Strange symptoms, no start..

I searched, but came up with no solution. This weekend I washed my 92 Cherokee to get it ready for a little brake/exhaust/maintenance work. I washed the motor, being careful to not get the TPS wet. While dinking around with the hose, I accidently gave my PCM (ECM?) a full on blast of water. Well, it didn't start so I pushed it out of the bay to let it dry in the sun.

First step, pulled the distributor cap and dried out some moisture that got inside. Still no start. I let it sit an hour. Still no start. OK, I call the wife, have her bring me home and let it sit for 4 more hours. When we drive up to the carwash, the lights are on... The switch is off, ignition off, lights stay on. No start...

The next day, I go to tow it home. When the battery is re-connected the lights come back on. When the ignition switch is on, my electric fan comes on. (cold engine, 20 degrees out)

It has been in a heated garage for 3 days with a fan blowing under the hood.
The lights no longer stay on, but the fan still comes on when the ignition is on, the motor cranks at normal speed, and it still won't start.
I have no spark, I have no fuel pressure at the rail, no current at the fuel pump resistor.
I checked all the fuses and relays, checked and cleaned connections and grounds.

Suggestions?

this is just my opinion, but i think you may have killed the pcm-the fan coming on anytime the ignition is on is the key, i believe. i've seen a couple chrysler pcm's that did that when the computer crapped itself.

Blow the distributor out with air, I'm thinking maybe the cam position sensor is wet shorting the 5 volt sensor circuit. The Cam position sensor and the CPS share the same 5 volts. You can test for 5 volts by back pinning the orange wire. Not often 5 volts will short through clean water, but you may have some soap in there or something lowering the typical resistance through water.
Pull the temp sensor plug at the thermostat housing and dry that off good. The lower the resistance and the hotter the sensor reading, could be a short through water.
Really no telling where the water got in (which connector), those are two places to start.
Forget the WD-40 and use air and contact cleaner. Hopefully it's something sucking down the 5 volt sensor power supply and not something permanent.
Does your ch3eck engine light illuminate with the key in the run position?

I feel terrible for you. Something so simple causing so much trouble. Keep us posted and good luck. I wish I was more help.

I would consider disconnecting the battery, and then disconnecting the ECM, and then try drying it out with a hair dryer on low or medium heat...you might want to try the hair dryer on the Distributor, and sensor connections, as well as the relays, PDC, fuse slots...

I sprayed the distributor with WD, blew it out with the compressor, then hit it with electrical cleaner followed by lower air pressure. Following the next no-start, I pulled the cap and let the fan blow on it overnight. I did the same treatment on the PCM and the underhood fuse panel on the following two nights. I would think everything should be dry by now.

I'm not an automotive electrical kind if guy, but I'll check the voltage at the cam position sensor in the AM.

Would the cam position sensor effect the fuel system??

What's a PDC?

When everything is working, CPS tells PCM when motor is at TDC when your crank it over, and then PCM knows when to fire spark plugs and injectors to get motor started. CAM position Sensor is involved but moreso once motor is started and running. If PCM doesn't see input from CPS, it will shut down fuel pump and not fire your coil...so no spark, no fuel, no start. But as 8Mud said, the PCM supplies 5volts to many sensors, TPS, MAP, CPS, CAM sensor, etc...so shorted sensor can suck down the PCM 5 volt source and disable PCM from functioning....you can test for the 5 volt output from PCM..if it is not there, unplug sensors one at a time to see if one of them is holding it down. No simple test to determine if PCM is dead. You can try pulling codes with a code reader to see if it will communicate with the PCM.

McQue said:

When everything is working, CPS tells PCM when motor is at TDC when your crank it over, and then PCM knows when to fire spark plugs and injectors to get motor started. CAM position Sensor is involved but moreso once motor is started and running. If PCM doesn't see input from CPS, it will shut down fuel pump and not fire your coil...so no spark, no fuel, no start. But as 8Mud said, the PCM supplies 5volts to many sensors, TPS, MAP, CPS, CAM sensor, etc...so shorted sensor can suck down the PCM 5 volt source and disable PCM from functioning....you can test for the 5 volt output from PCM..if it is not there, unplug sensors one at a time to see if one of them is holding it down. No simple test to determine if PCM is dead. You can try pulling codes with a code reader to see if it will communicate with the PCM.

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Good advice.
The cam position sensor and CPS share one 5 volt lead, the MAP and TPS another and the Engine tmeperature sensor a third, but I believe (don't know for a certainty) they share a common power supply. The orange wire to the Crank position sensor and the Cam position sensor is a good place to check for 5 volts.

If you can't get your hands on an FSM sign up for Alldata. Alldata is pretty good with electrical stuff and sensor tests.

You can test the MIL codes with the key method in your 92 (I'm fairly certain). If your check engine light isn't lighting with the key in run, this can be an idication there is a short in the 5 volt sensor supply someplace.

The Check engine light is coming on with the key on, but the only way I heard to extract the codes with the key involves running the engine first.....

Madmark said:

running the engine first.....

Click to expand...

not necessary.
Start with the ignition off. Within five seconds, switch the key on, off, on, off, on. (”On” is NOT “Start” and “Off” is NOT “Lock”). The “check engine” light will flash. Count the flashes. Each code is a two digit code, so a (for example) 23 would be FLASH FLASH (pause) FLASH FLASH FLASH (long pause). It will never flash more than 9 times, so watch for those pauses!

Some model years you can turn the key on and off three times and the check engine light will blink MIL codes. The codes are repeated twice. write them down. 12 and 55 are normal codes anything else is a problem.
It may take a couple of tries turning the key three times, I've found I need a rhythm to make it work.
I'm not sure you can do this with a 92 but it's likely. I've never tried it on a 92 personally.

I thought I'd post what my problem was. I checked for codes, but had no codes stored, and no power to the fuel or ignition.
I got a used PCM from a junkyard, tossed it in, and she started right up.
I dissassembled the old PCM, and found that the gel that covers the curcuit board had cracks all through it. Water was allowed to pass freely through the waterproof coating, dissabling the PCM.
Problem solved, thanks for all your help!

Woot glad to hear it! Hate to see people stuck.