No charging

[MBullwinkel]

I have a 93 W250 with a cummins & manual trans & the air "toaster" preheater



I am having a problem with charging system not activating. As best I can tell, it is caused by an intermittent failure with the the wait to start sequence not starting or completing.



When everything works fine: tun on the ignition, the wait to start light will come on, followed by the water in fuel light, fender relay activates (click), then they all go out. Start the truck and the voltage indicator jumps up to about 13 volts.





The problem is I usually only go about 10 miles per trip. When I turn on the ignition either the Wait to start light does not come on at all or it comes on for awhile and then nothing happens. The charging system does not come on so the voltage reads about 9 volts then progressively drops to 8 and below with each successive trip and then I have to recharge the battery.



The thing is the truck starts fine (as long as I recharge the battery), so i have given up waiting for the wait to start sequence.



The best way I can describe it is that everting is happening in slow motion.

Usually after I drive around for a couple of hours everything works fine: the wait to start light will come on, followed then the water in fuel light, fender relay activates (click), then all go out and the voltage indicator jumps up to about 13 volts.



If I try to start it a within about minute after everything is running OK, the whole system works fine. But if I wait much longer than that, the problem starts all over again.



I am confused about where to start troubleshooting because it works sometimes. I have tried:



The shop just replaced the alternator so I think that is OK



I replaced to the two fender mounted solenoids so I think those are OK.



Thinking that running the engine longer made it work because everything was warm, I have tried to fool the temperature sensor by heating up the air heater area with hot air gun while the ignition was on- a couple of times that could get the sequence going but it did not work reliably.



Since the engine truck starts fine, I would actually be happy if there were a way to bypass the preheater system if i could figure out how to activate the charging



Any suggestions would be greatly appreciated.



The shop guy suggested that it was a grounding problem and that I should trace all the ground wires. Does anyone know where I can get a wiring diagram of the system?

 

[dpuckett]

I'd say you either have a weak/borderline battery, or you just dont drive it long enough to recharge the batery. There is also a post heat that heats the air intermittently after the engine is running. It will pull down 2-3 volts while it is activated. Also, check your battery for water level, if applicable. Use distilled water (<$1/gal at any grocery store) if needed.



On the fender next to the relays for the preheaters, are 4 smaller wires (16gauge, I think) with 90deg rubber boots. 2 wires to each relay. Unplug those little boots, and you bypass your preheat.



On the core support in front of the battery is a small wire giong from the neg terminal to the core support. Make sure it is tightly fastened. It can wreak havoc with the charging system, too.



Good first post- Good, detailed information about your problem. Welcome to the TDR.



Daniel

 

[Philip]

Welcome to the TDR.



Your truck is the same years as mine. So for the grounds. There is one by the battery. It comes off the (-) battery termianal. This ground has paint under it. Sand the paint off and reattach it. The dash grounds are located under the dash behind the OD button to the right of the steering column. Drop the panel off from under the steering column. Look behind the OD switch and you can see them. It takes a 5/16's wrench or socket. Whichever you have on hand. There are 3 wires going to this ground. Clean all three.



Check the air gap on you RPM sensor. It located at the 11:00 position on the crank vibration damper. The gap should be around . 050". The PCM will not turn on the charging system if it does not see a RPM reading. At the front of #1 valve cover is a plug leading down to the RPM sensor. Check the connection and put some dialelectiac grease in the plug for good measure.



Then check back and let us know if you found anything there.

 

[MBullwinkel]

Charging thanks

Hi:



Thanks for the feedback. That gives me a few places to start-I'll let you know how it goes



Matt

 

[MBullwinkel]

Welcome to the TDR.



Your truck is the same years as mine. So for the grounds. There is one by the battery. It comes off the (-) battery termianal. This ground has paint under it. Sand the paint off and reattach it. The dash grounds are located under the dash behind the OD button to the right of the steering column. Drop the panel off from under the steering column. Look behind the OD switch and you can see them. It takes a 5/16's wrench or socket. Whichever you have on hand. There are 3 wires going to this ground. Clean all three.



Check the air gap on you RPM sensor. It located at the 11:00 position on the crank vibration damper. The gap should be around . 050". The PCM will not turn on the charging system if it does not see a RPM reading. At the front of #1 valve cover is a plug leading down to the RPM sensor. Check the connection and put some dialelectiac grease in the plug for good measure.



Then check back and let us know if you found anything there.

Stupid question:what is "OD" button-not sure i see button next to steering wheel

 

[Philip]

ROFLMAO.



I didn't notice you were a stick shift truck. The grounds are behind the cargo light button. Right of steering column lower panel.

 

[PToombs]

ROFLMAO.



I didn't notice you were a stick shift truck. The grounds are behind the cargo light button. Right of steering column lower panel.

:-laf :-laf :-laf

 

[Moab4x4]

Sounds to me like PCM is not seeing juice reliably. General ground cleanup as mentioned is what I would try first. I suspect that all PCM functions are dead from that first post, no Cruise Control, Battery Charge, WTS, WIF, etc.



Crank sensor, good thing to check too.



I would also disconnect the PCM connector and hook it back up again to see if there could be a bad connection there. (inside the driver's fender, behind the battery. It is a connector with a screw in the middle to keep it attached. 5/16, 3/8 somewhere in there.



After you drive around for a while, does the fender relay click when the truck is still warm? It should only click when the air sensor is <50 degrees.



PCM sounds flaky. Hopefully just a ground issue. If not, you can replace the PCM or install an old style voltage regulator. Just hook it up like the old Dodges were from the early 70's till 91?

 

[MBullwinkel]

Sounds to me like PCM is not seeing juice reliably. General ground cleanup as mentioned is what I would try first. I suspect that all PCM functions are dead from that first post, no Cruise Control, Battery Charge, WTS, WIF, etc.



Crank sensor, good thing to check too.



I would also disconnect the PCM connector and hook it back up again to see if there could be a bad connection there. (inside the driver's fender, behind the battery. It is a connector with a screw in the middle to keep it attached. 5/16, 3/8 somewhere in there.



After you drive around for a while, does the fender relay click when the truck is still warm? It should only click when the air sensor is <50 degrees.



PCM sounds flaky. Hopefully just a ground issue. If not, you can replace the PCM or install an old style voltage regulator. Just hook it up like the old Dodges were from the early 70's till 91?

Well No luck so far.

I tried:



Disconnect and reattach PCM

Checkin grounds: sanded and reattached

Battery tests at auto store: tested ok but low charge (as expected)

disconnect litle boots on relays for preheaters



Haven't done the rpm sensor check. in the quick look I had, i couldn't see how to get to it easily. But It seems to me even if this was causing a problem, it would just prevent the charging but it wouldn't affect the whole WTS and WIF sequence would it?



I am leaning towards Moab4x4 explanation of a bad PCM. Anyone know where to get one and cost. Also curious about the voltage regulator idea-where can i find out how to do that?

 

[dpuckett]

1stGen4evr has done it in a few of his. He didnt like the Dodge set up and I think went with a Ford regulator. Have to ask him for details.



I believe I have seen $400 for a reman (not new) PCM. The one in the 93 I had several years ago had been replaced 6mo before I got it, and the voltage regulation went out on my first trip with it.



DP

 

[MBullwinkel]

Thanks! New PCM Charging!

Well, I finally installed a new PCM and it solved the problems! Oo.



I found it at for about $350 (less $125 if I get my core deposit back)

(they call it an ECM)

http://mydodgeparts.com/



*************************

My experience if it helps someone else to do it

Getting the old PCM out was pain- should have only taken 15 minutes . First I removed the battery, then the PCM cable held in with a bolt. The three bolts holding the PCM to its bracket were rusted and I couldn't remove them from the holding bracket. Finally ended up removing the whole bracket with PCM from the truck and drilling out the bolts-had to get some new bolts. Reattahed the braket, cable and battery.

***************************



Anyway, now when I turn the key, the WTS and WIF turns on then WIF goes out and WTS stays on, I can hear the relay clicking and then it stops, the WTS light extinguishes, I start it and get full charging!



(Keeping my fingers crossed as I know someone else replaced theirs and it only worked for a month-probably will try a regulator if that does not work)



Now on to fix the spongy brakes and parking brake!



Anyway Thanks for everybody's help!