This is an updated post to a previous one, I'm hoping someone out there can chime in on what they believe the issue is. I also posted this over on the other Cherokee forum so sorry for the duplication but trying to reach the largest audience I can. It's a 1993 cherokee sport, manual trans.
Below is a link to the video. First two starts are relatively normal, the third one is what I'm experiencing. Does this every few startups, and when it does it has reduced power almost like it's in limp mode. No codes or check engine light. When it starts normally, it runs and idles fine, no real abnormal noises.
Things I've done:
-Battery voltage while cranking for normal starts stays above 11, bad starts it drops as low as 9.5 and dome light dims like its a bad battery. Battery, alternator and starter all tested good. Ended up replacing all three anyway and problem persists. Jumpered starter at relay and solenoid, turns over fine. Even stepped up to a 1000 cranking amp battery.
-Clean and repaired if necessary all ground connections. Checked all the "big 7" cables, all seem good with tight connections.
-Unplugged PCM and inspected pin connections, all looked good.
-Fuel pressure test. 35 psi on prime, pretty steady. Does not appreciably drop off after shutting engine off. Fuel injectors are new (4-hole from K Suspension), and by stethoscope sound like they're all firing.
-Compression test. All cylinders were about the same, just about 120psi and held. I had a hard time getting the test fitting sealed at the spark plug hole, but I believe 120 is acceptable.
-Replaced the crankshaft sensor.
-Disconnected exhaust at manifold to see if there was a back pressure issue or possibly failed cat, no change.
-It has a new distributor and coil. I swapped the old coil back in and it still does it.
-If I disconnect the ignition coil and just crank, engine and starter turn over fine. No abnormal noises.
-Measured voltage at starter relay while cranking, steady battery voltage. Measured voltage at ignition coil. With the positive voltmeter lead connected to the positive(?) of the coil input plug (the outer one) and the negative lead to the negative battery terminal, I get solid battery voltage in ON, and anywhere from 2-5 volts when cranking. With the positive voltmeter lead connected to negative(?) of the coil input plug (the inner one) and the negative to the negative battery terminal, I got a momentary 12.5 V when taken to ON and then a steady 11.2V when cranking.
-Swapped around fuel pump, starter and ASD relays. Also checked all fuses.
I'm all out of ideas and waving the white flag. Thanks for any help you can provide.
Below is a link to the video. First two starts are relatively normal, the third one is what I'm experiencing. Does this every few startups, and when it does it has reduced power almost like it's in limp mode. No codes or check engine light. When it starts normally, it runs and idles fine, no real abnormal noises.
Things I've done:
-Battery voltage while cranking for normal starts stays above 11, bad starts it drops as low as 9.5 and dome light dims like its a bad battery. Battery, alternator and starter all tested good. Ended up replacing all three anyway and problem persists. Jumpered starter at relay and solenoid, turns over fine. Even stepped up to a 1000 cranking amp battery.
-Clean and repaired if necessary all ground connections. Checked all the "big 7" cables, all seem good with tight connections.
-Unplugged PCM and inspected pin connections, all looked good.
-Fuel pressure test. 35 psi on prime, pretty steady. Does not appreciably drop off after shutting engine off. Fuel injectors are new (4-hole from K Suspension), and by stethoscope sound like they're all firing.
-Compression test. All cylinders were about the same, just about 120psi and held. I had a hard time getting the test fitting sealed at the spark plug hole, but I believe 120 is acceptable.
-Replaced the crankshaft sensor.
-Disconnected exhaust at manifold to see if there was a back pressure issue or possibly failed cat, no change.
-It has a new distributor and coil. I swapped the old coil back in and it still does it.
-If I disconnect the ignition coil and just crank, engine and starter turn over fine. No abnormal noises.
-Measured voltage at starter relay while cranking, steady battery voltage. Measured voltage at ignition coil. With the positive voltmeter lead connected to the positive(?) of the coil input plug (the outer one) and the negative lead to the negative battery terminal, I get solid battery voltage in ON, and anywhere from 2-5 volts when cranking. With the positive voltmeter lead connected to negative(?) of the coil input plug (the inner one) and the negative to the negative battery terminal, I got a momentary 12.5 V when taken to ON and then a steady 11.2V when cranking.
-Swapped around fuel pump, starter and ASD relays. Also checked all fuses.
I'm all out of ideas and waving the white flag. Thanks for any help you can provide.
