AZLumberJack

OK, I am at a point now where I have run out of money and patience for my jeep. Maybe somebody has an idea:

A month or so ago, The motor threw a rod, broke the cam, timing chain and gears left a big old hole in the block and timing cover. It ran wonderful prior to this no issues at all .I bought a motor from the exact same year jeep complete with everything on it but the power steering pump. This motor ran wonderfully I know because we ran it for 30 minutes before I paid him for it.

I pulled the motor and dropped in the new one with everything on it the only thing I changed over was the knock sensor as mine is new and the other was damaged. The starter (mine but it was on it's way out) ended up being bad so I had to swap it out but other than that nothing else.

It fired up and idled very well but when the gas is applied it boggs down, sputters and back fires through the carb and the exhaust as well. Never dies just goes right back to a nice idle. If I hold the throttle open and spray fuel in while smoking a cigarette it will accelerate nicely so this tells me it's fuel related. Map sensor tests good, cap and rotor are great, plug wires and firing order are straight. EGR is plugged and removed same as before. Vacuum lines are simple and legit.

WHAT I HAVE DONE
Swapped fuel rail/ injectors/fpr <~~ all at once but i did inspect the injectors and o-rings on both and they looked good. The ones on new motor were in great shape but I used my old ones just in case

Tried again, same result

swapped out tps and the stepper in the throttle body

same result

bypassed fuel filter just to test

replaced fuel pump and found 3 strainers at the bottom of the tank

same result

Swapped harness double checked injector driver plugs w diagram

same result...

replaced intake/exhaust manifold gasket (what a PITA)

same GRRR

(dont know if this is legit and probably should be on youtube in the fail section but) I pulled the fuel line by the FPR and tried to plug it with my thumb and had my buddy start it. this was to see if the FPR was doing it's job.....MISTAKE DO NOT TRY THIS I am bald now because of it. NO but seriously fuel sprayed at a very high rate EVERYWHERE. So after further inspection I decided to plug the line back in and pinch the rubber with a nice smooth pair of duck bills just enough to make some pressure.

Same result

I am at the end of my rope here can somebody give me an idea of what's going on here.

griff98xj

Sounds like a timing problem..

Radi

Did you adjust the TPS after swapping it? I believe the older ones (yours) need to be set up using a DVM. At least verify the output voltage is there and increases with throttle, you disturbed some pretty old wiring harnesses.
TPS signals the PCM for a shot of fuel when you accelerate like the old accelerator pumps did. Without it you rev up lean which can stumble and backfire.
Map sensor vacuum line in good condition? They're known for hidden cracks. Any intake leaks? Did you disturb the distributor in any way?

cruiser54

Get all the ground wires hooked up to a clean and shiny engine dipstick tube stud?

zkdawg

When u were running to motor before u bought it, did u test drive it? Did u rev it up? You should check your compression before you go any further and report back

AZLumberJack

Checked timing it's on the money

TPS: I did swap it out for my original one (forgot to mention that) I did put a pulse meter on my injectors and they're firing as I believe they should when the throttle body is opened up. Swapping this out changed nothing and the response from the two different parts.

Ground: I checked the grounds thoroughly and shined up my dipstick : I scraped the firewall and even replaced the crappy terminal where the multiple grounds come together with a bigger more bada** connector. this connector is so beefy that we couldn't figure out how to crimp it other than in a vice. (how'd you get it in a vice?) I'll post a pic it's rather amusing

Test drive? NO... There were no axles to roll on. The guy bought 1 tons and a cherry xj to build a crawler, ripped the axles out and gave up his man card. His wife made him scrap it. I did hammer the throttle several times looking for motor noise and such ... It's a nice quiet motor and it had no issues when I pulled it last week.

NO intake or vacuum leaks I smoked it BOB MARLEY style and I also went through several cans of carb cleaner on the top and bottom. I did mention that I changed the intake gasket. Didn't need to but I'll mark it up to PM

The more I think about it, the more I think crank sensor simply because it sits right there where the motor and trans are mated. Possibly got bumped. It's the only thing I don't have 2 of

I won't be able to pick up a new one til Friday but tomorrow my buddy is bringing his scanner by to get some real time data and maybe shed some light on this before I throw more money at it... or scrap it

cruiser54

Test your CPS.

But, you shouldn't have injector pulse if it's bad.

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 to 3/8" from the stock 5/16", 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 01-26-2013

AZLumberJack

I am heading to the shop tomorrow (friday) to test the TPS

Cruzer I have been studing your renix tips daily and I really appreciate all of the info! I see you're in Prescott, If I ever get it running we're headed up to spend the weekend at her grandpas place. We should meet up, so's I can shake your hand.

Hell, I'd pay you for your time or buy the beer if you are ever in the e valley to look it over. I'm 15 minutes from Canyon lake and I've got a RV spot with full water electric and sewer If you wanted to drive back the next day and you've got a T trailer or rv

cruiser54

Thanks for the offer.

Let us know the results of the TPS test. Be sure to perfoem the test using the flat 3 wire cnnector as that's the side for engine management. Also be sure to do the sensor ground test outlined in the TPS instructions if you haven't already done so.

I'm curious about the CPS test also. Seems odd that you would have an injector pulse with a bad CPS.

Take a peek on the driver's side inner fender and see if your fuel pump ballast resistor has bad connections, is broke, or whatever. At idle, test each side for voltage. One side should be battery voltage, the other about 9 volts or so. It's perfectly fine to bypass it. It's only there to reduce fuel pump noise.

AZLumberJack

Crank position sensor was worn and IF I had thought to notice the tone ring on the fly wheel of the old motor I would have noticed the wear marks earlier. The crank had obviously been wobbling and essentially ground down the metal tip on the sensor. This kept it far enough from the ring to get a weak signal. Thanks for all the help.

I guess I could have ground it a bit and slotted the holed and slid it down to get it closer but at this point I'm just glad it's new and my new motor runs!

*** I did make a mistake while changing it out; I ran the wires up against the manifold and burnt them up. The motor died and I had no spark. I noticed the problem after deciding to check to see if the sensor was damaged again so be sure to check this before you start! ***

My next project is to narrow the front end about 8 inches by tucking the fenders to the core support I'll post something when I get it done!

AZLumberJack

I used a bunch of extensions with a universal swivel in the middle to get at it with the aid of me from above my buddy Matt was able to get on it from below without dropping the trans or going through the floor.

I did notice that these bolts are shoulder bolts. If you lose one you will need to remember this. the thread is much smaller than the shoulder that goes thru the sensor. A valve cover bolt works in a pinch but it is a little narrow for the holes in the sensor so you need to make sure it's on there straight when tightening it down. you could probably make a sort of shim with a slice of tubing or the right washer to eliminate slop.

4wheeldrivenewbie

that's how they are on renix jeeps they say a slotted one works better or whatever I used a normal duralast and nothing changed my car still started hard like before you crank and crank and crank. jeeps just do that.

And your tip looks warn out somehow because the original I had had the same size tip as the new one. ??? does your jeep start any faster

cruiser54

CPS wire routing.

And in the second photo you can see how much gap a stock CPS has. Something was seriously wrong there. Wrong CPS bolts? Engine to trans bolts loose?

cruiser54

Can any of you more computer literate folks out there enlarge the CPS wire routing photo and post it back up so I can copy it?

DFlintstone

I just clicked on your image, held the "ctrl" key and hit "+" to blow it up, then photoed it!