...
I know this isn't a new thread, but hi-jacking is not in my culture, and quite frankly I think I have covered everything. I bought a 1985 XJ w/ 2.8L v6, converted to a 258ci 4.0L courtesy of a 1990 MJ w/ 5-speed. I transferred the Wire harness(both internal and engine bay), Engine, Transmission, Cluster, Fuel Pump/Sending Unit, Lines, and everything that goes in between. I finished this project about 9 months ago and everything has been great. Runs good, stays cool, no leaks(I rebuilt the motor when I pulled it from the MJ), Compression good @ 135lb. , 39psi on the Rail.

I have a long crank time before starting. I have to pump the gas pedal to get it to fire -only when it's cold. Once it is running, it will haul anything I put behind it.
-These are the parts I replaced when I did the conversion...
Crankshaft Position Sensor,
Distributor w/camshaft position sensor,
Idle Air Control Valve
Throttle positioning sensor with calibration of the 15% output voltage
Manifold absolute pressure Sensor
Intake air temperature sensor
Coolant Temperature Sensor,
Knock sensor(broke upon installation)
Fuel Filter
Fuel Pump w/ Sending unit including O-rings on all fittings
Coil, Cap Rotor, Champion Copper plugs, 8mm Accel wireset
I am absolutely stumped. I have good reset pressure at the rail after cool-down, and even after attempt to priming the rail, key on-key off, etc... it doesn't seem to help. I have 170 ohm of resistance with the CPS so that's still good, I Cleaned and tested the ballast resistor... that checks out good. What else is there? Am I missing something. I took all my ground connections, studs they connect to, terminals and cleaned them up. I even added a ground from the battery to the fender for better chassis ground, and added another ground from block to firewall(troublesome ground for all you XJers...) I'm going insane. I have covered everything I can think of, and hope you guys can jump in. Thanks

ZINGGG

How old is your battery?

cruiser54

Check your CPS this way:

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 the upper mounting hole, or slot it so the CPS bracket rests on the bell housing when pushed down. Then, when mounting it, hold the CPS down as close to the flywheel as you can while tightening the bolts.



　

　

Revised 07-30-2012

antiquexj

Sorry about that, the battery is an Interstate Megatron + number 65 w/ 850cca and I modified the battery plate/clamp to work with it. I purchased it new in February and under my PST-100 battery tester, it says it still puts out 840cca. The CPS is still a good idea, When I get extra hands I will test it. I might have to run my remote starter switch to do this, but can be done. If the voltage was low on the CPS, wouldn't it cause a long crank/hard start whether it was cold or hot? once it is running, I can't stop that Jeep. It's got power all through the band and never lets up.
Thanks for the replies!!

cruiser54

Don't over think this. The CPS is heat and cold sensitive. Crank it over with the ignition off and a remote starter switch to read the CPS.

antiquexj

Well... after consistent testing w/ a volt meter, I get a pretty consistent reading of .48V.

So what's next?

I have a block heater that I plug in (I'm in Michigan & it's cold) and when plugged it, it fires right up. -Not plugged in, it's a nightmare in this frigid temp.

cruiser54

Test the CTS and IAT.

antiquexj

What are the chances the starter is getting cold/ creating a slow crank and not firing?

Just a guess, but an un-explored option on my part.

cruiser54

Renix needs to spin +- 300 RPM for the CPS to generate a strong enough signal to the ECU......

antiquexj

well update:

I replaced the Crank Shaft Position Sensor with my spare that I have in the glove compartment from Mopar... Absolutely no difference in the cold start. The running performance has jumped up 10 fold, nice and smooth so there aren't any regrets in putting it in. But...

Still no cold crank/start resolve. I have noticed more recently that when I press on the gas and hold it, It wants to kick. My next step is fuel pump & Regulator. The pump is a cheap aftermarket one and am going to replace it with a good Bosch. Perhaps the TPS sensor is not correct? I am really.at.a.loss. Any more help would be appreciative. Thanks

-Antique XJ

cruiser54

Exactly how long does it crank? Does it crank at the same speed whether it's hot or cold?

XcherokeeJ

I do not want to steal this thread, but want to know what solves your problem. I may be having the same problem. I will keep doing some research and let anybody know what I find.

Jesse Hallum

I agree with the comment on overthinking this problem. It could easily be a combination of things, such as:

* Low cranking speed due to temp-related voltage drop in battery
* El-cheapo starter not up to spec
* Thick, petroleum-based engine oil gelling at low temps
* Low flow/pressure at the fuel rail or leaking regulator
* My favorite: cheap, low-quality fractions in the fuel you're using
* Dirty/rusted ground connections making a marginal problem worse

I once bought a motorcycle that had the same problem; the PO put 75w90 gear oil into the crankcase. An old Dodge did this too; I finally figured out that the El-Cheapo aftermarket starter drew so much juice that the Kettering ignition system was starved to the point where it would barely fire. Nothing surprises me anymore, however I do admire your tenacity.

cruiser54

Do the ground refreshing found in the link below for starters. No pun intended, of course.

And the c101 refreshing since you have an 88.

cruiser54

I agree totally. Ground refreshing is at the top of the list.