Engine/Transmission (1994 - 1998) Is the tack run off the alternator?

[SMOKIN01CUMMINS]

My 98 has an issue with the volts dropping but when they do my tack is all over the place. Are they connected some how?

 

[CKelley1]

yes, the tack looks at the three phase A.C. pulses. sounds like you need brushes

 

[SMOKIN01CUMMINS]

Thank you very much i will be doing that as well now. Thanks.

 

[cerberusiam]

Tach gets it signal from the crank position sensor not the alternator. The CPS has to sense rpm before the alternator is ever activated.

Whne you start seeing other electrical gauges effected by a voltage drop start checking\replacing batteries, battery cables, ground straps, etc. Don't completely rule out the alternator as they can test good and still kick AC current back into the electrical system and screw things up.

 

[CKelley1]

cerberusiam he has a p pump 98, not a vp44 it is off the alternator.

 

[CKelley1]

as cerb stated I also have seen the ground wire from the battery to the cab cause a similar problem.

 

[cerberusiam]

cerberusiam he has a p pump 98, not a vp44 it is off the alternator.

Pretty sure the tach is still run off the CPS not the alternator. All the 12V's have a CPS to tell the SBEC to turn on the alternator, cycle the grid heaters, etc.

 

[ata]

12 valves don't have a crank position sensor. They have a Magnetic sensor that works off the Crank Damper for the Tach and to tell the ECM the engine is running.

 

[cerberusiam]

All the 12V's have a CPS to tell the SBEC to turn on the alternator, cycle the grid heaters, etc.

 

[Cosmo]

12 valves don't have a crank position sensor. They have a Magnetic sensor that works off the Crank Damper for the Tach and to tell the ECM the engine is running.

Are you serious?

 

[LandShark]

My 95 12 valve does NOT have a CPS. It has a ESS (engine speed sensor) that generates a RPM signal to the PCM (PCM pin #24) to control the alternator and several other functions.

The tach gets it signal from PCM pin #43.

 

[cerberusiam]

My 95 12 valve does NOT have a CPS. It has a ESS (engine speed sensor) that generates a RPM signal to the PCM (PCM pin #24) to control the alternator and several other functions.

The tach gets it signal from PCM pin #43.

That is like saying your truck does NOT have an injection pump, it has a Bosch P7100 fuel pump. :-laf The rest of the statement is just as invalid, technically speaking since that seems to be the direction. That year truck does not have a PCM, only an engine controller because there are NO other power train components to control.

To satisfy the purists, changing the description to that sensor thingamajiggy bolted to the front of the engine and facing the damper pulley is what is responsible for telling the engine controller to display tach readings, turn on the AC, turn on the alternator, cycle the grid heaters, etc. When the tach starts going wonky in conjuntion with the loosing charging it is usually a bad connection somehwere.

 

[LandShark]

You can call the parts anything you want. The terms ESS and PCM are straight out of the 1995 Dodge factory service manual. I find it best to use the terms that Dodge uses, for the model year you are talking about.

 

[SheldonBates]

For some reason my original reply was completely fouled up when I entered it. Don't know what I am doing wrong when posting a reply. Frustrating. Sorry for any confusion.

I was just trying to say that I feel cerberusian was correct in helpfully directing SMOKIN01CUMMINS attention to the ESS unit as a place to start troubleshooting a malfunctioning tach since its sole purpose is to generate an rpm signal to the PCM (formerly SBEC or engine controller). Also, and I am just guessing here, I don't think that dropping voltage alone due to the alternator (generator) starting to malfunction would initially affect the operation of the tach. If that were the case wouldn't the voltage drops during the cycling of the manifold grid heaters for example affect the tach? That doesn't happen with my '96. Just some thoughts.

Just my opinion but I feel we should not let the correct/incorrect use of technical terminology-jargon interfere with meaningful and helpful problem solving discussions.

 

[Bob4x4]

Semantics...... Move along nothing to see here

 

[cerberusiam]

It would seem Chrysler does not share your adherence to archaic terminology. Maybe your FSM is missing the diesel supplements, the ones titled Except 5.9L Diesel Engines. That said, the correct name for the engine controller on 94-95 diesel ram trucks is SBEC, there is no comparitive PCM because nothing else is controlled on this particular platform.

http://www.factorychryslerparts.com...l-Eng--Auto-Trans--wRFI/4608656/R6027304.html

I find it best, and a lot more helpful, to use terms commonly recognized by the target audience. Insisting on using superceded terms will extend the time, possibly even the number of trips, to secure said part. Using ENGINE SPEED SENSOR in any context will result in a high percentage of understanding VEHICLE not ENGINE. Whereas CRANK POSITION SENSOR leaves little doubt as the meaning of the request, regardless of what some 20 year old publication written and edited by english as a second language group makes reference to. Part names supercede as well as part numbers.

I submit Chrysler and the aftermarket heartily agree and embrace said ideal.

http://www.ebay.com/sch/i.html?_nkw=1995+dodge+ram+crank+sensor
http://www.factorychryslerparts.com...line=7741&searchTerm=crankshaftpositionsensor

 

[cerberusiam]

Also, and I am just guessing here, I don't think that dropping voltage alone due to the alternator (generator) starting to malfunction would initially affect the operation of the tach.

In reality, it could. The alternator starting to short out dumps a lot of noise back into the system plus a partial short could be drawing voltage away form the engine controller. A lot depends on the actual failure point.

To the point you were making, the terminology is the major stumbling block. The terms have changed, the functions have not. Some cannot make the connection so the view is absolute, black and white.

The statements "does not have a CPS, only an ESS" and "The CPS is called an ESS" are not synonomous in perception. The knee jerk reaction is without a CPS everything mentioning CPS is invalid, regardless of function. Just the way some brains are wired.

 

[GAmes]

That is like saying your truck does NOT have an injection pump, it has a Bosch P7100 fuel pump. :-laf The rest of the statement is just as invalid, technically speaking since that seems to be the direction. That year truck does not have a PCM, only an engine controller because there are NO other power train components to control.

To satisfy the purists, changing the description to that sensor thingamajiggy bolted to the front of the engine and facing the damper pulley is what is responsible for telling the engine controller to display tach readings, turn on the AC, turn on the alternator, cycle the grid heaters, etc. When the tach starts going wonky in conjuntion with the loosing charging it is usually a bad connection somehwere.

Too bad you are a failure at satisfying the purists. The 12 valve has an engine speed sensor (ESS), because that is the only thing the tach requires to operate, it sends a signal to the powertrain control module (PCM), I'll get to that in a minute. A crank position sensor (CPS) is needed to tell the engine control module (ECM) when to change the timing of the fuel injection, something you overvalved owners need. The PCM is the only computer on a 12 valve, it controls alternator charging, automatic trans O/D, the grid heaters and a few other things. So what the OP is experiencing is possibly an ESS failure. It sends a signal to the PCM for the tach, cruise control, battery charging and trans O/D. It might also be dirty, have a bad ground, a broken wire or worked loose resulting in improper spacing from the damper.

 

[Missouri Mule]

Actually Engine speed sensor is a Chrysler term Crank position sensor is Cummins term, it also known as Crank speed sensor.
.
In 96 trucks (don't about older trucks) the ESS/CPS helps to operate several components one is the Auto Shut Down relay. The ESS, activates the ASD relay, the ASD relay sends line voltage to The EVR (electronic voltage regulator) which helps the EVR to determine what voltage the alternator will put out( the battery temp sensor is another component that sends data to the EVR to determine voltage output of the alternator.

 

[cerberusiam]

The MY96 models were the first year with an identifiable PCM functionality to them that was seprated from the engine controls. The SBEC used on the 94-95 trucks is the same style used on the 89-93 trucks with the same minimal control interfaces. The OD and lockup controls were crude and subject to many issues, more of an after thought than anything. MY96 was the first year for any meaningful PCM functionality to control the 47RE.

The CPS on anything prior to the 24V engine was a simple analog sensor. The signal could not be used by any computerized components because it wasn't digital, it has to be processed first. The CPS sent its signal directly to the SBEC\ECM for conversion then was used to activate the ASD, control the tach, and control the grid heater programming. Works exactly the same way on the newer trucks only the CPS now provides a digital signal with degrees of crank rotation in addition to the rpm. The rpm is a calculation passed to the PCM for it use.

The OP's problem could be sensor, connection, SBEC, or alternator. Only testing will tell.