Ok, so i bought an xj a few months ago with a bad trans. Once i put new trans in i drove it down the road and it was misfiring a lot on the bottom end of the rpm range, but seemed to do fine at full throttle. After driving a while longer it cut off on me and wouldn't start back until it cooled down for about an hour. So far i've replaced the plugs, wires, air filter, rotor button, ignition coil, pick-up coil and still nothing. Now it won't start at all. The ignition coil is putting out power but the power doesn't seem to be getting to the distributor. I'm not sure where to go from here so if anyone has any experience with these or could help out in any way it would be greatly appreciated. Thanks
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Please help! jeep won't start
- Thread starter rc_mx5
- Start date
birchlakeXJ
NAXJA Forum User
- Location
- Melrose, MN
Post year/engine for best results in helping you troubleshoot. If your XJ is new enough, have you checked for trouble codes?
If it needs to cool down for an hour before starting, you are probably experiencing a thermal failure of some component, the crankshaft position sensor is one that comes to mind as it is a common failure if you have a 4.0. Be aware that there are plenty of other possibilities. Bottom line is that you need to determine what part of the starting equation you are missing when it doesn't start; fuel or spark. I've included some info on the crank sensor. TEST your way to a solution; don't throw parts at it.
Good Luck!
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Crankshaft Position Sensor: Common Symptoms if bad:
*Both the fuel gauge and or voltage gauge may not work/display
*It is possible that you may see a No Bus on the odometer (on newer models only)
*You will have no spark. Fuel pressure may check okay but fuel won’t get to injectors
*For 96 + newer, sometimes the OBDII code reader has trouble connecting to /reading codes
*Crank sensors can be intermittent; "thermal failure" is pretty common. Means that the sensor fails when engine gets hot, but works again when cooled back down. Be aware of this when testing as if you have a sensor that suffers from thermal failure, it will probably test GOOD as soon as it cools down.
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CPS TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines
1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (A-B-C) looking into connector left to right with the part with the notch in the middle on the right) Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.
CPS TESTING PROCECURE for 1987 – 1990 4.0 L engines
Test # 1
Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 - 275 ohms. If the CPS is out of that range by much, replace it.
Test # 2
You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.
If it needs to cool down for an hour before starting, you are probably experiencing a thermal failure of some component, the crankshaft position sensor is one that comes to mind as it is a common failure if you have a 4.0. Be aware that there are plenty of other possibilities. Bottom line is that you need to determine what part of the starting equation you are missing when it doesn't start; fuel or spark. I've included some info on the crank sensor. TEST your way to a solution; don't throw parts at it.
Good Luck!
-------------------------------------
Crankshaft Position Sensor: Common Symptoms if bad:
*Both the fuel gauge and or voltage gauge may not work/display
*It is possible that you may see a No Bus on the odometer (on newer models only)
*You will have no spark. Fuel pressure may check okay but fuel won’t get to injectors
*For 96 + newer, sometimes the OBDII code reader has trouble connecting to /reading codes
*Crank sensors can be intermittent; "thermal failure" is pretty common. Means that the sensor fails when engine gets hot, but works again when cooled back down. Be aware of this when testing as if you have a sensor that suffers from thermal failure, it will probably test GOOD as soon as it cools down.
-------------------------------------------------------------------------------------------------------------
CPS TESTING PROCEDURE 1991 – 2001 4.0L H.O. engines
1. Near the rear of intake manifold, disconnect sensor pigtail harness connector from main wiring harness.
2. Place an ohmmeter across terminals B and C (A-B-C) looking into connector left to right with the part with the notch in the middle on the right) Ohmmeter should be set to 1K-to-1OK scale for this test.
3. The meter reading should be open (infinite resistance). Replace sensor if a low resistance is indicated.
CPS TESTING PROCECURE for 1987 – 1990 4.0 L engines
Test # 1
Get a volt/ohm meter and set it to read 0 - 500 ohms. Unplug the CPS and measure across the CPS connector's A & B leads. Your meter should show a CPS resistance of between 125 - 275 ohms. If the CPS is out of that range by much, replace it.
Test # 2
You'll need a helper for this one. Set the volt/ohm meter to read 0 - 5 AC volts or the closest AC Volts scale your meter has to this range. Measure across the CPS leads for voltage generated as your helper cranks the engine. (The engine can't fire up without the CPS connected but watch for moving parts just the same!) The meter should show .5 - .8 VAC when cranking. (That's between 1/2 and 1 volt AC.) If it's below .5vac, replace it.
birchlakeXJ
NAXJA Forum User
- Location
- Melrose, MN
Gotta know what you're missing to isolate. Fuel or spark.
Try spraying some fuel into the intake. If the engine starts and runs momentarily, you have a fuel delivery problem, not a spark problem.
A quick test for spark: Pull a spark plug and while it's hooked up to it's wire, place the spark plug electrode close to a good engine ground. Have a buddy crank the engine while you watch. You're looking for a strong, blue, snapping spark. Orange/yellow spark is no good, may not be strong enough to start the engine.
I'd check all wiring near the distributor as well as I know you already replaced the pickup coil. Testing the crank sensor is never a bad idea as it only takes a few minutes on your 95.
Good luck and let us know what you find....
Try spraying some fuel into the intake. If the engine starts and runs momentarily, you have a fuel delivery problem, not a spark problem.
A quick test for spark: Pull a spark plug and while it's hooked up to it's wire, place the spark plug electrode close to a good engine ground. Have a buddy crank the engine while you watch. You're looking for a strong, blue, snapping spark. Orange/yellow spark is no good, may not be strong enough to start the engine.
I'd check all wiring near the distributor as well as I know you already replaced the pickup coil. Testing the crank sensor is never a bad idea as it only takes a few minutes on your 95.
Good luck and let us know what you find....
missing spark. I've tried straight wiring the ignition coil and it sparked but the plugs won't. I've tried checking the cps, though i didn't know which post was a, b or c but i checked all combos and it read 1 every time. I don't really know how to use those things anyway
also there's a ground strap broken, the one from the block to the firewall i think4LowandGo
NAXJA Forum User
- Location
- Kennesaw, Georgia
The ground strap is pretty important.
Start there. Might want to double check the battery to block ground as well.
If something is obviously physically broken, why wouldn't you start there? Especially a ground strap when chasing electrical problems. Generally speaking, electrics/electronics with no/bad ground equals No Go.
ok, so the ground strap didn't solve it so i started back tracking. i put the old pick-up coil in and i got fire but no idle, put the old plug wires on and it idles but dies when i give it gas. i'm also gonna try putting the old rotor button back in to see if that makes a difference. when i rechecked the codes it doesn't come up with any other than the battery being disconnected
Matthew Currie
NAXJA Member #760
- Location
- Vermont, land of big clay
If you had the distributor out, you might want to check indexing. Idle but no acceleration is sometimes a symptom of too much ignition retard.
Also, don't take this wrong, but have you double-triple etc. checked that you got the firing order right?
Also, don't take this wrong, but have you double-triple etc. checked that you got the firing order right?
yeah, i've check all that many times, but i may end up doing it a few more times