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Car Forum / Jeep / August 200593 Grand Cherokee Ignition Question
My kid's Jeep now starts and run for 1-2 seconds, then stalls. I checked the ohms on the CPS and it's infinite as be between 2-3 pins. I also check the TPS voltage and fuel pressure and both were fine. The fuel pressure doesn't drop when the engine cuts out. I'm not sure if the injectors are shuting down cutting off fuel or the spark is quitting, or both. I'm thinking of replacing the pickup coil, but wonder if there's a test for this. It's a 3 wire model. BTW, I get no computer codes off the thing. Thanks for any help. Chuck did pass the time by typing: > My kid's Jeep now starts and run for 1-2 seconds, then stalls. I checked > the ohms on the CPS and it's infinite as be between 2-3 pins. I also [quoted text clipped - 9 lines] > > Thanks for any help. http://revbeergoggles.com/cps/ 1-2 second run indicates a sensor/relay fault is shutting down the engine or the computer isn't getting an indication the engine has actually started. This can be from a failed camshaft position sensor or crankshaft position sensor. In some cases it can also be a failing ASD relay or a blown fuse. Some times a faulty ignition coil can do this as well. The ASD relay is in the engine relay center http://revbeergoggles.com/Fixes/fuse-engine.jpg http://revbeergoggles.com/Fixes/fuse-engine-lid.jpg You can swap it with the AC relay Have you checked the distributor for oil? http://revbeergoggles.com/distributor/ The camshaft position sensor is in there, but to replace it you have to remove and dissasemble the distributor. If the distributor has oil/sludge and the rotor can be moved side (which it shouldn't be able to do) then the bushing is shot and your better off just putting a new unit in, as they come with a new sensor. Now before replacing any sensors, disconnect and reconnect the harnesses to the Crankshaft and camshaft position sensors, remove and reinsert the ASD relay, remove and reinsert the coil feed, and check the distributor for oil. Also if your measuring sensors use a digital mulitmeter. Analog multimeters are not safe for use on sensors these days.  SignatureDougW DougW did pass the time by typing: > Chuck did pass the time by typing: >> My kid's Jeep now starts and run for 1-2 seconds, then stalls. I checked [quoted text clipped - 6 lines] >> I'm thinking of replacing the pickup coil, but wonder if there's a test >> for this. It's a 3 wire model. Forgot :) http://www.asashop.org/autoinc/feb99/techtotech.htm >> BTW, I get no computer codes off the thing. >> [quoted text clipped - 32 lines] > Analog multimeters are not safe for use on sensors these > days. > DougW did pass the time by typing: >> Chuck did pass the time by typing: [quoted text clipped - 10 lines] > Forgot :) > http://www.asashop.org/autoinc/feb99/techtotech.htm This makes wonder. I guess I'll play around and put the distributor on both sides of my mark. There scary thing is that I saw other marks in the distributor that I didn't put there. >>> BTW, I get no computer codes off the thing. >>> [quoted text clipped - 32 lines] >> Analog multimeters are not safe for use on sensors these >> days. > DougW did pass the time by typing: > [quoted text clipped - 49 lines] >>Analog multimeters are not safe for use on sensors these >>days. DougW just wanted to say THANK YOU for your website. i don't have much access to JEEP technical information at my dealership. Big help! benji SignatureBen Jerew AKA PolarPuppy1976 New Country Lexus of Latham, NY, USA Amateur Off-Roader 93 YJ, 93 ZJ MudPuppy76 did pass the time by typing: > DougW > just wanted to say THANK YOU for your website. i > don't have much access to JEEP technical > information at my dealership. Big help! Your welcome. It's not advertised on the site but sometimes the temp directory has interesting things. http://www.revbeergoggles.com/temp/ If you need tech info the 93ZJ service manual is out there, I strongly recommend getting on. Not cheap but they pay for themselves in the first few jobs. SignatureDougW > Chuck did pass the time by typing: >> My kid's Jeep now starts and run for 1-2 seconds, then stalls. I checked [quoted text clipped - 19 lines] > be a failing ASD relay or a blown fuse. Some times a faulty ignition > coil can do this as well. I thought the sensors too. The CrankshaftPS ohmed out infinite with a Fluke digital meter. I also checked all the fuses and swapped around relays to eliminate this. > The ASD relay is in the engine relay center > http://revbeergoggles.com/Fixes/fuse-engine.jpg [quoted text clipped - 10 lines] > bushing is shot and your better off just putting a new > unit in, as they come with a new sensor. There was just a little slop and a little oil in the distributor so I replaced it. It was close to the same price of the sensor alone. > Now before replacing any sensors, disconnect and reconnect > the harnesses to the Crankshaft and camshaft position > sensors, remove and reinsert the ASD relay, remove and reinsert > the coil feed, and check the distributor for oil. I did all these things. > Also if your measuring sensors use a digital mulitmeter. > Analog multimeters are not safe for use on sensors these > days. I didn't know that, but I use a digital meter almost all the time now anyways. I'm still stumped. I'm beginning to think a computer problem. Chuck did pass the time by typing: > I thought the sensors too. The CrankshaftPS ohmed out infinite with a > Fluke digital meter. I also checked all the fuses and swapped around > relays to eliminate this. I use a Fluke 87 to back up by my trusty little Tektronix TDS2002 :) Ok.. so that is a bit nuts. The crankshaftPS is just your basic hall effect sensor. It outputs a 5v pulse once every rev. There should be 8V between the center pin (Black/light blue (ground)) and the White/Black wire. with a 5v pulse coming out the grey/black wire. There isn't an "ignition module", just the ECU/Computer. If it was fragged I doubt the engine would start at all. Just a thing to check, look on the engine block forward of the right engine mount where the O2 sensor wire goes up to the front of the wiring loom that runs along the injector rail. (man what a run-on sentence) Check the metal clip that holds that wire to the block to make sure it hasn't been pinched or burned/shorted out. You could remove/clean/replace the ECU connector. Just have to move the overflow bottle out of the way. If you do this, DO NOT.. use the center screw on that connector to suck it back in, that will crack the connector and that is $bigbucks$. Make sure the battery is disconnected. And when you go to hook the battery back up, put the key in the ignition and turn it to ON. That will tell the alarm system it's ok and your not some nefarious car thief. ;) SignatureDougW DougW did pass the time by typing: > Just a thing to check, look on the engine block forward > of the right engine mount where the O2 sensor wire goes ^^^^^ drivers side :) > up to the front of the wiring loom that runs along the > injector rail. (man what a run-on sentence) Check the metal > clip that holds that wire to the block to make sure it hasn't > been pinched or burned/shorted out. SignatureDougW There is no such thing as too much coffee. > I thought the sensors too. The CrankshaftPS ohmed out infinite with a > Fluke digital meter. I also checked all the fuses and swapped around > relays to eliminate this. Ohmic check of the CPS is a waste of time unless you do it right - it is a Hall Effect switch which is basically a transistor that is turned on by the change in the flux field. You may get some info if you make all your measurements the repeat with reversed leads. This causes some "0" readings to go to open while other open leads will indicate a small current flow. The only reliable way to measure it is with a scope while it's under power, altho some better digital VOLTMETERS (not OHMETERS) have a fast enough response time to show whether it is actually pulsing or not. An older analog VOM will also work to check the voltage. SignatureWill Honea > Chuck did pass the time by typing: >> My kid's Jeep now starts and run for 1-2 seconds, then stalls. I checked [quoted text clipped - 19 lines] > be a failing ASD relay or a blown fuse. Some times a faulty ignition > coil can do this as well. I have no idea what activates/deactivates the ASD relay. I've heard read of oil pressure ones and ones under the drivers seat, but haven't found one. I know a FSM would be nice. Chuck did pass the time by typing: > I have no idea what activates/deactivates the ASD relay. I've heard read > of oil pressure ones and ones under the drivers seat, but haven't found > one. The ECU/Computer controls the ASD realy. ASD or Automatic ShutDown is basically the engines panic button. http://www.revbeergoggles.com/temp/ ZJ-13 - 18 SignatureDougW > Chuck did pass the time by typing: > [quoted text clipped - 6 lines] > http://www.revbeergoggles.com/temp/ > ZJ-13 - 18 I guess I'm half blind. The third or fourth time of taking out the fuses, I spotted the burn in the 40 panel fuse. I should have known that the absence of any bells was wrong and I never tried windows, heater, radio, etc. I was too focused on the fact that the dash gauges/lights were working. It seems the thing is running better than before. I just wonder when the cause of the blown fuse will rear its ugly head again. Thanks, for all the help. Great stuff on the web site Doug, thanks. Chuck Just a thought, this happened to me when the battery went dead and we jumped started it some seven or so years ago on my old 93 GC 4.0. It was the alarm system. Once the alarm was (reset) it was OK. If you know this, please forgive the post. Bob > My kid's Jeep now starts and run for 1-2 seconds, then stalls. I checked > the ohms on the CPS and it's infinite as be between 2-3 pins. I also [quoted text clipped - 9 lines] > > Thanks for any help. > Just a thought, this happened to me when the battery went dead and we jumped > started it some seven or so years ago on my old 93 GC 4.0. It was the alarm > system. Once the alarm was (reset) it was OK. If you know this, please > forgive the post. > Bob Thanks for the input. This already happened to me before so I know the hard way. I didn't notice the 'security' lamp lit so I assume this isn't it. I don't remember it starting for a second when this happened before. >> My kid's Jeep now starts and run for 1-2 seconds, then stalls. I checked >> the ohms on the CPS and it's infinite as be between 2-3 pins. I also [quoted text clipped - 9 lines] >> >> Thanks for any help. |
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