Creeklurker

97 jeep cherokee 4.0l 4wd just bought it from a guy who couldn't get it running he replaced the cap ,rotor, ignition coil , crankshaft position sensor all that failed so he ordered a new computer by serial number took three months to get and he gave up that's when I bought it I have drained the fuel out of it by jumping in fuse box and put three gallons of fresh gas ...stunk to high heaven and gas was orange im sure its not all out but I also have cleaned all grounds I also checked and I have 5 volts to the camshaft,(wires coming out of distributor) crank,tps,map I also checked continuity through them and ground as well I also made sure the computer was sending power so seems the new computer is working even though I had power to all that I have replaced the ignition coil again ,crankshaft position sensor again, ignition switch
I have also checked all fuses and the asd is getting power and ground when i turn on key itll get 12 volts to ignition coil just for a second and then itll drop out before i even crank ill crank for 6 to 10 seconds voltage never comes back i put a inline spark tester with bulb right off the ignition coil and it's barely lighting up so I guess it's getting some power if you don't cup your hands over it and make it dark you'll miss it tried with both ignition coils no change I'm getting codes for high voltage to throttle position sensor and a couple other things I know the 02 sensors are not plugged in for whatever reason if you spray a crap ton of starting fluid it'll stumble like it wants too first couple of seconds but nothing to get excited about far from firing up tried everything with gas pedal I'm left with check fuel pressure and a compression test maybe a new distributor, camshaft position sensor , plugs, wires ,pull off fuel rail make sure injectors are clear from old fuel and junk I'm stumped all the basics are recieveing power and ground I'm pretty sure story was it was a daily driver and then it quit running guy got it for cheap sent it to his buddy to fix he stopped throwing money at it and I picked it up and replaced same parts but computer it looks like it came from pull apart it has orange marker numbers on it i hooked up scanner its saying the throttle postion is at 100%and something else was at 100% when it shouldnt of been being off and not on the throttle i mashed it nothing changed in live data wish I still had o.e computer but he sent back for core I might be fighting more than one problem this computer got me sketch at this point I wanna trust it I did the probing its sending power ohh and did I mention idk if it has security system either keeping it shut down when the guy got it he said it only had a crank position sensor code but that didn't fix the problem any help much oblige

cspaltro

As for the security system, you'll just have to poke around all over and you'll see where they installed the module which would be wired into the fuse box to interrupt the ignition or starter relay and prevent it from starting. If you can't find anything or any out of place wires around the fuse box, then it most likely doesn't have a security system. If it did, previous owner should have given you the fob to enable / disable the system as well as the manual (one would think).
Your no start could be one of the various issues that you have yet to check. plugged up injectors from the old gas, could even be a plugged-up fuel line from the old gas. Are the injectors fried also? sometimes when the ECU goes it can send a surge and fry the injectors. You can ohm test the cam position sensor by probing each pair. if you see resistance on any two pair of wires, it's bad. You should see 0 or - (infinite) between any two of the three wires. One is ground, on is 5V, the other is signal back to ECU. None of these should be shorted in the sensor. A bad sensor will usually have a short between two of these connections inside. Cam Shaft Sensors don't go bad often, it's the impossible to reach CPS that breaks when we most need it. Have you thought to replace or even test the throttle position sensor and the "something else" that is at 100% but isn't supposed to be? If you are getting a code on those, they might not be preventing it from starting, but they need to be addressed anyway, or those readings are false due to your bigger problem that is causing the engine to no-start. When the CPS was replaced, did the previous owner or you (whoever replaced it) use a Mopar original sensor? After market CPS are notorious for being sketchy and bad. If you bought it at a parts store, you might just have a non-op CPS.

I just went through this same issue, threw a bunch of parts at it and found that the ECU was fried, as in the capacitor blew up and cooked my board causing multiple shorts across traces on the board. Too far gone to fix it. Looking for a 91 automatic ECU that is exactly the same as mine because the early OBD1 computers are ALL different and I don't care what anyone says, not a one of those darn things is the same. It's like they had each one custom made as the Jeeps were rolling off the assembly line, a guy had a box of electronic parts and he was told to make the Jeep run. He put a bunch of parts together and boom, done. Next Jeep got a bunch of different parts, and so on and so on.

Good Luck, keep us posted as you work through this. Others benefit from your struggles.

Creeklurker

I took out the fuel injectors and bench tested them with quick alligator leads they are all alive and I cleared them completely out of old gas.
I took out spark plugs they are deffinetly aged and super black from carbon /faulted out I don't think they could possibly fire

Random plug
they was all super dry like it hadn't been getting fuel.
I have 5v and continuity to camshaft position.
The computer is sending all power to sensors.
The guy replaced the crankshaft with auto zone and so did I and got the same results I still have weak spark.
I'm going to get new plugs and wires , new fuel injector o-rings definitely needs it.
The fuel rail is getting gas just don't know pressure yet, im getting a fuel pressure tester next couple of days but I hot legged the fuel pump, took off fuel line from fuel rail and empty the gas tank that way. I ran out all old gas and put in three gallons of fresh fuel and ran it again untill fresh gas got up to fuel rail and then some just to be safe.
I will keep posted for more updates.
Still not sure about tps and throttle body sensors, I am going to clean and test those as well before attempting to fire again because the tps and "iac" in live data with truck off are saying they are both at 100 % , If i push the gas nothing changes . I also seen there was a transmission code, I heard that the tps acting up can cause transmission problems/codes. ( I'm thinking out loud if it's reading 100 % throttle the computer isn't going to let fuel spray due to being at 100% it'll be in some sort of flood mode ? Is that a possibility?) Hence why spark plugs are dry it doesn't seem like the fuel injectors fired at all, with the bad gas being broke down as bad as it was they should be soaked no way it could've evaporated off with that old fuel.
I have a lock fob but no panic button on it idk if that helps if i have the security system.
I have a plug two wire about 6 -7 inches long that was dangling behind the ac canister up against the fire wall don't know where it goes I posted picture of it

awg

sorry to say bro, but i just cant make sense of a that without proper spacings, punctuations and that ****

not being a smart **** here, you can edit it so we can read it

Creeklurker

My apologies I edited the post