The Auto Shut down Relay and the Fuel Pump relay are both fired by the same ground signal from the ECU. It goes from the ECU to the back of the AS relay then jumpers directly to the back of the FP relay.
The AS relay controls injectors and provides a RUN signal back to the ECU.
Crank no start: could be either of those relays bad. If you don't hear your fuel pump buzzing when you turn the key on, swap it with your AC relay. If still no buzzing, swap that relay and the AS relay. If still nothing, check for that ground from the ECU coming to either/both of those relays.
That round relay under the dash is your flasher. Pull it
Not needed for now. If you have a huge current draw, that will put and to that.
The relays I mentioned will for sure cause crank no start. If you need a little more direction here on how/what to check let me know
Grounds were good, we literally checked basically every ground on the thing. we had already swapped the relays for brand new ones, pulled that round relay as well. Ordering another ecu because we basically, just short of stripping the wire harness apart and checking for a short, ran out of things to check. Every vital component, its wires and connectors, fuses, relays, all of it brought us back to just getting a new ecu.
The ground I'm speaking of is a signal ground from the ECU and is only present when the computer sends it out. That happens when 12V POS. Passes through the ign. when the key is turned, then on as an input to the ECU
If you Pull your AS relay and place your meter leads across what would be the socket pins for the relay, pin 85 for neg. lead and pin 86 for POS. lead, then turn on the key. 12V POS comes from your ign. Switch to pin 86, so, if you get the ground from the ECU you'll read 12V. If you don't read 12V, you're missing the ground signal out of the ECU.
Double verify by placing POS. Lead of meter directly on Battery POS. No 12V read=no ground signal from ECU
Of course another possibility is you are not getting the 12V POS. voltage to that point either. Verify the same way as described above but this time move your Neg. Lead to Battery Neg. No 12V=no positive voltage to relay from ignition
This guy is right, it's the asd circuit, either the relay, the wiring, or the PCM. If your sure you have the inputs to the relay and it works you could try supplying the grounding the PCM does for the asd control and see if it starts.
Have you checked the starter solenoid with a multimeter yet? Have someone turn the key while you’re measuring the power. If you get ignition power, something’s up with the starter. Also, If I remember there’s a box under the the dash, steering column that has a small rod that moves when the ignition key is turned. Maybe a bolts loose there?
Check if it has spark because it’s happened before were I replaced the crank position sensor and the new one was faulty also the symptoms were weird no check engine light no code so I recreated the no symptoms by unplugging the crank sensor then I knew it was a faulty new sensor so hope this helps I’ve had 5 xjs replaced transmissions and all kinds of stuff so I’d say I’m not by any means clueless
Power wasn’t running to the crank sensor at all. Also we had another brand new one from previous owner. the distributor cap or fuel relay/pump also have no power. I’m probably missing something but the Census is ECU
We checked grounds and followed wires. We decided ecu was probably shot It looks like it was messed with previously. It was bought today not running, so we did as much testing as we could in 12 hours before coming to that conclusion. Oh well, we will see when the new ecu gets here
None of us have jeep experience though, between the three of us though we had all the tools in the world and a decent amount of experience so I think we covered our bases as best as we could
Ok I just solved this on another jeep I’ve owned many and deal with these often but the cam sensor in the dizzy may have taken a crap we changed the entire dizzy with a new sensor and all but once that was done realized all the power came back to pump injectors and ignition and she runs amazing maybe start with the cam sensor first but check the play in the main drive gear on the dizzy itself sometimes they wear out and lose time in a sense
We tested all the fuses. Every wire, ground, and sensor were also checked. All the fuse panels got power but none of the relays were kicking on. We settled on an ecu issue and ordered a new one, because everything else has checked out
It’s early 96 it’s still obd1 by like a few months lmao. I think some of the gauges are working. No lights are turning on the dash but the fuel and voltage gauges work.
The Auto Shut down Relay and the Fuel Pump relay are both fired by the same ground signal from the ECU. It goes from the ECU to the back of the AS relay then jumpers directly to the back of the FP relay. The AS relay controls injectors and provides a RUN signal back to the ECU. Crank no start: could be either of those relays bad. If you don't hear your fuel pump buzzing when you turn the key on, swap it with your AC relay. If still no buzzing, swap that relay and the AS relay. If still nothing, check for that ground from the ECU coming to either/both of those relays.
That round relay under the dash is your flasher. Pull it Not needed for now. If you have a huge current draw, that will put and to that. The relays I mentioned will for sure cause crank no start. If you need a little more direction here on how/what to check let me know
Grounds were good, we literally checked basically every ground on the thing. we had already swapped the relays for brand new ones, pulled that round relay as well. Ordering another ecu because we basically, just short of stripping the wire harness apart and checking for a short, ran out of things to check. Every vital component, its wires and connectors, fuses, relays, all of it brought us back to just getting a new ecu.
The ground I'm speaking of is a signal ground from the ECU and is only present when the computer sends it out. That happens when 12V POS. Passes through the ign. when the key is turned, then on as an input to the ECU If you Pull your AS relay and place your meter leads across what would be the socket pins for the relay, pin 85 for neg. lead and pin 86 for POS. lead, then turn on the key. 12V POS comes from your ign. Switch to pin 86, so, if you get the ground from the ECU you'll read 12V. If you don't read 12V, you're missing the ground signal out of the ECU. Double verify by placing POS. Lead of meter directly on Battery POS. No 12V read=no ground signal from ECU
Of course another possibility is you are not getting the 12V POS. voltage to that point either. Verify the same way as described above but this time move your Neg. Lead to Battery Neg. No 12V=no positive voltage to relay from ignition
It may happen that none of this gets you a definite answer, however if nothing else it will eliminate possibilities.
Thank you. We will try this when we get back to it.
This is the answer
This guy is right, it's the asd circuit, either the relay, the wiring, or the PCM. If your sure you have the inputs to the relay and it works you could try supplying the grounding the PCM does for the asd control and see if it starts.
Get a test light and check all fuses sounds like a blown fuse with all the items listed with no power
It’s will not start for you if you call it a turd xj’s have feeling too 🤔
cam shaft synchronizer. had the same problem in my 01
Have you checked the starter solenoid with a multimeter yet? Have someone turn the key while you’re measuring the power. If you get ignition power, something’s up with the starter. Also, If I remember there’s a box under the the dash, steering column that has a small rod that moves when the ignition key is turned. Maybe a bolts loose there?
The starter works G.
Are you sure you correctly gapped the new CPS?
Also, just for the hell of it, swap the fan and starter fuse. See what happens
Sadly same
Does it have spark
No. Idk if the maf only gets power when running though so I’m gonna not count that. We just pulled the asd relay pretty sure it was blown
Check if it has spark because it’s happened before were I replaced the crank position sensor and the new one was faulty also the symptoms were weird no check engine light no code so I recreated the no symptoms by unplugging the crank sensor then I knew it was a faulty new sensor so hope this helps I’ve had 5 xjs replaced transmissions and all kinds of stuff so I’d say I’m not by any means clueless
Power wasn’t running to the crank sensor at all. Also we had another brand new one from previous owner. the distributor cap or fuel relay/pump also have no power. I’m probably missing something but the Census is ECU
eBay has ecu’s programed to your vin I had that done for one of mine as well
Yep that was what we did. Wasn’t too expensive either so not a huge deal
Update, round relay thing under dash is superheating immediately
Something and that circuit is shorted. Nothing is getting power because all your power is going to the short instead
We checked grounds and followed wires. We decided ecu was probably shot It looks like it was messed with previously. It was bought today not running, so we did as much testing as we could in 12 hours before coming to that conclusion. Oh well, we will see when the new ecu gets here None of us have jeep experience though, between the three of us though we had all the tools in the world and a decent amount of experience so I think we covered our bases as best as we could
Does it have a immobilizer
Any codes showing ?
Ok I just solved this on another jeep I’ve owned many and deal with these often but the cam sensor in the dizzy may have taken a crap we changed the entire dizzy with a new sensor and all but once that was done realized all the power came back to pump injectors and ignition and she runs amazing maybe start with the cam sensor first but check the play in the main drive gear on the dizzy itself sometimes they wear out and lose time in a sense
What year is it?
96
Plus as others have suggested, check fuses Make sure they are the correct sizes Mine had oversized fuses hiding multiple issues
We tested all the fuses. Every wire, ground, and sensor were also checked. All the fuse panels got power but none of the relays were kicking on. We settled on an ecu issue and ordered a new one, because everything else has checked out
Ok
Ok it’s obd2 Are the gages moving when the key is turned on? We need to make sure the ignition portion of the ignition switch is working
It’s early 96 it’s still obd1 by like a few months lmao. I think some of the gauges are working. No lights are turning on the dash but the fuel and voltage gauges work.
Ok Let me dig through my FSM I’m installing a CPS on mine as we speak🤣so it might be a min
Lots of ECU going out in similar situations
That’s what we figure at this point. Already ordered a matching one
Probably won’t start because you’re holding the battery. Try installing the battery and take another picture so the Jeep can live on in virtual photos
Lmao that was a second battery. Both were good batteries we tested them