Tach Dropping to Zero
06-18-2008, 06:10 PM
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Tach Dropping to Zero
I've got a 96 Ram and just a few days ago I noticed on start up the tach dropped to zero and the Check Engine and GEN lights came on. It only seemed to do that at start up but today it did it while driving. While driving the tach goes to zero but none of the lights come on but I can see the volt meter drop and my converter unlocks. Is that just a bad alternator? Thanks for any insight.
06-19-2008, 09:44 AM
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Check the engine speed sensor located at the lower engine pulley (dampener).
Wiring could be messed up, connector dirty.
Gap between sensor and dampener should be about the thickness of a matchbook cover.
Wiring could be messed up, connector dirty.
Gap between sensor and dampener should be about the thickness of a matchbook cover.
06-20-2008, 01:05 AM
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look into the tach sensor located above the harmonic balancer. the pcm has to see a signal to for the charging system to work. ran into this problem on a 98 12v the sensor came loose i readjusted it and it worked fine. the specs from a 98 12v manual says
0.49 minimum air gap
0.51 maximun air gap
hope this helps!
0.49 minimum air gap
0.51 maximun air gap
hope this helps!
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07-06-2008, 07:37 AM
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I haven't really had time to do much with it yet, its been hectic around here. I did re-adjust the sensor above the balancer and now the tach doesn't work at all and it doesn't charge.
I thought that sensor was the crank position sensor but it sounds like thats just the engine speed sensor. Am I correct in thinking that? Theres another sensor behind the starter?
I thought that sensor was the crank position sensor but it sounds like thats just the engine speed sensor. Am I correct in thinking that? Theres another sensor behind the starter?
07-06-2008, 09:28 AM
#9
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I thought that sensor was the crank position sensor but it sounds like that's just the engine speed sensor. Am I correct in thinking that? There's another sensor behind the starter?
The CPS behind the starter is only used on 24 valves.
07-06-2008, 09:44 AM
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Thanks for the clarification. Well I've adjusted it a few times and checked the connections and wires and everything seems good with that. Are the ESS's known to fail? Would a bad one cause all my symptoms, no tach, not charging, no converter lock up, no control of OD lock out?
Thanks again, I just don't want to throw down the money for a new sensor if thats not the problem. We all know how returning electrical parts goes.....
Thanks again, I just don't want to throw down the money for a new sensor if thats not the problem. We all know how returning electrical parts goes.....
07-06-2008, 06:04 PM
#11
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ESS's do fail but more often the problem is bad connections.
The ESS tells the PCM if the engine is running or not.
If the PCM thinks the engine isn't running nothing electronic will work.
The ESS tells the PCM if the engine is running or not.
If the PCM thinks the engine isn't running nothing electronic will work.
07-06-2008, 07:26 PM
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I checked the connection and its not corroded or anything, I threw some dielectric grease on it just to make sure but still nothing. It was all fine until I did the KDP, I must have disturbed something. Is the ESS a dealer item only?
Thanks again.
Thanks again.
07-07-2008, 02:20 AM
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I'd look at some wiring schematics and trace the ESS wires to the PCM and do a continuity test on it. Since it was working before you moved it for the KDP, I'm gonna bet its a broken wire.
07-07-2008, 02:58 PM
#14
The ess went bad on my 95 a while back - no tach, no speedo, no charge & the auto tranny wouldn't shift right. Very easy to change, about a 5 min job. Don't go to the dealership to get it though - you'll pay a lot less if you get it from Cummins ($60-$80).
07-10-2008, 03:21 PM
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I had the ESS go bad on my 97 with same symptoms as you. I tried removing and cleaning but it still did not work. Realize that the ESS is a magnetic type sensor so the gap needs to be set for 0.050 inch with a bronze feeler gage or use a matchbook cover or business card but make sure it is straight and not hitting the balancer.
I replaced my PCM before I realized it could be the ESS and it still did not work. I would bet your ESS is dead if all the connections are good. Check the 3 pin connector on top of engine that the ESS plugs into to see if its connected or bad wires.
The ESS has about a 2 foot pigtail on it to where it plugs into the connector. Get a voltmeter and probe the pins of the connector with ESS off to look for a 5 volt and Gnd signal coming from the PCM with engine running. If all is good then replace the ESS.
You can get the ESS from Cummins or I got mine from napa for $75. It fixed my problem.
Dave
I replaced my PCM before I realized it could be the ESS and it still did not work. I would bet your ESS is dead if all the connections are good. Check the 3 pin connector on top of engine that the ESS plugs into to see if its connected or bad wires.
The ESS has about a 2 foot pigtail on it to where it plugs into the connector. Get a voltmeter and probe the pins of the connector with ESS off to look for a 5 volt and Gnd signal coming from the PCM with engine running. If all is good then replace the ESS.
You can get the ESS from Cummins or I got mine from napa for $75. It fixed my problem.
Dave