Archived No Charge

[LandShark]

Truck stopped charging. Tried a backup alternator I had, but no change. Crank sensor looks ok. Cleaned the grounds just behing the crank sensor plug. Checked the 3 way crank sensor plug with key on: ground, 1. 5v, and . 45v. The 1. 5v sometimes was not steady; jumped around from 1v to 4v, but mostly 1. 5v.

Checked and cleaned the large wires going into the fuse box. They were clean. At one point, with the key on, I could hear what sounded like a relay clicking numerous times near the fuse box, put could not tell where because it would of course stop within a few seconds. All fuses appear good.

Tach also does not work. MIL does not work. At one point the MIL came on for a few minutes today and I checked for codes. Normal. Started truck and the tach starting working and the volts went up to 17!. Then back to no charge, no tach and no MIL.

Batteries are 7 years old, but start the truck with ease. I noticed today that one of the cells had fluid close to the top. I'm sure I never over filled it. Volts are about 12. 5 for each battery. Could old batteries cause a problem like this.

Any ideas on what to check next?

 

[RON'S RAM]

Check the 120 amp fuse in the fuse block under the hood. I just replaced mine. Some call it a circuit breaker, not sure if it can open & close or if it is a one time thing. Test the voltage on both sides of the fuse with the truck running.

 

[LandShark]

120 Amp looks good and has battery voltage on both sides. Checked the screws and they were tight. Started the truck and had MIL and tach, but also 17+ volts. Battery with the full cell started to overflow. Anyone know if the 120 amp is a fuse or breaker?

First thing in the AM I'm off to Costco for two new batteries.

 

[LandShark]

Installed 2 new Everstart Maxx Walmart batteries this morning. Still no charge. Problem is intermittent. Mostly no charge with no MIL and no tach. Sometimes, for a few seconds I will get MIL and tach and 17+ volts.

Any ideas?

 

[Rams-n-Hogs]

Have you checked all of the grounds?

 

[LandShark]

I've checked and tightened all the obvious grounds. They have all been tight and fairly clean, so far. Is there any particular ground that is hidden?

I have not popped off the front of the PCM yet. Is that something I should do?

 

[Missouri Mule]

The EVR inside of the PCM determines what voltage the alternator will put out.

The EVR gets input from the ASD relay (autommatic shut down) and the Battery temp sensor.

The ASD relay sends line votage to the EVR as I recall the Engine Speed Sensor turns on ASD relay.



Over charging has to be caused by the EVR. I don't think that the alternator could do on its own. Check the battery voltage and the alternator output with multi-meter to see if they match the voltmeter.

I think you have loose connection (connector/pins) or broken wire or the EVR and PCM are going/gone.

 

[LandShark]

<TABLE cellSpacing=0 cellPadding=0 width="100%" border=0><TBODY><TR><TD align=left><!-- google_ad_section_start(weight=ignore) -->Missouri Mule<!-- google_ad_section_end --> : I guess you are saying that you think my PCM is dead?

I spent most of the day replacing batteries, and checking grounds. Also disconnected the field input to the alternator and wired in a external voltage regulator. Did this because I was committed to using the truck to move a boat this weekend and a trailer on Monday. Couldn't afford to lose those jobs. Alternator seems to work fine with the add on voltage regulator. Just don't have a tach and Air Conditioning. Maybe other problems that I haven't discovered yet.

Also took the alternator to NAPA for a bench test. They said the diodes were bad, but it works fine with the new regulator. ???

Anyone know what the voltage should be to the crankshaft speed sensor? The OEM manual doesn't have much on the speed sensor. How about ohms reading on the speed sensor? Or any other way to check it?

It sure seems like the PCM is not seeing the speed sensor and/or the PCM is toast; maybe caused by a flakey alternator?

So in summary: Still no MIL (engine check light - prior to start), no tach, and the alternator has been jury rigged to work for now. This sucks. First major problem in 12 years and 178,000 miles.

My next step is to take the alternator to a real auto electric rebuilder Monday and make sure it's OK.

</TD></TR></TBODY></TABLE>

 

[B.G. Smith]

I have never owned a 1st generation but I was under the impression that the crank position sensor ran the tachometer and turned on the alternator??? bg

 

[GAmes]

The give-away here is no tach. Either there is a broken wire or bad ground to the crank sensor or it has failed. It should have a . 050 inch clearance to the damper.

 

[LandShark]

GAmes: I agree. There is also no MIL (engine check lamp) prior to start. The sensor has not moved (not that it would matter prior to starting) and the wires look good. Ground for the sensor has been cleaned.

If anyone with a similar truck could let me know the volts on each pin to the crank speed sensor that would help. The 3 prong plug is located behind the upper radiator hose at the front of the head and is easy to get to. I get 0 volts on one pin, 0. 5 volts on one, and a unsteady 1 to 2 volts on the other pin.

 

[Joe G.]

The sensor is a hall effect device so it may be bad and the voltages still read ok. It's supposed to send pulses to the PCM when the engine turns. Unless you have a scope to look at the pulses you are going to have to replace it or borrow one to see if that is the problem. If the alternator is not charging for some reason and the engine is turning you should get a CEL. That is not happening and your alternator is working with the add on regulator. The AC also doesn't work unless the engine is turning. This makes me think the sensor is bad. Normally, I don't recommend replacing a part just to see if that is it, but I don't know of any way to check the sensor.

 

[Rams-n-Hogs]

120 Amp looks good and has battery voltage on both sides. Checked the screws and they were tight. Started the truck and had MIL and tach, but also 17+ volts. Battery with the full cell started to overflow. Anyone know if the 120 amp is a fuse or breaker?



First thing in the AM I'm off to Costco for two new batteries.

According to my service manual, the 120 amp is a fuse. The book also says +5 volts are supposed to be supplied to the crank sensor from the PCM. The ground also comes from the PCM. I will check to see what my voltages are today, when I climb under the truck.

 

[LandShark]

Drove the truck today. My bypass voltage regulator works good, but I discovered the the transmission won't lock up in third and will not go into 4th at all. Also the speedometer and odometer do not work.

I see from the manual that one thing all these systems (the crankshaft speed sensor and transmission speed sensor) have in common is that they are supplied with 8 volts from the PCM.

 

[K5IP]

I go with the guys who say your crank sensor (engine speed sensor) is not functioning. Since is is intermittant, be sure to check the sensor connector located just above the sensor. These are a source of intermittant problems.

Open it, clean it and hold it together with a nylon tye wrap.

The sensor on the 95 recieves 5. 2 Vdc reference signal from the PCM. The hall effect switch looks for lthe two notches in the balance wheel and each time one of them passes the sensor, the output of the sensor switches between zero and 5. 2 vdc. As mentioned, a scope is the best way to observe the output, but it can be observed with a voltmeter, analog, while cranking the engine with the starter.

As said. this is the root cause of all your problems.

Rog

 

[dsldoug]

LandShark there is an ecm fuse in your little fuse bos (the one on the drivers side of the dash). Check to make shure you are getting good connection on the fuse spades, and that there are not any electrical add-ons on that fuse.

 

[LandShark]

dsldoug: Fuse is good and clean. No add ons at all in either fuse box.

K5IP: I've checked the 3 prong connector for the crank sensor. It's clean and tight. Problem is not really intermittent any more. My book shows that the crank sensor and the transmission speed sensor both get 8 volts from the PCM. I only see about 1 volt (sometimes as much as 3 volts) at the crank sensor connector with the key on. This makes me lean toward the PCM being bad. I'm guessing that the transmission speed sensor is also not getting it's 8 volts, since I also don't have speedometer or odometer.

I need to drive the truck on Monday for about 200 miles. This will be a pain with no trans lockup or 4th gear.

 

[Joe G.]

Have you replaced the sensor? Clean and tight connectors don't mean anything if the sensor has some sort of problem.

 

[LandShark]

Joe G: Haven't replaced the sensor yet. Sensor and wires appear to be in good shape. Nothing externally has damaged them anyway. If it's not getting the 8 volts, how would it work?

I made a sharp probe so I can check the pin outs for sensor grounds and the 8 volts for the crank and transmission speed sensors. That's tomorrows project.

If the PCM is not putting out the 8 volts, wouldn't that mean it's bad?

 

[Missouri Mule]

LandShark, In 96 service manual it states that sensors receive 5 volts from the PCM.

Your Engine speed sensor helps to determine when 3-4 shift occurs.

With air conditioning/tach/overdrive /alternator(alternator was working just to many volts or no volts) not working it could be the ground wire to the Engine speed sensor has broke somwhere. You will need to do remote ground to it if this is the case.

You can check the pins on the PCM at connectors related to volts output and ground to sensors.

But with the the over charge and that a remote regulator works I beleive that indicates that your EVR had problems. Which mite or mite not mean that the PCM that is going out (other members had the EVR go out but PCM did all other functions). The PCM controls ac/tach/overdrive shifts/alternator.