SV Forty Two

Hello! Need some help with a no start issue. I have searched through the various forums and tried all of the suggestions. Some details... Have a 1999 XJ 4.0 2wd auto. Ran fine, zero issues. Never stalled or hesitate to start. Until it just didn't. Fortunately was parked at home when refused to start. So far I have changed the crankshaft position sensor, the camshaft position sensor, the IAC, checked and cleaned all grounds and cleaned/tightened battery terminals. When I turn key, the ASD relay buzzes and the gauges, other than the oil pressure gauge do not work. I disconnected the crankshaft position sensor, thinking it may be faulty, although just replaced, and the gauges still do not work. Jeep will start when I jump the relay. When running in this manner, the volotmeter drops to just above 9. I am sure this is some kind of clue....I have also disconnected the camshaft position sensor and the gauges still do not work. Any suggestions?

SV Forty Two

Sorry, some additional info.....It cranks just won't start. If I spray starting fluid down her throat she will fire but not start completely. Tried hooking up a new battery still nothing....

jordan96xj

What happens when you jump start the vehicle from another vehicle? I ask because it sounds like there may be a low voltage issue going on. The ASD relay buzzing instead of closing during startup attempts, but starting when jumped, points me in this direction.

SV Forty Two

I have not tried to jump it with another vehicle. I put a brand new battery, fully charged in it with no change. Would using another vehicle change the equation?

jordan96xj

No probably not. Moving on.


The fact that you got some firing activity when adding fuel manually is typically a sign of fuel delivery issues. But your observation of weak/failing firing when adding fuel, and the fact that you can start when jumping the ASD relay, probably leads us back to the relay and the things it depends on.


If you have swapped the ASD relay with a known good and get the same behavior, then it is not the relay, but what the relay depends on that is missing. For example, the control side of the relay gets its positive from the ignition switch, and its ground from the PCM. This closes the relay. The load side of the relay comes from the battery through the fusible link through the PDC and ASD fuse.


Perhaps its time to test the voltages on the ignition switch outputs to make sure it is not weak. If it is weak (low voltage) due to age and resistance it can cause the ASD relay to open/close (flutter) which could explain the buzzing and the fact that you get some sputter when adding fuel, but not good firing. It could also explain why you get a start when the relay is jumped.


If that all checks out, then it would leave the ground on the control side of the relay on the table. This is provided by the computer when it is happy with CAM/CRANK and RPM data (when it knows that things are spinning fast enough and in proper relation with each other).

SV Forty Two

Ok, testing ignition switch sounds like a promising lead...how does one go about doing that? I apologize but electrical issues are not a strength! I do have a voltmeter, so I'm sure that will help!

jordan96xj

You can probably test for voltage coming from the ignition switch at the ASD relay itself if you know the proper cavity to check. I don't have a diagram in front of me to know for sure. But with the ignition key in the "on" or "start" positions it should be providing voltage to control side of the relay (the side that drives the electromagnet that causes the relay to open/close). Being absolutely sure that your multimeter is in volts mode, you would put the red probe in the appropriate relay cavity (relay removed) and the black probe on a known good ground (black/negative battery terminal would work fine). The voltage you read should be something close to battery voltage (battery should be somewhere in the 12.6v range). The ASD relay from the ignition switch should be seeing at lease 11.9 - 12.2 (just a ball park). But if you see something like 8-10v that would be cause for concern and could point to a problem in the ignition switch or circuit.


96 and older ignition switches get burned out easily because of the high amperage that goes through them, so it is more of a common thing. Yours is newer and does not run the full amperage for things like the AC blower fan through the ignition switch, so it is not as common to have the connector/wires burning and or melting at the ignition switch connector. But the ignition switch itself can get dirty, sooty, etc and start to cause voltage drop between the switch and the ASD relay.


You will need to research a little to find out precisely which cavity in the ASD relay is the cavity for the + coming from the ignition switch. Perhaps someone with 99 FSM can chime in.

SV Forty Two

Ok, sounds straight forward enough. Will test on my lunch break (I work at home) looks like positive should be 30.

SV Forty Two

I was wrong, it was not the 30 pin, that one is always hot, but found the right one, and it is reading just over 12. is an analog gauge so couldn't get precise number, but over 12.

jordan96xj

If you were a shop, and you had heard that relay buzzing, you would probably next put a "relay buddy" on that relay to get a feel for what that relay was doing when things are trying to start.


Based on the fact that you observe 12+ volts at the relay for both the load side and the control side coming from the ignition switch (12v +) that leaves the ground on the control side (provided by PCM) as being suspect.


A shop would use a "relay buddy" on that relay to detect what is going on with the relay. If the relay is getting a spotty ground from the PCM, then it is usually because the PCM is not happy (does not mean the PCM has failed) or it is a wiring problem between the PCM and ASD relay.


With a good PCM wiring diagram you can isolate the wire that leaves the PCM connectors that provides the ground to the ASD relay and see what the PCM is putting out. But even if you see a quality ground being provided by the PCM, you would still need to be able to test the ASD relay side to see if it is getting that good ground. If not, it would imply that something between the PCM and the ASD relay on the circuit is problematic (chaffed wires, bad splice, etc.). If the ASD relay were to show that it was getting everything it needed (+ from ignition switch, - from PCM, and + for the main load) then your troubleshooting would have to move in a different direction because the ASD relay could be ruled out. But because you said that jumping the ASD relay lead to a successful startup, it very much means that the ASD relay (or the items it depends on) are your culprits.

SV Forty Two

hmmmm, this is starting to sound like it well above my level of ability with electrical gremlins.....

jordan96xj

One thing that is still within your scope is to test the quality of spark on all cylinders. If there is a problem with the ASD relay, or anything down stream, it will present itself in the presence and quality of the spark. If the sparks all look good, then it will mean you need to rethink your observations so far. Because that would point more back to a fuel delivery problem or timing (good spark but at the wrong time). But timing problems don't usually just come out of the blue on XJs. They usually happen right after someone rebuilds a motor or replaces their plugs/wires and gets things in the wrong order, or fails to set their distributor in the correct orientation.


Btw, when you added fuel manually and it tried to fire, that normally points people in the fuel delivery direction (fuel pump, etc). However, you mentioned that it started when you jumped the ASD relay. Can you confirm that is what you meant? that it successfully started and ran with a jumped ASD relay?


Also the failure of gauges sounds a little like something is knocking out the OBD2 bus on the vehicle. Have you attempted connecting an OBD2 scanner to the vehicle? I'm guess that it will fail to make a connection and read anything. This can be caused by a failing sensor/component on the engine control circuits (CPS, camshaft sensor, map, tps, engine coolant sensor) and of course can also be caused by ground connections being compromised (are you sure you checked all of them? Did you actually service them? or just visually look at them?).

SV Forty Two

Yes, it did run, albeit rough when I jumped the asd relay. it actually ran for a second or three after I turned the key off, which is not normal either. I did hook up a scanner to it and it was unable to establish a link. I had disconnected the crankshaft and then camshaft position sensors to see if that was where the issue lay , thinking that the gauges would respond positively if I did so. is this thinking correct? should I disconnect the above mentioned sensor in turn and check gauges for life? I did service all of the ground locations, 7 in total at 5 separate locations. wire brushed them til they were as shiny as possible. will check quality of spark after work....

and I certainly appreciate all of the assistance thus far!

jordan96xj

Sounds like you are doing the right things. Yes, you might try disconnecting all of the sensors mentioned and see if there is any change (gauges coming back, or making a connection with the scanner). If you can get a change in behavior, that would be great, because you could probably narrow it down from there.


When you jump the ASD relay, engine shut-off is going to be a little abnormal. After all, you are jumping the "automatic shutdown relay". lol. It is what the computer uses to turn the vehicle off by disabling ignition. You basically overruled the computer and said that you would like the ignition permanently on. Which means that the only thing shutting off the engine would be the fuel injector pulses stopping. I'm not sure if that happens right at the same time, but also the cylinders are breathing in a mix of air/fuel that is atomized in the intake manifold, so it would take 1-3 seconds to burn through that even if the injectors were off. So what you saw was probably normal.


But back to the facts. The fact that your OBD2 bus is currently knocked-out is a pretty decent clue that something is clobbering the engine controls.

SV Forty Two

will try disconnecting the map, tps, enginecoolantsensors sequentially after work to check for a pulse.