David Edmondson

2001 Cherokee Sport, 4.0 engine. Just performed a substantial engine rebuild. Cracked 0331 head lead to coolant in oil, bearing failure, cracked piston. Bought new head from Clearwater, installed new Pistons, rings, rod and main bearings without removing engine. Primed engine by spinning oil pump under the camshaft position sensor. In the 3+ months Jeep was down, I never bothered to disconnect battery, which was new in January. Battery died. Recharging it doesn't seem to get the ammeter to show above 13v. I also tried putting a good battery in it but that battery is from a smaller 2 liter Ford. Neither battery seems to crank really well, but it seems like it's cranking well enough to start. No start. I don't know engine electronics very well. Borrowed OBD says "Throttle/Pedal Position Sensor A Circuit Low Input". I pulled the TPS and resistance drops as you turn the potentiometer. Took battery back where I got it and they said its fully charged and not showing any drop when they load it (handheld tool). My battery charger shows the battery is not fully charged. The needle on that charger got nearly to the top of the gauge after charging overnight but after cranking, the needle has dropped to the point where it's showing it needs another 4 hours of charging. I'm sure the shop's tool is more accurate than my battery charger.

I'm stumped. Any ideas?

investinwaffles

Few things going on

1. the PCM/ECU needs proper voltage to run properly. I diagnosed a no-start issue for an entire day and finally swapped in a 100% tested good battery and it solved the issue. My battery was dropping below 11v when cranking but I never bothered to check until I already went through everything else. You could try jump starting from a running car with a large enough battery/alternator to see if it makes any difference.

2. Make sure you have proper fuel pressure at the fuel rail.

3. Make sure you have spark (kind of a PITA since you have a single-rail coil system). Check this video


4. The TPS should not cause a no-start condition, the code may be false/unrelated

5. Check the Crank Position Sensor with a multimeter to make sure it is not internally shorted
https://www.cherokeeforum.com/f51/testing-cps-5563/



Does the motor sound like it is trying to fire, or is it just "dry cranking"?

EDIT:

Did you check all engine grounds as well??

David Edmondson

Investinwaffles - Thanks for the response and the links. I'll check the spark and CPS module as you suggested. Something tells me its the battery though - the fact that the shop shows it as fine with no drop under load but when I install it, it sure drops quickly. A couple of times it sounded like it started to catch, but mostly it sounds like dry cranking. Somewhere I read that if the CPS is bad, the oil pressure gauge will not move up under cranking and it is moving up. The thing that has had me concerned through the rebuild is moving all the electronic connectors with their very old wires - I was worried about wires cracking and shorting.

madmanmarty

Take the battery back.
Ask for a manager.
Get a new one,then let us know after install.

investinwaffles

I agree,
First get a battery that you know is working, or jump start off of a strong enough truck or car.

If there is no change, then make sure you have fuel & spark

If you have fuel and spark, it is probably an engine sensor so check the CPS with a multi-meter (takes all of 5 minutes). Did you try starting it in neutral (if you have an automatic)? If your neutral safety switch is bad, your reverse lights won't work I think (I have a manual trans).

David Edmondson

Got spark. CPS checked - I think - not real sure I did it correctly. I found no connector at back of manifold. The CPS wires go to a connector right beside the shift linkage on tranny. I had to crawl underneath to disconnect it, then feed it up toward the manifold to check it from above. Haynes manual says connectors are marked ABC - they were not. I did see resistance though. In looking at youtube vids I saw one that said if you have spark, then CPS has to be okay. Is that accurate? Anyway, I'm out $100 for a new battery. My local auto parts shop has been good to me and I didn't want to fight them on it, but you all had me convinced that was it. I had me convinced that was it. It wasn't. Well, the old battery wouldn't crank very long even with a jump start, so it probably wasn't up to par. It does crank better now, but still won't start. Not even a catch. I pulled spark plugs to check for spark and some of them were wet from fuel. Fuel comes out the rail if I press that schrader valve. After I crank the engine for a bit, I smell fuel, almost like a flooded carburetor.

The thing that concerns me most - I've checked and rechecked - that's the timing on the camshaft position sensor. I pulled it to prime the engine with oil. I did set the timing at TDC prior to pulling the sensor and marked the sensor body to the block prior to pulling it. Maybe....my method of finding TDC was off, but I don't think so. Here's how I did it. I didn't have any help, so I couldn't enlist someone to hold their finger in cylinder #1 plug hole to check for compression stroke. Remember, you can have TDC marks lined up at top or bottom of piston stroke. Since I didn't have help, I checked the rockers when the timing marks were aligned. The first try, one rocker was loose and one was tight, meaning one valve was at least partially open (remember the lifters weren't pumped up yet). I guessed that was actually BDC. When I turned the crank to line up TDC again, both rockers were loose. That should mean the cam lobes were in down position and the valves were closed so the timing marks were aligned at true TDC. Does this sound like a correct method? I then proceeded with removing cam position sensor to prime engine, then aligning the sensor with the middle part (whatever it's called) using a small drill bit before re-installing to the original marks.

Oh yes, I also tried starting in neutral. Nothing. I've got about $1500 into this job so far and I'm getting damn tired of spending time on. Grrr.

David Edmondson

Here's the latest. Turns out, I was reading the CPS test incorrectly - told you I have a limited grasp on electrical. So, what you want is a Zero reading on resistance. My CPS definitely showed a short. Replaced it - only took about 30 minutes - and....nothing. Still no start. I keep thinking a timing issue, but I've gone over re-installing the cam position sensor again and again, and it's fine. The OBD tells me nothing besides the TPS reading I posted earlier. Stumped. Thoroughly. And I'd love to have this Jeep available again. Help!

cpnwrench

David;

2001, on the throttle body is there an IAC attached? IF that is bad the Jeep will never start.
Also you say you pressed your finger onto the Schraeder valve at the fuel rail, I presume while the jeep was off. when you did, was there a "LARGE" hiss sound and seemingly lots of pressure, or was it just a dribble/so-so fuel eminating? if the latter, fuel filter/fuel pump problem.

YOU DID CHANGE THE FUEL FILTER AFTER A MOTOR REBUILD YA?

ok so you did change filter, and Yes you are getting large hiss when you check schraeder valve, ( to truly verify tho, get a fuel pressure gauge and check, recommended pressure is somewhere between 15-40psi [not 100% sure cuz it varies on diff models]), next is Grounds...

WHEN YOU PUT MOTOR BACK TOGETHER........EVERY SINGLE GROUND MUST BE SECURE AND ON BARE METAL>>>>>>>>

Next, Alternator and "AUTO-SHUTDOWN" RELAY..... Have you had alternator checked? this will kill a battery faster than you can blink.

"AUTO-SHUTDOWN" relay if bad, Jeep wont ever start.

FUSES- check with meter

Lastly, it could possibly be, and I have done this myself........not every connector is secure or in the "RIGHT" place.

hope it helps and best of luck sir!

cpnwrench

Cheers!

David Edmondson

Cpnwrench - Thank you for responding with this list.

No, I did not change the fuel filter. There is no large hiss from the rail when I push the Schrader valve. Fuel spews out, but didn't seem like a lot of pressure. I picked up a fuel pressure gauge and also some starting fluid. Figured, if the starting fluid got the engine to at least pop that would be a good indicator. Starting fluid did nothing - and I realize that doesn't mean that I don't a fuel problem. I was out of town for the weekend and am not sure I'll be able to get to it today, but I'll start going through this list as soon as I can.

I appreciate the input from everyone. I'll keep you posted.

David Edmondson

Fuel pressure is over 40, and no pressure loss when I shut off ignition.
Removed throttle body and IAC for cleaning. There is voltage to the IAC but I don't know how to check it otherwise. Pulled coil rail again to check for spark again. Before replacing CPS I was getting spark at all 6 plugs. Now, #2 and #5 are no spark. Haynes manual says to test for voltage at coil rail connector, specifically at wire from Auto Shutdown Relay. There is no voltage there. Done for the day.

David Edmondson

https://www.cherokeeforum.com/f2/iac-effect-223368/

I used the above link to check IAC - it is out of spec and now the OBD showed it. Replaced it. Nothing. It's a good thing I'm made out of money.

The thing that concerns me is that when I initially made a check of the CPS, I had checked and saw that I had spark at all 6 cylinders. CPS showed a short, so I replaced that and nothing. Did some other tests, and then when I checked spark again, I wasn't getting spark at cylinders 2 and 5. Haynes manual shows to check wire from ASD relay at the coil rail connection. There should be voltage. I showed nothing, and the wire doesn't show a short. Replaced that relay and still no voltage there.

How is it that the Jeep started even after the piston broke. But now that I've done all this mechanical work I'm getting all kinds of electrical parts showing out of spec? Could the new CPS be to blame? Gaaaaaaaahhhhhhh!

David Edmondson

I'm onto something here! When timing marks are aligned, #1 piston is no where near TDC - on compression or exhaust stroke. When the piston is at the top of the stroke, the harmonic balancer mark is 60-80 degrees BTDC timing mark. Maybe the balancer pulley has slipped? I bought this Jeep with 35K miles and to my knowledge the harmonic balancer has never been removed. Anyone with similar experience? Hoping I can just eyeball TDC and reset the cam position sensor...

investinwaffles

Its definitely possible that the timing is off, it would cause cylinders to not fire when they are supposed to.

I am unfortunately out of my element here, and the best I could do is google "setting timing on a 4.0 Jeep Cherokee" (I'm only 26 and only know what I have messed with)

https://www.cherokeeforum.com/f2/200...roblem-201805/


Someone with engine knowledge help this guy out!

EDIT:
If you have spark, and starting fluid didn't make it cough or sound like it wanted to fire, then it has to be ignition/timing related (I think). If your injectors are firing, then the plugs should be wet with fuel, with an unburnt fuel smell from the exhaust pipe

David Edmondson

Cylinders are definitely getting fuel.

I reset the timing by putting piston #1 at TDC on Compression stroke - the timing marks weren't even close - seriously 60-80 degrees off. Now I'm not getting spark at all. Shop gave me a new crank position sensor. I've taken the old one off. The new one is registering ohms between terminals B&C - it's not supposed to register any continuity. Pulled out the crank position sensor that I just installed and my analog multimeter shows no continuity, buy my digital shows about 13 ohms. I'm seriously going crazy with this thing.

David Edmondson

Did some other poking around the interwebs and seems the balancer spinning on the old rubber is not uncommon. Looks like I'll need to install a new harmonic balancer now too. Excellent, as I'd far rather spend time working on the Jeep rather than driving it.