no spark

1992 xj 4.0l stock engine.

back story: put my jeep in my parents backyard back in mid december. my mom started it one weekend in january but it has sat since then.

current: went to start it two weeks ago and nothing, battery was pretty drained. charged it today and still wouldnt start. pulled the distributor cap off and sprayed some electrical dryer into it, let it evaporate then reasembled. still no fire. pulled the coil wire and put it next to the block, no spark coming out.


any advice on things to trouble shoot to see why i am not getting any fire?

thank you for any help you can provide. has never let me down in the past!

First, you need to be sure your battery is up to snuff. Periods of storage can kill a battery. Take it to a parts store and have them "load test" it. Load testing is the only accurate way of determining battery condition.

The #1 cause of no spark on the 4.0 engine is the crankshaft position sensor. The #2 cause is the ignition coil. Both can be tested, but crank sensor testing is not always conclusive. If you end up buying a crank sensor, do yourself a favor and buy it directly from Jeep for the best reliability and longevity. No lack of issues with some (not all) aftermarket crank sensors.

Also something easy for you to try is to open the power distribution center (black box under the hood on the passenger side) and swap the ASD relay with another relay that is non-critical like e-fan. That ASD circuit can inhibit spark as well.

No-starts are a process of elimination. Get started and good luck, be sure to update us!

well a little update on this, checked the coil with a tester and it is working just fine. i pulled the connector for the CPS and let it sit for a few minutes and then put it back together. still no spark, i have swapped all the relays around aswell and nothing. how do i test the CPS? im really out of ideas at this point. any help is appreciated

Here is a thread that shows testing of the crank sensor. Note that testing is not always conclusive.
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http://www.naxja.org/forum/showthread.php?t=1044073

The connector on my cps doesn't look like that. Its round and the terminals are in a triangle configuration. Is that correct? I have a multi meter but not an ohm tester, will that work?

A MIL test, (blinking check engine light) may work on your 92 (probably) it may also take a few tries. The timing working the ignition switch can be a problem. If you turn the ignition switch to quickly, sometimes you get no codes, the same with too slowly. A Code 11 means there is something wrong with the CPS, either the sensor or the wiring. MIL tests aren't definitive, but can point you in a direction. A code 12 (often) or code 55 (always) usually show up during tests and don't mean much, but does let you know the system is working. This info is for a 93 but likely to be relevant.

MIL Diagnostic Mode
1) Start engine (if possible). Move transmission shift lever
through all positions, ending in Park. Turn A/C switch on and then off
(if equipped).
2) Turn engine off. Without starting engine again, turn
ignition on, off, on, off and on within 5 seconds. Record 2-digit
fault codes as displayed by flashing MIL.
3) For example, fault code 23 is displayed as flash, flash,
4-second pause, flash, flash, flash. After a slightly longer pause,
other codes stored are displayed in numerical order. When MIL begins
to flash fault codes, it cannot be stopped. Start over if count is
lost. Code 55 indicates end of fault code display.
4) Refer to FAULT CODES/MESSAGE table to translate trouble
code number to a DRB-II fault message. Once trouble area is
identified, refer to TEST FC-1A. Use DRB-II fault messages to find
appropriate test.
5) As an example, a 2.5L engine starts and runs but has a
driveability problem. MIL indicates Code 14. Refer to FAULT
CODES/MESSAGES to translate trouble code number to DRB-II fault
message. When DRB-II fault message is obtained, refer to appropriate
test number. To clear fault codes, see CLEARING FAULTS.

When the key is turned to the run position, before the start, the Check Engine light should light, this is just a bulb test
If you get no "Check Engine" light, the bulb may be burned out . But can also indicate a 8 volt supply voltage problem to the CPS or possibly a short in another sensor messing with the 5 volt supply voltage to the CPS. In other words no "Check Engine" light can indicate a major problem or just a faulty bulb.

Well more update.

Turn key on. No check engine light, I know it used you work

Put a tester on the terminal of the cps and no reading. So I'm thinking it is the cps, any other ideas before I drop the money on a new one?

I'd recommend springing for a Mopar crank sensor from the dealer. No lack of problems with some (not all) aftermarket crank sensors.

The extra money you spend is well worth it in reliability and longevity.

I'd try unplugging the CPS and see if my Check Engine Light comes back on.
Could be the bulb in the check engine light, may also be a sensor/computer problem.

Check the orange wire (pretty sure that is the 8 volt sensor supply voltage wire color) to the CPS for 8 volts when the key is in run.

There are numerous sensors, that if they short out, suck the supply voltage to the CPS down to a voltage too low for it to function.

CPS is a good guess, but just a guess unless you dig in a little deeper.

I don't have the FSM for a 92, but from memory, unplugged CPS, the two of the three poles on the CPS side of the connector, not the orange wire (supply voltage wire), should have no continuity, be open, if they show a low resistance reading (less than infinite resistance) it means the CPS is likely bad.

With the CPS connector plugged in, the orange (8 volt supply) when checked back pinned, should read near 8 volts. I've seen a shorted sensor suck the supply voltage down to 2-3 volts, nearly a dead short. I have seen a shorted CPS test good by the book.

So the check engine light should come back when you disconnect the cps? Because mine doesn't. I really hate electrical issues

Xjcj3a said:

So the check engine light should come back when you disconnect the cps? Because mine doesn't. I really hate electrical issues

Click to expand...

If the Check Engine light came back on after you unplugged the CPS. it would be an indicator the CPS is the cause of the 8 volt power supply problem.
I've seen the Check Engine fail to light when you turn the key to run, because of a short in a sensor circuit. May be just the bulb is burned out. May be a fuse is blown, no power to the computer, no check engine light. Maybe put your finger in top of the ASD relay and see if you can feel it activate.

The orange wire running to the CPS should have power around 8 volts, if it doesn't you can start working backwards from there.

If the computer doesn't get a pulse signal from the CPS when the engine is turning over, the ASD relay will open and shut down a bunch of stuff, the injectors, the coil, the fuel pump relay etc. A fairly common problem.

The no "Check Engine Light" makes me suspicious though, it may be any number of things causing the computer grief so the check engine light doesn't illuninate.. Doesn't mean there is a computer problem, it may be something simple, like a fuse or even a contact in the ignition switch.

If it has been sitting for awhile, look close, some critter may have been chewing on your cables. It's happened to me, a Weasel made a meal of some of my wiring and crapped on my motor. Rats and Mice will do the same thing.

I really have no idea what to look for now, i have swapped relays around. checked every fuse under dash and under hood. unplugged every connector. checked wiring and still nothing. does anyone have a diagram for this system? so i can just go from point a to z? i really appreciate everyone posting comments and suggestions for me to try because i have no idea what to test on my own. thank you!

also, i tested the CPS. i got no reading. forgot to mention that.

I'd start by checking the voltage at the CPS connector, the engine side of the connector. Believe it is the orange wire, could be another color, I don't have a 92 wiring diagram. There should be voltage going into the CPS.
The CPS has three wires, one is voltage in 8 volts (5 volts on some later years). The other wire is ground through the PCM, the other wire is the pulse signal to the PCM.

If you have no 8 volt, you aren't going to have any pulse. If the, pulse signal out of the CPS is shorted, you will have no pulse signal out. There should be no ohm reading between the pulse signal out and the CPS ground (or chassis ground), there shouldn't be any reading at the 1 K setting on your ohm meter. If there is no pulse signal out of the CPS, the ASD relay will open while cranking and shut down most everything, coil, fuel pump, injectors etc.

I may be wrong, the 92 may be different from the 93 I'm referring to, possible, but unlikely. I haven't worked on every year of XJ, 92 is one I've not worked on. I'm guessing it is basically the same as the 93.

I know I've tested a CPS before that ohm tested good and was bad.

Your check engine light being out may indicate your problem is a power problem to the sensor circuits and/or PCM. The easiest place to check is for 8 volts at the CPS connector, on the engine side. If you are getting 8 volts, everything upstream from the CPS (CPS to the PCM) is likely to be OK and the problem is likely downstream, wiring, relay or sensor, divide and conquer. I usually start troubleshooting in the middle, check for power and go from there.

The quick way is to start swapping out sensors and hope to get lucky, the inexpensive way it to test the likely culprits.

I tested my 95 by unplugging the lead wires going into the coil. If when you are cranking the engine you get voltage to the wires going to your coil, the cps is good and your coil is bad. Easy enough. If not, test cps per the previous link.
My coil was bad. Battery has a lot to do with this also.

so i attach my tester to the orange wire(red terminal on the tester) and then place the ground line on the tester to the ground on the cps engine side connector? that should read 8 volts, if it does then bad cps. if it doesnt then bad something else. I may have access to a computer diagnostic tool. but Im really new to this wiring game so not sure if that will tell me or not. thanks again for everyones help.

so an update, i tested the cps connector. it only has 2.5 volts. Ive had the battery tested and it seems good. going to charge it overnight and then test again for 5 volts.

also i was able to get the maint req'd light to come on when disconnecting the cps.

any ideas what to test if the volts stays at 2.5?

If the vehicle has been sitting a while, you should probably also check your wiring cables to the battery, depending on the type you have, the terminals can oxidize on the inside (where the wire comes into the battery terminal) so you will get a normal engine turnover because the starter has it's own dedicated 2ga cable.

I would also check fuel delivery, I've had that issue a few times when the vehicle was sitting for an extended period. if you bleed the fuel rail (open the cap and push into the valve thing with a nail either gas or air will come out, if it's air, try turning the vehicle on and off a few times, you may have to pull the fuel pump relay and jumper it).

Generally a no-spark condition is caused by your CPS, however I see this issue more often with running vehicles that suddenly die than with jeeps that have been sitting.

Xjcj3a said:

so an update, i tested the cps connector. it only has 2.5 volts. Ive had the battery tested and it seems good. going to charge it overnight and then test again for 5 volts.

also i was able to get the maint req'd light to come on when disconnecting the cps.

any ideas what to test if the volts stays at 2.5?

Click to expand...

The last time the same happened to me it was a short in the CPS. I had about 3 volts at the CPS connector and my check engine light wasn't working, unplugged the CPS and the check engine light came back on. Replaced the CPS and all was good again. Or it may also be the cam position sensor (sometimes called the sync sensor). Either the supply voltage is too low or there is someplace the supply voltage is partially shorting to ground, most likely to be a bad sensor.

I usually test the CPS to chassis ground, to make sure I have good supply voltage, then ohm test the ground side. The CPS and the sync sensor ground through the PCM to chassis ground, anything bad in the ground circuit will show up as low voltage also, but can be picked up pretty easily with an ohm test. Your problem may be a rub through on a wire someplace. The most common is the CPS wire between the CPS and the connector.

Not beyond the realm of possibility you are getting low voltage into the PCM, low voltage in, low voltage out. The whole system gets a bit iffy with less than 9 volts or so into the PCM.



Bulletmaker is right about what he suggested. The basics are always a good place to begin. Gas does go bad and can really gum things up.

Old batteries are unreliable also, the starter sucks a lot of voltage and the battery may not have enough left over to successfully power the PCM at startup. Any bad ground or corroded connections add to the problem.