hit a pothole , stalled and wont start,,help!! on 1997 Jeep Grand Cherokee

jeep has no power to coil no power to fuel pump still cranks replaced crankshaft position sensor, checked all fuses and grouunds, battery hookup ,gauges not working, some idiot lights checked fuel pump wires checked power distribution center

by in Forked River, NJ on December 22, 2013
2 answers 7 comments
ANSWER by on December 22, 2013
You need to connect a scan tool that has bi-directional capability. The fuel pump, ignition coil and more are all powered up by the ASD relay. The strategy is the relay gets turned on for about two seconds at key on, then it gets turned back off until the PCM see's the crankshaft sensor signal. With a scan tool you can command the PCM to turn the ASD relay on/off for several minutes at a time and you can test to prove where that circuit is failing. You'll probably need a tech to diagnose this for you, but this is a short outline of what it takes to do it.
COMMENT by on December 22, 2013
hi,and ty,what supplies the ecm power for the fuel pump to come on for thefirst few seconds?i checked relays and fuses
COMMENT by on December 22, 2013
The ECM should have power all of the time pin A22 red/yellow wire for keep alive functions, and it gets switched power from the ignition switch on pin A2 Orange. Upon getting that switched power it starts its priming and starting routine by turning on the ASD for two seconds. The trick here is for a scan tool can communicate with the computer, it has to have power. If don't have communication one of my next steps is to manually try and check for a 5v reference to the easiest sensor that I can reach. (Usually a TPS). If I have my 5v reference then I have good power and ground. If the voltage is too high, I'm looking for a ground circuit issue. If the voltage is too low, then I'm looking for power to the PCM. (Bear in mind these are just the first steps to narrow the focus, there is still much more to this in many cases)
ANSWER by on December 22, 2013
That must have been some pothole! Did it stall immediately when you hit this pothole, just like you turned the key off? Do you have the owners manual? There is a couple of things that YOU can check out.
COMMENT by on December 22, 2013
yes, it immediatley stalled out.yes, i have manual,i tried everythingggggggggg
COMMENT by on December 22, 2013
No you have not tried everythinggggggg!!! Find the ASD relay and switch it out with another since most of them are the same. You need to know which is the ASD though! Now, think about what happened when you hit this hole, it shook everything around prety good! After you switch the relay, just to be sure, turn the key to on, go under the hood and start shaking the wire harness to different componets like the fuse relay box the computer, anything that you can find wiggle it around. Listen for any clicking of relays etc while doing this. If "stuff" starts coming on there is your problem at that point. Also there are fuseable links by the battery that need to be tested. If no luck after this, i suggest getting it to a repair shop for more testing. That is about all YOU can do!
COMMENT by on December 22, 2013
ty, i already did a swich out with the asd..:((
COMMENT by on December 22, 2013
Oh i am sure you tried the wigglee test too!!! Well, off to the shop then!!! Good luck.
COMMENT by on December 22, 2013
ty pushrod