I have a 2003 Grand Cherokee 4L with a good engine that we swapped into a 2000 Grand Cherokee with a good body... connected everything up and got no start.

The security key light is flashing on the dash so I took it to a dealer and got two keys programmed but that didnt work, still no start. They diagnosed a failed SKIM module. However, other techs are telling me that it should still start and then die after a few seconds even with a failed SKIM module. So Im reluctant to put in a new SKIM next because of the cost and then the keys need to be reprogrammed again and the dealer charges a lot for that.

Should it start even with a failed SKIM?

It turns over, but there's no spark from the plugs. Ive checked and replaced the Crank Position Sensor which often gets damaged in a swap so I dont think its that. Only wire that doesnt match up is the one going to the Oil Sensor. Harness seems to have a 3 prong but sensor is two prong.

What else should I check?

 

You are right. I believe it should start when you have a failed SKIM. The SKIM should shut off the fuel after it starts, but it should not effect losing spark like that..

The ASD shuts down both the spark and fuel. Are you getting fuel at the rail?

It sounds like at minimum, you are going to have to go hunting down the spark pathway to see if you can get it to start.

You may want to double check all of the different fuses and the relays to make sure they are okay?

Maybe also verify the new Crankshaft Position Sensor (CkPS) has a proper power, ground, and a signal going to/from it.

 

First time anyone has mentioned the ASD, that would make sense.

Not sure if Im getting fuel at the rail or not. Do I need a pressure tester for that, or is there a schrader valve on these, or ??

I think Ive checked all the fuses but not all relays... how do you test them other than swapping them around?

 

There should be a shrader valve located on the fuel rail. Uscrew the shrader valve cap, and push on the valve to see if fuel sprays out of it or not? This will give you an indication of having fuel pressure being built up or not by the pump. You should really use a fuel pressure gauge, but it is not necessary when just trying to verify wether or not the fuel system operating any at all...

The power supplied to the fuel pump, ignition coil, fuel injectors, and parts of the power module is controlled by the logic module through the Automatic Shutdown (ASD) relay; the idea is to shut off fuel pressure and the ignition systems whenever the key is turned off to prevent fires, diesling, and and some other problems which may possibly otherwise occur.

Also, you could listen to hear wether or not the fuel pump is being energized. The fuel pump energizes for about two seconds priming all of the fuel lines whenever you first turn the ignition key into the run position. You could have a helper turn the ignition key into the run position for you, while you stand near to the fuel tank. It is easiest to hear the fuel pump prime when you remove the fuel cap, and keep your ear listening at near to the fuel filler neck location. You could probably hear it while sitting in the Jeep turning the key yourself too. But, if you are unable to hear the fuel pump prime when doing it that way.. have a helper turn the key for you while you are standing listening for it with your ear placed near to the fuel filler neck with the fuel cap removed to be certain about it.

You can easily check the ASD relay. There are a few different ways you can go about checking in on it, to see if things there are working okay. I say remove it and use the windshield wipers relay if you will be swapping the relays around, since you do not need windshield wipers. If you were to use one of the more necessary relays to do this, the results obtained may not be very helpful. For example, if the ASD relay is bad and you were to swap it with the fuel pump specific relay.. it still would not start for you, because all you would have done was to put the faulty ASD relay into the fuel pump relays spot you know? This could be misleading.

You could also have a helper turn the key for you while you stand by the engine compartment listening for a 'click' sound, and feeling the different relays with your fingers being pinched on them to feel the 'click' sound at the same time.

You could also use a voltmeter to check the cavities, or the relay terminals where the relay plugs up into, and see if there is current being sent to the relays here at their terminals by checking for voltage. You could also use a voltmeter to check the actual relays out themselves too. By checking the resistance at the relay pins, it will be able to tell you wether or not they are showing as faulty that way.

If you have no spark.. and, also have no fuel? This is a pretty good indicator that there may be something going wrong within the ASD circuit...

 

I think I got it figured thanks to your suggestion... there was no ASD relay installed. Guess buddy must have taken it out before I bought the body but I had no idea what an ASD circuit does til now.
Grabbed a spare relay I had, popped it in and sure enough, I had fuel pressure and she FINALLY fired when I turned it over. Hasnt run yet but looking at the plugs the gap is huge and they're pretty worn so I think it will once I clean or change those out. THEN I can figure out if the SKIM is actually defective.
Thanks SO much for your suggestion! I've been beating my head against the wall on this thing and I had a feeling it was something simple because everything else seems to be working but I had run out of things to check. Now that I know about it, the ASD makes total sense.
Thanks again!

 

Well, took out the plugs, cleaned and regapped them (they were really off) and put 'em back. She fireD, but only on a couple of cylinders.
Checked the Crank position sensor and it wasn't gapped far enough away from the flywheel. Moved it out and sure enough now she runs. Only for two seconds but now I know its the faulty SKIM shutting it down. Finally down to one solvable problem.
Thanks again for your help! I owe you a beer.

 

As long as it is a Root Beer!

It's great when the issue turns out to be something simple.

It starts and shuts off after a few seconds.. and it sounds like there is still the SKIM problem to deal with now? Is that what you are saying is happening?

(edited to add):
If you would not mind, let us know how you figure it out and get the SKIM fixed... Maybe, someone here will know what to do if you are not sure how to fix this type of issue?

 

It's common practice to pull out the ASD relay when doing a compression test. Probably wasn't put back in. Also, it's good security to pull it if you can't lock it and are going to leave it awhile.

You can get your PCM reprogrammed to eliminate the SKIM if you're so inclined. One guy in Alaska had that done because the only way to leave his town and surrounding area was on a ship! He sent the PCM somewhere to have it done. IDK where. If I could remember his name, I could probably find his posts.

 

Yeah I saw a guy online who got it done. It was about 100 to do it and you gotta send the PCM to Florida. Im in Canada so the shipping and time would be too much. It would eliminate the hassle but since I already have a SKIM from the donor Jeep which Im going to assume is NOT faulty, reprogramming the keys is faster/easier.