No start xj

About two weeks ago I tried to start my 96 jeep cherokee with auto transmisssion and 4.0 6 cylinder motor and the starter would turn the engine over but it would not start. It ran fine the day before, when I tried to start it the next morning, no start. The same thing happened about a year ago and I ended up having to replace the ECM with one from a salvage yard and that cured the problem that time. I checked for spark at the distributer and coil and there is none. I hooked my code reader up and it says "no link" just like when the ECM died last year. So I buy a rebuilt ecm that is supposed to have a life time warrantee and when I install it in my jeep, no start, no fire from the distributer. So, I check the coil, coil wire, replace the distributer cap and rotor and and distributer pick up coil and perform the tests with my ohm meter to the cps and O2 sensors and every other sensor that my manual says that I can test without the engine running (it says that I can't check the map sensor, to take it to the dealer to have that checked) and everything tests good with the tester. I am getting 12 volts to pin # 1 and 11 volts to pin 15 at the ecm and 5 volts to the coil. So, I call the place that I bought the ecm from and the guy tells me that I must have a problem with my jeeps wiring harness since the code reader won't communicate with the ecm when I turn the key on. So, I unplug and check every electrical connection under the hood and clean the connectors with electrical contact cleaner. The connector beneath the ecm was very corroded inside and at both ends where the wires plug in but it still made no difference. Still turns over and no spark. The rotor turns when the engine is cranked and the engine has good compression so its not a broken timing chain. The place where I bought the ecm is supposed to be sending me a replacement but until it gets here, I am open to suguestions as to what I can try next. When I pulled a spark plug to do a compression test it was not wet from fuel so I am assuming that it is not getting fuel either as the plug was not wet after repeated starting attempts. I have never been able to hear the fuel pump switch on when I turn on the ignition key even when the jeep was new because its always been very quiet. I haven't investigated the fuel system because I've been concentrating on the electrical system to find out why the ignition doesn't fire. The wire going to the cps is good and it tests good with my ohm meter. All the fuses check good. I have no way to check the relays so I tried switching the ASD and fuel pump relays and still no start, no fire. I'm hoping that someone has had a similar experiance and can tell me what to try next.

Thanks,
jeepngdave

1. One suggestion--use paragraphs! That is real hard to read.

2. Welcome to !

3. On the OBDII usual cause of NO BUS or a failure to connect to the PCM is a shorted to ground CPS. As that would also give no spark, I would start there.

Good luck, and again, welcome!